json.hpp

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/*
    __ _____ _____ _____
 __|  |   __|     |   | |  JSON for Modern C++
|  |  |__   |  |  | | | |  version 2.1.1
|_____|_____|_____|_|___|  https://github.com/nlohmann/json

Licensed under the MIT License <http://opensource.org/licenses/MIT>.
Copyright (c) 2013-2017 Niels Lohmann <http://nlohmann.me>.

Permission is hereby  granted, free of charge, to any  person obtaining a copy
of this software and associated  documentation files (the "Software"), to deal
in the Software  without restriction, including without  limitation the rights
to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

#ifndef NLOHMANN_JSON_HPP
#define NLOHMANN_JSON_HPP

#include <algorithm> // all_of, copy, fill, find, for_each, none_of, remove, reverse, transform
#include <array> // array
#include <cassert> // assert
#include <ciso646> // and, not, or
#include <clocale> // lconv, localeconv
#include <cmath> // isfinite, labs, ldexp, signbit
#include <cstddef> // nullptr_t, ptrdiff_t, size_t
#include <cstdint> // int64_t, uint64_t
#include <cstdlib> // abort, strtod, strtof, strtold, strtoul, strtoll, strtoull
#include <cstring> // memcpy, strlen
#include <forward_list> // forward_list
#include <functional> // function, hash, less
#include <initializer_list> // initializer_list
#include <iomanip> // hex
#include <iostream> // istream, ostream
#include <iterator> // advance, begin, back_inserter, bidirectional_iterator_tag, distance, end, inserter, iterator, iterator_traits, next, random_access_iterator_tag, reverse_iterator
#include <limits> // numeric_limits
#include <locale> // locale
#include <map> // map
#include <memory> // addressof, allocator, allocator_traits, unique_ptr
#include <numeric> // accumulate
#include <sstream> // stringstream
#include <string> // getline, stoi, string, to_string
#include <type_traits> // add_pointer, conditional, decay, enable_if, false_type, integral_constant, is_arithmetic, is_base_of, is_const, is_constructible, is_convertible, is_default_constructible, is_enum, is_floating_point, is_integral, is_nothrow_move_assignable, is_nothrow_move_constructible, is_pointer, is_reference, is_same, is_scalar, is_signed, remove_const, remove_cv, remove_pointer, remove_reference, true_type, underlying_type
#include <utility> // declval, forward, make_pair, move, pair, swap
#include <vector> // vector

// exclude unsupported compilers
#if defined(__clang__)
    #if (__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__) < 30400
        #error "unsupported Clang version - see https://github.com/nlohmann/json#supported-compilers"
    #endif
#elif defined(__GNUC__)
    #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 40900
        #error "unsupported GCC version - see https://github.com/nlohmann/json#supported-compilers"
    #endif
#endif

// disable float-equal warnings on GCC/clang
#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
    #pragma GCC diagnostic push
    #pragma GCC diagnostic ignored "-Wfloat-equal"
#endif

// disable documentation warnings on clang
#if defined(__clang__)
    #pragma GCC diagnostic push
    #pragma GCC diagnostic ignored "-Wdocumentation"
#endif

// allow for portable deprecation warnings
#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
    #define JSON_DEPRECATED __attribute__((deprecated))
#elif defined(_MSC_VER)
    #define JSON_DEPRECATED __declspec(deprecated)
#else
    #define JSON_DEPRECATED
#endif

// allow to disable exceptions
#if (defined(__cpp_exceptions) || defined(__EXCEPTIONS) || defined(_CPPUNWIND)) && not defined(JSON_NOEXCEPTION)
    #define JSON_THROW(exception) throw exception
    #define JSON_TRY try
    #define JSON_CATCH(exception) catch(exception)
#else
    #define JSON_THROW(exception) std::abort()
    #define JSON_TRY if(true)
    #define JSON_CATCH(exception) if(false)
#endif

// manual branch prediction
#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
    #define JSON_LIKELY(x)      __builtin_expect(!!(x), 1)
    #define JSON_UNLIKELY(x)    __builtin_expect(!!(x), 0)
#else
    #define JSON_LIKELY(x)      x
    #define JSON_UNLIKELY(x)    x
#endif

namespace nlohmann
{

namespace detail
{
// exceptions //

class exception : public std::exception
{
  public:
    virtual const char* what() const noexcept override
    {
        return m.what();
    }

    const int id;

  protected:
    exception(int id_, const char* what_arg)
        : id(id_), m(what_arg)
    {}

    static std::string name(const std::string& ename, int id)
    {
        return "[json.exception." + ename + "." + std::to_string(id) + "] ";
    }

  private:
    std::runtime_error m;
};

class parse_error : public exception
{
  public:
    static parse_error create(int id, size_t byte_, const std::string& what_arg)
    {
        std::string w = exception::name("parse_error", id) + "parse error" +
                        (byte_ != 0 ? (" at " + std::to_string(byte_)) : "") +
                        ": " + what_arg;
        return parse_error(id, byte_, w.c_str());
    }

    const size_t byte;

  private:
    parse_error(int id_, size_t byte_, const char* what_arg)
        : exception(id_, what_arg), byte(byte_)
    {}
};

class invalid_iterator : public exception
{
  public:
    static invalid_iterator create(int id, const std::string& what_arg)
    {
        std::string w = exception::name("invalid_iterator", id) + what_arg;
        return invalid_iterator(id, w.c_str());
    }

  private:
    invalid_iterator(int id_, const char* what_arg)
        : exception(id_, what_arg)
    {}
};

class type_error : public exception
{
  public:
    static type_error create(int id, const std::string& what_arg)
    {
        std::string w = exception::name("type_error", id) + what_arg;
        return type_error(id, w.c_str());
    }

  private:
    type_error(int id_, const char* what_arg)
        : exception(id_, what_arg)
    {}
};

class out_of_range : public exception
{
  public:
    static out_of_range create(int id, const std::string& what_arg)
    {
        std::string w = exception::name("out_of_range", id) + what_arg;
        return out_of_range(id, w.c_str());
    }

  private:
    out_of_range(int id_, const char* what_arg)
        : exception(id_, what_arg)
    {}
};

class other_error : public exception
{
  public:
    static other_error create(int id, const std::string& what_arg)
    {
        std::string w = exception::name("other_error", id) + what_arg;
        return other_error(id, w.c_str());
    }

  private:
    other_error(int id_, const char* what_arg)
        : exception(id_, what_arg)
    {}
};



// JSON type enumeration //

enum class value_t : uint8_t
{
    null,            
    object,          
    array,           
    string,          
    boolean,         
    number_integer,  
    number_unsigned, 
    number_float,    
    discarded        
};

inline bool operator<(const value_t lhs, const value_t rhs) noexcept
{
    static constexpr std::array<uint8_t, 8> order = {{
            0, // null
            3, // object
            4, // array
            5, // string
            1, // boolean
            2, // integer
            2, // unsigned
            2, // float
        }
    };

    // discarded values are not comparable
    if (lhs == value_t::discarded or rhs == value_t::discarded)
    {
        return false;
    }

    return order[static_cast<std::size_t>(lhs)] <
           order[static_cast<std::size_t>(rhs)];
}


// helpers //

// alias templates to reduce boilerplate
template<bool B, typename T = void>
using enable_if_t = typename std::enable_if<B, T>::type;

template<typename T>
using uncvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;

/*
Implementation of two C++17 constructs: conjunction, negation. This is needed
to avoid evaluating all the traits in a condition

For example: not std::is_same<void, T>::value and has_value_type<T>::value
will not compile when T = void (on MSVC at least). Whereas
conjunction<negation<std::is_same<void, T>>, has_value_type<T>>::value will
stop evaluating if negation<...>::value == false

Please note that those constructs must be used with caution, since symbols can
become very long quickly (which can slow down compilation and cause MSVC
internal compiler errors). Only use it when you have to (see example ahead).
*/
template<class...> struct conjunction : std::true_type {};
template<class B1> struct conjunction<B1> : B1 {};
template<class B1, class... Bn>
struct conjunction<B1, Bn...> : std::conditional<bool(B1::value), conjunction<Bn...>, B1>::type {};

template<class B> struct negation : std::integral_constant < bool, !B::value > {};

// dispatch utility (taken from ranges-v3)
template<unsigned N> struct priority_tag : priority_tag < N - 1 > {};
template<> struct priority_tag<0> {};


// constructors //

template<value_t> struct external_constructor;

template<>
struct external_constructor<value_t::boolean>
{
    template<typename BasicJsonType>
    static void construct(BasicJsonType& j, typename BasicJsonType::boolean_t b) noexcept
    {
        j.m_type = value_t::boolean;
        j.m_value = b;
        j.assert_invariant();
    }
};

template<>
struct external_constructor<value_t::string>
{
    template<typename BasicJsonType>
    static void construct(BasicJsonType& j, const typename BasicJsonType::string_t& s)
    {
        j.m_type = value_t::string;
        j.m_value = s;
        j.assert_invariant();
    }
};

template<>
struct external_constructor<value_t::number_float>
{
    template<typename BasicJsonType>
    static void construct(BasicJsonType& j, typename BasicJsonType::number_float_t val) noexcept
    {
        j.m_type = value_t::number_float;
        j.m_value = val;
        j.assert_invariant();
    }
};

template<>
struct external_constructor<value_t::number_unsigned>
{
    template<typename BasicJsonType>
    static void construct(BasicJsonType& j, typename BasicJsonType::number_unsigned_t val) noexcept
    {
        j.m_type = value_t::number_unsigned;
        j.m_value = val;
        j.assert_invariant();
    }
};

template<>
struct external_constructor<value_t::number_integer>
{
    template<typename BasicJsonType>
    static void construct(BasicJsonType& j, typename BasicJsonType::number_integer_t val) noexcept
    {
        j.m_type = value_t::number_integer;
        j.m_value = val;
        j.assert_invariant();
    }
};

template<>
struct external_constructor<value_t::array>
{
    template<typename BasicJsonType>
    static void construct(BasicJsonType& j, const typename BasicJsonType::array_t& arr)
    {
        j.m_type = value_t::array;
        j.m_value = arr;
        j.assert_invariant();
    }

    template<typename BasicJsonType, typename CompatibleArrayType,
             enable_if_t<not std::is_same<CompatibleArrayType,
                                          typename BasicJsonType::array_t>::value,
                         int> = 0>
    static void construct(BasicJsonType& j, const CompatibleArrayType& arr)
    {
        using std::begin;
        using std::end;
        j.m_type = value_t::array;
        j.m_value.array = j.template create<typename BasicJsonType::array_t>(begin(arr), end(arr));
        j.assert_invariant();
    }

    template<typename BasicJsonType>
    static void construct(BasicJsonType& j, const std::vector<bool>& arr)
    {
        j.m_type = value_t::array;
        j.m_value = value_t::array;
        j.m_value.array->reserve(arr.size());
        for (bool x : arr)
        {
            j.m_value.array->push_back(x);
        }
        j.assert_invariant();
    }
};

template<>
struct external_constructor<value_t::object>
{
    template<typename BasicJsonType>
    static void construct(BasicJsonType& j, const typename BasicJsonType::object_t& obj)
    {
        j.m_type = value_t::object;
        j.m_value = obj;
        j.assert_invariant();
    }

    template<typename BasicJsonType, typename CompatibleObjectType,
             enable_if_t<not std::is_same<CompatibleObjectType,
                                          typename BasicJsonType::object_t>::value,
                         int> = 0>
    static void construct(BasicJsonType& j, const CompatibleObjectType& obj)
    {
        using std::begin;
        using std::end;

        j.m_type = value_t::object;
        j.m_value.object = j.template create<typename BasicJsonType::object_t>(begin(obj), end(obj));
        j.assert_invariant();
    }
};


// has_/is_ functions //

#define NLOHMANN_JSON_HAS_HELPER(type)                                        \
    template<typename T> struct has_##type {                                  \
    private:                                                                  \
        template<typename U, typename = typename U::type>                     \
        static int detect(U &&);                                              \
        static void detect(...);                                              \
    public:                                                                   \
        static constexpr bool value =                                         \
                std::is_integral<decltype(detect(std::declval<T>()))>::value; \
    }

NLOHMANN_JSON_HAS_HELPER(mapped_type);
NLOHMANN_JSON_HAS_HELPER(key_type);
NLOHMANN_JSON_HAS_HELPER(value_type);
NLOHMANN_JSON_HAS_HELPER(iterator);

#undef NLOHMANN_JSON_HAS_HELPER


template<bool B, class RealType, class CompatibleObjectType>
struct is_compatible_object_type_impl : std::false_type {};

template<class RealType, class CompatibleObjectType>
struct is_compatible_object_type_impl<true, RealType, CompatibleObjectType>
{
    static constexpr auto value =
        std::is_constructible<typename RealType::key_type,
        typename CompatibleObjectType::key_type>::value and
        std::is_constructible<typename RealType::mapped_type,
        typename CompatibleObjectType::mapped_type>::value;
};

template<class BasicJsonType, class CompatibleObjectType>
struct is_compatible_object_type
{
    static auto constexpr value = is_compatible_object_type_impl <
                                  conjunction<negation<std::is_same<void, CompatibleObjectType>>,
                                  has_mapped_type<CompatibleObjectType>,
                                  has_key_type<CompatibleObjectType>>::value,
                                  typename BasicJsonType::object_t, CompatibleObjectType >::value;
};

template<typename BasicJsonType, typename T>
struct is_basic_json_nested_type
{
    static auto constexpr value = std::is_same<T, typename BasicJsonType::iterator>::value or
                                  std::is_same<T, typename BasicJsonType::const_iterator>::value or
                                  std::is_same<T, typename BasicJsonType::reverse_iterator>::value or
                                  std::is_same<T, typename BasicJsonType::const_reverse_iterator>::value or
                                  std::is_same<T, typename BasicJsonType::json_pointer>::value;
};

template<class BasicJsonType, class CompatibleArrayType>
struct is_compatible_array_type
{
    static auto constexpr value =
        conjunction<negation<std::is_same<void, CompatibleArrayType>>,
        negation<is_compatible_object_type<
        BasicJsonType, CompatibleArrayType>>,
        negation<std::is_constructible<typename BasicJsonType::string_t,
        CompatibleArrayType>>,
        negation<is_basic_json_nested_type<BasicJsonType, CompatibleArrayType>>,
        has_value_type<CompatibleArrayType>,
        has_iterator<CompatibleArrayType>>::value;
};

template<bool, typename, typename>
struct is_compatible_integer_type_impl : std::false_type {};

template<typename RealIntegerType, typename CompatibleNumberIntegerType>
struct is_compatible_integer_type_impl<true, RealIntegerType, CompatibleNumberIntegerType>
{
    // is there an assert somewhere on overflows?
    using RealLimits = std::numeric_limits<RealIntegerType>;
    using CompatibleLimits = std::numeric_limits<CompatibleNumberIntegerType>;

    static constexpr auto value =
        std::is_constructible<RealIntegerType,
        CompatibleNumberIntegerType>::value and
        CompatibleLimits::is_integer and
        RealLimits::is_signed == CompatibleLimits::is_signed;
};

template<typename RealIntegerType, typename CompatibleNumberIntegerType>
struct is_compatible_integer_type
{
    static constexpr auto value =
        is_compatible_integer_type_impl <
        std::is_integral<CompatibleNumberIntegerType>::value and
        not std::is_same<bool, CompatibleNumberIntegerType>::value,
        RealIntegerType, CompatibleNumberIntegerType > ::value;
};


// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
template<typename BasicJsonType, typename T>
struct has_from_json
{
  private:
    // also check the return type of from_json
    template<typename U, typename = enable_if_t<std::is_same<void, decltype(uncvref_t<U>::from_json(
                 std::declval<BasicJsonType>(), std::declval<T&>()))>::value>>
    static int detect(U&&);
    static void detect(...);

  public:
    static constexpr bool value = std::is_integral<decltype(
                                      detect(std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
};

// This trait checks if JSONSerializer<T>::from_json(json const&) exists
// this overload is used for non-default-constructible user-defined-types
template<typename BasicJsonType, typename T>
struct has_non_default_from_json
{
  private:
    template <
        typename U,
        typename = enable_if_t<std::is_same<
                                   T, decltype(uncvref_t<U>::from_json(std::declval<BasicJsonType>()))>::value >>
    static int detect(U&&);
    static void detect(...);

  public:
    static constexpr bool value = std::is_integral<decltype(detect(
                                      std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
};

// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
template<typename BasicJsonType, typename T>
struct has_to_json
{
  private:
    template<typename U, typename = decltype(uncvref_t<U>::to_json(
                 std::declval<BasicJsonType&>(), std::declval<T>()))>
    static int detect(U&&);
    static void detect(...);

  public:
    static constexpr bool value = std::is_integral<decltype(detect(
                                      std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
};


// to_json //

template<typename BasicJsonType, typename T, enable_if_t<
             std::is_same<T, typename BasicJsonType::boolean_t>::value, int> = 0>
void to_json(BasicJsonType& j, T b) noexcept
{
    external_constructor<value_t::boolean>::construct(j, b);
}

template<typename BasicJsonType, typename CompatibleString,
         enable_if_t<std::is_constructible<typename BasicJsonType::string_t,
                     CompatibleString>::value, int> = 0>
void to_json(BasicJsonType& j, const CompatibleString& s)
{
    external_constructor<value_t::string>::construct(j, s);
}

template<typename BasicJsonType, typename FloatType,
         enable_if_t<std::is_floating_point<FloatType>::value, int> = 0>
void to_json(BasicJsonType& j, FloatType val) noexcept
{
    external_constructor<value_t::number_float>::construct(j, static_cast<typename BasicJsonType::number_float_t>(val));
}

template <
    typename BasicJsonType, typename CompatibleNumberUnsignedType,
    enable_if_t<is_compatible_integer_type<typename BasicJsonType::number_unsigned_t,
                CompatibleNumberUnsignedType>::value, int> = 0 >
void to_json(BasicJsonType& j, CompatibleNumberUnsignedType val) noexcept
{
    external_constructor<value_t::number_unsigned>::construct(j, static_cast<typename BasicJsonType::number_unsigned_t>(val));
}

template <
    typename BasicJsonType, typename CompatibleNumberIntegerType,
    enable_if_t<is_compatible_integer_type<typename BasicJsonType::number_integer_t,
                CompatibleNumberIntegerType>::value, int> = 0 >
void to_json(BasicJsonType& j, CompatibleNumberIntegerType val) noexcept
{
    external_constructor<value_t::number_integer>::construct(j, static_cast<typename BasicJsonType::number_integer_t>(val));
}

template<typename BasicJsonType, typename EnumType,
         enable_if_t<std::is_enum<EnumType>::value, int> = 0>
void to_json(BasicJsonType& j, EnumType e) noexcept
{
    using underlying_type = typename std::underlying_type<EnumType>::type;
    external_constructor<value_t::number_integer>::construct(j, static_cast<underlying_type>(e));
}

template<typename BasicJsonType>
void to_json(BasicJsonType& j, const std::vector<bool>& e)
{
    external_constructor<value_t::array>::construct(j, e);
}

template <
    typename BasicJsonType, typename CompatibleArrayType,
    enable_if_t <
        is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value or
        std::is_same<typename BasicJsonType::array_t, CompatibleArrayType>::value,
        int > = 0 >
void to_json(BasicJsonType& j, const  CompatibleArrayType& arr)
{
    external_constructor<value_t::array>::construct(j, arr);
}

template <
    typename BasicJsonType, typename CompatibleObjectType,
    enable_if_t<is_compatible_object_type<BasicJsonType, CompatibleObjectType>::value,
                int> = 0 >
void to_json(BasicJsonType& j, const  CompatibleObjectType& arr)
{
    external_constructor<value_t::object>::construct(j, arr);
}

template <typename BasicJsonType, typename T, std::size_t N,
          enable_if_t<not std::is_constructible<
                          typename BasicJsonType::string_t, T (&)[N]>::value,
                      int> = 0>
void to_json(BasicJsonType& j, T (&arr)[N])
{
    external_constructor<value_t::array>::construct(j, arr);
}

// from_json //

// overloads for basic_json template parameters
template<typename BasicJsonType, typename ArithmeticType,
         enable_if_t<std::is_arithmetic<ArithmeticType>::value and
                     not std::is_same<ArithmeticType,
                                      typename BasicJsonType::boolean_t>::value,
                     int> = 0>
void get_arithmetic_value(const BasicJsonType& j, ArithmeticType& val)
{
    switch (static_cast<value_t>(j))
    {
        case value_t::number_unsigned:
        {
            val = static_cast<ArithmeticType>(
                      *j.template get_ptr<const typename BasicJsonType::number_unsigned_t*>());
            break;
        }
        case value_t::number_integer:
        {
            val = static_cast<ArithmeticType>(
                      *j.template get_ptr<const typename BasicJsonType::number_integer_t*>());
            break;
        }
        case value_t::number_float:
        {
            val = static_cast<ArithmeticType>(
                      *j.template get_ptr<const typename BasicJsonType::number_float_t*>());
            break;
        }
        default:
        {
            JSON_THROW(type_error::create(302, "type must be number, but is " + j.type_name()));
        }
    }
}

template<typename BasicJsonType>
void from_json(const BasicJsonType& j, typename BasicJsonType::boolean_t& b)
{
    if (not j.is_boolean())
    {
        JSON_THROW(type_error::create(302, "type must be boolean, but is " + j.type_name()));
    }
    b = *j.template get_ptr<const typename BasicJsonType::boolean_t*>();
}

template<typename BasicJsonType>
void from_json(const BasicJsonType& j, typename BasicJsonType::string_t& s)
{
    if (not j.is_string())
    {
        JSON_THROW(type_error::create(302, "type must be string, but is " + j.type_name()));
    }
    s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
}

template<typename BasicJsonType>
void from_json(const BasicJsonType& j, typename BasicJsonType::number_float_t& val)
{
    get_arithmetic_value(j, val);
}

template<typename BasicJsonType>
void from_json(const BasicJsonType& j, typename BasicJsonType::number_unsigned_t& val)
{
    get_arithmetic_value(j, val);
}

template<typename BasicJsonType>
void from_json(const BasicJsonType& j, typename BasicJsonType::number_integer_t& val)
{
    get_arithmetic_value(j, val);
}

template<typename BasicJsonType, typename EnumType,
         enable_if_t<std::is_enum<EnumType>::value, int> = 0>
void from_json(const BasicJsonType& j, EnumType& e)
{
    typename std::underlying_type<EnumType>::type val;
    get_arithmetic_value(j, val);
    e = static_cast<EnumType>(val);
}

template<typename BasicJsonType>
void from_json(const BasicJsonType& j, typename BasicJsonType::array_t& arr)
{
    if (not j.is_array())
    {
        JSON_THROW(type_error::create(302, "type must be array, but is " + j.type_name()));
    }
    arr = *j.template get_ptr<const typename BasicJsonType::array_t*>();
}

// forward_list doesn't have an insert method
template<typename BasicJsonType, typename T, typename Allocator,
         enable_if_t<std::is_convertible<BasicJsonType, T>::value, int> = 0>
void from_json(const BasicJsonType& j, std::forward_list<T, Allocator>& l)
{
    if (not j.is_array())
    {
        JSON_THROW(type_error::create(302, "type must be array, but is " + j.type_name()));
    }

    for (auto it = j.rbegin(), end = j.rend(); it != end; ++it)
    {
        l.push_front(it->template get<T>());
    }
}

template<typename BasicJsonType, typename CompatibleArrayType>
void from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, priority_tag<0>)
{
    using std::begin;
    using std::end;

    std::transform(j.begin(), j.end(),
                   std::inserter(arr, end(arr)), [](const BasicJsonType & i)
    {
        // get<BasicJsonType>() returns *this, this won't call a from_json
        // method when value_type is BasicJsonType
        return i.template get<typename CompatibleArrayType::value_type>();
    });
}

template<typename BasicJsonType, typename CompatibleArrayType>
auto from_json_array_impl(const BasicJsonType& j, CompatibleArrayType& arr, priority_tag<1>)
-> decltype(
    arr.reserve(std::declval<typename CompatibleArrayType::size_type>()),
    void())
{
    using std::begin;
    using std::end;

    arr.reserve(j.size());
    std::transform(j.begin(), j.end(),
                   std::inserter(arr, end(arr)), [](const BasicJsonType & i)
    {
        // get<BasicJsonType>() returns *this, this won't call a from_json
        // method when value_type is BasicJsonType
        return i.template get<typename CompatibleArrayType::value_type>();
    });
}

template<typename BasicJsonType, typename CompatibleArrayType,
         enable_if_t<is_compatible_array_type<BasicJsonType, CompatibleArrayType>::value and
                     std::is_convertible<BasicJsonType, typename CompatibleArrayType::value_type>::value and
                     not std::is_same<typename BasicJsonType::array_t, CompatibleArrayType>::value, int> = 0>
void from_json(const BasicJsonType& j, CompatibleArrayType& arr)
{
    if (not j.is_array())
    {
        JSON_THROW(type_error::create(302, "type must be array, but is " + j.type_name()));
    }

    from_json_array_impl(j, arr, priority_tag<1> {});
}

template<typename BasicJsonType, typename CompatibleObjectType,
         enable_if_t<is_compatible_object_type<BasicJsonType, CompatibleObjectType>::value, int> = 0>
void from_json(const BasicJsonType& j, CompatibleObjectType& obj)
{
    if (not j.is_object())
    {
        JSON_THROW(type_error::create(302, "type must be object, but is " + j.type_name()));
    }

    auto inner_object = j.template get_ptr<const typename BasicJsonType::object_t*>();
    using std::begin;
    using std::end;
    // we could avoid the assignment, but this might require a for loop, which
    // might be less efficient than the container constructor for some
    // containers (would it?)
    obj = CompatibleObjectType(begin(*inner_object), end(*inner_object));
}

// overload for arithmetic types, not chosen for basic_json template arguments
// (BooleanType, etc..); note: Is it really necessary to provide explicit
// overloads for boolean_t etc. in case of a custom BooleanType which is not
// an arithmetic type?
template<typename BasicJsonType, typename ArithmeticType,
         enable_if_t <
             std::is_arithmetic<ArithmeticType>::value and
             not std::is_same<ArithmeticType, typename BasicJsonType::number_unsigned_t>::value and
             not std::is_same<ArithmeticType, typename BasicJsonType::number_integer_t>::value and
             not std::is_same<ArithmeticType, typename BasicJsonType::number_float_t>::value and
             not std::is_same<ArithmeticType, typename BasicJsonType::boolean_t>::value,
             int> = 0>
void from_json(const BasicJsonType& j, ArithmeticType& val)
{
    switch (static_cast<value_t>(j))
    {
        case value_t::number_unsigned:
        {
            val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_unsigned_t*>());
            break;
        }
        case value_t::number_integer:
        {
            val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_integer_t*>());
            break;
        }
        case value_t::number_float:
        {
            val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_float_t*>());
            break;
        }
        case value_t::boolean:
        {
            val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::boolean_t*>());
            break;
        }
        default:
        {
            JSON_THROW(type_error::create(302, "type must be number, but is " + j.type_name()));
        }
    }
}

struct to_json_fn
{
  private:
    template<typename BasicJsonType, typename T>
    auto call(BasicJsonType& j, T&& val, priority_tag<1>) const noexcept(noexcept(to_json(j, std::forward<T>(val))))
    -> decltype(to_json(j, std::forward<T>(val)), void())
    {
        return to_json(j, std::forward<T>(val));
    }

    template<typename BasicJsonType, typename T>
    void call(BasicJsonType&, T&&, priority_tag<0>) const noexcept
    {
        static_assert(sizeof(BasicJsonType) == 0,
                      "could not find to_json() method in T's namespace");
    }

  public:
    template<typename BasicJsonType, typename T>
    void operator()(BasicJsonType& j, T&& val) const
    noexcept(noexcept(std::declval<to_json_fn>().call(j, std::forward<T>(val), priority_tag<1> {})))
    {
        return call(j, std::forward<T>(val), priority_tag<1> {});
    }
};

struct from_json_fn
{
  private:
    template<typename BasicJsonType, typename T>
    auto call(const BasicJsonType& j, T& val, priority_tag<1>) const
    noexcept(noexcept(from_json(j, val)))
    -> decltype(from_json(j, val), void())
    {
        return from_json(j, val);
    }

    template<typename BasicJsonType, typename T>
    void call(const BasicJsonType&, T&, priority_tag<0>) const noexcept
    {
        static_assert(sizeof(BasicJsonType) == 0,
                      "could not find from_json() method in T's namespace");
    }

  public:
    template<typename BasicJsonType, typename T>
    void operator()(const BasicJsonType& j, T& val) const
    noexcept(noexcept(std::declval<from_json_fn>().call(j, val, priority_tag<1> {})))
    {
        return call(j, val, priority_tag<1> {});
    }
};

// taken from ranges-v3
template<typename T>
struct static_const
{
    static constexpr T value{};
};

template<typename T>
constexpr T static_const<T>::value;
} // namespace detail


namespace
{
constexpr const auto& to_json = detail::static_const<detail::to_json_fn>::value;
constexpr const auto& from_json = detail::static_const<detail::from_json_fn>::value;
}


template<typename = void, typename = void>
struct adl_serializer
{
    template<typename BasicJsonType, typename ValueType>
    static void from_json(BasicJsonType&& j, ValueType& val) noexcept(
        noexcept(::nlohmann::from_json(std::forward<BasicJsonType>(j), val)))
    {
        ::nlohmann::from_json(std::forward<BasicJsonType>(j), val);
    }

    template<typename BasicJsonType, typename ValueType>
    static void to_json(BasicJsonType& j, ValueType&& val) noexcept(
        noexcept(::nlohmann::to_json(j, std::forward<ValueType>(val))))
    {
        ::nlohmann::to_json(j, std::forward<ValueType>(val));
    }
};


template <
    template<typename U, typename V, typename... Args> class ObjectType = std::map,
    template<typename U, typename... Args> class ArrayType = std::vector,
    class StringType = std::string,
    class BooleanType = bool,
    class NumberIntegerType = std::int64_t,
    class NumberUnsignedType = std::uint64_t,
    class NumberFloatType = double,
    template<typename U> class AllocatorType = std::allocator,
    template<typename T, typename SFINAE = void> class JSONSerializer = adl_serializer
    >
class basic_json
{
  private:
    template<detail::value_t> friend struct detail::external_constructor;
    using basic_json_t = basic_json<ObjectType, ArrayType, StringType,
          BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType,
          AllocatorType, JSONSerializer>;

  public:
    using value_t = detail::value_t;
    // forward declarations
    template<typename U> class iter_impl;
    template<typename Base> class json_reverse_iterator;
    class json_pointer;
    template<typename T, typename SFINAE>
    using json_serializer = JSONSerializer<T, SFINAE>;


    // exceptions //


    using exception = detail::exception;
    using parse_error = detail::parse_error;
    using invalid_iterator = detail::invalid_iterator;
    using type_error = detail::type_error;
    using out_of_range = detail::out_of_range;
    using other_error = detail::other_error;



    // container types //


    using value_type = basic_json;

    using reference = value_type&;
    using const_reference = const value_type&;

    using difference_type = std::ptrdiff_t;
    using size_type = std::size_t;

    using allocator_type = AllocatorType<basic_json>;

    using pointer = typename std::allocator_traits<allocator_type>::pointer;
    using const_pointer = typename std::allocator_traits<allocator_type>::const_pointer;

    using iterator = iter_impl<basic_json>;
    using const_iterator = iter_impl<const basic_json>;
    using reverse_iterator = json_reverse_iterator<typename basic_json::iterator>;
    using const_reverse_iterator = json_reverse_iterator<typename basic_json::const_iterator>;



    static allocator_type get_allocator()
    {
        return allocator_type();
    }

    static basic_json meta()
    {
        basic_json result;

        result["copyright"] = "(C) 2013-2017 Niels Lohmann";
        result["name"] = "JSON for Modern C++";
        result["url"] = "https://github.com/nlohmann/json";
        result["version"] =
        {
            {"string", "2.1.1"}, {"major", 2}, {"minor", 1}, {"patch", 1}
        };

#ifdef _WIN32
        result["platform"] = "win32";
#elif defined __linux__
        result["platform"] = "linux";
#elif defined __APPLE__
        result["platform"] = "apple";
#elif defined __unix__
        result["platform"] = "unix";
#else
        result["platform"] = "unknown";
#endif

#if defined(__clang__)
        result["compiler"] = {{"family", "clang"}, {"version", __clang_version__}};
#elif defined(__ICC) || defined(__INTEL_COMPILER)
        result["compiler"] = {{"family", "icc"}, {"version", __INTEL_COMPILER}};
#elif defined(__GNUC__) || defined(__GNUG__)
        result["compiler"] = {{"family", "gcc"}, {"version", std::to_string(__GNUC__) + "." + std::to_string(__GNUC_MINOR__) + "." + std::to_string(__GNUC_PATCHLEVEL__)}};
#elif defined(__HP_cc) || defined(__HP_aCC)
        result["compiler"] = "hp"
#elif defined(__IBMCPP__)
        result["compiler"] = {{"family", "ilecpp"}, {"version", __IBMCPP__}};
#elif defined(_MSC_VER)
        result["compiler"] = {{"family", "msvc"}, {"version", _MSC_VER}};
#elif defined(__PGI)
        result["compiler"] = {{"family", "pgcpp"}, {"version", __PGI}};
#elif defined(__SUNPRO_CC)
        result["compiler"] = {{"family", "sunpro"}, {"version", __SUNPRO_CC}};
#else
        result["compiler"] = {{"family", "unknown"}, {"version", "unknown"}};
#endif

#ifdef __cplusplus
        result["compiler"]["c++"] = std::to_string(__cplusplus);
#else
        result["compiler"]["c++"] = "unknown";
#endif
        return result;
    }


    // JSON value data types //


    using object_t = ObjectType<StringType,
          basic_json,
          std::less<StringType>,
          AllocatorType<std::pair<const StringType,
          basic_json>>>;

    using array_t = ArrayType<basic_json, AllocatorType<basic_json>>;

    using string_t = StringType;

    using boolean_t = BooleanType;

    using number_integer_t = NumberIntegerType;

    using number_unsigned_t = NumberUnsignedType;

    using number_float_t = NumberFloatType;


  private:

    template<typename T, typename... Args>
    static T* create(Args&& ... args)
    {
        AllocatorType<T> alloc;
        auto deleter = [&](T * object)
        {
            alloc.deallocate(object, 1);
        };
        std::unique_ptr<T, decltype(deleter)> object(alloc.allocate(1), deleter);
        alloc.construct(object.get(), std::forward<Args>(args)...);
        assert(object != nullptr);
        return object.release();
    }

    // JSON value storage //

    union json_value
    {
        object_t* object;
        array_t* array;
        string_t* string;
        boolean_t boolean;
        number_integer_t number_integer;
        number_unsigned_t number_unsigned;
        number_float_t number_float;

        json_value() = default;
        json_value(boolean_t v) noexcept : boolean(v) {}
        json_value(number_integer_t v) noexcept : number_integer(v) {}
        json_value(number_unsigned_t v) noexcept : number_unsigned(v) {}
        json_value(number_float_t v) noexcept : number_float(v) {}
        json_value(value_t t)
        {
            switch (t)
            {
                case value_t::object:
                {
                    object = create<object_t>();
                    break;
                }

                case value_t::array:
                {
                    array = create<array_t>();
                    break;
                }

                case value_t::string:
                {
                    string = create<string_t>("");
                    break;
                }

                case value_t::boolean:
                {
                    boolean = boolean_t(false);
                    break;
                }

                case value_t::number_integer:
                {
                    number_integer = number_integer_t(0);
                    break;
                }

                case value_t::number_unsigned:
                {
                    number_unsigned = number_unsigned_t(0);
                    break;
                }

                case value_t::number_float:
                {
                    number_float = number_float_t(0.0);
                    break;
                }

                case value_t::null:
                {
                    break;
                }

                default:
                {
                    if (JSON_UNLIKELY(t == value_t::null))
                    {
                        JSON_THROW(other_error::create(500, "961c151d2e87f2686a955a9be24d316f1362bf21 2.1.1")); // LCOV_EXCL_LINE
                    }
                    break;
                }
            }
        }

        json_value(const string_t& value)
        {
            string = create<string_t>(value);
        }

        json_value(const object_t& value)
        {
            object = create<object_t>(value);
        }

        json_value(const array_t& value)
        {
            array = create<array_t>(value);
        }
    };

    void assert_invariant() const
    {
        assert(m_type != value_t::object or m_value.object != nullptr);
        assert(m_type != value_t::array or m_value.array != nullptr);
        assert(m_type != value_t::string or m_value.string != nullptr);
    }

  public:
    // JSON parser callback //

    enum class parse_event_t : uint8_t
    {
        object_start,
        object_end,
        array_start,
        array_end,
        key,
        value
    };

    using parser_callback_t = std::function<bool(int depth,
                              parse_event_t event,
                              basic_json& parsed)>;


    // constructors //


    basic_json(const value_t value_type)
        : m_type(value_type), m_value(value_type)
    {
        assert_invariant();
    }

    basic_json(std::nullptr_t = nullptr) noexcept
        : basic_json(value_t::null)
    {
        assert_invariant();
    }

    template<typename CompatibleType, typename U = detail::uncvref_t<CompatibleType>,
             detail::enable_if_t<not std::is_base_of<std::istream, U>::value and
                                 not std::is_same<U, basic_json_t>::value and
                                 not detail::is_basic_json_nested_type<
                                     basic_json_t, U>::value and
                                 detail::has_to_json<basic_json, U>::value,
                                 int> = 0>
    basic_json(CompatibleType && val) noexcept(noexcept(JSONSerializer<U>::to_json(
                std::declval<basic_json_t&>(), std::forward<CompatibleType>(val))))
    {
        JSONSerializer<U>::to_json(*this, std::forward<CompatibleType>(val));
        assert_invariant();
    }

    basic_json(std::initializer_list<basic_json> init,
               bool type_deduction = true,
               value_t manual_type = value_t::array)
    {
        // check if each element is an array with two elements whose first
        // element is a string
        bool is_an_object = std::all_of(init.begin(), init.end(),
                                        [](const basic_json & element)
        {
            return element.is_array() and element.size() == 2 and element[0].is_string();
        });

        // adjust type if type deduction is not wanted
        if (not type_deduction)
        {
            // if array is wanted, do not create an object though possible
            if (manual_type == value_t::array)
            {
                is_an_object = false;
            }

            // if object is wanted but impossible, throw an exception
            if (manual_type == value_t::object and not is_an_object)
            {
                JSON_THROW(type_error::create(301, "cannot create object from initializer list"));
            }
        }

        if (is_an_object)
        {
            // the initializer list is a list of pairs -> create object
            m_type = value_t::object;
            m_value = value_t::object;

            std::for_each(init.begin(), init.end(), [this](const basic_json & element)
            {
                m_value.object->emplace(*(element[0].m_value.string), element[1]);
            });
        }
        else
        {
            // the initializer list describes an array -> create array
            m_type = value_t::array;
            m_value.array = create<array_t>(init);
        }

        assert_invariant();
    }

    static basic_json array(std::initializer_list<basic_json> init =
                                std::initializer_list<basic_json>())
    {
        return basic_json(init, false, value_t::array);
    }

    static basic_json object(std::initializer_list<basic_json> init =
                                 std::initializer_list<basic_json>())
    {
        return basic_json(init, false, value_t::object);
    }

    basic_json(size_type cnt, const basic_json& val)
        : m_type(value_t::array)
    {
        m_value.array = create<array_t>(cnt, val);
        assert_invariant();
    }

    template<class InputIT, typename std::enable_if<
                 std::is_same<InputIT, typename basic_json_t::iterator>::value or
                 std::is_same<InputIT, typename basic_json_t::const_iterator>::value, int>::type = 0>
    basic_json(InputIT first, InputIT last)
    {
        assert(first.m_object != nullptr);
        assert(last.m_object != nullptr);

        // make sure iterator fits the current value
        if (first.m_object != last.m_object)
        {
            JSON_THROW(invalid_iterator::create(201, "iterators are not compatible"));
        }

        // copy type from first iterator
        m_type = first.m_object->m_type;

        // check if iterator range is complete for primitive values
        switch (m_type)
        {
            case value_t::boolean:
            case value_t::number_float:
            case value_t::number_integer:
            case value_t::number_unsigned:
            case value_t::string:
            {
                if (not first.m_it.primitive_iterator.is_begin() or not last.m_it.primitive_iterator.is_end())
                {
                    JSON_THROW(invalid_iterator::create(204, "iterators out of range"));
                }
                break;
            }

            default:
            {
                break;
            }
        }

        switch (m_type)
        {
            case value_t::number_integer:
            {
                m_value.number_integer = first.m_object->m_value.number_integer;
                break;
            }

            case value_t::number_unsigned:
            {
                m_value.number_unsigned = first.m_object->m_value.number_unsigned;
                break;
            }

            case value_t::number_float:
            {
                m_value.number_float = first.m_object->m_value.number_float;
                break;
            }

            case value_t::boolean:
            {
                m_value.boolean = first.m_object->m_value.boolean;
                break;
            }

            case value_t::string:
            {
                m_value = *first.m_object->m_value.string;
                break;
            }

            case value_t::object:
            {
                m_value.object = create<object_t>(first.m_it.object_iterator,
                                                  last.m_it.object_iterator);
                break;
            }

            case value_t::array:
            {
                m_value.array = create<array_t>(first.m_it.array_iterator,
                                                last.m_it.array_iterator);
                break;
            }

            default:
            {
                JSON_THROW(invalid_iterator::create(206, "cannot construct with iterators from " +
                                                    first.m_object->type_name()));
            }
        }

        assert_invariant();
    }


    // other constructors and destructor //

    basic_json(const basic_json& other)
        : m_type(other.m_type)
    {
        // check of passed value is valid
        other.assert_invariant();

        switch (m_type)
        {
            case value_t::object:
            {
                m_value = *other.m_value.object;
                break;
            }

            case value_t::array:
            {
                m_value = *other.m_value.array;
                break;
            }

            case value_t::string:
            {
                m_value = *other.m_value.string;
                break;
            }

            case value_t::boolean:
            {
                m_value = other.m_value.boolean;
                break;
            }

            case value_t::number_integer:
            {
                m_value = other.m_value.number_integer;
                break;
            }

            case value_t::number_unsigned:
            {
                m_value = other.m_value.number_unsigned;
                break;
            }

            case value_t::number_float:
            {
                m_value = other.m_value.number_float;
                break;
            }

            default:
            {
                break;
            }
        }

        assert_invariant();
    }

    basic_json(basic_json&& other) noexcept
        : m_type(std::move(other.m_type)),
          m_value(std::move(other.m_value))
    {
        // check that passed value is valid
        other.assert_invariant();

        // invalidate payload
        other.m_type = value_t::null;
        other.m_value = {};

        assert_invariant();
    }

    reference& operator=(basic_json other) noexcept (
        std::is_nothrow_move_constructible<value_t>::value and
        std::is_nothrow_move_assignable<value_t>::value and
        std::is_nothrow_move_constructible<json_value>::value and
        std::is_nothrow_move_assignable<json_value>::value
    )
    {
        // check that passed value is valid
        other.assert_invariant();

        using std::swap;
        swap(m_type, other.m_type);
        swap(m_value, other.m_value);

        assert_invariant();
        return *this;
    }

    ~basic_json()
    {
        assert_invariant();

        switch (m_type)
        {
            case value_t::object:
            {
                AllocatorType<object_t> alloc;
                alloc.destroy(m_value.object);
                alloc.deallocate(m_value.object, 1);
                break;
            }

            case value_t::array:
            {
                AllocatorType<array_t> alloc;
                alloc.destroy(m_value.array);
                alloc.deallocate(m_value.array, 1);
                break;
            }

            case value_t::string:
            {
                AllocatorType<string_t> alloc;
                alloc.destroy(m_value.string);
                alloc.deallocate(m_value.string, 1);
                break;
            }

            default:
            {
                // all other types need no specific destructor
                break;
            }
        }
    }


  public:
    // object inspection //


    string_t dump(const int indent = -1, const char indent_char = ' ') const
    {
        string_t result;
        serializer s(output_adapter<char>::create(result), indent_char);

        if (indent >= 0)
        {
            s.dump(*this, true, static_cast<unsigned int>(indent));
        }
        else
        {
            s.dump(*this, false, 0);
        }

        return result;
    }

    constexpr value_t type() const noexcept
    {
        return m_type;
    }

    constexpr bool is_primitive() const noexcept
    {
        return is_null() or is_string() or is_boolean() or is_number();
    }

    constexpr bool is_structured() const noexcept
    {
        return is_array() or is_object();
    }

    constexpr bool is_null() const noexcept
    {
        return m_type == value_t::null;
    }

    constexpr bool is_boolean() const noexcept
    {
        return m_type == value_t::boolean;
    }

    constexpr bool is_number() const noexcept
    {
        return is_number_integer() or is_number_float();
    }

    constexpr bool is_number_integer() const noexcept
    {
        return m_type == value_t::number_integer or m_type == value_t::number_unsigned;
    }

    constexpr bool is_number_unsigned() const noexcept
    {
        return m_type == value_t::number_unsigned;
    }

    constexpr bool is_number_float() const noexcept
    {
        return m_type == value_t::number_float;
    }

    constexpr bool is_object() const noexcept
    {
        return m_type == value_t::object;
    }

    constexpr bool is_array() const noexcept
    {
        return m_type == value_t::array;
    }

    constexpr bool is_string() const noexcept
    {
        return m_type == value_t::string;
    }

    constexpr bool is_discarded() const noexcept
    {
        return m_type == value_t::discarded;
    }

    constexpr operator value_t() const noexcept
    {
        return m_type;
    }


  private:
    // value access //

    boolean_t get_impl(boolean_t* /*unused*/) const
    {
        if (is_boolean())
        {
            return m_value.boolean;
        }

        JSON_THROW(type_error::create(302, "type must be boolean, but is " + type_name()));
    }

    object_t* get_impl_ptr(object_t* /*unused*/) noexcept
    {
        return is_object() ? m_value.object : nullptr;
    }

    constexpr const object_t* get_impl_ptr(const object_t* /*unused*/) const noexcept
    {
        return is_object() ? m_value.object : nullptr;
    }

    array_t* get_impl_ptr(array_t* /*unused*/) noexcept
    {
        return is_array() ? m_value.array : nullptr;
    }

    constexpr const array_t* get_impl_ptr(const array_t* /*unused*/) const noexcept
    {
        return is_array() ? m_value.array : nullptr;
    }

    string_t* get_impl_ptr(string_t* /*unused*/) noexcept
    {
        return is_string() ? m_value.string : nullptr;
    }

    constexpr const string_t* get_impl_ptr(const string_t* /*unused*/) const noexcept
    {
        return is_string() ? m_value.string : nullptr;
    }

    boolean_t* get_impl_ptr(boolean_t* /*unused*/) noexcept
    {
        return is_boolean() ? &m_value.boolean : nullptr;
    }

    constexpr const boolean_t* get_impl_ptr(const boolean_t* /*unused*/) const noexcept
    {
        return is_boolean() ? &m_value.boolean : nullptr;
    }

    number_integer_t* get_impl_ptr(number_integer_t* /*unused*/) noexcept
    {
        return is_number_integer() ? &m_value.number_integer : nullptr;
    }

    constexpr const number_integer_t* get_impl_ptr(const number_integer_t* /*unused*/) const noexcept
    {
        return is_number_integer() ? &m_value.number_integer : nullptr;
    }

    number_unsigned_t* get_impl_ptr(number_unsigned_t* /*unused*/) noexcept
    {
        return is_number_unsigned() ? &m_value.number_unsigned : nullptr;
    }

    constexpr const number_unsigned_t* get_impl_ptr(const number_unsigned_t* /*unused*/) const noexcept
    {
        return is_number_unsigned() ? &m_value.number_unsigned : nullptr;
    }

    number_float_t* get_impl_ptr(number_float_t* /*unused*/) noexcept
    {
        return is_number_float() ? &m_value.number_float : nullptr;
    }

    constexpr const number_float_t* get_impl_ptr(const number_float_t* /*unused*/) const noexcept
    {
        return is_number_float() ? &m_value.number_float : nullptr;
    }

    template<typename ReferenceType, typename ThisType>
    static ReferenceType get_ref_impl(ThisType& obj)
    {
        // helper type
        using PointerType = typename std::add_pointer<ReferenceType>::type;

        // delegate the call to get_ptr<>()
        auto ptr = obj.template get_ptr<PointerType>();

        if (ptr != nullptr)
        {
            return *ptr;
        }

        JSON_THROW(type_error::create(303, "incompatible ReferenceType for get_ref, actual type is " + obj.type_name()));
    }

  public:

    template <
        typename BasicJsonType,
        detail::enable_if_t<std::is_same<typename std::remove_const<BasicJsonType>::type,
                                         basic_json_t>::value,
                            int> = 0 >
    basic_json get() const
    {
        return *this;
    }

    template <
        typename ValueTypeCV,
        typename ValueType = detail::uncvref_t<ValueTypeCV>,
        detail::enable_if_t <
            not std::is_same<basic_json_t, ValueType>::value and
            detail::has_from_json<basic_json_t, ValueType>::value and
            not detail::has_non_default_from_json<basic_json_t, ValueType>::value,
            int > = 0 >
    ValueType get() const noexcept(noexcept(
                                       JSONSerializer<ValueType>::from_json(std::declval<const basic_json_t&>(), std::declval<ValueType&>())))
    {
        // we cannot static_assert on ValueTypeCV being non-const, because
        // there is support for get<const basic_json_t>(), which is why we
        // still need the uncvref
        static_assert(not std::is_reference<ValueTypeCV>::value,
                      "get() cannot be used with reference types, you might want to use get_ref()");
        static_assert(std::is_default_constructible<ValueType>::value,
                      "types must be DefaultConstructible when used with get()");

        ValueType ret;
        JSONSerializer<ValueType>::from_json(*this, ret);
        return ret;
    }

    template <
        typename ValueTypeCV,
        typename ValueType = detail::uncvref_t<ValueTypeCV>,
        detail::enable_if_t<not std::is_same<basic_json_t, ValueType>::value and
                            detail::has_non_default_from_json<basic_json_t,
                                    ValueType>::value, int> = 0 >
    ValueType get() const noexcept(noexcept(
                                       JSONSerializer<ValueTypeCV>::from_json(std::declval<const basic_json_t&>())))
    {
        static_assert(not std::is_reference<ValueTypeCV>::value,
                      "get() cannot be used with reference types, you might want to use get_ref()");
        return JSONSerializer<ValueTypeCV>::from_json(*this);
    }

    template<typename PointerType, typename std::enable_if<
                 std::is_pointer<PointerType>::value, int>::type = 0>
    PointerType get() noexcept
    {
        // delegate the call to get_ptr
        return get_ptr<PointerType>();
    }

    template<typename PointerType, typename std::enable_if<
                 std::is_pointer<PointerType>::value, int>::type = 0>
    constexpr const PointerType get() const noexcept
    {
        // delegate the call to get_ptr
        return get_ptr<PointerType>();
    }

    template<typename PointerType, typename std::enable_if<
                 std::is_pointer<PointerType>::value, int>::type = 0>
    PointerType get_ptr() noexcept
    {
        // get the type of the PointerType (remove pointer and const)
        using pointee_t = typename std::remove_const<typename
                          std::remove_pointer<typename
                          std::remove_const<PointerType>::type>::type>::type;
        // make sure the type matches the allowed types
        static_assert(
            std::is_same<object_t, pointee_t>::value
            or std::is_same<array_t, pointee_t>::value
            or std::is_same<string_t, pointee_t>::value
            or std::is_same<boolean_t, pointee_t>::value
            or std::is_same<number_integer_t, pointee_t>::value
            or std::is_same<number_unsigned_t, pointee_t>::value
            or std::is_same<number_float_t, pointee_t>::value
            , "incompatible pointer type");

        // delegate the call to get_impl_ptr<>()
        return get_impl_ptr(static_cast<PointerType>(nullptr));
    }

    template<typename PointerType, typename std::enable_if<
                 std::is_pointer<PointerType>::value and
                 std::is_const<typename std::remove_pointer<PointerType>::type>::value, int>::type = 0>
    constexpr const PointerType get_ptr() const noexcept
    {
        // get the type of the PointerType (remove pointer and const)
        using pointee_t = typename std::remove_const<typename
                          std::remove_pointer<typename
                          std::remove_const<PointerType>::type>::type>::type;
        // make sure the type matches the allowed types
        static_assert(
            std::is_same<object_t, pointee_t>::value
            or std::is_same<array_t, pointee_t>::value
            or std::is_same<string_t, pointee_t>::value
            or std::is_same<boolean_t, pointee_t>::value
            or std::is_same<number_integer_t, pointee_t>::value
            or std::is_same<number_unsigned_t, pointee_t>::value
            or std::is_same<number_float_t, pointee_t>::value
            , "incompatible pointer type");

        // delegate the call to get_impl_ptr<>() const
        return get_impl_ptr(static_cast<const PointerType>(nullptr));
    }

    template<typename ReferenceType, typename std::enable_if<
                 std::is_reference<ReferenceType>::value, int>::type = 0>
    ReferenceType get_ref()
    {
        // delegate call to get_ref_impl
        return get_ref_impl<ReferenceType>(*this);
    }

    template<typename ReferenceType, typename std::enable_if<
                 std::is_reference<ReferenceType>::value and
                 std::is_const<typename std::remove_reference<ReferenceType>::type>::value, int>::type = 0>
    ReferenceType get_ref() const
    {
        // delegate call to get_ref_impl
        return get_ref_impl<ReferenceType>(*this);
    }

    template < typename ValueType, typename std::enable_if <
                   not std::is_pointer<ValueType>::value and
                   not std::is_same<ValueType, typename string_t::value_type>::value
#ifndef _MSC_VER  // fix for issue #167 operator<< ambiguity under VS2015
                   and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
#endif
#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(_MSC_VER) && _MSC_VER >1900 && defined(_HAS_CXX17) && _HAS_CXX17 == 1) // fix for issue #464
                   and not std::is_same<ValueType, typename std::string_view>::value
#endif
                   , int >::type = 0 >
    operator ValueType() const
    {
        // delegate the call to get<>() const
        return get<ValueType>();
    }



    // element access //


    reference at(size_type idx)
    {
        // at only works for arrays
        if (is_array())
        {
            JSON_TRY
            {
                return m_value.array->at(idx);
            }
            JSON_CATCH (std::out_of_range&)
            {
                // create better exception explanation
                JSON_THROW(out_of_range::create(401, "array index " + std::to_string(idx) + " is out of range"));
            }
        }
        else
        {
            JSON_THROW(type_error::create(304, "cannot use at() with " + type_name()));
        }
    }

    const_reference at(size_type idx) const
    {
        // at only works for arrays
        if (is_array())
        {
            JSON_TRY
            {
                return m_value.array->at(idx);
            }
            JSON_CATCH (std::out_of_range&)
            {
                // create better exception explanation
                JSON_THROW(out_of_range::create(401, "array index " + std::to_string(idx) + " is out of range"));
            }
        }
        else
        {
            JSON_THROW(type_error::create(304, "cannot use at() with " + type_name()));
        }
    }

    reference at(const typename object_t::key_type& key)
    {
        // at only works for objects
        if (is_object())
        {
            JSON_TRY
            {
                return m_value.object->at(key);
            }
            JSON_CATCH (std::out_of_range&)
            {
                // create better exception explanation
                JSON_THROW(out_of_range::create(403, "key '" + key + "' not found"));
            }
        }
        else
        {
            JSON_THROW(type_error::create(304, "cannot use at() with " + type_name()));
        }
    }

    const_reference at(const typename object_t::key_type& key) const
    {
        // at only works for objects
        if (is_object())
        {
            JSON_TRY
            {
                return m_value.object->at(key);
            }
            JSON_CATCH (std::out_of_range&)
            {
                // create better exception explanation
                JSON_THROW(out_of_range::create(403, "key '" + key + "' not found"));
            }
        }
        else
        {
            JSON_THROW(type_error::create(304, "cannot use at() with " + type_name()));
        }
    }

    reference operator[](size_type idx)
    {
        // implicitly convert null value to an empty array
        if (is_null())
        {
            m_type = value_t::array;
            m_value.array = create<array_t>();
            assert_invariant();
        }

        // operator[] only works for arrays
        if (is_array())
        {
            // fill up array with null values if given idx is outside range
            if (idx >= m_value.array->size())
            {
                m_value.array->insert(m_value.array->end(),
                                      idx - m_value.array->size() + 1,
                                      basic_json());
            }

            return m_value.array->operator[](idx);
        }

        JSON_THROW(type_error::create(305, "cannot use operator[] with " + type_name()));
    }

    const_reference operator[](size_type idx) const
    {
        // const operator[] only works for arrays
        if (is_array())
        {
            return m_value.array->operator[](idx);
        }

        JSON_THROW(type_error::create(305, "cannot use operator[] with " + type_name()));
    }

    reference operator[](const typename object_t::key_type& key)
    {
        // implicitly convert null value to an empty object
        if (is_null())
        {
            m_type = value_t::object;
            m_value.object = create<object_t>();
            assert_invariant();
        }

        // operator[] only works for objects
        if (is_object())
        {
            return m_value.object->operator[](key);
        }

        JSON_THROW(type_error::create(305, "cannot use operator[] with " + type_name()));
    }

    const_reference operator[](const typename object_t::key_type& key) const
    {
        // const operator[] only works for objects
        if (is_object())
        {
            assert(m_value.object->find(key) != m_value.object->end());
            return m_value.object->find(key)->second;
        }

        JSON_THROW(type_error::create(305, "cannot use operator[] with " + type_name()));
    }

    template<typename T, std::size_t n>
    reference operator[](T * (&key)[n])
    {
        return operator[](static_cast<const T>(key));
    }

    template<typename T, std::size_t n>
    const_reference operator[](T * (&key)[n]) const
    {
        return operator[](static_cast<const T>(key));
    }

    template<typename T>
    reference operator[](T* key)
    {
        // implicitly convert null to object
        if (is_null())
        {
            m_type = value_t::object;
            m_value = value_t::object;
            assert_invariant();
        }

        // at only works for objects
        if (is_object())
        {
            return m_value.object->operator[](key);
        }

        JSON_THROW(type_error::create(305, "cannot use operator[] with " + type_name()));
    }

    template<typename T>
    const_reference operator[](T* key) const
    {
        // at only works for objects
        if (is_object())
        {
            assert(m_value.object->find(key) != m_value.object->end());
            return m_value.object->find(key)->second;
        }

        JSON_THROW(type_error::create(305, "cannot use operator[] with " + type_name()));
    }

    template<class ValueType, typename std::enable_if<
                 std::is_convertible<basic_json_t, ValueType>::value, int>::type = 0>
    ValueType value(const typename object_t::key_type& key, ValueType default_value) const
    {
        // at only works for objects
        if (is_object())
        {
            // if key is found, return value and given default value otherwise
            const auto it = find(key);
            if (it != end())
            {
                return *it;
            }

            return default_value;
        }
        else
        {
            JSON_THROW(type_error::create(306, "cannot use value() with " + type_name()));
        }
    }

    string_t value(const typename object_t::key_type& key, const char* default_value) const
    {
        return value(key, string_t(default_value));
    }

    template<class ValueType, typename std::enable_if<
                 std::is_convertible<basic_json_t, ValueType>::value, int>::type = 0>
    ValueType value(const json_pointer& ptr, ValueType default_value) const
    {
        // at only works for objects
        if (is_object())
        {
            // if pointer resolves a value, return it or use default value
            JSON_TRY
            {
                return ptr.get_checked(this);
            }
            JSON_CATCH (out_of_range&)
            {
                return default_value;
            }
        }

        JSON_THROW(type_error::create(306, "cannot use value() with " + type_name()));
    }

    string_t value(const json_pointer& ptr, const char* default_value) const
    {
        return value(ptr, string_t(default_value));
    }

    reference front()
    {
        return *begin();
    }

    const_reference front() const
    {
        return *cbegin();
    }

    reference back()
    {
        auto tmp = end();
        --tmp;
        return *tmp;
    }

    const_reference back() const
    {
        auto tmp = cend();
        --tmp;
        return *tmp;
    }

    template<class IteratorType, typename std::enable_if<
                 std::is_same<IteratorType, typename basic_json_t::iterator>::value or
                 std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int>::type
             = 0>
    IteratorType erase(IteratorType pos)
    {
        // make sure iterator fits the current value
        if (this != pos.m_object)
        {
            JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
        }

        IteratorType result = end();

        switch (m_type)
        {
            case value_t::boolean:
            case value_t::number_float:
            case value_t::number_integer:
            case value_t::number_unsigned:
            case value_t::string:
            {
                if (not pos.m_it.primitive_iterator.is_begin())
                {
                    JSON_THROW(invalid_iterator::create(205, "iterator out of range"));
                }

                if (is_string())
                {
                    AllocatorType<string_t> alloc;
                    alloc.destroy(m_value.string);
                    alloc.deallocate(m_value.string, 1);
                    m_value.string = nullptr;
                }

                m_type = value_t::null;
                assert_invariant();
                break;
            }

            case value_t::object:
            {
                result.m_it.object_iterator = m_value.object->erase(pos.m_it.object_iterator);
                break;
            }

            case value_t::array:
            {
                result.m_it.array_iterator = m_value.array->erase(pos.m_it.array_iterator);
                break;
            }

            default:
            {
                JSON_THROW(type_error::create(307, "cannot use erase() with " + type_name()));
            }
        }

        return result;
    }

    template<class IteratorType, typename std::enable_if<
                 std::is_same<IteratorType, typename basic_json_t::iterator>::value or
                 std::is_same<IteratorType, typename basic_json_t::const_iterator>::value, int>::type
             = 0>
    IteratorType erase(IteratorType first, IteratorType last)
    {
        // make sure iterator fits the current value
        if (this != first.m_object or this != last.m_object)
        {
            JSON_THROW(invalid_iterator::create(203, "iterators do not fit current value"));
        }

        IteratorType result = end();

        switch (m_type)
        {
            case value_t::boolean:
            case value_t::number_float:
            case value_t::number_integer:
            case value_t::number_unsigned:
            case value_t::string:
            {
                if (not first.m_it.primitive_iterator.is_begin() or not last.m_it.primitive_iterator.is_end())
                {
                    JSON_THROW(invalid_iterator::create(204, "iterators out of range"));
                }

                if (is_string())
                {
                    AllocatorType<string_t> alloc;
                    alloc.destroy(m_value.string);
                    alloc.deallocate(m_value.string, 1);
                    m_value.string = nullptr;
                }

                m_type = value_t::null;
                assert_invariant();
                break;
            }

            case value_t::object:
            {
                result.m_it.object_iterator = m_value.object->erase(first.m_it.object_iterator,
                                              last.m_it.object_iterator);
                break;
            }

            case value_t::array:
            {
                result.m_it.array_iterator = m_value.array->erase(first.m_it.array_iterator,
                                             last.m_it.array_iterator);
                break;
            }

            default:
            {
                JSON_THROW(type_error::create(307, "cannot use erase() with " + type_name()));
            }
        }

        return result;
    }

    size_type erase(const typename object_t::key_type& key)
    {
        // this erase only works for objects
        if (is_object())
        {
            return m_value.object->erase(key);
        }

        JSON_THROW(type_error::create(307, "cannot use erase() with " + type_name()));
    }

    void erase(const size_type idx)
    {
        // this erase only works for arrays
        if (is_array())
        {
            if (idx >= size())
            {
                JSON_THROW(out_of_range::create(401, "array index " + std::to_string(idx) + " is out of range"));
            }

            m_value.array->erase(m_value.array->begin() + static_cast<difference_type>(idx));
        }
        else
        {
            JSON_THROW(type_error::create(307, "cannot use erase() with " + type_name()));
        }
    }



    // lookup //


    iterator find(typename object_t::key_type key)
    {
        auto result = end();

        if (is_object())
        {
            result.m_it.object_iterator = m_value.object->find(key);
        }

        return result;
    }

    const_iterator find(typename object_t::key_type key) const
    {
        auto result = cend();

        if (is_object())
        {
            result.m_it.object_iterator = m_value.object->find(key);
        }

        return result;
    }

    size_type count(typename object_t::key_type key) const
    {
        // return 0 for all nonobject types
        return is_object() ? m_value.object->count(key) : 0;
    }



    // iterators //


    iterator begin() noexcept
    {
        iterator result(this);
        result.set_begin();
        return result;
    }

    const_iterator begin() const noexcept
    {
        return cbegin();
    }

    const_iterator cbegin() const noexcept
    {
        const_iterator result(this);
        result.set_begin();
        return result;
    }

    iterator end() noexcept
    {
        iterator result(this);
        result.set_end();
        return result;
    }

    const_iterator end() const noexcept
    {
        return cend();
    }

    const_iterator cend() const noexcept
    {
        const_iterator result(this);
        result.set_end();
        return result;
    }

    reverse_iterator rbegin() noexcept
    {
        return reverse_iterator(end());
    }

    const_reverse_iterator rbegin() const noexcept
    {
        return crbegin();
    }

    reverse_iterator rend() noexcept
    {
        return reverse_iterator(begin());
    }

    const_reverse_iterator rend() const noexcept
    {
        return crend();
    }

    const_reverse_iterator crbegin() const noexcept
    {
        return const_reverse_iterator(cend());
    }

    const_reverse_iterator crend() const noexcept
    {
        return const_reverse_iterator(cbegin());
    }

  private:
    // forward declaration
    template<typename IteratorType> class iteration_proxy;

  public:
    static iteration_proxy<iterator> iterator_wrapper(reference cont)
    {
        return iteration_proxy<iterator>(cont);
    }

    static iteration_proxy<const_iterator> iterator_wrapper(const_reference cont)
    {
        return iteration_proxy<const_iterator>(cont);
    }



    // capacity //


    bool empty() const noexcept
    {
        switch (m_type)
        {
            case value_t::null:
            {
                // null values are empty
                return true;
            }

            case value_t::array:
            {
                // delegate call to array_t::empty()
                return m_value.array->empty();
            }

            case value_t::object:
            {
                // delegate call to object_t::empty()
                return m_value.object->empty();
            }

            default:
            {
                // all other types are nonempty
                return false;
            }
        }
    }

    size_type size() const noexcept
    {
        switch (m_type)
        {
            case value_t::null:
            {
                // null values are empty
                return 0;
            }

            case value_t::array:
            {
                // delegate call to array_t::size()
                return m_value.array->size();
            }

            case value_t::object:
            {
                // delegate call to object_t::size()
                return m_value.object->size();
            }

            default:
            {
                // all other types have size 1
                return 1;
            }
        }
    }

    size_type max_size() const noexcept
    {
        switch (m_type)
        {
            case value_t::array:
            {
                // delegate call to array_t::max_size()
                return m_value.array->max_size();
            }

            case value_t::object:
            {
                // delegate call to object_t::max_size()
                return m_value.object->max_size();
            }

            default:
            {
                // all other types have max_size() == size()
                return size();
            }
        }
    }



    // modifiers //


    void clear() noexcept
    {
        switch (m_type)
        {
            case value_t::number_integer:
            {
                m_value.number_integer = 0;
                break;
            }

            case value_t::number_unsigned:
            {
                m_value.number_unsigned = 0;
                break;
            }

            case value_t::number_float:
            {
                m_value.number_float = 0.0;
                break;
            }

            case value_t::boolean:
            {
                m_value.boolean = false;
                break;
            }

            case value_t::string:
            {
                m_value.string->clear();
                break;
            }

            case value_t::array:
            {
                m_value.array->clear();
                break;
            }

            case value_t::object:
            {
                m_value.object->clear();
                break;
            }

            default:
            {
                break;
            }
        }
    }

    void push_back(basic_json&& val)
    {
        // push_back only works for null objects or arrays
        if (not(is_null() or is_array()))
        {
            JSON_THROW(type_error::create(308, "cannot use push_back() with " + type_name()));
        }

        // transform null object into an array
        if (is_null())
        {
            m_type = value_t::array;
            m_value = value_t::array;
            assert_invariant();
        }

        // add element to array (move semantics)
        m_value.array->push_back(std::move(val));
        // invalidate object
        val.m_type = value_t::null;
    }

    reference operator+=(basic_json&& val)
    {
        push_back(std::move(val));
        return *this;
    }

    void push_back(const basic_json& val)
    {
        // push_back only works for null objects or arrays
        if (not(is_null() or is_array()))
        {
            JSON_THROW(type_error::create(308, "cannot use push_back() with " + type_name()));
        }

        // transform null object into an array
        if (is_null())
        {
            m_type = value_t::array;
            m_value = value_t::array;
            assert_invariant();
        }

        // add element to array
        m_value.array->push_back(val);
    }

    reference operator+=(const basic_json& val)
    {
        push_back(val);
        return *this;
    }

    void push_back(const typename object_t::value_type& val)
    {
        // push_back only works for null objects or objects
        if (not(is_null() or is_object()))
        {
            JSON_THROW(type_error::create(308, "cannot use push_back() with " + type_name()));
        }

        // transform null object into an object
        if (is_null())
        {
            m_type = value_t::object;
            m_value = value_t::object;
            assert_invariant();
        }

        // add element to array
        m_value.object->insert(val);
    }

    reference operator+=(const typename object_t::value_type& val)
    {
        push_back(val);
        return *this;
    }

    void push_back(std::initializer_list<basic_json> init)
    {
        if (is_object() and init.size() == 2 and init.begin()->is_string())
        {
            const string_t key = *init.begin();
            push_back(typename object_t::value_type(key, *(init.begin() + 1)));
        }
        else
        {
            push_back(basic_json(init));
        }
    }

    reference operator+=(std::initializer_list<basic_json> init)
    {
        push_back(init);
        return *this;
    }

    template<class... Args>
    void emplace_back(Args&& ... args)
    {
        // emplace_back only works for null objects or arrays
        if (not(is_null() or is_array()))
        {
            JSON_THROW(type_error::create(311, "cannot use emplace_back() with " + type_name()));
        }

        // transform null object into an array
        if (is_null())
        {
            m_type = value_t::array;
            m_value = value_t::array;
            assert_invariant();
        }

        // add element to array (perfect forwarding)
        m_value.array->emplace_back(std::forward<Args>(args)...);
    }

    template<class... Args>
    std::pair<iterator, bool> emplace(Args&& ... args)
    {
        // emplace only works for null objects or arrays
        if (not(is_null() or is_object()))
        {
            JSON_THROW(type_error::create(311, "cannot use emplace() with " + type_name()));
        }

        // transform null object into an object
        if (is_null())
        {
            m_type = value_t::object;
            m_value = value_t::object;
            assert_invariant();
        }

        // add element to array (perfect forwarding)
        auto res = m_value.object->emplace(std::forward<Args>(args)...);
        // create result iterator and set iterator to the result of emplace
        auto it = begin();
        it.m_it.object_iterator = res.first;

        // return pair of iterator and boolean
        return {it, res.second};
    }

    iterator insert(const_iterator pos, const basic_json& val)
    {
        // insert only works for arrays
        if (is_array())
        {
            // check if iterator pos fits to this JSON value
            if (pos.m_object != this)
            {
                JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
            }

            // insert to array and return iterator
            iterator result(this);
            result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, val);
            return result;
        }

        JSON_THROW(type_error::create(309, "cannot use insert() with " + type_name()));
    }

    iterator insert(const_iterator pos, basic_json&& val)
    {
        return insert(pos, val);
    }

    iterator insert(const_iterator pos, size_type cnt, const basic_json& val)
    {
        // insert only works for arrays
        if (is_array())
        {
            // check if iterator pos fits to this JSON value
            if (pos.m_object != this)
            {
                JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
            }

            // insert to array and return iterator
            iterator result(this);
            result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, cnt, val);
            return result;
        }

        JSON_THROW(type_error::create(309, "cannot use insert() with " + type_name()));
    }

    iterator insert(const_iterator pos, const_iterator first, const_iterator last)
    {
        // insert only works for arrays
        if (not is_array())
        {
            JSON_THROW(type_error::create(309, "cannot use insert() with " + type_name()));
        }

        // check if iterator pos fits to this JSON value
        if (pos.m_object != this)
        {
            JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
        }

        // check if range iterators belong to the same JSON object
        if (first.m_object != last.m_object)
        {
            JSON_THROW(invalid_iterator::create(210, "iterators do not fit"));
        }

        if (first.m_object == this or last.m_object == this)
        {
            JSON_THROW(invalid_iterator::create(211, "passed iterators may not belong to container"));
        }

        // insert to array and return iterator
        iterator result(this);
        result.m_it.array_iterator = m_value.array->insert(
                                         pos.m_it.array_iterator,
                                         first.m_it.array_iterator,
                                         last.m_it.array_iterator);
        return result;
    }

    iterator insert(const_iterator pos, std::initializer_list<basic_json> ilist)
    {
        // insert only works for arrays
        if (not is_array())
        {
            JSON_THROW(type_error::create(309, "cannot use insert() with " + type_name()));
        }

        // check if iterator pos fits to this JSON value
        if (pos.m_object != this)
        {
            JSON_THROW(invalid_iterator::create(202, "iterator does not fit current value"));
        }

        // insert to array and return iterator
        iterator result(this);
        result.m_it.array_iterator = m_value.array->insert(pos.m_it.array_iterator, ilist);
        return result;
    }

    void insert(const_iterator first, const_iterator last)
    {
        // insert only works for objects
        if (not is_object())
        {
            JSON_THROW(type_error::create(309, "cannot use insert() with " + type_name()));
        }

        // check if range iterators belong to the same JSON object
        if (first.m_object != last.m_object)
        {
            JSON_THROW(invalid_iterator::create(210, "iterators do not fit"));
        }

        // passed iterators must belong to objects
        if (not first.m_object->is_object() or not first.m_object->is_object())
        {
            JSON_THROW(invalid_iterator::create(202, "iterators first and last must point to objects"));
        }

        m_value.object->insert(first.m_it.object_iterator, last.m_it.object_iterator);
    }

    void swap(reference other) noexcept (
        std::is_nothrow_move_constructible<value_t>::value and
        std::is_nothrow_move_assignable<value_t>::value and
        std::is_nothrow_move_constructible<json_value>::value and
        std::is_nothrow_move_assignable<json_value>::value
    )
    {
        std::swap(m_type, other.m_type);
        std::swap(m_value, other.m_value);
        assert_invariant();
    }

    void swap(array_t& other)
    {
        // swap only works for arrays
        if (is_array())
        {
            std::swap(*(m_value.array), other);
        }
        else
        {
            JSON_THROW(type_error::create(310, "cannot use swap() with " + type_name()));
        }
    }

    void swap(object_t& other)
    {
        // swap only works for objects
        if (is_object())
        {
            std::swap(*(m_value.object), other);
        }
        else
        {
            JSON_THROW(type_error::create(310, "cannot use swap() with " + type_name()));
        }
    }

    void swap(string_t& other)
    {
        // swap only works for strings
        if (is_string())
        {
            std::swap(*(m_value.string), other);
        }
        else
        {
            JSON_THROW(type_error::create(310, "cannot use swap() with " + type_name()));
        }
    }


  public:
    // lexicographical comparison operators //


    friend bool operator==(const_reference lhs, const_reference rhs) noexcept
    {
        const auto lhs_type = lhs.type();
        const auto rhs_type = rhs.type();

        if (lhs_type == rhs_type)
        {
            switch (lhs_type)
            {
                case value_t::array:
                {
                    return *lhs.m_value.array == *rhs.m_value.array;
                }
                case value_t::object:
                {
                    return *lhs.m_value.object == *rhs.m_value.object;
                }
                case value_t::null:
                {
                    return true;
                }
                case value_t::string:
                {
                    return *lhs.m_value.string == *rhs.m_value.string;
                }
                case value_t::boolean:
                {
                    return lhs.m_value.boolean == rhs.m_value.boolean;
                }
                case value_t::number_integer:
                {
                    return lhs.m_value.number_integer == rhs.m_value.number_integer;
                }
                case value_t::number_unsigned:
                {
                    return lhs.m_value.number_unsigned == rhs.m_value.number_unsigned;
                }
                case value_t::number_float:
                {
                    return lhs.m_value.number_float == rhs.m_value.number_float;
                }
                default:
                {
                    return false;
                }
            }
        }
        else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
        {
            return static_cast<number_float_t>(lhs.m_value.number_integer) == rhs.m_value.number_float;
        }
        else if (lhs_type == value_t::number_float and rhs_type == value_t::number_integer)
        {
            return lhs.m_value.number_float == static_cast<number_float_t>(rhs.m_value.number_integer);
        }
        else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_float)
        {
            return static_cast<number_float_t>(lhs.m_value.number_unsigned) == rhs.m_value.number_float;
        }
        else if (lhs_type == value_t::number_float and rhs_type == value_t::number_unsigned)
        {
            return lhs.m_value.number_float == static_cast<number_float_t>(rhs.m_value.number_unsigned);
        }
        else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_integer)
        {
            return static_cast<number_integer_t>(lhs.m_value.number_unsigned) == rhs.m_value.number_integer;
        }
        else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_unsigned)
        {
            return lhs.m_value.number_integer == static_cast<number_integer_t>(rhs.m_value.number_unsigned);
        }

        return false;
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator==(const_reference lhs, const ScalarType rhs) noexcept
    {
        return (lhs == basic_json(rhs));
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator==(const ScalarType lhs, const_reference rhs) noexcept
    {
        return (basic_json(lhs) == rhs);
    }

    friend bool operator!=(const_reference lhs, const_reference rhs) noexcept
    {
        return not (lhs == rhs);
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator!=(const_reference lhs, const ScalarType rhs) noexcept
    {
        return (lhs != basic_json(rhs));
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator!=(const ScalarType lhs, const_reference rhs) noexcept
    {
        return (basic_json(lhs) != rhs);
    }

    friend bool operator<(const_reference lhs, const_reference rhs) noexcept
    {
        const auto lhs_type = lhs.type();
        const auto rhs_type = rhs.type();

        if (lhs_type == rhs_type)
        {
            switch (lhs_type)
            {
                case value_t::array:
                {
                    //return *lhs.m_value.array < *rhs.m_value.array;
                    //return *lhs.m_value.array.operator<(rhs);
                    return (*lhs.m_value.array) < *rhs.m_value.array;
                   // return nlohmann::detail::operator<(lhs, rhs);
                }
                case value_t::object:
                {
                    return *lhs.m_value.object < *rhs.m_value.object;
                }
                case value_t::null:
                {
                    return false;
                }
                case value_t::string:
                {
                    return *lhs.m_value.string < *rhs.m_value.string;
                }
                case value_t::boolean:
                {
                    return lhs.m_value.boolean < rhs.m_value.boolean;
                }
                case value_t::number_integer:
                {
                    return lhs.m_value.number_integer < rhs.m_value.number_integer;
                }
                case value_t::number_unsigned:
                {
                    return lhs.m_value.number_unsigned < rhs.m_value.number_unsigned;
                }
                case value_t::number_float:
                {
                    return lhs.m_value.number_float < rhs.m_value.number_float;
                }
                default:
                {
                    return false;
                }
            }
        }
        else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_float)
        {
            return static_cast<number_float_t>(lhs.m_value.number_integer) < rhs.m_value.number_float;
        }
        else if (lhs_type == value_t::number_float and rhs_type == value_t::number_integer)
        {
            return lhs.m_value.number_float < static_cast<number_float_t>(rhs.m_value.number_integer);
        }
        else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_float)
        {
            return static_cast<number_float_t>(lhs.m_value.number_unsigned) < rhs.m_value.number_float;
        }
        else if (lhs_type == value_t::number_float and rhs_type == value_t::number_unsigned)
        {
            return lhs.m_value.number_float < static_cast<number_float_t>(rhs.m_value.number_unsigned);
        }
        else if (lhs_type == value_t::number_integer and rhs_type == value_t::number_unsigned)
        {
            return lhs.m_value.number_integer < static_cast<number_integer_t>(rhs.m_value.number_unsigned);
        }
        else if (lhs_type == value_t::number_unsigned and rhs_type == value_t::number_integer)
        {
            return static_cast<number_integer_t>(lhs.m_value.number_unsigned) < rhs.m_value.number_integer;
        }

        // We only reach this line if we cannot compare values. In that case,
        // we compare types. Note we have to call the operator explicitly,
        // because MSVC has problems otherwise.
        return operator<(lhs_type, rhs_type);
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator<(const_reference lhs, const ScalarType rhs) noexcept
    {
        return (lhs < basic_json(rhs));
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator<(const ScalarType lhs, const_reference rhs) noexcept
    {
        return (basic_json(lhs) < rhs);
    }

    friend bool operator<=(const_reference lhs, const_reference rhs) noexcept
    {
        return not (rhs < lhs);
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator<=(const_reference lhs, const ScalarType rhs) noexcept
    {
        return (lhs <= basic_json(rhs));
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator<=(const ScalarType lhs, const_reference rhs) noexcept
    {
        return (basic_json(lhs) <= rhs);
    }

    friend bool operator>(const_reference lhs, const_reference rhs) noexcept
    {
        return not (lhs <= rhs);
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator>(const_reference lhs, const ScalarType rhs) noexcept
    {
        return (lhs > basic_json(rhs));
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator>(const ScalarType lhs, const_reference rhs) noexcept
    {
        return (basic_json(lhs) > rhs);
    }

    friend bool operator>=(const_reference lhs, const_reference rhs) noexcept
    {
        return not (lhs < rhs);
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator>=(const_reference lhs, const ScalarType rhs) noexcept
    {
        return (lhs >= basic_json(rhs));
    }

    template<typename ScalarType, typename std::enable_if<
                 std::is_scalar<ScalarType>::value, int>::type = 0>
    friend bool operator>=(const ScalarType lhs, const_reference rhs) noexcept
    {
        return (basic_json(lhs) >= rhs);
    }


  private:
    // output adapters //

    template<typename CharType>
    class output_adapter
    {
      public:
        virtual void write_character(CharType c) = 0;
        virtual void write_characters(const CharType* s, size_t length) = 0;
        virtual ~output_adapter() {}

        static std::shared_ptr<output_adapter<CharType>> create(std::vector<CharType>& vec)
        {
            return std::shared_ptr<output_adapter>(new output_vector_adapter<CharType>(vec));
        }

        static std::shared_ptr<output_adapter<CharType>> create(std::ostream& s)
        {
            return std::shared_ptr<output_adapter>(new output_stream_adapter<CharType>(s));
        }

        static std::shared_ptr<output_adapter<CharType>> create(std::string& s)
        {
            return std::shared_ptr<output_adapter>(new output_string_adapter<CharType>(s));
        }
    };

    template<typename CharType>
    using output_adapter_t = std::shared_ptr<output_adapter<CharType>>;

    template<typename CharType>
    class output_vector_adapter : public output_adapter<CharType>
    {
      public:
        output_vector_adapter(std::vector<CharType>& vec)
            : v(vec)
        {}

        void write_character(CharType c) override
        {
            v.push_back(c);
        }

        void write_characters(const CharType* s, size_t length) override
        {
            std::copy(s, s + length, std::back_inserter(v));
        }

      private:
        std::vector<CharType>& v;
    };

    template<typename CharType>
    class output_stream_adapter : public output_adapter<CharType>
    {
      public:
        output_stream_adapter(std::basic_ostream<CharType>& s)
            : stream(s)
        {}

        void write_character(CharType c) override
        {
            stream.put(c);
        }

        void write_characters(const CharType* s, size_t length) override
        {
            stream.write(s, static_cast<std::streamsize>(length));
        }

      private:
        std::basic_ostream<CharType>& stream;
    };

    template<typename CharType>
    class output_string_adapter : public output_adapter<CharType>
    {
      public:
        output_string_adapter(std::string& s)
            : str(s)
        {}

        void write_character(CharType c) override
        {
            str.push_back(c);
        }

        void write_characters(const CharType* s, size_t length) override
        {
            str.append(s, length);
        }

      private:
        std::basic_string<CharType>& str;
    };


    // serialization //


  private:
    class serializer
    {
      private:
        serializer(const serializer&) = delete;
        serializer& operator=(const serializer&) = delete;

      public:
        serializer(output_adapter_t<char> s, const char ichar)
            : o(s), loc(std::localeconv()),
              thousands_sep(!loc->thousands_sep ? '\0' : loc->thousands_sep[0]),
              decimal_point(!loc->decimal_point ? '\0' : loc->decimal_point[0]),
              indent_char(ichar), indent_string(512, indent_char)
        {}

        void dump(const basic_json& val,
                  const bool pretty_print,
                  const unsigned int indent_step,
                  const unsigned int current_indent = 0)
        {
            switch (val.m_type)
            {
                case value_t::object:
                {
                    if (val.m_value.object->empty())
                    {
                        o->write_characters("{}", 2);
                        return;
                    }

                    if (pretty_print)
                    {
                        o->write_characters("{\n", 2);

                        // variable to hold indentation for recursive calls
                        const auto new_indent = current_indent + indent_step;
                        if (indent_string.size() < new_indent)
                        {
                            indent_string.resize(new_indent, ' ');
                        }

                        // first n-1 elements
                        auto i = val.m_value.object->cbegin();
                        for (size_t cnt = 0; cnt < val.m_value.object->size() - 1; ++cnt, ++i)
                        {
                            o->write_characters(indent_string.c_str(), new_indent);
                            o->write_character('\"');
                            dump_escaped(i->first);
                            o->write_characters("\": ", 3);
                            dump(i->second, true, indent_step, new_indent);
                            o->write_characters(",\n", 2);
                        }

                        // last element
                        assert(i != val.m_value.object->cend());
                        o->write_characters(indent_string.c_str(), new_indent);
                        o->write_character('\"');
                        dump_escaped(i->first);
                        o->write_characters("\": ", 3);
                        dump(i->second, true, indent_step, new_indent);

                        o->write_character('\n');
                        o->write_characters(indent_string.c_str(), current_indent);
                        o->write_character('}');
                    }
                    else
                    {
                        o->write_character('{');

                        // first n-1 elements
                        auto i = val.m_value.object->cbegin();
                        for (size_t cnt = 0; cnt < val.m_value.object->size() - 1; ++cnt, ++i)
                        {
                            o->write_character('\"');
                            dump_escaped(i->first);
                            o->write_characters("\":", 2);
                            dump(i->second, false, indent_step, current_indent);
                            o->write_character(',');
                        }

                        // last element
                        assert(i != val.m_value.object->cend());
                        o->write_character('\"');
                        dump_escaped(i->first);
                        o->write_characters("\":", 2);
                        dump(i->second, false, indent_step, current_indent);

                        o->write_character('}');
                    }

                    return;
                }

                case value_t::array:
                {
                    if (val.m_value.array->empty())
                    {
                        o->write_characters("[]", 2);
                        return;
                    }

                    if (pretty_print)
                    {
                        o->write_characters("[\n", 2);

                        // variable to hold indentation for recursive calls
                        const auto new_indent = current_indent + indent_step;
                        if (indent_string.size() < new_indent)
                        {
                            indent_string.resize(new_indent, ' ');
                        }

                        // first n-1 elements
                        for (auto i = val.m_value.array->cbegin(); i != val.m_value.array->cend() - 1; ++i)
                        {
                            o->write_characters(indent_string.c_str(), new_indent);
                            dump(*i, true, indent_step, new_indent);
                            o->write_characters(",\n", 2);
                        }

                        // last element
                        assert(not val.m_value.array->empty());
                        o->write_characters(indent_string.c_str(), new_indent);
                        dump(val.m_value.array->back(), true, indent_step, new_indent);

                        o->write_character('\n');
                        o->write_characters(indent_string.c_str(), current_indent);
                        o->write_character(']');
                    }
                    else
                    {
                        o->write_character('[');

                        // first n-1 elements
                        for (auto i = val.m_value.array->cbegin(); i != val.m_value.array->cend() - 1; ++i)
                        {
                            dump(*i, false, indent_step, current_indent);
                            o->write_character(',');
                        }

                        // last element
                        assert(not val.m_value.array->empty());
                        dump(val.m_value.array->back(), false, indent_step, current_indent);

                        o->write_character(']');
                    }

                    return;
                }

                case value_t::string:
                {
                    o->write_character('\"');
                    dump_escaped(*val.m_value.string);
                    o->write_character('\"');
                    return;
                }

                case value_t::boolean:
                {
                    if (val.m_value.boolean)
                    {
                        o->write_characters("true", 4);
                    }
                    else
                    {
                        o->write_characters("false", 5);
                    }
                    return;
                }

                case value_t::number_integer:
                {
                    dump_integer(val.m_value.number_integer);
                    return;
                }

                case value_t::number_unsigned:
                {
                    dump_integer(val.m_value.number_unsigned);
                    return;
                }

                case value_t::number_float:
                {
                    dump_float(val.m_value.number_float);
                    return;
                }

                case value_t::discarded:
                {
                    o->write_characters("<discarded>", 11);
                    return;
                }

                case value_t::null:
                {
                    o->write_characters("null", 4);
                    return;
                }
            }
        }

      private:
        static std::size_t extra_space(const string_t& s) noexcept
        {
            return std::accumulate(s.begin(), s.end(), size_t{},
                                   [](size_t res, typename string_t::value_type c)
            {
                switch (c)
                {
                    case '"':
                    case '\\':
                    case '\b':
                    case '\f':
                    case '\n':
                    case '\r':
                    case '\t':
                    {
                        // from c (1 byte) to \x (2 bytes)
                        return res + 1;
                    }

                    case 0x00:
                    case 0x01:
                    case 0x02:
                    case 0x03:
                    case 0x04:
                    case 0x05:
                    case 0x06:
                    case 0x07:
                    case 0x0b:
                    case 0x0e:
                    case 0x0f:
                    case 0x10:
                    case 0x11:
                    case 0x12:
                    case 0x13:
                    case 0x14:
                    case 0x15:
                    case 0x16:
                    case 0x17:
                    case 0x18:
                    case 0x19:
                    case 0x1a:
                    case 0x1b:
                    case 0x1c:
                    case 0x1d:
                    case 0x1e:
                    case 0x1f:
                    {
                        // from c (1 byte) to \uxxxx (6 bytes)
                        return res + 5;
                    }

                    default:
                    {
                        return res;
                    }
                }
            });
        }

        void dump_escaped(const string_t& s) const
        {
            const auto space = extra_space(s);
            if (space == 0)
            {
                o->write_characters(s.c_str(), s.size());
                return;
            }

            // create a result string of necessary size
            string_t result(s.size() + space, '\\');
            std::size_t pos = 0;

            for (const auto& c : s)
            {
                switch (c)
                {
                    // quotation mark (0x22)
                    case '"':
                    {
                        result[pos + 1] = '"';
                        pos += 2;
                        break;
                    }

                    // reverse solidus (0x5c)
                    case '\\':
                    {
                        // nothing to change
                        pos += 2;
                        break;
                    }

                    // backspace (0x08)
                    case '\b':
                    {
                        result[pos + 1] = 'b';
                        pos += 2;
                        break;
                    }

                    // formfeed (0x0c)
                    case '\f':
                    {
                        result[pos + 1] = 'f';
                        pos += 2;
                        break;
                    }

                    // newline (0x0a)
                    case '\n':
                    {
                        result[pos + 1] = 'n';
                        pos += 2;
                        break;
                    }

                    // carriage return (0x0d)
                    case '\r':
                    {
                        result[pos + 1] = 'r';
                        pos += 2;
                        break;
                    }

                    // horizontal tab (0x09)
                    case '\t':
                    {
                        result[pos + 1] = 't';
                        pos += 2;
                        break;
                    }

                    case 0x00:
                    case 0x01:
                    case 0x02:
                    case 0x03:
                    case 0x04:
                    case 0x05:
                    case 0x06:
                    case 0x07:
                    case 0x0b:
                    case 0x0e:
                    case 0x0f:
                    case 0x10:
                    case 0x11:
                    case 0x12:
                    case 0x13:
                    case 0x14:
                    case 0x15:
                    case 0x16:
                    case 0x17:
                    case 0x18:
                    case 0x19:
                    case 0x1a:
                    case 0x1b:
                    case 0x1c:
                    case 0x1d:
                    case 0x1e:
                    case 0x1f:
                    {
                        // convert a number 0..15 to its hex representation
                        // (0..f)
                        static const char hexify[16] =
                        {
                            '0', '1', '2', '3', '4', '5', '6', '7',
                            '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
                        };

                        // print character c as \uxxxx
                        for (const char m :
                    { 'u', '0', '0', hexify[c >> 4], hexify[c & 0x0f]
                        })
                        {
                            result[++pos] = m;
                        }

                        ++pos;
                        break;
                    }

                    default:
                    {
                        // all other characters are added as-is
                        result[pos++] = c;
                        break;
                    }
                }
            }

            assert(pos == s.size() + space);
            o->write_characters(result.c_str(), result.size());
        }

        template<typename NumberType, detail::enable_if_t <
                     std::is_same<NumberType, number_unsigned_t>::value or
                     std::is_same<NumberType, number_integer_t>::value, int> = 0>
        void dump_integer(NumberType x)
        {
            // special case for "0"
            if (x == 0)
            {
                o->write_character('0');
                return;
            }

            const bool is_negative = x < 0;
            size_t i = 0;

            // spare 1 byte for '\0'
            while (x != 0 and i < number_buffer.size() - 1)
            {
                const auto digit = std::labs(static_cast<long>(x % 10));
                number_buffer[i++] = static_cast<char>('0' + digit);
                x /= 10;
            }

            // make sure the number has been processed completely
            assert(x == 0);

            if (is_negative)
            {
                // make sure there is capacity for the '-'
                assert(i < number_buffer.size() - 2);
                number_buffer[i++] = '-';
            }

            std::reverse(number_buffer.begin(), number_buffer.begin() + i);
            o->write_characters(number_buffer.data(), i);
        }

        void dump_float(number_float_t x)
        {
            // NaN / inf
            if (not std::isfinite(x) or std::isnan(x))
            {
                o->write_characters("null", 4);
                return;
            }

            // special case for 0.0 and -0.0
            if (x == 0)
            {
                if (std::signbit(x))
                {
                    o->write_characters("-0.0", 4);
                }
                else
                {
                    o->write_characters("0.0", 3);
                }
                return;
            }

            // get number of digits for a text -> float -> text round-trip
            static constexpr auto d = std::numeric_limits<number_float_t>::digits10;

            // the actual conversion
            std::ptrdiff_t len = snprintf(number_buffer.data(), number_buffer.size(),
                                          "%.*g", d, x);

            // negative value indicates an error
            assert(len > 0);
            // check if buffer was large enough
            assert(static_cast<size_t>(len) < number_buffer.size());

            // erase thousands separator
            if (thousands_sep != '\0')
            {
                const auto end = std::remove(number_buffer.begin(),
                                             number_buffer.begin() + len,
                                             thousands_sep);
                std::fill(end, number_buffer.end(), '\0');
                assert((end - number_buffer.begin()) <= len);
                len = (end - number_buffer.begin());
            }

            // convert decimal point to '.'
            if (decimal_point != '\0' and decimal_point != '.')
            {
                for (auto& c : number_buffer)
                {
                    if (c == decimal_point)
                    {
                        c = '.';
                        break;
                    }
                }
            }

            o->write_characters(number_buffer.data(), static_cast<size_t>(len));

            // determine if need to append ".0"
            const bool value_is_int_like = std::none_of(number_buffer.begin(),
                                           number_buffer.begin() + len + 1,
                                           [](char c)
            {
                return c == '.' or c == 'e';
            });

            if (value_is_int_like)
            {
                o->write_characters(".0", 2);
            }
        }

      private:
        output_adapter_t<char> o = nullptr;

        std::array<char, 64> number_buffer{{}};

        const std::lconv* loc = nullptr;
        const char thousands_sep = '\0';
        const char decimal_point = '\0';

        const char indent_char;

        string_t indent_string;
    };

  public:
    friend std::ostream& operator<<(std::ostream& o, const basic_json& j)
    {
        // read width member and use it as indentation parameter if nonzero
        const bool pretty_print = (o.width() > 0);
        const auto indentation = (pretty_print ? o.width() : 0);

        // reset width to 0 for subsequent calls to this stream
        o.width(0);

        // do the actual serialization
        serializer s(output_adapter<char>::create(o), o.fill());
        s.dump(j, pretty_print, static_cast<unsigned int>(indentation));
        return o;
    }

    JSON_DEPRECATED
    friend std::ostream& operator>>(const basic_json& j, std::ostream& o)
    {
        return o << j;
    }



    // deserialization //


    template<class T, std::size_t N>
    static basic_json parse(T (&array)[N],
                            const parser_callback_t cb = nullptr)
    {
        // delegate the call to the iterator-range parse overload
        return parse(std::begin(array), std::end(array), cb);
    }

    template<typename CharT, typename std::enable_if<
                 std::is_pointer<CharT>::value and
                 std::is_integral<typename std::remove_pointer<CharT>::type>::value and
                 sizeof(typename std::remove_pointer<CharT>::type) == 1, int>::type = 0>
    static basic_json parse(const CharT s,
                            const parser_callback_t cb = nullptr)
    {
        return parser(input_adapter::create(s), cb).parse(true);
    }

    static basic_json parse(std::istream& i,
                            const parser_callback_t cb = nullptr)
    {
        return parser(input_adapter::create(i), cb).parse(true);
    }

    static basic_json parse(std::istream&& i,
                            const parser_callback_t cb = nullptr)
    {
        return parser(input_adapter::create(i), cb).parse(true);
    }

    template<class IteratorType, typename std::enable_if<
                 std::is_base_of<
                     std::random_access_iterator_tag,
                     typename std::iterator_traits<IteratorType>::iterator_category>::value, int>::type = 0>
    static basic_json parse(IteratorType first, IteratorType last,
                            const parser_callback_t cb = nullptr)
    {
        return parser(input_adapter::create(first, last), cb).parse(true);
    }

    template<class ContiguousContainer, typename std::enable_if<
                 not std::is_pointer<ContiguousContainer>::value and
                 std::is_base_of<
                     std::random_access_iterator_tag,
                     typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value
                 , int>::type = 0>
    static basic_json parse(const ContiguousContainer& c,
                            const parser_callback_t cb = nullptr)
    {
        // delegate the call to the iterator-range parse overload
        return parse(std::begin(c), std::end(c), cb);
    }

    JSON_DEPRECATED
    friend std::istream& operator<<(basic_json& j, std::istream& i)
    {
        j = parser(input_adapter::create(i)).parse(false);
        return i;
    }

    friend std::istream& operator>>(std::istream& i, basic_json& j)
    {
        j = parser(input_adapter::create(i)).parse(false);
        return i;
    }


    // convenience functions //

    std::string type_name() const
    {
        {
            switch (m_type)
            {
                case value_t::null:
                    return "null";
                case value_t::object:
                    return "object";
                case value_t::array:
                    return "array";
                case value_t::string:
                    return "string";
                case value_t::boolean:
                    return "boolean";
                case value_t::discarded:
                    return "discarded";
                default:
                    return "number";
            }
        }
    }


  private:
    // member variables //

    value_t m_type = value_t::null;

    json_value m_value = {};


  private:
    // iterators //

    class primitive_iterator_t
    {
      public:

        difference_type get_value() const noexcept
        {
            return m_it;
        }
        void set_begin() noexcept
        {
            m_it = begin_value;
        }

        void set_end() noexcept
        {
            m_it = end_value;
        }

        constexpr bool is_begin() const noexcept
        {
            return (m_it == begin_value);
        }

        constexpr bool is_end() const noexcept
        {
            return (m_it == end_value);
        }

        friend constexpr bool operator==(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
        {
            return lhs.m_it == rhs.m_it;
        }

        friend constexpr bool operator!=(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
        {
            return !(lhs == rhs);
        }

        friend constexpr bool operator<(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
        {
            return lhs.m_it < rhs.m_it;
        }

        friend constexpr bool operator<=(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
        {
            return lhs.m_it <= rhs.m_it;
        }

        friend constexpr bool operator>(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
        {
            return lhs.m_it > rhs.m_it;
        }

        friend constexpr bool operator>=(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
        {
            return lhs.m_it >= rhs.m_it;
        }

        primitive_iterator_t operator+(difference_type i)
        {
            auto result = *this;
            result += i;
            return result;
        }

        friend constexpr difference_type operator-(primitive_iterator_t lhs, primitive_iterator_t rhs) noexcept
        {
            return lhs.m_it - rhs.m_it;
        }

        friend std::ostream& operator<<(std::ostream& os, primitive_iterator_t it)
        {
            return os << it.m_it;
        }

        primitive_iterator_t& operator++()
        {
            ++m_it;
            return *this;
        }

        primitive_iterator_t operator++(int)
        {
            auto result = *this;
            m_it++;
            return result;
        }

        primitive_iterator_t& operator--()
        {
            --m_it;
            return *this;
        }

        primitive_iterator_t operator--(int)
        {
            auto result = *this;
            m_it--;
            return result;
        }

        primitive_iterator_t& operator+=(difference_type n)
        {
            m_it += n;
            return *this;
        }

        primitive_iterator_t& operator-=(difference_type n)
        {
            m_it -= n;
            return *this;
        }

      private:
        static constexpr difference_type begin_value = 0;
        static constexpr difference_type end_value = begin_value + 1;

        difference_type m_it = std::numeric_limits<std::ptrdiff_t>::denorm_min();
    };

    struct internal_iterator
    {
        typename object_t::iterator object_iterator;
        typename array_t::iterator array_iterator;
        primitive_iterator_t primitive_iterator;

        internal_iterator() noexcept
            : object_iterator(), array_iterator(), primitive_iterator()
        {}
    };

    template<typename IteratorType>
    class iteration_proxy
    {
      private:
        class iteration_proxy_internal
        {
          private:
            IteratorType anchor;
            size_t array_index = 0;

          public:
            explicit iteration_proxy_internal(IteratorType it) noexcept
                : anchor(it)
            {}

            iteration_proxy_internal& operator*()
            {
                return *this;
            }

            iteration_proxy_internal& operator++()
            {
                ++anchor;
                ++array_index;

                return *this;
            }

            bool operator!= (const iteration_proxy_internal& o) const
            {
                return anchor != o.anchor;
            }

            typename basic_json::string_t key() const
            {
                assert(anchor.m_object != nullptr);

                switch (anchor.m_object->type())
                {
                    // use integer array index as key
                    case value_t::array:
                    {
                        return std::to_string(array_index);
                    }

                    // use key from the object
                    case value_t::object:
                    {
                        return anchor.key();
                    }

                    // use an empty key for all primitive types
                    default:
                    {
                        return "";
                    }
                }
            }

            typename IteratorType::reference value() const
            {
                return anchor.value();
            }
        };

        typename IteratorType::reference container;

      public:
        explicit iteration_proxy(typename IteratorType::reference cont)
            : container(cont)
        {}

        iteration_proxy_internal begin() noexcept
        {
            return iteration_proxy_internal(container.begin());
        }

        iteration_proxy_internal end() noexcept
        {
            return iteration_proxy_internal(container.end());
        }
    };

  public:
    template<typename U>
    class iter_impl : public std::iterator<std::random_access_iterator_tag, U>
    {
        friend class basic_json;

        // make sure U is basic_json or const basic_json
        static_assert(std::is_same<U, basic_json>::value
                      or std::is_same<U, const basic_json>::value,
                      "iter_impl only accepts (const) basic_json");

      public:
        using value_type = typename basic_json::value_type;
        using difference_type = typename basic_json::difference_type;
        using pointer = typename std::conditional<std::is_const<U>::value,
              typename basic_json::const_pointer,
              typename basic_json::pointer>::type;
        using reference = typename std::conditional<std::is_const<U>::value,
              typename basic_json::const_reference,
              typename basic_json::reference>::type;
        using iterator_category = std::bidirectional_iterator_tag;

        iter_impl() = default;

        explicit iter_impl(pointer object) noexcept
            : m_object(object)
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    m_it.object_iterator = typename object_t::iterator();
                    break;
                }

                case basic_json::value_t::array:
                {
                    m_it.array_iterator = typename array_t::iterator();
                    break;
                }

                default:
                {
                    m_it.primitive_iterator = primitive_iterator_t();
                    break;
                }
            }
        }

        /*
        Use operator `const_iterator` instead of `const_iterator(const iterator&
        other) noexcept` to avoid two class definitions for @ref iterator and
        @ref const_iterator.

        This function is only called if this class is an @ref iterator. If this
        class is a @ref const_iterator this function is not called.
        */
        operator const_iterator() const
        {
            const_iterator ret;

            if (m_object)
            {
                ret.m_object = m_object;
                ret.m_it = m_it;
            }

            return ret;
        }

        iter_impl(const iter_impl& other) noexcept
            : m_object(other.m_object), m_it(other.m_it)
        {}

        iter_impl& operator=(iter_impl other) noexcept(
            std::is_nothrow_move_constructible<pointer>::value and
            std::is_nothrow_move_assignable<pointer>::value and
            std::is_nothrow_move_constructible<internal_iterator>::value and
            std::is_nothrow_move_assignable<internal_iterator>::value
        )
        {
            std::swap(m_object, other.m_object);
            std::swap(m_it, other.m_it);
            return *this;
        }

      private:
        void set_begin() noexcept
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    m_it.object_iterator = m_object->m_value.object->begin();
                    break;
                }

                case basic_json::value_t::array:
                {
                    m_it.array_iterator = m_object->m_value.array->begin();
                    break;
                }

                case basic_json::value_t::null:
                {
                    // set to end so begin()==end() is true: null is empty
                    m_it.primitive_iterator.set_end();
                    break;
                }

                default:
                {
                    m_it.primitive_iterator.set_begin();
                    break;
                }
            }
        }

        void set_end() noexcept
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    m_it.object_iterator = m_object->m_value.object->end();
                    break;
                }

                case basic_json::value_t::array:
                {
                    m_it.array_iterator = m_object->m_value.array->end();
                    break;
                }

                default:
                {
                    m_it.primitive_iterator.set_end();
                    break;
                }
            }
        }

      public:
        reference operator*() const
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    assert(m_it.object_iterator != m_object->m_value.object->end());
                    return m_it.object_iterator->second;
                }

                case basic_json::value_t::array:
                {
                    assert(m_it.array_iterator != m_object->m_value.array->end());
                    return *m_it.array_iterator;
                }

                case basic_json::value_t::null:
                {
                    JSON_THROW(invalid_iterator::create(214, "cannot get value"));
                }

                default:
                {
                    if (m_it.primitive_iterator.is_begin())
                    {
                        return *m_object;
                    }

                    JSON_THROW(invalid_iterator::create(214, "cannot get value"));
                }
            }
        }

        pointer operator->() const
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    assert(m_it.object_iterator != m_object->m_value.object->end());
                    return &(m_it.object_iterator->second);
                }

                case basic_json::value_t::array:
                {
                    assert(m_it.array_iterator != m_object->m_value.array->end());
                    return &*m_it.array_iterator;
                }

                default:
                {
                    if (m_it.primitive_iterator.is_begin())
                    {
                        return m_object;
                    }

                    JSON_THROW(invalid_iterator::create(214, "cannot get value"));
                }
            }
        }

        iter_impl operator++(int)
        {
            auto result = *this;
            ++(*this);
            return result;
        }

        iter_impl& operator++()
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    std::advance(m_it.object_iterator, 1);
                    break;
                }

                case basic_json::value_t::array:
                {
                    std::advance(m_it.array_iterator, 1);
                    break;
                }

                default:
                {
                    ++m_it.primitive_iterator;
                    break;
                }
            }

            return *this;
        }

        iter_impl operator--(int)
        {
            auto result = *this;
            --(*this);
            return result;
        }

        iter_impl& operator--()
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    std::advance(m_it.object_iterator, -1);
                    break;
                }

                case basic_json::value_t::array:
                {
                    std::advance(m_it.array_iterator, -1);
                    break;
                }

                default:
                {
                    --m_it.primitive_iterator;
                    break;
                }
            }

            return *this;
        }

        bool operator==(const iter_impl& other) const
        {
            // if objects are not the same, the comparison is undefined
            if (m_object != other.m_object)
            {
                JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers"));
            }

            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    return (m_it.object_iterator == other.m_it.object_iterator);
                }

                case basic_json::value_t::array:
                {
                    return (m_it.array_iterator == other.m_it.array_iterator);
                }

                default:
                {
                    return (m_it.primitive_iterator == other.m_it.primitive_iterator);
                }
            }
        }

        bool operator!=(const iter_impl& other) const
        {
            return not operator==(other);
        }

        bool operator<(const iter_impl& other) const
        {
            // if objects are not the same, the comparison is undefined
            if (m_object != other.m_object)
            {
                JSON_THROW(invalid_iterator::create(212, "cannot compare iterators of different containers"));
            }

            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    JSON_THROW(invalid_iterator::create(213, "cannot compare order of object iterators"));
                }

                case basic_json::value_t::array:
                {
                    return (m_it.array_iterator < other.m_it.array_iterator);
                }

                default:
                {
                    return (m_it.primitive_iterator < other.m_it.primitive_iterator);
                }
            }
        }

        bool operator<=(const iter_impl& other) const
        {
            return not other.operator < (*this);
        }

        bool operator>(const iter_impl& other) const
        {
            return not operator<=(other);
        }

        bool operator>=(const iter_impl& other) const
        {
            return not operator<(other);
        }

        iter_impl& operator+=(difference_type i)
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    JSON_THROW(invalid_iterator::create(209, "cannot use offsets with object iterators"));
                }

                case basic_json::value_t::array:
                {
                    std::advance(m_it.array_iterator, i);
                    break;
                }

                default:
                {
                    m_it.primitive_iterator += i;
                    break;
                }
            }

            return *this;
        }

        iter_impl& operator-=(difference_type i)
        {
            return operator+=(-i);
        }

        iter_impl operator+(difference_type i)
        {
            auto result = *this;
            result += i;
            return result;
        }

        iter_impl operator-(difference_type i)
        {
            auto result = *this;
            result -= i;
            return result;
        }

        difference_type operator-(const iter_impl& other) const
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    JSON_THROW(invalid_iterator::create(209, "cannot use offsets with object iterators"));
                }

                case basic_json::value_t::array:
                {
                    return m_it.array_iterator - other.m_it.array_iterator;
                }

                default:
                {
                    return m_it.primitive_iterator - other.m_it.primitive_iterator;
                }
            }
        }

        reference operator[](difference_type n) const
        {
            assert(m_object != nullptr);

            switch (m_object->m_type)
            {
                case basic_json::value_t::object:
                {
                    JSON_THROW(invalid_iterator::create(208, "cannot use operator[] for object iterators"));
                }

                case basic_json::value_t::array:
                {
                    return *std::next(m_it.array_iterator, n);
                }

                case basic_json::value_t::null:
                {
                    JSON_THROW(invalid_iterator::create(214, "cannot get value"));
                }

                default:
                {
                    if (m_it.primitive_iterator.get_value() == -n)
                    {
                        return *m_object;
                    }

                    JSON_THROW(invalid_iterator::create(214, "cannot get value"));
                }
            }
        }

        typename object_t::key_type key() const
        {
            assert(m_object != nullptr);

            if (m_object->is_object())
            {
                return m_it.object_iterator->first;
            }

            JSON_THROW(invalid_iterator::create(207, "cannot use key() for non-object iterators"));
        }

        reference value() const
        {
            return operator*();
        }

      private:
        pointer m_object = nullptr;
        internal_iterator m_it = internal_iterator();
    };

    template<typename Base>
    class json_reverse_iterator : public std::reverse_iterator<Base>
    {
      public:
        using base_iterator = std::reverse_iterator<Base>;
        using reference = typename Base::reference;

        json_reverse_iterator(const typename base_iterator::iterator_type& it) noexcept
            : base_iterator(it)
        {}

        json_reverse_iterator(const base_iterator& it) noexcept
            : base_iterator(it)
        {}

        json_reverse_iterator operator++(int)
        {
            return base_iterator::operator++(1);
        }

        json_reverse_iterator& operator++()
        {
            base_iterator::operator++();
            return *this;
        }

        json_reverse_iterator operator--(int)
        {
            return base_iterator::operator--(1);
        }

        json_reverse_iterator& operator--()
        {
            base_iterator::operator--();
            return *this;
        }

        json_reverse_iterator& operator+=(difference_type i)
        {
            base_iterator::operator+=(i);
            return *this;
        }

        json_reverse_iterator operator+(difference_type i) const
        {
            auto result = *this;
            result += i;
            return result;
        }

        json_reverse_iterator operator-(difference_type i) const
        {
            auto result = *this;
            result -= i;
            return result;
        }

        difference_type operator-(const json_reverse_iterator& other) const
        {
            return this->base() - other.base();
        }

        reference operator[](difference_type n) const
        {
            return *(this->operator+(n));
        }

        typename object_t::key_type key() const
        {
            auto it = --this->base();
            return it.key();
        }

        reference value() const
        {
            auto it = --this->base();
            return it.operator * ();
        }
    };


  private:
    // input adapters //

    class input_adapter
    {
      public:
        virtual int get_character() = 0;
        virtual std::string read(size_t offset, size_t length) = 0;
        virtual ~input_adapter() {}

        // native support

        static std::shared_ptr<input_adapter> create(std::istream& i, const size_t buffer_size = 16384)
        {
            return std::shared_ptr<input_adapter>(new cached_input_stream_adapter(i, buffer_size));
        }

        static std::shared_ptr<input_adapter> create(std::istream&& i, const size_t buffer_size = 16384)
        {
            return std::shared_ptr<input_adapter>(new cached_input_stream_adapter(i, buffer_size));
        }

        static std::shared_ptr<input_adapter> create(const char* b, size_t l)
        {
            return std::shared_ptr<input_adapter>(new input_buffer_adapter(b, l));
        }

        // derived support

        template<typename CharT, typename std::enable_if<
                     std::is_pointer<CharT>::value and
                     std::is_integral<typename std::remove_pointer<CharT>::type>::value and
                     sizeof(typename std::remove_pointer<CharT>::type) == 1, int>::type = 0>
        static std::shared_ptr<input_adapter> create(CharT b)
        {
            return create(reinterpret_cast<const char*>(b),
                          std::strlen(reinterpret_cast<const char*>(b)));
        }

        template<class IteratorType, typename std::enable_if<
                     std::is_same<typename std::iterator_traits<IteratorType>::iterator_category, std::random_access_iterator_tag>::value
                     , int>::type
                 = 0>
        static std::shared_ptr<input_adapter> create(IteratorType first, IteratorType last)
        {
            // assertion to check that the iterator range is indeed contiguous,
            // see http://stackoverflow.com/a/35008842/266378 for more discussion
            assert(std::accumulate(first, last, std::pair<bool, int>(true, 0),
                                   [&first](std::pair<bool, int> res, decltype(*first) val)
            {
                res.first &= (val == *(std::next(std::addressof(*first), res.second++)));
                return res;
            }).first);

            // assertion to check that each element is 1 byte long
            static_assert(sizeof(typename std::iterator_traits<IteratorType>::value_type) == 1,
                          "each element in the iterator range must have the size of 1 byte");

            return create(reinterpret_cast<const char*>(&(*first)),
                          static_cast<size_t>(std::distance(first, last)));
        }

        template<class T, std::size_t N>
        static std::shared_ptr<input_adapter> create(T (&array)[N])
        {
            // delegate the call to the iterator-range overload
            return create(std::begin(array), std::end(array));
        }

        template<class ContiguousContainer, typename std::enable_if<
                     not std::is_pointer<ContiguousContainer>::value and
                     std::is_base_of<
                         std::random_access_iterator_tag,
                         typename std::iterator_traits<decltype(std::begin(std::declval<ContiguousContainer const>()))>::iterator_category>::value
                     , int>::type = 0>
        static std::shared_ptr<input_adapter> create(const ContiguousContainer& c)
        {
            // delegate the call to the iterator-range overload
            return create(std::begin(c), std::end(c));
        }
    };

    using input_adapter_t = std::shared_ptr<input_adapter>;

    class cached_input_stream_adapter : public input_adapter
    {
      public:
        cached_input_stream_adapter(std::istream& i, const size_t buffer_size)
            : is(i), start_position(is.tellg()), buffer(buffer_size, '\0')
        {
            // immediately abort if stream is erroneous
            if (JSON_UNLIKELY(i.fail()))
            {
                JSON_THROW(parse_error::create(111, 0, "bad input stream"));
            }

            // initial fill
            is.read(buffer.data(), static_cast<std::streamsize>(buffer.size()));
            // store number of bytes in the buffer
            fill_size = static_cast<size_t>(is.gcount());

            // skip byte order mark
            if (fill_size >= 3 and buffer[0] == '\xEF' and buffer[1] == '\xBB' and buffer[2] == '\xBF')
            {
                buffer_pos += 3;
                processed_chars += 3;
            }
        }

        ~cached_input_stream_adapter() override
        {
            // clear stream flags
            is.clear();
            // We initially read a lot of characters into the buffer, and we
            // may not have processed all of them. Therefore, we need to
            // "rewind" the stream after the last processed char.
            is.seekg(start_position + static_cast<std::streamoff>(processed_chars));
            // clear stream flags
            is.clear();
        }

        int get_character() override
        {
            // check if refilling is necessary and possible
            if (buffer_pos == fill_size and not eof)
            {
                // refill
                is.read(buffer.data(), static_cast<std::streamsize>(buffer.size()));
                // store number of bytes in the buffer
                fill_size = static_cast<size_t>(is.gcount());

                // the buffer is ready
                buffer_pos = 0;

                // remember that filling did not yield new input
                if (fill_size == 0)
                {
                    eof = true;
                    return std::char_traits<char>::eof();
                }
            }

            ++processed_chars;
            return buffer[buffer_pos++] & 0xFF;;
        }

        std::string read(size_t offset, size_t length) override
        {
            // create buffer
            std::string result(length, '\0');

            // save stream position
            auto current_pos = is.tellg();
            // save stream flags
            auto flags = is.rdstate();

            // clear stream flags
            is.clear();
            // set stream position
            is.seekg(static_cast<std::streamoff>(offset));
            // read bytes
            is.read(&result[0], static_cast<std::streamsize>(length));

            // reset stream position
            is.seekg(current_pos);
            // reset stream flags
            is.setstate(flags);

            return result;
        }

      private:
        std::istream& is;

        size_t processed_chars = 0;
        size_t buffer_pos = 0;

        bool eof = false;
        size_t fill_size = 0;

        const std::streampos start_position;

        std::vector<char> buffer;
    };

    class input_buffer_adapter : public input_adapter
    {
      public:
        input_buffer_adapter(const char* b, size_t l)
            : input_adapter(), cursor(b), limit(b + l), start(b)
        {
            // skip byte order mark
            if (l >= 3 and b[0] == '\xEF' and b[1] == '\xBB' and b[2] == '\xBF')
            {
                cursor += 3;
            }
        }

        // delete because of pointer members
        input_buffer_adapter(const input_buffer_adapter&) = delete;
        input_buffer_adapter& operator=(input_buffer_adapter&) = delete;

        int get_character() override
        {
            if (JSON_LIKELY(cursor < limit))
            {
                return *(cursor++) & 0xFF;
            }
            else
            {
                return std::char_traits<char>::eof();
            }
        }

        std::string read(size_t offset, size_t length) override
        {
            // avoid reading too many characters
            const size_t max_length = static_cast<size_t>(limit - start);
            return std::string(start + offset, std::min(length, max_length - offset));
        }

      private:
        const char* cursor;
        const char* limit;
        const char* start;
    };

    // binary serialization/deserialization //


  private:
    class binary_reader
    {
      public:
        explicit binary_reader(input_adapter_t adapter)
            : ia(adapter), is_little_endian(little_endianess())
        {
            assert(ia);
        }

        basic_json parse_cbor(const bool get_char = true)
        {
            switch (get_char ? get() : current)
            {
                // EOF
                case std::char_traits<char>::eof():
                {
                    JSON_THROW(parse_error::create(110, chars_read, "unexpected end of input"));
                }

                // Integer 0x00..0x17 (0..23)
                case 0x00:
                case 0x01:
                case 0x02:
                case 0x03:
                case 0x04:
                case 0x05:
                case 0x06:
                case 0x07:
                case 0x08:
                case 0x09:
                case 0x0a:
                case 0x0b:
                case 0x0c:
                case 0x0d:
                case 0x0e:
                case 0x0f:
                case 0x10:
                case 0x11:
                case 0x12:
                case 0x13:
                case 0x14:
                case 0x15:
                case 0x16:
                case 0x17:
                {
                    return static_cast<number_unsigned_t>(current);
                }

                case 0x18: // Unsigned integer (one-byte uint8_t follows)
                {
                    return get_number<uint8_t>();
                }

                case 0x19: // Unsigned integer (two-byte uint16_t follows)
                {
                    return get_number<uint16_t>();
                }

                case 0x1a: // Unsigned integer (four-byte uint32_t follows)
                {
                    return get_number<uint32_t>();
                }

                case 0x1b: // Unsigned integer (eight-byte uint64_t follows)
                {
                    return get_number<uint64_t>();
                }

                // Negative integer -1-0x00..-1-0x17 (-1..-24)
                case 0x20:
                case 0x21:
                case 0x22:
                case 0x23:
                case 0x24:
                case 0x25:
                case 0x26:
                case 0x27:
                case 0x28:
                case 0x29:
                case 0x2a:
                case 0x2b:
                case 0x2c:
                case 0x2d:
                case 0x2e:
                case 0x2f:
                case 0x30:
                case 0x31:
                case 0x32:
                case 0x33:
                case 0x34:
                case 0x35:
                case 0x36:
                case 0x37:
                {
                    return static_cast<int8_t>(0x20 - 1 - current);
                }

                case 0x38: // Negative integer (one-byte uint8_t follows)
                {
                    // must be uint8_t !
                    return static_cast<number_integer_t>(-1) - get_number<uint8_t>();
                }

                case 0x39: // Negative integer -1-n (two-byte uint16_t follows)
                {
                    return static_cast<number_integer_t>(-1) - get_number<uint16_t>();
                }

                case 0x3a: // Negative integer -1-n (four-byte uint32_t follows)
                {
                    return static_cast<number_integer_t>(-1) - get_number<uint32_t>();
                }

                case 0x3b: // Negative integer -1-n (eight-byte uint64_t follows)
                {
                    return static_cast<number_integer_t>(-1) - static_cast<number_integer_t>(get_number<uint64_t>());
                }

                // UTF-8 string (0x00..0x17 bytes follow)
                case 0x60:
                case 0x61:
                case 0x62:
                case 0x63:
                case 0x64:
                case 0x65:
                case 0x66:
                case 0x67:
                case 0x68:
                case 0x69:
                case 0x6a:
                case 0x6b:
                case 0x6c:
                case 0x6d:
                case 0x6e:
                case 0x6f:
                case 0x70:
                case 0x71:
                case 0x72:
                case 0x73:
                case 0x74:
                case 0x75:
                case 0x76:
                case 0x77:
                case 0x78: // UTF-8 string (one-byte uint8_t for n follows)
                case 0x79: // UTF-8 string (two-byte uint16_t for n follow)
                case 0x7a: // UTF-8 string (four-byte uint32_t for n follow)
                case 0x7b: // UTF-8 string (eight-byte uint64_t for n follow)
                case 0x7f: // UTF-8 string (indefinite length)
                {
                    return get_cbor_string();
                }

                // array (0x00..0x17 data items follow)
                case 0x80:
                case 0x81:
                case 0x82:
                case 0x83:
                case 0x84:
                case 0x85:
                case 0x86:
                case 0x87:
                case 0x88:
                case 0x89:
                case 0x8a:
                case 0x8b:
                case 0x8c:
                case 0x8d:
                case 0x8e:
                case 0x8f:
                case 0x90:
                case 0x91:
                case 0x92:
                case 0x93:
                case 0x94:
                case 0x95:
                case 0x96:
                case 0x97:
                {
                    basic_json result = value_t::array;
                    const auto len = static_cast<size_t>(current & 0x1f);
                    for (size_t i = 0; i < len; ++i)
                    {
                        result.push_back(parse_cbor());
                    }
                    return result;
                }

                case 0x98: // array (one-byte uint8_t for n follows)
                {
                    basic_json result = value_t::array;
                    const auto len = static_cast<size_t>(get_number<uint8_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        result.push_back(parse_cbor());
                    }
                    return result;
                }

                case 0x99: // array (two-byte uint16_t for n follow)
                {
                    basic_json result = value_t::array;
                    const auto len = static_cast<size_t>(get_number<uint16_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        result.push_back(parse_cbor());
                    }
                    return result;
                }

                case 0x9a: // array (four-byte uint32_t for n follow)
                {
                    basic_json result = value_t::array;
                    const auto len = static_cast<size_t>(get_number<uint32_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        result.push_back(parse_cbor());
                    }
                    return result;
                }

                case 0x9b: // array (eight-byte uint64_t for n follow)
                {
                    basic_json result = value_t::array;
                    const auto len = static_cast<size_t>(get_number<uint64_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        result.push_back(parse_cbor());
                    }
                    return result;
                }

                case 0x9f: // array (indefinite length)
                {
                    basic_json result = value_t::array;
                    while (get() != 0xff)
                    {
                        result.push_back(parse_cbor(false));
                    }
                    return result;
                }

                // map (0x00..0x17 pairs of data items follow)
                case 0xa0:
                case 0xa1:
                case 0xa2:
                case 0xa3:
                case 0xa4:
                case 0xa5:
                case 0xa6:
                case 0xa7:
                case 0xa8:
                case 0xa9:
                case 0xaa:
                case 0xab:
                case 0xac:
                case 0xad:
                case 0xae:
                case 0xaf:
                case 0xb0:
                case 0xb1:
                case 0xb2:
                case 0xb3:
                case 0xb4:
                case 0xb5:
                case 0xb6:
                case 0xb7:
                {
                    basic_json result = value_t::object;
                    const auto len = static_cast<size_t>(current & 0x1f);
                    for (size_t i = 0; i < len; ++i)
                    {
                        get();
                        auto key = get_cbor_string();
                        result[key] = parse_cbor();
                    }
                    return result;
                }

                case 0xb8: // map (one-byte uint8_t for n follows)
                {
                    basic_json result = value_t::object;
                    const auto len = static_cast<size_t>(get_number<uint8_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        get();
                        auto key = get_cbor_string();
                        result[key] = parse_cbor();
                    }
                    return result;
                }

                case 0xb9: // map (two-byte uint16_t for n follow)
                {
                    basic_json result = value_t::object;
                    const auto len = static_cast<size_t>(get_number<uint16_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        get();
                        auto key = get_cbor_string();
                        result[key] = parse_cbor();
                    }
                    return result;
                }

                case 0xba: // map (four-byte uint32_t for n follow)
                {
                    basic_json result = value_t::object;
                    const auto len = static_cast<size_t>(get_number<uint32_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        get();
                        auto key = get_cbor_string();
                        result[key] = parse_cbor();
                    }
                    return result;
                }

                case 0xbb: // map (eight-byte uint64_t for n follow)
                {
                    basic_json result = value_t::object;
                    const auto len = static_cast<size_t>(get_number<uint64_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        get();
                        auto key = get_cbor_string();
                        result[key] = parse_cbor();
                    }
                    return result;
                }

                case 0xbf: // map (indefinite length)
                {
                    basic_json result = value_t::object;
                    while (get() != 0xff)
                    {
                        auto key = get_cbor_string();
                        result[key] = parse_cbor();
                    }
                    return result;
                }

                case 0xf4: // false
                {
                    return false;
                }

                case 0xf5: // true
                {
                    return true;
                }

                case 0xf6: // null
                {
                    return value_t::null;
                }

                case 0xf9: // Half-Precision Float (two-byte IEEE 754)
                {
                    const int byte1 = get();
                    check_eof();
                    const int byte2 = get();
                    check_eof();

                    // code from RFC 7049, Appendix D, Figure 3:
                    // As half-precision floating-point numbers were only added
                    // to IEEE 754 in 2008, today's programming platforms often
                    // still only have limited support for them. It is very
                    // easy to include at least decoding support for them even
                    // without such support. An example of a small decoder for
                    // half-precision floating-point numbers in the C language
                    // is shown in Fig. 3.
                    const int half = (byte1 << 8) + byte2;
                    const int exp = (half >> 10) & 0x1f;
                    const int mant = half & 0x3ff;
                    double val;
                    if (exp == 0)
                    {
                        val = std::ldexp(mant, -24);
                    }
                    else if (exp != 31)
                    {
                        val = std::ldexp(mant + 1024, exp - 25);
                    }
                    else
                    {
                        val = mant == 0
                              ? std::numeric_limits<double>::infinity()
                              : std::numeric_limits<double>::quiet_NaN();
                    }
                    return (half & 0x8000) != 0 ? -val : val;
                }

                case 0xfa: // Single-Precision Float (four-byte IEEE 754)
                {
                    return get_number<float>();
                }

                case 0xfb: // Double-Precision Float (eight-byte IEEE 754)
                {
                    return get_number<double>();
                }

                default: // anything else (0xFF is handled inside the other types)
                {
                    std::stringstream ss;
                    ss << std::setw(2) << std::setfill('0') << std::hex << current;
                    JSON_THROW(parse_error::create(112, chars_read, "error reading CBOR; last byte: 0x" + ss.str()));
                }
            }
        }

        basic_json parse_msgpack()
        {
            switch (get())
            {
                // EOF
                case std::char_traits<char>::eof():
                {
                    JSON_THROW(parse_error::create(110, chars_read, "unexpected end of input"));
                }

                // positive fixint
                case 0x00:
                case 0x01:
                case 0x02:
                case 0x03:
                case 0x04:
                case 0x05:
                case 0x06:
                case 0x07:
                case 0x08:
                case 0x09:
                case 0x0a:
                case 0x0b:
                case 0x0c:
                case 0x0d:
                case 0x0e:
                case 0x0f:
                case 0x10:
                case 0x11:
                case 0x12:
                case 0x13:
                case 0x14:
                case 0x15:
                case 0x16:
                case 0x17:
                case 0x18:
                case 0x19:
                case 0x1a:
                case 0x1b:
                case 0x1c:
                case 0x1d:
                case 0x1e:
                case 0x1f:
                case 0x20:
                case 0x21:
                case 0x22:
                case 0x23:
                case 0x24:
                case 0x25:
                case 0x26:
                case 0x27:
                case 0x28:
                case 0x29:
                case 0x2a:
                case 0x2b:
                case 0x2c:
                case 0x2d:
                case 0x2e:
                case 0x2f:
                case 0x30:
                case 0x31:
                case 0x32:
                case 0x33:
                case 0x34:
                case 0x35:
                case 0x36:
                case 0x37:
                case 0x38:
                case 0x39:
                case 0x3a:
                case 0x3b:
                case 0x3c:
                case 0x3d:
                case 0x3e:
                case 0x3f:
                case 0x40:
                case 0x41:
                case 0x42:
                case 0x43:
                case 0x44:
                case 0x45:
                case 0x46:
                case 0x47:
                case 0x48:
                case 0x49:
                case 0x4a:
                case 0x4b:
                case 0x4c:
                case 0x4d:
                case 0x4e:
                case 0x4f:
                case 0x50:
                case 0x51:
                case 0x52:
                case 0x53:
                case 0x54:
                case 0x55:
                case 0x56:
                case 0x57:
                case 0x58:
                case 0x59:
                case 0x5a:
                case 0x5b:
                case 0x5c:
                case 0x5d:
                case 0x5e:
                case 0x5f:
                case 0x60:
                case 0x61:
                case 0x62:
                case 0x63:
                case 0x64:
                case 0x65:
                case 0x66:
                case 0x67:
                case 0x68:
                case 0x69:
                case 0x6a:
                case 0x6b:
                case 0x6c:
                case 0x6d:
                case 0x6e:
                case 0x6f:
                case 0x70:
                case 0x71:
                case 0x72:
                case 0x73:
                case 0x74:
                case 0x75:
                case 0x76:
                case 0x77:
                case 0x78:
                case 0x79:
                case 0x7a:
                case 0x7b:
                case 0x7c:
                case 0x7d:
                case 0x7e:
                case 0x7f:
                {
                    return static_cast<number_unsigned_t>(current);
                }

                // fixmap
                case 0x80:
                case 0x81:
                case 0x82:
                case 0x83:
                case 0x84:
                case 0x85:
                case 0x86:
                case 0x87:
                case 0x88:
                case 0x89:
                case 0x8a:
                case 0x8b:
                case 0x8c:
                case 0x8d:
                case 0x8e:
                case 0x8f:
                {
                    basic_json result = value_t::object;
                    const auto len = static_cast<size_t>(current & 0x0f);
                    for (size_t i = 0; i < len; ++i)
                    {
                        get();
                        auto key = get_msgpack_string();
                        result[key] = parse_msgpack();
                    }
                    return result;
                }

                // fixarray
                case 0x90:
                case 0x91:
                case 0x92:
                case 0x93:
                case 0x94:
                case 0x95:
                case 0x96:
                case 0x97:
                case 0x98:
                case 0x99:
                case 0x9a:
                case 0x9b:
                case 0x9c:
                case 0x9d:
                case 0x9e:
                case 0x9f:
                {
                    basic_json result = value_t::array;
                    const auto len = static_cast<size_t>(current & 0x0f);
                    for (size_t i = 0; i < len; ++i)
                    {
                        result.push_back(parse_msgpack());
                    }
                    return result;
                }

                // fixstr
                case 0xa0:
                case 0xa1:
                case 0xa2:
                case 0xa3:
                case 0xa4:
                case 0xa5:
                case 0xa6:
                case 0xa7:
                case 0xa8:
                case 0xa9:
                case 0xaa:
                case 0xab:
                case 0xac:
                case 0xad:
                case 0xae:
                case 0xaf:
                case 0xb0:
                case 0xb1:
                case 0xb2:
                case 0xb3:
                case 0xb4:
                case 0xb5:
                case 0xb6:
                case 0xb7:
                case 0xb8:
                case 0xb9:
                case 0xba:
                case 0xbb:
                case 0xbc:
                case 0xbd:
                case 0xbe:
                case 0xbf:
                {
                    return get_msgpack_string();
                }

                case 0xc0: // nil
                {
                    return value_t::null;
                }

                case 0xc2: // false
                {
                    return false;
                }

                case 0xc3: // true
                {
                    return true;
                }

                case 0xca: // float 32
                {
                    return get_number<float>();
                }

                case 0xcb: // float 64
                {
                    return get_number<double>();
                }

                case 0xcc: // uint 8
                {
                    return get_number<uint8_t>();
                }

                case 0xcd: // uint 16
                {
                    return get_number<uint16_t>();
                }

                case 0xce: // uint 32
                {
                    return get_number<uint32_t>();
                }

                case 0xcf: // uint 64
                {
                    return get_number<uint64_t>();
                }

                case 0xd0: // int 8
                {
                    return get_number<int8_t>();
                }

                case 0xd1: // int 16
                {
                    return get_number<int16_t>();
                }

                case 0xd2: // int 32
                {
                    return get_number<int32_t>();
                }

                case 0xd3: // int 64
                {
                    return get_number<int64_t>();
                }

                case 0xd9: // str 8
                case 0xda: // str 16
                case 0xdb: // str 32
                {
                    return get_msgpack_string();
                }

                case 0xdc: // array 16
                {
                    basic_json result = value_t::array;
                    const auto len = static_cast<size_t>(get_number<uint16_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        result.push_back(parse_msgpack());
                    }
                    return result;
                }

                case 0xdd: // array 32
                {
                    basic_json result = value_t::array;
                    const auto len = static_cast<size_t>(get_number<uint32_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        result.push_back(parse_msgpack());
                    }
                    return result;
                }

                case 0xde: // map 16
                {
                    basic_json result = value_t::object;
                    const auto len = static_cast<size_t>(get_number<uint16_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        get();
                        auto key = get_msgpack_string();
                        result[key] = parse_msgpack();
                    }
                    return result;
                }

                case 0xdf: // map 32
                {
                    basic_json result = value_t::object;
                    const auto len = static_cast<size_t>(get_number<uint32_t>());
                    for (size_t i = 0; i < len; ++i)
                    {
                        get();
                        auto key = get_msgpack_string();
                        result[key] = parse_msgpack();
                    }
                    return result;
                }

                // positive fixint
                case 0xe0:
                case 0xe1:
                case 0xe2:
                case 0xe3:
                case 0xe4:
                case 0xe5:
                case 0xe6:
                case 0xe7:
                case 0xe8:
                case 0xe9:
                case 0xea:
                case 0xeb:
                case 0xec:
                case 0xed:
                case 0xee:
                case 0xef:
                case 0xf0:
                case 0xf1:
                case 0xf2:
                case 0xf3:
                case 0xf4:
                case 0xf5:
                case 0xf6:
                case 0xf7:
                case 0xf8:
                case 0xf9:
                case 0xfa:
                case 0xfb:
                case 0xfc:
                case 0xfd:
                case 0xfe:
                case 0xff:
                {
                    return static_cast<int8_t>(current);
                }

                default: // anything else
                {
                    std::stringstream ss;
                    ss << std::setw(2) << std::setfill('0') << std::hex << current;
                    JSON_THROW(parse_error::create(112, chars_read, "error reading MessagePack; last byte: 0x" + ss.str()));
                }
            }
        }

        static bool little_endianess() noexcept
        {
            int num = 1;
            return (*reinterpret_cast<char*>(&num) == 1);
        }

      private:
        int get()
        {
            ++chars_read;
            return (current = ia->get_character());
        }

        /*
        @brief read a number from the input

        @tparam T the type of the number

        @return number of type @a T

        @note This function needs to respect the system's endianess, because
              bytes in CBOR and MessagePack are stored in network order (big
              endian) and therefore need reordering on little endian systems.

        @throw parse_error.110 if input has less than `sizeof(T)` bytes
        */
        template<typename T>
        T get_number()
        {
            // step 1: read input into array with system's byte order
            std::array<uint8_t, sizeof(T)> vec;
            for (size_t i = 0; i < sizeof(T); ++i)
            {
                get();
                check_eof();

                // reverse byte order prior to conversion if necessary
                if (is_little_endian)
                {
                    vec[sizeof(T) - i - 1] = static_cast<uint8_t>(current);
                }
                else
                {
                    vec[i] = static_cast<uint8_t>(current);
                }
            }

            // step 2: convert array into number of type T and return
            T result;
            std::memcpy(&result, vec.data(), sizeof(T));
            return result;
        }

        std::string get_string(const size_t len)
        {
            std::string result;
            for (size_t i = 0; i < len; ++i)
            {
                get();
                check_eof();
                result.append(1, static_cast<char>(current));
            }
            return result;
        }

        std::string get_cbor_string()
        {
            check_eof();

            switch (current)
            {
                // UTF-8 string (0x00..0x17 bytes follow)
                case 0x60:
                case 0x61:
                case 0x62:
                case 0x63:
                case 0x64:
                case 0x65:
                case 0x66:
                case 0x67:
                case 0x68:
                case 0x69:
                case 0x6a:
                case 0x6b:
                case 0x6c:
                case 0x6d:
                case 0x6e:
                case 0x6f:
                case 0x70:
                case 0x71:
                case 0x72:
                case 0x73:
                case 0x74:
                case 0x75:
                case 0x76:
                case 0x77:
                {
                    const auto len = static_cast<size_t>(current & 0x1f);
                    return get_string(len);
                }

                case 0x78: // UTF-8 string (one-byte uint8_t for n follows)
                {
                    const auto len = static_cast<size_t>(get_number<uint8_t>());
                    return get_string(len);
                }

                case 0x79: // UTF-8 string (two-byte uint16_t for n follow)
                {
                    const auto len = static_cast<size_t>(get_number<uint16_t>());
                    return get_string(len);
                }

                case 0x7a: // UTF-8 string (four-byte uint32_t for n follow)
                {
                    const auto len = static_cast<size_t>(get_number<uint32_t>());
                    return get_string(len);
                }

                case 0x7b: // UTF-8 string (eight-byte uint64_t for n follow)
                {
                    const auto len = static_cast<size_t>(get_number<uint64_t>());
                    return get_string(len);
                }

                case 0x7f: // UTF-8 string (indefinite length)
                {
                    std::string result;
                    while (get() != 0xff)
                    {
                        check_eof();
                        result.append(1, static_cast<char>(current));
                    }
                    return result;
                }

                default:
                {
                    std::stringstream ss;
                    ss << std::setw(2) << std::setfill('0') << std::hex << current;
                    JSON_THROW(parse_error::create(113, chars_read, "expected a CBOR string; last byte: 0x" + ss.str()));
                }
            }
        }

        std::string get_msgpack_string()
        {
            check_eof();

            switch (current)
            {
                // fixstr
                case 0xa0:
                case 0xa1:
                case 0xa2:
                case 0xa3:
                case 0xa4:
                case 0xa5:
                case 0xa6:
                case 0xa7:
                case 0xa8:
                case 0xa9:
                case 0xaa:
                case 0xab:
                case 0xac:
                case 0xad:
                case 0xae:
                case 0xaf:
                case 0xb0:
                case 0xb1:
                case 0xb2:
                case 0xb3:
                case 0xb4:
                case 0xb5:
                case 0xb6:
                case 0xb7:
                case 0xb8:
                case 0xb9:
                case 0xba:
                case 0xbb:
                case 0xbc:
                case 0xbd:
                case 0xbe:
                case 0xbf:
                {
                    const auto len = static_cast<size_t>(current & 0x1f);
                    return get_string(len);
                }

                case 0xd9: // str 8
                {
                    const auto len = static_cast<size_t>(get_number<uint8_t>());
                    return get_string(len);
                }

                case 0xda: // str 16
                {
                    const auto len = static_cast<size_t>(get_number<uint16_t>());
                    return get_string(len);
                }

                case 0xdb: // str 32
                {
                    const auto len = static_cast<size_t>(get_number<uint32_t>());
                    return get_string(len);
                }

                default:
                {
                    std::stringstream ss;
                    ss << std::setw(2) << std::setfill('0') << std::hex << current;
                    JSON_THROW(parse_error::create(113, chars_read, "expected a MessagePack string; last byte: 0x" + ss.str()));
                }
            }
        }

        void check_eof() const
        {
            if (JSON_UNLIKELY(current == std::char_traits<char>::eof()))
            {
                JSON_THROW(parse_error::create(110, chars_read, "unexpected end of input"));
            }
        }

      private:
        input_adapter_t ia = nullptr;

        int current = std::char_traits<char>::eof();

        size_t chars_read = 0;

        const bool is_little_endian = true;
    };

    class binary_writer
    {
      public:
        explicit binary_writer(output_adapter_t<uint8_t> adapter)
            : is_little_endian(binary_reader::little_endianess()), oa(adapter)
        {
            assert(oa);
        }

        void write_cbor(const basic_json& j)
        {
            switch (j.type())
            {
                case value_t::null:
                {
                    oa->write_character(0xf6);
                    break;
                }

                case value_t::boolean:
                {
                    oa->write_character(j.m_value.boolean ? 0xf5 : 0xf4);
                    break;
                }

                case value_t::number_integer:
                {
                    if (j.m_value.number_integer >= 0)
                    {
                        // CBOR does not differentiate between positive signed
                        // integers and unsigned integers. Therefore, we used the
                        // code from the value_t::number_unsigned case here.
                        if (j.m_value.number_integer <= 0x17)
                        {
                            write_number(static_cast<uint8_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_integer <= (std::numeric_limits<uint8_t>::max)())
                        {
                            oa->write_character(0x18);
                            write_number(static_cast<uint8_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_integer <= (std::numeric_limits<uint16_t>::max)())
                        {
                            oa->write_character(0x19);
                            write_number(static_cast<uint16_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_integer <= (std::numeric_limits<uint32_t>::max)())
                        {
                            oa->write_character(0x1a);
                            write_number(static_cast<uint32_t>(j.m_value.number_integer));
                        }
                        else
                        {
                            oa->write_character(0x1b);
                            write_number(static_cast<uint64_t>(j.m_value.number_integer));
                        }
                    }
                    else
                    {
                        // The conversions below encode the sign in the first
                        // byte, and the value is converted to a positive number.
                        const auto positive_number = -1 - j.m_value.number_integer;
                        if (j.m_value.number_integer >= -24)
                        {
                            write_number(static_cast<uint8_t>(0x20 + positive_number));
                        }
                        else if (positive_number <= (std::numeric_limits<uint8_t>::max)())
                        {
                            oa->write_character(0x38);
                            write_number(static_cast<uint8_t>(positive_number));
                        }
                        else if (positive_number <= (std::numeric_limits<uint16_t>::max)())
                        {
                            oa->write_character(0x39);
                            write_number(static_cast<uint16_t>(positive_number));
                        }
                        else if (positive_number <= (std::numeric_limits<uint32_t>::max)())
                        {
                            oa->write_character(0x3a);
                            write_number(static_cast<uint32_t>(positive_number));
                        }
                        else
                        {
                            oa->write_character(0x3b);
                            write_number(static_cast<uint64_t>(positive_number));
                        }
                    }
                    break;
                }

                case value_t::number_unsigned:
                {
                    if (j.m_value.number_unsigned <= 0x17)
                    {
                        write_number(static_cast<uint8_t>(j.m_value.number_unsigned));
                    }
                    else if (j.m_value.number_unsigned <= (std::numeric_limits<uint8_t>::max)())
                    {
                        oa->write_character(0x18);
                        write_number(static_cast<uint8_t>(j.m_value.number_unsigned));
                    }
                    else if (j.m_value.number_unsigned <= (std::numeric_limits<uint16_t>::max)())
                    {
                        oa->write_character(0x19);
                        write_number(static_cast<uint16_t>(j.m_value.number_unsigned));
                    }
                    else if (j.m_value.number_unsigned <= (std::numeric_limits<uint32_t>::max)())
                    {
                        oa->write_character(0x1a);
                        write_number(static_cast<uint32_t>(j.m_value.number_unsigned));
                    }
                    else
                    {
                        oa->write_character(0x1b);
                        write_number(static_cast<uint64_t>(j.m_value.number_unsigned));
                    }
                    break;
                }

                case value_t::number_float:
                {
                    // Double-Precision Float
                    oa->write_character(0xfb);
                    write_number(j.m_value.number_float);
                    break;
                }

                case value_t::string:
                {
                    // step 1: write control byte and the string length
                    const auto N = j.m_value.string->size();
                    if (N <= 0x17)
                    {
                        write_number(static_cast<uint8_t>(0x60 + N));
                    }
                    else if (N <= 0xff)
                    {
                        oa->write_character(0x78);
                        write_number(static_cast<uint8_t>(N));
                    }
                    else if (N <= 0xffff)
                    {
                        oa->write_character(0x79);
                        write_number(static_cast<uint16_t>(N));
                    }
                    else if (N <= 0xffffffff)
                    {
                        oa->write_character(0x7a);
                        write_number(static_cast<uint32_t>(N));
                    }
                    // LCOV_EXCL_START
                    else if (N <= 0xffffffffffffffff)
                    {
                        oa->write_character(0x7b);
                        write_number(static_cast<uint64_t>(N));
                    }
                    // LCOV_EXCL_STOP

                    // step 2: write the string
                    oa->write_characters(reinterpret_cast<const uint8_t*>(j.m_value.string->c_str()),
                                         j.m_value.string->size());
                    break;
                }

                case value_t::array:
                {
                    // step 1: write control byte and the array size
                    const auto N = j.m_value.array->size();
                    if (N <= 0x17)
                    {
                        write_number(static_cast<uint8_t>(0x80 + N));
                    }
                    else if (N <= 0xff)
                    {
                        oa->write_character(0x98);
                        write_number(static_cast<uint8_t>(N));
                    }
                    else if (N <= 0xffff)
                    {
                        oa->write_character(0x99);
                        write_number(static_cast<uint16_t>(N));
                    }
                    else if (N <= 0xffffffff)
                    {
                        oa->write_character(0x9a);
                        write_number(static_cast<uint32_t>(N));
                    }
                    // LCOV_EXCL_START
                    else if (N <= 0xffffffffffffffff)
                    {
                        oa->write_character(0x9b);
                        write_number(static_cast<uint64_t>(N));
                    }
                    // LCOV_EXCL_STOP

                    // step 2: write each element
                    for (const auto& el : *j.m_value.array)
                    {
                        write_cbor(el);
                    }
                    break;
                }

                case value_t::object:
                {
                    // step 1: write control byte and the object size
                    const auto N = j.m_value.object->size();
                    if (N <= 0x17)
                    {
                        write_number(static_cast<uint8_t>(0xa0 + N));
                    }
                    else if (N <= 0xff)
                    {
                        oa->write_character(0xb8);
                        write_number(static_cast<uint8_t>(N));
                    }
                    else if (N <= 0xffff)
                    {
                        oa->write_character(0xb9);
                        write_number(static_cast<uint16_t>(N));
                    }
                    else if (N <= 0xffffffff)
                    {
                        oa->write_character(0xba);
                        write_number(static_cast<uint32_t>(N));
                    }
                    // LCOV_EXCL_START
                    else if (N <= 0xffffffffffffffff)
                    {
                        oa->write_character(0xbb);
                        write_number(static_cast<uint64_t>(N));
                    }
                    // LCOV_EXCL_STOP

                    // step 2: write each element
                    for (const auto& el : *j.m_value.object)
                    {
                        write_cbor(el.first);
                        write_cbor(el.second);
                    }
                    break;
                }

                default:
                {
                    break;
                }
            }
        }

        void write_msgpack(const basic_json& j)
        {
            switch (j.type())
            {
                case value_t::null:
                {
                    // nil
                    oa->write_character(0xc0);
                    break;
                }

                case value_t::boolean:
                {
                    // true and false
                    oa->write_character(j.m_value.boolean ? 0xc3 : 0xc2);
                    break;
                }

                case value_t::number_integer:
                {
                    if (j.m_value.number_integer >= 0)
                    {
                        // MessagePack does not differentiate between positive
                        // signed integers and unsigned integers. Therefore, we
                        // used the code from the value_t::number_unsigned case
                        // here.
                        if (j.m_value.number_unsigned < 128)
                        {
                            // positive fixnum
                            write_number(static_cast<uint8_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_unsigned <= (std::numeric_limits<uint8_t>::max)())
                        {
                            // uint 8
                            oa->write_character(0xcc);
                            write_number(static_cast<uint8_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_unsigned <= (std::numeric_limits<uint16_t>::max)())
                        {
                            // uint 16
                            oa->write_character(0xcd);
                            write_number(static_cast<uint16_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_unsigned <= (std::numeric_limits<uint32_t>::max)())
                        {
                            // uint 32
                            oa->write_character(0xce);
                            write_number(static_cast<uint32_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_unsigned <= (std::numeric_limits<uint64_t>::max)())
                        {
                            // uint 64
                            oa->write_character(0xcf);
                            write_number(static_cast<uint64_t>(j.m_value.number_integer));
                        }
                    }
                    else
                    {
                        if (j.m_value.number_integer >= -32)
                        {
                            // negative fixnum
                            write_number(static_cast<int8_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_integer >= (std::numeric_limits<int8_t>::min)() and j.m_value.number_integer <= (std::numeric_limits<int8_t>::max)())
                        {
                            // int 8
                            oa->write_character(0xd0);
                            write_number(static_cast<int8_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_integer >= (std::numeric_limits<int16_t>::min)() and j.m_value.number_integer <= (std::numeric_limits<int16_t>::max)())
                        {
                            // int 16
                            oa->write_character(0xd1);
                            write_number(static_cast<int16_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_integer >= (std::numeric_limits<int32_t>::min)() and j.m_value.number_integer <= (std::numeric_limits<int32_t>::max)())
                        {
                            // int 32
                            oa->write_character(0xd2);
                            write_number(static_cast<int32_t>(j.m_value.number_integer));
                        }
                        else if (j.m_value.number_integer >= (std::numeric_limits<int64_t>::min)() and j.m_value.number_integer <= (std::numeric_limits<int64_t>::max)())
                        {
                            // int 64
                            oa->write_character(0xd3);
                            write_number(static_cast<int64_t>(j.m_value.number_integer));
                        }
                    }
                    break;
                }

                case value_t::number_unsigned:
                {
                    if (j.m_value.number_unsigned < 128)
                    {
                        // positive fixnum
                        write_number(static_cast<uint8_t>(j.m_value.number_integer));
                    }
                    else if (j.m_value.number_unsigned <= (std::numeric_limits<uint8_t>::max)())
                    {
                        // uint 8
                        oa->write_character(0xcc);
                        write_number(static_cast<uint8_t>(j.m_value.number_integer));
                    }
                    else if (j.m_value.number_unsigned <= (std::numeric_limits<uint16_t>::max)())
                    {
                        // uint 16
                        oa->write_character(0xcd);
                        write_number(static_cast<uint16_t>(j.m_value.number_integer));
                    }
                    else if (j.m_value.number_unsigned <= (std::numeric_limits<uint32_t>::max)())
                    {
                        // uint 32
                        oa->write_character(0xce);
                        write_number(static_cast<uint32_t>(j.m_value.number_integer));
                    }
                    else if (j.m_value.number_unsigned <= (std::numeric_limits<uint64_t>::max)())
                    {
                        // uint 64
                        oa->write_character(0xcf);
                        write_number(static_cast<uint64_t>(j.m_value.number_integer));
                    }
                    break;
                }

                case value_t::number_float:
                {
                    // float 64
                    oa->write_character(0xcb);
                    write_number(j.m_value.number_float);
                    break;
                }

                case value_t::string:
                {
                    // step 1: write control byte and the string length
                    const auto N = j.m_value.string->size();
                    if (N <= 31)
                    {
                        // fixstr
                        write_number(static_cast<uint8_t>(0xa0 | N));
                    }
                    else if (N <= 255)
                    {
                        // str 8
                        oa->write_character(0xd9);
                        write_number(static_cast<uint8_t>(N));
                    }
                    else if (N <= 65535)
                    {
                        // str 16
                        oa->write_character(0xda);
                        write_number(static_cast<uint16_t>(N));
                    }
                    else if (N <= 4294967295)
                    {
                        // str 32
                        oa->write_character(0xdb);
                        write_number(static_cast<uint32_t>(N));
                    }

                    // step 2: write the string
                    oa->write_characters(reinterpret_cast<const uint8_t*>(j.m_value.string->c_str()),
                                         j.m_value.string->size());
                    break;
                }

                case value_t::array:
                {
                    // step 1: write control byte and the array size
                    const auto N = j.m_value.array->size();
                    if (N <= 15)
                    {
                        // fixarray
                        write_number(static_cast<uint8_t>(0x90 | N));
                    }
                    else if (N <= 0xffff)
                    {
                        // array 16
                        oa->write_character(0xdc);
                        write_number(static_cast<uint16_t>(N));
                    }
                    else if (N <= 0xffffffff)
                    {
                        // array 32
                        oa->write_character(0xdd);
                        write_number(static_cast<uint32_t>(N));
                    }

                    // step 2: write each element
                    for (const auto& el : *j.m_value.array)
                    {
                        write_msgpack(el);
                    }
                    break;
                }

                case value_t::object:
                {
                    // step 1: write control byte and the object size
                    const auto N = j.m_value.object->size();
                    if (N <= 15)
                    {
                        // fixmap
                        write_number(static_cast<uint8_t>(0x80 | (N & 0xf)));
                    }
                    else if (N <= 65535)
                    {
                        // map 16
                        oa->write_character(0xde);
                        write_number(static_cast<uint16_t>(N));
                    }
                    else if (N <= 4294967295)
                    {
                        // map 32
                        oa->write_character(0xdf);
                        write_number(static_cast<uint32_t>(N));
                    }

                    // step 2: write each element
                    for (const auto& el : *j.m_value.object)
                    {
                        write_msgpack(el.first);
                        write_msgpack(el.second);
                    }
                    break;
                }

                default:
                {
                    break;
                }
            }
        }

      private:
        /*
        @brief write a number to output input

        @param[in] n number of type @a T
        @tparam T the type of the number

        @note This function needs to respect the system's endianess, because
              bytes in CBOR and MessagePack are stored in network order (big
              endian) and therefore need reordering on little endian systems.
        */
        template<typename T>
        void write_number(T n)
        {
            // step 1: write number to array of length T
            std::array<uint8_t, sizeof(T)> vec;
            std::memcpy(vec.data(), &n, sizeof(T));

            // step 2: write array to output (with possible reordering)
            for (size_t i = 0; i < sizeof(T); ++i)
            {
                // reverse byte order prior to conversion if necessary
                if (is_little_endian)
                {
                    oa->write_character(vec[sizeof(T) - i - 1]);
                }
                else
                {
                    oa->write_character(vec[i]);
                }
            }
        }

      private:
        const bool is_little_endian = true;

        output_adapter_t<uint8_t> oa = nullptr;
    };

  public:
    static std::vector<uint8_t> to_cbor(const basic_json& j)
    {
        std::vector<uint8_t> result;
        binary_writer bw(output_adapter<uint8_t>::create(result));
        bw.write_cbor(j);
        return result;
    }

    static std::vector<uint8_t> to_msgpack(const basic_json& j)
    {
        std::vector<uint8_t> result;
        binary_writer bw(output_adapter<uint8_t>::create(result));
        bw.write_msgpack(j);
        return result;
    }

    static basic_json from_cbor(const std::vector<uint8_t>& v,
                                const size_t start_index = 0)
    {
        binary_reader br(input_adapter::create(v.begin() + static_cast<difference_type>(start_index), v.end()));
        return br.parse_cbor();
    }


    static basic_json from_msgpack(const std::vector<uint8_t>& v,
                                   const size_t start_index = 0)
    {
        binary_reader br(input_adapter::create(v.begin() + static_cast<difference_type>(start_index), v.end()));
        return br.parse_msgpack();
    }


    // lexer and parser //

  private:
    class lexer
    {
      public:
        enum class token_type
        {
            uninitialized,   
            literal_true,    
            literal_false,   
            literal_null,    
            value_string,    
            value_unsigned,  
            value_integer,   
            value_float,     
            begin_array,     
            begin_object,    
            end_array,       
            end_object,      
            name_separator,  
            value_separator, 
            parse_error,     
            end_of_input     
        };

        static const char* token_type_name(const token_type t) noexcept
        {
            switch (t)
            {
                case token_type::uninitialized:
                    return "<uninitialized>";
                case token_type::literal_true:
                    return "true literal";
                case token_type::literal_false:
                    return "false literal";
                case token_type::literal_null:
                    return "null literal";
                case token_type::value_string:
                    return "string literal";
                case lexer::token_type::value_unsigned:
                case lexer::token_type::value_integer:
                case lexer::token_type::value_float:
                    return "number literal";
                case token_type::begin_array:
                    return "'['";
                case token_type::begin_object:
                    return "'{'";
                case token_type::end_array:
                    return "']'";
                case token_type::end_object:
                    return "'}'";
                case token_type::name_separator:
                    return "':'";
                case token_type::value_separator:
                    return "','";
                case token_type::parse_error:
                    return "<parse error>";
                case token_type::end_of_input:
                    return "end of input";
                default:
                {
                    // catch non-enum values
                    return "unknown token"; // LCOV_EXCL_LINE
                }
            }
        }

        explicit lexer(input_adapter_t adapter)
            : ia(adapter), decimal_point_char(get_decimal_point())
        {}

      private:
        // locales

        static char get_decimal_point() noexcept
        {
            const auto loc = localeconv();
            assert(loc != nullptr);
            return (loc->decimal_point == nullptr) ? '.' : loc->decimal_point[0];
        }

        // scan functions

        int get_codepoint()
        {
            // this function only makes sense after reading `\u`
            assert(current == 'u');
            int codepoint = 0;

            // byte 1: \uXxxx
            switch (get())
            {
                case '0':
                    break;
                case '1':
                    codepoint += 0x1000;
                    break;
                case '2':
                    codepoint += 0x2000;
                    break;
                case '3':
                    codepoint += 0x3000;
                    break;
                case '4':
                    codepoint += 0x4000;
                    break;
                case '5':
                    codepoint += 0x5000;
                    break;
                case '6':
                    codepoint += 0x6000;
                    break;
                case '7':
                    codepoint += 0x7000;
                    break;
                case '8':
                    codepoint += 0x8000;
                    break;
                case '9':
                    codepoint += 0x9000;
                    break;
                case 'A':
                case 'a':
                    codepoint += 0xa000;
                    break;
                case 'B':
                case 'b':
                    codepoint += 0xb000;
                    break;
                case 'C':
                case 'c':
                    codepoint += 0xc000;
                    break;
                case 'D':
                case 'd':
                    codepoint += 0xd000;
                    break;
                case 'E':
                case 'e':
                    codepoint += 0xe000;
                    break;
                case 'F':
                case 'f':
                    codepoint += 0xf000;
                    break;
                default:
                    return -1;
            }

            // byte 2: \uxXxx
            switch (get())
            {
                case '0':
                    break;
                case '1':
                    codepoint += 0x0100;
                    break;
                case '2':
                    codepoint += 0x0200;
                    break;
                case '3':
                    codepoint += 0x0300;
                    break;
                case '4':
                    codepoint += 0x0400;
                    break;
                case '5':
                    codepoint += 0x0500;
                    break;
                case '6':
                    codepoint += 0x0600;
                    break;
                case '7':
                    codepoint += 0x0700;
                    break;
                case '8':
                    codepoint += 0x0800;
                    break;
                case '9':
                    codepoint += 0x0900;
                    break;
                case 'A':
                case 'a':
                    codepoint += 0x0a00;
                    break;
                case 'B':
                case 'b':
                    codepoint += 0x0b00;
                    break;
                case 'C':
                case 'c':
                    codepoint += 0x0c00;
                    break;
                case 'D':
                case 'd':
                    codepoint += 0x0d00;
                    break;
                case 'E':
                case 'e':
                    codepoint += 0x0e00;
                    break;
                case 'F':
                case 'f':
                    codepoint += 0x0f00;
                    break;
                default:
                    return -1;
            }

            // byte 3: \uxxXx
            switch (get())
            {
                case '0':
                    break;
                case '1':
                    codepoint += 0x0010;
                    break;
                case '2':
                    codepoint += 0x0020;
                    break;
                case '3':
                    codepoint += 0x0030;
                    break;
                case '4':
                    codepoint += 0x0040;
                    break;
                case '5':
                    codepoint += 0x0050;
                    break;
                case '6':
                    codepoint += 0x0060;
                    break;
                case '7':
                    codepoint += 0x0070;
                    break;
                case '8':
                    codepoint += 0x0080;
                    break;
                case '9':
                    codepoint += 0x0090;
                    break;
                case 'A':
                case 'a':
                    codepoint += 0x00a0;
                    break;
                case 'B':
                case 'b':
                    codepoint += 0x00b0;
                    break;
                case 'C':
                case 'c':
                    codepoint += 0x00c0;
                    break;
                case 'D':
                case 'd':
                    codepoint += 0x00d0;
                    break;
                case 'E':
                case 'e':
                    codepoint += 0x00e0;
                    break;
                case 'F':
                case 'f':
                    codepoint += 0x00f0;
                    break;
                default:
                    return -1;
            }

            // byte 4: \uxxxX
            switch (get())
            {
                case '0':
                    break;
                case '1':
                    codepoint += 0x0001;
                    break;
                case '2':
                    codepoint += 0x0002;
                    break;
                case '3':
                    codepoint += 0x0003;
                    break;
                case '4':
                    codepoint += 0x0004;
                    break;
                case '5':
                    codepoint += 0x0005;
                    break;
                case '6':
                    codepoint += 0x0006;
                    break;
                case '7':
                    codepoint += 0x0007;
                    break;
                case '8':
                    codepoint += 0x0008;
                    break;
                case '9':
                    codepoint += 0x0009;
                    break;
                case 'A':
                case 'a':
                    codepoint += 0x000a;
                    break;
                case 'B':
                case 'b':
                    codepoint += 0x000b;
                    break;
                case 'C':
                case 'c':
                    codepoint += 0x000c;
                    break;
                case 'D':
                case 'd':
                    codepoint += 0x000d;
                    break;
                case 'E':
                case 'e':
                    codepoint += 0x000e;
                    break;
                case 'F':
                case 'f':
                    codepoint += 0x000f;
                    break;
                default:
                    return -1;
            }

            return codepoint;
        }

        static std::string codepoint_to_string(int codepoint)
        {
            std::stringstream ss;
            ss << "U+" << std::setw(4) << std::uppercase << std::setfill('0') << std::hex << codepoint;
            return ss.str();
        }

        token_type scan_string()
        {
            // reset yytext (ignore opening quote)
            reset();

            // we entered the function by reading an open quote
            assert(current == '\"');

            while (true)
            {
                // get next character
                get();

                switch (current)
                {
                    // end of file while parsing string
                    case std::char_traits<char>::eof():
                    {
                        error_message = "invalid string: missing closing quote";
                        return token_type::parse_error;
                    }

                    // closing quote
                    case '\"':
                    {
                        // terminate yytext
                        add('\0');
                        --yylen;
                        return token_type::value_string;
                    }

                    // escapes
                    case '\\':
                    {
                        switch (get())
                        {
                            // quotation mark
                            case '\"':
                                add('\"');
                                break;
                            // reverse solidus
                            case '\\':
                                add('\\');
                                break;
                            // solidus
                            case '/':
                                add('/');
                                break;
                            // backspace
                            case 'b':
                                add('\b');
                                break;
                            // form feed
                            case 'f':
                                add('\f');
                                break;
                            // line feed
                            case 'n':
                                add('\n');
                                break;
                            // carriage return
                            case 'r':
                                add('\r');
                                break;
                            // tab
                            case 't':
                                add('\t');
                                break;

                            // unicode escapes
                            case 'u':
                            {
                                int codepoint;
                                int codepoint1 = get_codepoint();

                                if (JSON_UNLIKELY(codepoint1 == -1))
                                {
                                    error_message = "invalid string: '\\u' must be followed by 4 hex digits";
                                    return token_type::parse_error;
                                }

                                // check if code point is a high surrogate
                                if (0xD800 <= codepoint1 and codepoint1 <= 0xDBFF)
                                {
                                    // expect next \uxxxx entry
                                    if (JSON_LIKELY(get() == '\\' and get() == 'u'))
                                    {
                                        const int codepoint2 = get_codepoint();

                                        if (JSON_UNLIKELY(codepoint2 == -1))
                                        {
                                            error_message = "invalid string: '\\u' must be followed by 4 hex digits";
                                            return token_type::parse_error;
                                        }

                                        // check if codepoint2 is a low surrogate
                                        if (JSON_LIKELY(0xDC00 <= codepoint2 and codepoint2 <= 0xDFFF))
                                        {
                                            codepoint =
                                                // high surrogate occupies the most significant 22 bits
                                                (codepoint1 << 10)
                                                // low surrogate occupies the least significant 15 bits
                                                + codepoint2
                                                // there is still the 0xD800, 0xDC00 and 0x10000 noise
                                                // in the result so we have to subtract with:
                                                // (0xD800 << 10) + DC00 - 0x10000 = 0x35FDC00
                                                - 0x35FDC00;
                                        }
                                        else
                                        {
                                            error_message = "invalid string: surrogate " + codepoint_to_string(codepoint1) + " must be followed by U+DC00..U+DFFF instead of " + codepoint_to_string(codepoint2);
                                            return token_type::parse_error;
                                        }
                                    }
                                    else
                                    {
                                        error_message = "invalid string: surrogate " + codepoint_to_string(codepoint1) + " must be followed by U+DC00..U+DFFF";
                                        return token_type::parse_error;
                                    }
                                }
                                else
                                {
                                    if (JSON_UNLIKELY(0xDC00 <= codepoint1 and codepoint1 <= 0xDFFF))
                                    {
                                        error_message = "invalid string: surrogate " + codepoint_to_string(codepoint1) + " must follow U+D800..U+DBFF";
                                        return token_type::parse_error;
                                    }

                                    // only work with first code point
                                    codepoint = codepoint1;
                                }

                                // result of the above calculation yields a proper codepoint
                                assert(0x00 <= codepoint and codepoint <= 0x10FFFF);

                                // translate code point to bytes
                                if (codepoint < 0x80)
                                {
                                    // 1-byte characters: 0xxxxxxx (ASCII)
                                    add(codepoint);
                                }
                                else if (codepoint <= 0x7ff)
                                {
                                    // 2-byte characters: 110xxxxx 10xxxxxx
                                    add(0xC0 | (codepoint >> 6));
                                    add(0x80 | (codepoint & 0x3F));
                                }
                                else if (codepoint <= 0xffff)
                                {
                                    // 3-byte characters: 1110xxxx 10xxxxxx 10xxxxxx
                                    add(0xE0 | (codepoint >> 12));
                                    add(0x80 | ((codepoint >> 6) & 0x3F));
                                    add(0x80 | (codepoint & 0x3F));
                                }
                                else
                                {
                                    // 4-byte characters: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
                                    add(0xF0 | (codepoint >> 18));
                                    add(0x80 | ((codepoint >> 12) & 0x3F));
                                    add(0x80 | ((codepoint >> 6) & 0x3F));
                                    add(0x80 | (codepoint & 0x3F));
                                }

                                break;
                            }

                            // other characters after escape
                            default:
                                error_message = "invalid string: forbidden character after backslash";
                                return token_type::parse_error;
                        }

                        break;
                    }

                    // invalid control characters
                    case 0x00:
                    case 0x01:
                    case 0x02:
                    case 0x03:
                    case 0x04:
                    case 0x05:
                    case 0x06:
                    case 0x07:
                    case 0x08:
                    case 0x09:
                    case 0x0a:
                    case 0x0b:
                    case 0x0c:
                    case 0x0d:
                    case 0x0e:
                    case 0x0f:
                    case 0x10:
                    case 0x11:
                    case 0x12:
                    case 0x13:
                    case 0x14:
                    case 0x15:
                    case 0x16:
                    case 0x17:
                    case 0x18:
                    case 0x19:
                    case 0x1a:
                    case 0x1b:
                    case 0x1c:
                    case 0x1d:
                    case 0x1e:
                    case 0x1f:
                    {
                        error_message = "invalid string: control character " + codepoint_to_string(current) + " must be escaped";
                        return token_type::parse_error;
                    }

                    // U+0020..U+007F (except U+0022 (quote) and U+005C (backspace))
                    case 0x20:
                    case 0x21:
                    case 0x23:
                    case 0x24:
                    case 0x25:
                    case 0x26:
                    case 0x27:
                    case 0x28:
                    case 0x29:
                    case 0x2a:
                    case 0x2b:
                    case 0x2c:
                    case 0x2d:
                    case 0x2e:
                    case 0x2f:
                    case 0x30:
                    case 0x31:
                    case 0x32:
                    case 0x33:
                    case 0x34:
                    case 0x35:
                    case 0x36:
                    case 0x37:
                    case 0x38:
                    case 0x39:
                    case 0x3a:
                    case 0x3b:
                    case 0x3c:
                    case 0x3d:
                    case 0x3e:
                    case 0x3f:
                    case 0x40:
                    case 0x41:
                    case 0x42:
                    case 0x43:
                    case 0x44:
                    case 0x45:
                    case 0x46:
                    case 0x47:
                    case 0x48:
                    case 0x49:
                    case 0x4a:
                    case 0x4b:
                    case 0x4c:
                    case 0x4d:
                    case 0x4e:
                    case 0x4f:
                    case 0x50:
                    case 0x51:
                    case 0x52:
                    case 0x53:
                    case 0x54:
                    case 0x55:
                    case 0x56:
                    case 0x57:
                    case 0x58:
                    case 0x59:
                    case 0x5a:
                    case 0x5b:
                    case 0x5d:
                    case 0x5e:
                    case 0x5f:
                    case 0x60:
                    case 0x61:
                    case 0x62:
                    case 0x63:
                    case 0x64:
                    case 0x65:
                    case 0x66:
                    case 0x67:
                    case 0x68:
                    case 0x69:
                    case 0x6a:
                    case 0x6b:
                    case 0x6c:
                    case 0x6d:
                    case 0x6e:
                    case 0x6f:
                    case 0x70:
                    case 0x71:
                    case 0x72:
                    case 0x73:
                    case 0x74:
                    case 0x75:
                    case 0x76:
                    case 0x77:
                    case 0x78:
                    case 0x79:
                    case 0x7a:
                    case 0x7b:
                    case 0x7c:
                    case 0x7d:
                    case 0x7e:
                    case 0x7f:
                    {
                        add(current);
                        break;
                    }

                    // U+0080..U+07FF: bytes C2..DF 80..BF
                    case 0xc2:
                    case 0xc3:
                    case 0xc4:
                    case 0xc5:
                    case 0xc6:
                    case 0xc7:
                    case 0xc8:
                    case 0xc9:
                    case 0xca:
                    case 0xcb:
                    case 0xcc:
                    case 0xcd:
                    case 0xce:
                    case 0xcf:
                    case 0xd0:
                    case 0xd1:
                    case 0xd2:
                    case 0xd3:
                    case 0xd4:
                    case 0xd5:
                    case 0xd6:
                    case 0xd7:
                    case 0xd8:
                    case 0xd9:
                    case 0xda:
                    case 0xdb:
                    case 0xdc:
                    case 0xdd:
                    case 0xde:
                    case 0xdf:
                    {
                        add(current);
                        get();
                        if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                        {
                            add(current);
                            continue;
                        }

                        error_message = "invalid string: ill-formed UTF-8 byte";
                        return token_type::parse_error;
                    }

                    // U+0800..U+0FFF: bytes E0 A0..BF 80..BF
                    case 0xe0:
                    {
                        add(current);
                        get();
                        if (JSON_LIKELY(0xa0 <= current and current <= 0xbf))
                        {
                            add(current);
                            get();
                            if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                            {
                                add(current);
                                continue;
                            }
                        }

                        error_message = "invalid string: ill-formed UTF-8 byte";
                        return token_type::parse_error;
                    }

                    // U+1000..U+CFFF: bytes E1..EC 80..BF 80..BF
                    // U+E000..U+FFFF: bytes EE..EF 80..BF 80..BF
                    case 0xe1:
                    case 0xe2:
                    case 0xe3:
                    case 0xe4:
                    case 0xe5:
                    case 0xe6:
                    case 0xe7:
                    case 0xe8:
                    case 0xe9:
                    case 0xea:
                    case 0xeb:
                    case 0xec:
                    case 0xee:
                    case 0xef:
                    {
                        add(current);
                        get();
                        if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                        {
                            add(current);
                            get();
                            if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                            {
                                add(current);
                                continue;
                            }
                        }

                        error_message = "invalid string: ill-formed UTF-8 byte";
                        return token_type::parse_error;
                    }

                    // U+D000..U+D7FF: bytes ED 80..9F 80..BF
                    case 0xed:
                    {
                        add(current);
                        get();
                        if (JSON_LIKELY(0x80 <= current and current <= 0x9f))
                        {
                            add(current);
                            get();
                            if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                            {
                                add(current);
                                continue;
                            }
                        }

                        error_message = "invalid string: ill-formed UTF-8 byte";
                        return token_type::parse_error;
                    }

                    // U+10000..U+3FFFF F0 90..BF 80..BF 80..BF
                    case 0xf0:
                    {
                        add(current);
                        get();
                        if (JSON_LIKELY(0x90 <= current and current <= 0xbf))
                        {
                            add(current);
                            get();
                            if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                            {
                                add(current);
                                get();
                                if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                                {
                                    add(current);
                                    continue;
                                }
                            }
                        }

                        error_message = "invalid string: ill-formed UTF-8 byte";
                        return token_type::parse_error;
                    }

                    // U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF
                    case 0xf1:
                    case 0xf2:
                    case 0xf3:
                    {
                        add(current);
                        get();
                        if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                        {
                            add(current);
                            get();
                            if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                            {
                                add(current);
                                get();
                                if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                                {
                                    add(current);
                                    continue;
                                }
                            }
                        }

                        error_message = "invalid string: ill-formed UTF-8 byte";
                        return token_type::parse_error;
                    }

                    // U+100000..U+10FFFF F4 80..8F 80..BF 80..BF
                    case 0xf4:
                    {
                        add(current);
                        get();
                        if (JSON_LIKELY(0x80 <= current and current <= 0x8f))
                        {
                            add(current);
                            get();
                            if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                            {
                                add(current);
                                get();
                                if (JSON_LIKELY(0x80 <= current and current <= 0xbf))
                                {
                                    add(current);
                                    continue;
                                }
                            }
                        }

                        error_message = "invalid string: ill-formed UTF-8 byte";
                        return token_type::parse_error;
                    }

                    // remaining bytes (80..C1 and F5..FF) are ill-formed
                    default:
                    {
                        error_message = "invalid string: ill-formed UTF-8 byte";
                        return token_type::parse_error;
                    }
                }
            }
        }

        static void strtof(float& f, const char* str, char** endptr) noexcept
        {
            f = std::strtof(str, endptr);
        }

        static void strtof(double& f, const char* str, char** endptr) noexcept
        {
            f = std::strtod(str, endptr);
        }

        static void strtof(long double& f, const char* str, char** endptr) noexcept
        {
            f = std::strtold(str, endptr);
        }

        token_type scan_number()
        {
            // reset yytext to store the number's bytes
            reset();

            // the type of the parsed number; initially set to unsigned; will be
            // changed if minus sign, decimal point or exponent is read
            token_type number_type = token_type::value_unsigned;

            // state (init): we just found out we need to scan a number
            switch (current)
            {
                case '-':
                {
                    add(current);
                    goto scan_number_minus;
                }

                case '0':
                {
                    add(current);
                    goto scan_number_zero;
                }

                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                {
                    add(current);
                    goto scan_number_any1;
                }

                default:
                {
                    // all other characters are rejected outside scan_number()
                    assert(false);  // LCOV_EXCL_LINE
                }
            }

scan_number_minus:
            // state: we just parsed a leading minus sign
            number_type = token_type::value_integer;
            switch (get())
            {
                case '0':
                {
                    add(current);
                    goto scan_number_zero;
                }

                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                {
                    add(current);
                    goto scan_number_any1;
                }

                default:
                {
                    error_message = "invalid number; expected digit after '-'";
                    return token_type::parse_error;
                }
            }

scan_number_zero:
            // state: we just parse a zero (maybe with a leading minus sign)
            switch (get())
            {
                case '.':
                {
                    add(decimal_point_char);
                    goto scan_number_decimal1;
                }

                case 'e':
                case 'E':
                {
                    add(current);
                    goto scan_number_exponent;
                }

                default:
                {
                    goto scan_number_done;
                }
            }

scan_number_any1:
            // state: we just parsed a number 0-9 (maybe with a leading minus sign)
            switch (get())
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                {
                    add(current);
                    goto scan_number_any1;
                }

                case '.':
                {
                    add(decimal_point_char);
                    goto scan_number_decimal1;
                }

                case 'e':
                case 'E':
                {
                    add(current);
                    goto scan_number_exponent;
                }

                default:
                {
                    goto scan_number_done;
                }
            }

scan_number_decimal1:
            // state: we just parsed a decimal point
            number_type = token_type::value_float;
            switch (get())
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                {
                    add(current);
                    goto scan_number_decimal2;
                }

                default:
                {
                    error_message = "invalid number; expected digit after '.'";
                    return token_type::parse_error;
                }
            }

scan_number_decimal2:
            // we just parsed at least one number after a decimal point
            switch (get())
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                {
                    add(current);
                    goto scan_number_decimal2;
                }

                case 'e':
                case 'E':
                {
                    add(current);
                    goto scan_number_exponent;
                }

                default:
                {
                    goto scan_number_done;
                }
            }

scan_number_exponent:
            // we just parsed an exponent
            number_type = token_type::value_float;
            switch (get())
            {
                case '+':
                case '-':
                {
                    add(current);
                    goto scan_number_sign;
                }

                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                {
                    add(current);
                    goto scan_number_any2;
                }

                default:
                {
                    error_message = "invalid number; expected '+', '-', or digit after exponent";
                    return token_type::parse_error;
                }
            }

scan_number_sign:
            // we just parsed an exponent sign
            switch (get())
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                {
                    add(current);
                    goto scan_number_any2;
                }

                default:
                {
                    error_message = "invalid number; expected digit after exponent sign";
                    return token_type::parse_error;
                }
            }

scan_number_any2:
            // we just parsed a number after the exponent or exponent sign
            switch (get())
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                {
                    add(current);
                    goto scan_number_any2;
                }

                default:
                {
                    goto scan_number_done;
                }
            }

scan_number_done:
            // unget the character after the number (we only read it to know
            // that we are done scanning a number)
            --chars_read;
            next_unget = true;

            // terminate token
            add('\0');
            --yylen;

            // try to parse integers first and fall back to floats
            if (number_type == token_type::value_unsigned)
            {
                char* endptr = nullptr;
                errno = 0;
                const auto x = std::strtoull(yytext.data(), &endptr, 10);

                // we checked the number format before
                assert(endptr == yytext.data() + yylen);

                if (errno == 0)
                {
                    value_unsigned = static_cast<number_unsigned_t>(x);
                    if (value_unsigned == x)
                    {
                        return token_type::value_unsigned;
                    }
                }
            }
            else if (number_type == token_type::value_integer)
            {
                char* endptr = nullptr;
                errno = 0;
                const auto x = std::strtoll(yytext.data(), &endptr, 10);

                // we checked the number format before
                assert(endptr == yytext.data() + yylen);

                if (errno == 0)
                {
                    value_integer = static_cast<number_integer_t>(x);
                    if (value_integer == x)
                    {
                        return token_type::value_integer;
                    }
                }
            }

            // this code is reached if we parse a floating-point number or if
            // an integer conversion above failed
            strtof(value_float, yytext.data(), nullptr);
            return token_type::value_float;
        }

        token_type scan_true()
        {
            assert(current == 't');
            if (JSON_LIKELY((get() == 'r' and get() == 'u' and get() == 'e')))
            {
                return token_type::literal_true;
            }

            error_message = "invalid literal; expected 'true'";
            return token_type::parse_error;
        }

        token_type scan_false()
        {
            assert(current == 'f');
            if (JSON_LIKELY((get() == 'a' and get() == 'l' and get() == 's' and get() == 'e')))
            {
                return token_type::literal_false;
            }

            error_message = "invalid literal; expected 'false'";
            return token_type::parse_error;
        }

        token_type scan_null()
        {
            assert(current == 'n');
            if (JSON_LIKELY((get() == 'u' and get() == 'l' and get() == 'l')))
            {
                return token_type::literal_null;
            }

            error_message = "invalid literal; expected 'null'";
            return token_type::parse_error;
        }

        // input management

        void reset() noexcept
        {
            yylen = 0;
            start_pos = chars_read - 1;
        }

        int get()
        {
            ++chars_read;
            return next_unget
                   ? (next_unget = false, current)
                   : (current = ia->get_character());
        }

        void add(int c)
        {
            // resize yytext if necessary; this condition is deemed unlikely,
            // because we start with a 1024-byte buffer
            if (JSON_UNLIKELY((yylen + 1 > yytext.capacity())))
            {
                yytext.resize(2 * yytext.capacity(), '\0');
            }
            yytext[yylen++] = static_cast<char>(c);
        }

      public:
        // value getters

        constexpr number_integer_t get_number_integer() const noexcept
        {
            return value_integer;
        }

        constexpr number_unsigned_t get_number_unsigned() const noexcept
        {
            return value_unsigned;
        }

        constexpr number_float_t get_number_float() const noexcept
        {
            return value_float;
        }

        const std::string get_string()
        {
            // yytext cannot be returned as char*, because it may contain a
            // null byte (parsed as "\u0000")
            return std::string(yytext.data(), yylen);
        }

        // diagnostics

        constexpr size_t get_position() const noexcept
        {
            return chars_read;
        }

        std::string get_token_string() const
        {
            // get the raw byte sequence of the last token
            std::string s = ia->read(start_pos, chars_read - start_pos);

            // escape control characters
            std::string result;
            for (auto c : s)
            {
                if (c == '\0' or c == std::char_traits<char>::eof())
                {
                    // ignore EOF
                    continue;
                }
                else if ('\x00' <= c and c <= '\x1f')
                {
                    // escape control characters
                    result += "<" + codepoint_to_string(c) + ">";
                }
                else
                {
                    // add character as is
                    result.append(1, c);
                }
            }

            return result;
        }

        const std::string& get_error_message() const noexcept
        {
            return error_message;
        }

        // actual scanner

        token_type scan()
        {
            // read next character and ignore whitespace
            do
            {
                get();
            }
            while (current == ' ' or current == '\t' or current == '\n' or current == '\r');

            switch (current)
            {
                // structural characters
                case '[':
                    return token_type::begin_array;
                case ']':
                    return token_type::end_array;
                case '{':
                    return token_type::begin_object;
                case '}':
                    return token_type::end_object;
                case ':':
                    return token_type::name_separator;
                case ',':
                    return token_type::value_separator;

                // literals
                case 't':
                    return scan_true();
                case 'f':
                    return scan_false();
                case 'n':
                    return scan_null();

                // string
                case '\"':
                    return scan_string();

                // number
                case '-':
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                    return scan_number();

                // end of input (the null byte is needed when parsing from
                // string literals)
                case '\0':
                case std::char_traits<char>::eof():
                    return token_type::end_of_input;

                // error
                default:
                    error_message = "invalid literal";
                    return token_type::parse_error;
            }
        }

      private:
        input_adapter_t ia = nullptr;

        int current = std::char_traits<char>::eof();

        bool next_unget = false;

        size_t chars_read = 0;
        size_t start_pos = 0;

        std::vector<char> yytext = std::vector<char>(1024, '\0');
        size_t yylen = 0;

        std::string error_message = "";

        // number values
        number_integer_t value_integer = 0;
        number_unsigned_t value_unsigned = 0;
        number_float_t value_float = 0;

        const char decimal_point_char = '.';
    };

    class parser
    {
      public:
        explicit parser(input_adapter_t adapter,
                        const parser_callback_t cb = nullptr)
            : callback(cb), m_lexer(adapter)
        {}

        basic_json parse(const bool strict = true)
        {
            // read first token
            get_token();

            basic_json result = parse_internal(true);
            result.assert_invariant();

            if (strict)
            {
                get_token();
                expect(lexer::token_type::end_of_input);
            }

            // return parser result and replace it with null in case the
            // top-level value was discarded by the callback function
            return result.is_discarded() ? basic_json() : std::move(result);
        }

        bool accept(const bool strict = true)
        {
            // read first token
            get_token();

            if (not accept_internal())
            {
                return false;
            }

            if (strict and get_token() != lexer::token_type::end_of_input)
            {
                return false;
            }

            return true;
        }

      private:
        basic_json parse_internal(bool keep)
        {
            auto result = basic_json(value_t::discarded);

            switch (last_token)
            {
                case lexer::token_type::begin_object:
                {
                    if (keep and (not callback
                                  or ((keep = callback(depth++, parse_event_t::object_start, result)) != 0)))
                    {
                        // explicitly set result to object to cope with {}
                        result.m_type = value_t::object;
                        result.m_value = value_t::object;
                    }

                    // read next token
                    get_token();

                    // closing } -> we are done
                    if (last_token == lexer::token_type::end_object)
                    {
                        if (keep and callback and not callback(--depth, parse_event_t::object_end, result))
                        {
                            result = basic_json(value_t::discarded);
                        }
                        return result;
                    }

                    // parse values
                    while (true)
                    {
                        // store key
                        expect(lexer::token_type::value_string);
                        const auto key = m_lexer.get_string();

                        bool keep_tag = false;
                        if (keep)
                        {
                            if (callback)
                            {
                                basic_json k(key);
                                keep_tag = callback(depth, parse_event_t::key, k);
                            }
                            else
                            {
                                keep_tag = true;
                            }
                        }

                        // parse separator (:)
                        get_token();
                        expect(lexer::token_type::name_separator);

                        // parse and add value
                        get_token();
                        auto value = parse_internal(keep);
                        if (keep and keep_tag and not value.is_discarded())
                        {
                            result[key] = std::move(value);
                        }

                        // comma -> next value
                        get_token();
                        if (last_token == lexer::token_type::value_separator)
                        {
                            get_token();
                            continue;
                        }

                        // closing }
                        expect(lexer::token_type::end_object);
                        break;
                    }

                    if (keep and callback and not callback(--depth, parse_event_t::object_end, result))
                    {
                        result = basic_json(value_t::discarded);
                    }

                    return result;
                }

                case lexer::token_type::begin_array:
                {
                    if (keep and (not callback
                                  or ((keep = callback(depth++, parse_event_t::array_start, result)) != 0)))
                    {
                        // explicitly set result to object to cope with []
                        result.m_type = value_t::array;
                        result.m_value = value_t::array;
                    }

                    // read next token
                    get_token();

                    // closing ] -> we are done
                    if (last_token == lexer::token_type::end_array)
                    {
                        if (callback and not callback(--depth, parse_event_t::array_end, result))
                        {
                            result = basic_json(value_t::discarded);
                        }
                        return result;
                    }

                    // parse values
                    while (true)
                    {
                        // parse value
                        auto value = parse_internal(keep);
                        if (keep and not value.is_discarded())
                        {
                            result.push_back(std::move(value));
                        }

                        // comma -> next value
                        get_token();
                        if (last_token == lexer::token_type::value_separator)
                        {
                            get_token();
                            continue;
                        }

                        // closing ]
                        expect(lexer::token_type::end_array);
                        break;
                    }

                    if (keep and callback and not callback(--depth, parse_event_t::array_end, result))
                    {
                        result = basic_json(value_t::discarded);
                    }

                    return result;
                }

                case lexer::token_type::literal_null:
                {
                    result.m_type = value_t::null;
                    break;
                }

                case lexer::token_type::value_string:
                {
                    result = basic_json(m_lexer.get_string());
                    break;
                }

                case lexer::token_type::literal_true:
                {
                    result.m_type = value_t::boolean;
                    result.m_value = true;
                    break;
                }

                case lexer::token_type::literal_false:
                {
                    result.m_type = value_t::boolean;
                    result.m_value = false;
                    break;
                }

                case lexer::token_type::value_unsigned:
                {
                    result.m_type = value_t::number_unsigned;
                    result.m_value = m_lexer.get_number_unsigned();
                    break;
                }

                case lexer::token_type::value_integer:
                {
                    result.m_type = value_t::number_integer;
                    result.m_value = m_lexer.get_number_integer();
                    break;
                }

                case lexer::token_type::value_float:
                {
                    result.m_type = value_t::number_float;
                    result.m_value = m_lexer.get_number_float();

                    // throw in case of infinity or NAN
                    if (JSON_UNLIKELY(not std::isfinite(result.m_value.number_float)))
                    {
                        JSON_THROW(out_of_range::create(406, "number overflow parsing '" + m_lexer.get_token_string() + "'"));
                    }

                    break;
                }

                default:
                {
                    // the last token was unexpected
                    unexpect(last_token);
                }
            }

            if (keep and callback and not callback(depth, parse_event_t::value, result))
            {
                result = basic_json(value_t::discarded);
            }
            return result;
        }

        bool accept_internal()
        {
            switch (last_token)
            {
                case lexer::token_type::begin_object:
                {
                    // read next token
                    get_token();

                    // closing } -> we are done
                    if (last_token == lexer::token_type::end_object)
                    {
                        return true;
                    }

                    // parse values
                    while (true)
                    {
                        // parse key
                        if (last_token != lexer::token_type::value_string)
                        {
                            return false;
                        }

                        // parse separator (:)
                        get_token();
                        if (last_token != lexer::token_type::name_separator)
                        {
                            return false;
                        }

                        // parse value
                        get_token();
                        if (not accept_internal())
                        {
                            return false;
                        }

                        // comma -> next value
                        get_token();
                        if (last_token == lexer::token_type::value_separator)
                        {
                            get_token();
                            continue;
                        }

                        // closing }
                        if (last_token != lexer::token_type::end_object)
                        {
                            return false;
                        }

                        return true;
                    }
                }

                case lexer::token_type::begin_array:
                {
                    // read next token
                    get_token();

                    // closing ] -> we are done
                    if (last_token == lexer::token_type::end_array)
                    {
                        return true;
                    }

                    // parse values
                    while (true)
                    {
                        // parse value
                        if (not accept_internal())
                        {
                            return false;
                        }

                        // comma -> next value
                        get_token();
                        if (last_token == lexer::token_type::value_separator)
                        {
                            get_token();
                            continue;
                        }

                        // closing ]
                        if (last_token != lexer::token_type::end_array)
                        {
                            return false;
                        }

                        return true;
                    }
                }

                case lexer::token_type::literal_false:
                case lexer::token_type::literal_null:
                case lexer::token_type::literal_true:
                case lexer::token_type::value_float:
                case lexer::token_type::value_integer:
                case lexer::token_type::value_string:
                case lexer::token_type::value_unsigned:
                {
                    return true;
                }

                default:
                {
                    // the last token was unexpected
                    return false;
                }
            }
        }

        typename lexer::token_type get_token()
        {
            last_token = m_lexer.scan();
            return last_token;
        }

        void expect(typename lexer::token_type t) const
        {
            if (JSON_UNLIKELY(t != last_token))
            {
                std::string error_msg = "syntax error - ";
                if (last_token == lexer::token_type::parse_error)
                {
                    error_msg += m_lexer.get_error_message() + "; last read: '" + m_lexer.get_token_string() + "'";
                }
                else
                {
                    error_msg += "unexpected " + std::string(lexer::token_type_name(last_token));
                }

                error_msg += "; expected " + std::string(lexer::token_type_name(t));
                JSON_THROW(parse_error::create(101, m_lexer.get_position(), error_msg));
            }
        }

        void unexpect(typename lexer::token_type t) const
        {
            if (JSON_UNLIKELY(t == last_token))
            {
                std::string error_msg = "syntax error - ";
                if (last_token == lexer::token_type::parse_error)
                {
                    error_msg += m_lexer.get_error_message() + "; last read '" + m_lexer.get_token_string() + "'";
                }
                else
                {
                    error_msg += "unexpected " + std::string(lexer::token_type_name(last_token));
                }

                JSON_THROW(parse_error::create(101, m_lexer.get_position(), error_msg));
            }
        }

      private:
        int depth = 0;
        const parser_callback_t callback = nullptr;
        typename lexer::token_type last_token = lexer::token_type::uninitialized;
        lexer m_lexer;
    };

  public:
    class json_pointer
    {
        friend class basic_json;

      public:
        explicit json_pointer(const std::string& s = "")
            : reference_tokens(split(s))
        {}

        std::string to_string() const noexcept
        {
            return std::accumulate(reference_tokens.begin(),
                                   reference_tokens.end(), std::string{},
                                   [](const std::string & a, const std::string & b)
            {
                return a + "/" + escape(b);
            });
        }

        operator std::string() const
        {
            return to_string();
        }

      private:
        std::string pop_back()
        {
            if (is_root())
            {
                JSON_THROW(out_of_range::create(405, "JSON pointer has no parent"));
            }

            auto last = reference_tokens.back();
            reference_tokens.pop_back();
            return last;
        }

        bool is_root() const
        {
            return reference_tokens.empty();
        }

        json_pointer top() const
        {
            if (is_root())
            {
                JSON_THROW(out_of_range::create(405, "JSON pointer has no parent"));
            }

            json_pointer result = *this;
            result.reference_tokens = {reference_tokens[0]};
            return result;
        }

        reference get_and_create(reference j) const
        {
            pointer result = &j;

            // in case no reference tokens exist, return a reference to the
            // JSON value j which will be overwritten by a primitive value
            for (const auto& reference_token : reference_tokens)
            {
                switch (result->m_type)
                {
                    case value_t::null:
                    {
                        if (reference_token == "0")
                        {
                            // start a new array if reference token is 0
                            result = &result->operator[](0);
                        }
                        else
                        {
                            // start a new object otherwise
                            result = &result->operator[](reference_token);
                        }
                        break;
                    }

                    case value_t::object:
                    {
                        // create an entry in the object
                        result = &result->operator[](reference_token);
                        break;
                    }

                    case value_t::array:
                    {
                        // create an entry in the array
                        JSON_TRY
                        {
                            result = &result->operator[](static_cast<size_type>(std::stoi(reference_token)));
                        }
                        JSON_CATCH (std::invalid_argument&)
                        {
                            JSON_THROW(parse_error::create(109, 0, "array index '" + reference_token + "' is not a number"));
                        }
                        break;
                    }

                    /*
                    The following code is only reached if there exists a
                    reference token _and_ the current value is primitive. In
                    this case, we have an error situation, because primitive
                    values may only occur as single value; that is, with an
                    empty list of reference tokens.
                    */
                    default:
                    {
                        JSON_THROW(type_error::create(313, "invalid value to unflatten"));
                    }
                }
            }

            return *result;
        }

        reference get_unchecked(pointer ptr) const
        {
            for (const auto& reference_token : reference_tokens)
            {
                // convert null values to arrays or objects before continuing
                if (ptr->m_type == value_t::null)
                {
                    // check if reference token is a number
                    const bool nums = std::all_of(reference_token.begin(),
                                                  reference_token.end(),
                                                  [](const char x)
                    {
                        return (x >= '0' and x <= '9');
                    });

                    // change value to array for numbers or "-" or to object
                    // otherwise
                    if (nums or reference_token == "-")
                    {
                        *ptr = value_t::array;
                    }
                    else
                    {
                        *ptr = value_t::object;
                    }
                }

                switch (ptr->m_type)
                {
                    case value_t::object:
                    {
                        // use unchecked object access
                        ptr = &ptr->operator[](reference_token);
                        break;
                    }

                    case value_t::array:
                    {
                        // error condition (cf. RFC 6901, Sect. 4)
                        if (reference_token.size() > 1 and reference_token[0] == '0')
                        {
                            JSON_THROW(parse_error::create(106, 0, "array index '" + reference_token + "' must not begin with '0'"));
                        }

                        if (reference_token == "-")
                        {
                            // explicitly treat "-" as index beyond the end
                            ptr = &ptr->operator[](ptr->m_value.array->size());
                        }
                        else
                        {
                            // convert array index to number; unchecked access
                            JSON_TRY
                            {
                                ptr = &ptr->operator[](static_cast<size_type>(std::stoi(reference_token)));
                            }
                            JSON_CATCH (std::invalid_argument&)
                            {
                                JSON_THROW(parse_error::create(109, 0, "array index '" + reference_token + "' is not a number"));
                            }
                        }
                        break;
                    }

                    default:
                    {
                        JSON_THROW(out_of_range::create(404, "unresolved reference token '" + reference_token + "'"));
                    }
                }
            }

            return *ptr;
        }

        reference get_checked(pointer ptr) const
        {
            for (const auto& reference_token : reference_tokens)
            {
                switch (ptr->m_type)
                {
                    case value_t::object:
                    {
                        // note: at performs range check
                        ptr = &ptr->at(reference_token);
                        break;
                    }

                    case value_t::array:
                    {
                        if (reference_token == "-")
                        {
                            // "-" always fails the range check
                            JSON_THROW(out_of_range::create(402, "array index '-' (" +
                                                            std::to_string(ptr->m_value.array->size()) +
                                                            ") is out of range"));
                        }

                        // error condition (cf. RFC 6901, Sect. 4)
                        if (reference_token.size() > 1 and reference_token[0] == '0')
                        {
                            JSON_THROW(parse_error::create(106, 0, "array index '" + reference_token + "' must not begin with '0'"));
                        }

                        // note: at performs range check
                        JSON_TRY
                        {
                            ptr = &ptr->at(static_cast<size_type>(std::stoi(reference_token)));
                        }
                        JSON_CATCH (std::invalid_argument&)
                        {
                            JSON_THROW(parse_error::create(109, 0, "array index '" + reference_token + "' is not a number"));
                        }
                        break;
                    }

                    default:
                    {
                        JSON_THROW(out_of_range::create(404, "unresolved reference token '" + reference_token + "'"));
                    }
                }
            }

            return *ptr;
        }

        const_reference get_unchecked(const_pointer ptr) const
        {
            for (const auto& reference_token : reference_tokens)
            {
                switch (ptr->m_type)
                {
                    case value_t::object:
                    {
                        // use unchecked object access
                        ptr = &ptr->operator[](reference_token);
                        break;
                    }

                    case value_t::array:
                    {
                        if (reference_token == "-")
                        {
                            // "-" cannot be used for const access
                            JSON_THROW(out_of_range::create(402, "array index '-' (" +
                                                            std::to_string(ptr->m_value.array->size()) +
                                                            ") is out of range"));
                        }

                        // error condition (cf. RFC 6901, Sect. 4)
                        if (reference_token.size() > 1 and reference_token[0] == '0')
                        {
                            JSON_THROW(parse_error::create(106, 0, "array index '" + reference_token + "' must not begin with '0'"));
                        }

                        // use unchecked array access
                        JSON_TRY
                        {
                            ptr = &ptr->operator[](static_cast<size_type>(std::stoi(reference_token)));
                        }
                        JSON_CATCH (std::invalid_argument&)
                        {
                            JSON_THROW(parse_error::create(109, 0, "array index '" + reference_token + "' is not a number"));
                        }
                        break;
                    }

                    default:
                    {
                        JSON_THROW(out_of_range::create(404, "unresolved reference token '" + reference_token + "'"));
                    }
                }
            }

            return *ptr;
        }

        const_reference get_checked(const_pointer ptr) const
        {
            for (const auto& reference_token : reference_tokens)
            {
                switch (ptr->m_type)
                {
                    case value_t::object:
                    {
                        // note: at performs range check
                        ptr = &ptr->at(reference_token);
                        break;
                    }

                    case value_t::array:
                    {
                        if (reference_token == "-")
                        {
                            // "-" always fails the range check
                            JSON_THROW(out_of_range::create(402, "array index '-' (" +
                                                            std::to_string(ptr->m_value.array->size()) +
                                                            ") is out of range"));
                        }

                        // error condition (cf. RFC 6901, Sect. 4)
                        if (reference_token.size() > 1 and reference_token[0] == '0')
                        {
                            JSON_THROW(parse_error::create(106, 0, "array index '" + reference_token + "' must not begin with '0'"));
                        }

                        // note: at performs range check
                        JSON_TRY
                        {
                            ptr = &ptr->at(static_cast<size_type>(std::stoi(reference_token)));
                        }
                        JSON_CATCH (std::invalid_argument&)
                        {
                            JSON_THROW(parse_error::create(109, 0, "array index '" + reference_token + "' is not a number"));
                        }
                        break;
                    }

                    default:
                    {
                        JSON_THROW(out_of_range::create(404, "unresolved reference token '" + reference_token + "'"));
                    }
                }
            }

            return *ptr;
        }

        static std::vector<std::string> split(const std::string& reference_string)
        {
            std::vector<std::string> result;

            // special case: empty reference string -> no reference tokens
            if (reference_string.empty())
            {
                return result;
            }

            // check if nonempty reference string begins with slash
            if (reference_string[0] != '/')
            {
                JSON_THROW(parse_error::create(107, 1, "JSON pointer must be empty or begin with '/' - was: '" + reference_string + "'"));
            }

            // extract the reference tokens:
            // - slash: position of the last read slash (or end of string)
            // - start: position after the previous slash
            for (
                // search for the first slash after the first character
                size_t slash = reference_string.find_first_of('/', 1),
                // set the beginning of the first reference token
                start = 1;
                // we can stop if start == string::npos+1 = 0
                start != 0;
                // set the beginning of the next reference token
                // (will eventually be 0 if slash == std::string::npos)
                start = slash + 1,
                // find next slash
                slash = reference_string.find_first_of('/', start))
            {
                // use the text between the beginning of the reference token
                // (start) and the last slash (slash).
                auto reference_token = reference_string.substr(start, slash - start);

                // check reference tokens are properly escaped
                for (size_t pos = reference_token.find_first_of('~');
                        pos != std::string::npos;
                        pos = reference_token.find_first_of('~', pos + 1))
                {
                    assert(reference_token[pos] == '~');

                    // ~ must be followed by 0 or 1
                    if (pos == reference_token.size() - 1 or
                            (reference_token[pos + 1] != '0' and
                             reference_token[pos + 1] != '1'))
                    {
                        JSON_THROW(parse_error::create(108, 0, "escape character '~' must be followed with '0' or '1'"));
                    }
                }

                // finally, store the reference token
                unescape(reference_token);
                result.push_back(reference_token);
            }

            return result;
        }

        static void replace_substring(std::string& s,
                                      const std::string& f,
                                      const std::string& t)
        {
            assert(not f.empty());

            for (
                size_t pos = s.find(f);         // find first occurrence of f
                pos != std::string::npos;       // make sure f was found
                s.replace(pos, f.size(), t),    // replace with t
                pos = s.find(f, pos + t.size()) // find next occurrence of f
            );
        }

        static std::string escape(std::string s)
        {
            // escape "~"" to "~0" and "/" to "~1"
            replace_substring(s, "~", "~0");
            replace_substring(s, "/", "~1");
            return s;
        }

        static void unescape(std::string& s)
        {
            // first transform any occurrence of the sequence '~1' to '/'
            replace_substring(s, "~1", "/");
            // then transform any occurrence of the sequence '~0' to '~'
            replace_substring(s, "~0", "~");
        }

        static void flatten(const std::string& reference_string,
                            const basic_json& value,
                            basic_json& result)
        {
            switch (value.m_type)
            {
                case value_t::array:
                {
                    if (value.m_value.array->empty())
                    {
                        // flatten empty array as null
                        result[reference_string] = nullptr;
                    }
                    else
                    {
                        // iterate array and use index as reference string
                        for (size_t i = 0; i < value.m_value.array->size(); ++i)
                        {
                            flatten(reference_string + "/" + std::to_string(i),
                                    value.m_value.array->operator[](i), result);
                        }
                    }
                    break;
                }

                case value_t::object:
                {
                    if (value.m_value.object->empty())
                    {
                        // flatten empty object as null
                        result[reference_string] = nullptr;
                    }
                    else
                    {
                        // iterate object and use keys as reference string
                        for (const auto& element : *value.m_value.object)
                        {
                            flatten(reference_string + "/" + escape(element.first),
                                    element.second, result);
                        }
                    }
                    break;
                }

                default:
                {
                    // add primitive value with its reference string
                    result[reference_string] = value;
                    break;
                }
            }
        }

        static basic_json unflatten(const basic_json& value)
        {
            if (not value.is_object())
            {
                JSON_THROW(type_error::create(314, "only objects can be unflattened"));
            }

            basic_json result;

            // iterate the JSON object values
            for (const auto& element : *value.m_value.object)
            {
                if (not element.second.is_primitive())
                {
                    JSON_THROW(type_error::create(315, "values in object must be primitive"));
                }

                // assign value to reference pointed to by JSON pointer; Note
                // that if the JSON pointer is "" (i.e., points to the whole
                // value), function get_and_create returns a reference to
                // result itself. An assignment will then create a primitive
                // value.
                json_pointer(element.first).get_and_create(result) = element.second;
            }

            return result;
        }

        friend bool operator==(json_pointer const& lhs,
                               json_pointer const& rhs) noexcept
        {
            return lhs.reference_tokens == rhs.reference_tokens;
        }

        friend bool operator!=(json_pointer const& lhs,
                               json_pointer const& rhs) noexcept
        {
            return !(lhs == rhs);
        }

        std::vector<std::string> reference_tokens {};
    };

    // JSON Pointer support //


    reference operator[](const json_pointer& ptr)
    {
        return ptr.get_unchecked(this);
    }

    const_reference operator[](const json_pointer& ptr) const
    {
        return ptr.get_unchecked(this);
    }

    reference at(const json_pointer& ptr)
    {
        return ptr.get_checked(this);
    }

    const_reference at(const json_pointer& ptr) const
    {
        return ptr.get_checked(this);
    }

    basic_json flatten() const
    {
        basic_json result(value_t::object);
        json_pointer::flatten("", *this, result);
        return result;
    }

    basic_json unflatten() const
    {
        return json_pointer::unflatten(*this);
    }


    // JSON Patch functions //


    basic_json patch(const basic_json& json_patch) const
    {
        // make a working copy to apply the patch to
        basic_json result = *this;

        // the valid JSON Patch operations
        enum class patch_operations {add, remove, replace, move, copy, test, invalid};

        const auto get_op = [](const std::string & op)
        {
            if (op == "add")
            {
                return patch_operations::add;
            }
            if (op == "remove")
            {
                return patch_operations::remove;
            }
            if (op == "replace")
            {
                return patch_operations::replace;
            }
            if (op == "move")
            {
                return patch_operations::move;
            }
            if (op == "copy")
            {
                return patch_operations::copy;
            }
            if (op == "test")
            {
                return patch_operations::test;
            }

            return patch_operations::invalid;
        };

        // wrapper for "add" operation; add value at ptr
        const auto operation_add = [&result](json_pointer & ptr, basic_json val)
        {
            // adding to the root of the target document means replacing it
            if (ptr.is_root())
            {
                result = val;
            }
            else
            {
                // make sure the top element of the pointer exists
                json_pointer top_pointer = ptr.top();
                if (top_pointer != ptr)
                {
                    result.at(top_pointer);
                }

                // get reference to parent of JSON pointer ptr
                const auto last_path = ptr.pop_back();
                basic_json& parent = result[ptr];

                switch (parent.m_type)
                {
                    case value_t::null:
                    case value_t::object:
                    {
                        // use operator[] to add value
                        parent[last_path] = val;
                        break;
                    }

                    case value_t::array:
                    {
                        if (last_path == "-")
                        {
                            // special case: append to back
                            parent.push_back(val);
                        }
                        else
                        {
                            const auto idx = std::stoi(last_path);
                            if (static_cast<size_type>(idx) > parent.size())
                            {
                                // avoid undefined behavior
                                JSON_THROW(out_of_range::create(401, "array index " + std::to_string(idx) + " is out of range"));
                            }
                            else
                            {
                                // default case: insert add offset
                                parent.insert(parent.begin() + static_cast<difference_type>(idx), val);
                            }
                        }
                        break;
                    }

                    default:
                    {
                        // if there exists a parent it cannot be primitive
                        assert(false);  // LCOV_EXCL_LINE
                    }
                }
            }
        };

        // wrapper for "remove" operation; remove value at ptr
        const auto operation_remove = [&result](json_pointer & ptr)
        {
            // get reference to parent of JSON pointer ptr
            const auto last_path = ptr.pop_back();
            basic_json& parent = result.at(ptr);

            // remove child
            if (parent.is_object())
            {
                // perform range check
                auto it = parent.find(last_path);
                if (it != parent.end())
                {
                    parent.erase(it);
                }
                else
                {
                    JSON_THROW(out_of_range::create(403, "key '" + last_path + "' not found"));
                }
            }
            else if (parent.is_array())
            {
                // note erase performs range check
                parent.erase(static_cast<size_type>(std::stoi(last_path)));
            }
        };

        // type check: top level value must be an array
        if (not json_patch.is_array())
        {
            JSON_THROW(parse_error::create(104, 0, "JSON patch must be an array of objects"));
        }

        // iterate and apply the operations
        for (const auto& val : json_patch)
        {
            // wrapper to get a value for an operation
            const auto get_value = [&val](const std::string & op,
                                          const std::string & member,
                                          bool string_type) -> basic_json&
            {
                // find value
                auto it = val.m_value.object->find(member);

                // context-sensitive error message
                const auto error_msg = (op == "op") ? "operation" : "operation '" + op + "'";

                // check if desired value is present
                if (it == val.m_value.object->end())
                {
                    JSON_THROW(parse_error::create(105, 0, error_msg + " must have member '" + member + "'"));
                }

                // check if result is of type string
                if (string_type and not it->second.is_string())
                {
                    JSON_THROW(parse_error::create(105, 0, error_msg + " must have string member '" + member + "'"));
                }

                // no error: return value
                return it->second;
            };

            // type check: every element of the array must be an object
            if (not val.is_object())
            {
                JSON_THROW(parse_error::create(104, 0, "JSON patch must be an array of objects"));
            }

            // collect mandatory members
            const std::string op = get_value("op", "op", true);
            const std::string path = get_value(op, "path", true);
            json_pointer ptr(path);

            switch (get_op(op))
            {
                case patch_operations::add:
                {
                    operation_add(ptr, get_value("add", "value", false));
                    break;
                }

                case patch_operations::remove:
                {
                    operation_remove(ptr);
                    break;
                }

                case patch_operations::replace:
                {
                    // the "path" location must exist - use at()
                    result.at(ptr) = get_value("replace", "value", false);
                    break;
                }

                case patch_operations::move:
                {
                    const std::string from_path = get_value("move", "from", true);
                    json_pointer from_ptr(from_path);

                    // the "from" location must exist - use at()
                    basic_json v = result.at(from_ptr);

                    // The move operation is functionally identical to a
                    // "remove" operation on the "from" location, followed
                    // immediately by an "add" operation at the target
                    // location with the value that was just removed.
                    operation_remove(from_ptr);
                    operation_add(ptr, v);
                    break;
                }

                case patch_operations::copy:
                {
                    const std::string from_path = get_value("copy", "from", true);;
                    const json_pointer from_ptr(from_path);

                    // the "from" location must exist - use at()
                    result[ptr] = result.at(from_ptr);
                    break;
                }

                case patch_operations::test:
                {
                    bool success = false;
                    JSON_TRY
                    {
                        // check if "value" matches the one at "path"
                        // the "path" location must exist - use at()
                        success = (result.at(ptr) == get_value("test", "value", false));
                    }
                    JSON_CATCH (out_of_range&)
                    {
                        // ignore out of range errors: success remains false
                    }

                    // throw an exception if test fails
                    if (not success)
                    {
                        JSON_THROW(other_error::create(501, "unsuccessful: " + val.dump()));
                    }

                    break;
                }

                case patch_operations::invalid:
                {
                    // op must be "add", "remove", "replace", "move", "copy", or
                    // "test"
                    JSON_THROW(parse_error::create(105, 0, "operation value '" + op + "' is invalid"));
                }
            }
        }

        return result;
    }

    static basic_json diff(const basic_json& source,
                           const basic_json& target,
                           const std::string& path = "")
    {
        // the patch
        basic_json result(value_t::array);

        // if the values are the same, return empty patch
        if (source == target)
        {
            return result;
        }

        if (source.type() != target.type())
        {
            // different types: replace value
            result.push_back(
            {
                {"op", "replace"},
                {"path", path},
                {"value", target}
            });
        }
        else
        {
            switch (source.type())
            {
                case value_t::array:
                {
                    // first pass: traverse common elements
                    size_t i = 0;
                    while (i < source.size() and i < target.size())
                    {
                        // recursive call to compare array values at index i
                        auto temp_diff = diff(source[i], target[i], path + "/" + std::to_string(i));
                        result.insert(result.end(), temp_diff.begin(), temp_diff.end());
                        ++i;
                    }

                    // i now reached the end of at least one array
                    // in a second pass, traverse the remaining elements

                    // remove my remaining elements
                    const auto end_index = static_cast<difference_type>(result.size());
                    while (i < source.size())
                    {
                        // add operations in reverse order to avoid invalid
                        // indices
                        result.insert(result.begin() + end_index, object(
                        {
                            {"op", "remove"},
                            {"path", path + "/" + std::to_string(i)}
                        }));
                        ++i;
                    }

                    // add other remaining elements
                    while (i < target.size())
                    {
                        result.push_back(
                        {
                            {"op", "add"},
                            {"path", path + "/" + std::to_string(i)},
                            {"value", target[i]}
                        });
                        ++i;
                    }

                    break;
                }

                case value_t::object:
                {
                    // first pass: traverse this object's elements
                    for (auto it = source.begin(); it != source.end(); ++it)
                    {
                        // escape the key name to be used in a JSON patch
                        const auto key = json_pointer::escape(it.key());

                        if (target.find(it.key()) != target.end())
                        {
                            // recursive call to compare object values at key it
                            auto temp_diff = diff(it.value(), target[it.key()], path + "/" + key);
                            result.insert(result.end(), temp_diff.begin(), temp_diff.end());
                        }
                        else
                        {
                            // found a key that is not in o -> remove it
                            result.push_back(object(
                            {
                                {"op", "remove"},
                                {"path", path + "/" + key}
                            }));
                        }
                    }

                    // second pass: traverse other object's elements
                    for (auto it = target.begin(); it != target.end(); ++it)
                    {
                        if (source.find(it.key()) == source.end())
                        {
                            // found a key that is not in this -> add it
                            const auto key = json_pointer::escape(it.key());
                            result.push_back(
                            {
                                {"op", "add"},
                                {"path", path + "/" + key},
                                {"value", it.value()}
                            });
                        }
                    }

                    break;
                }

                default:
                {
                    // both primitive type: replace value
                    result.push_back(
                    {
                        {"op", "replace"},
                        {"path", path},
                        {"value", target}
                    });
                    break;
                }
            }
        }

        return result;
    }

};

// presets //

using json = basic_json<>;
} // namespace nlohmann


// nonmember support //

// specialization of std::swap, and std::hash
namespace std
{
template<>
inline void swap(nlohmann::json& j1,
                 nlohmann::json& j2) noexcept(
                     is_nothrow_move_constructible<nlohmann::json>::value and
                     is_nothrow_move_assignable<nlohmann::json>::value
                 )
{
    j1.swap(j2);
}

template<>
struct hash<nlohmann::json>
{
    std::size_t operator()(const nlohmann::json& j) const
    {
        // a naive hashing via the string representation
        const auto& h = hash<nlohmann::json::string_t>();
        return h(j.dump());
    }
};

template <>
struct less<::nlohmann::detail::value_t>
{
    bool operator()(nlohmann::detail::value_t lhs,
                    nlohmann::detail::value_t rhs) const noexcept
    {
        return nlohmann::detail::operator<(lhs, rhs);
    }
};

} // namespace std

inline nlohmann::json operator "" _json(const char* s, std::size_t n)
{
    return nlohmann::json::parse(s, s + n);
}

inline nlohmann::json::json_pointer operator "" _json_pointer(const char* s, std::size_t n)
{
    return nlohmann::json::json_pointer(std::string(s, n));
}

// restore GCC/clang diagnostic settings
#if defined(__clang__) || defined(__GNUC__) || defined(__GNUG__)
    #pragma GCC diagnostic pop
#endif
#if defined(__clang__)
    #pragma GCC diagnostic pop
#endif

// clean up
#undef JSON_CATCH
#undef JSON_THROW
#undef JSON_TRY
#undef JSON_LIKELY
#undef JSON_UNLIKELY
#undef JSON_DEPRECATED

#endif