zipendofcentraldirectory.cpp

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/*
  Zipios -- a small C++ library that provides easy access to .zip files.

  Copyright (C) 2000-2007  Thomas Sondergaard
  Copyright (c) 2015-2022  Made to Order Software Corp.  All Rights Reserved

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "zipendofcentraldirectory.hpp"

#include "zipios/zipiosexceptions.hpp"


namespace zipios
{


namespace
{


uint32_t const g_signature = 0x06054b50;


} // no name namespace


ZipEndOfCentralDirectory::ZipEndOfCentralDirectory(std::string const & zip_comment)
    : m_zip_comment(zip_comment)
{
}


size_t ZipEndOfCentralDirectory::getCentralDirectorySize() const
{
    return m_central_directory_size;
}


size_t ZipEndOfCentralDirectory::getCount() const
{
    return m_central_directory_entries;
}


offset_t ZipEndOfCentralDirectory::getOffset() const
{
    return m_central_directory_offset;
}


void ZipEndOfCentralDirectory::setCentralDirectorySize(size_t size)
{
    m_central_directory_size = size;
}


void ZipEndOfCentralDirectory::setCount(size_t count)
{
    m_central_directory_entries = count;
}


void ZipEndOfCentralDirectory::setOffset(offset_t start_offset)
{
    m_central_directory_offset = start_offset;
}


bool ZipEndOfCentralDirectory::read(::zipios::buffer_t const & buf, size_t pos)
{
    // the number of bytes we are going to read in the buffer
    // (including the signature)
    ssize_t const HEADER_SIZE(static_cast<ssize_t>(sizeof(uint32_t) * 3 + sizeof(uint16_t) * 5));

    // enough data in the buffer?
    //
    // Note: this quick check assumes a 0 length comment which is possible;
    //       if there is a comment and we find the signature too early, then
    //       it will throw
    //
    if(static_cast<ssize_t>(buf.size() - pos) < HEADER_SIZE)
    {
        return false;
    }

    // first read and check the signature
    uint32_t signature;
    zipRead(buf, pos, signature);               // 32
    if(signature != g_signature)
    {
        return false;
    }

    // next we read the other parameters
    uint16_t disk_number;
    uint16_t central_directory_entries;
    uint16_t central_directory_total_entries;
    uint32_t central_directory_size;
    uint32_t central_directory_offset;
    uint16_t comment_len;

    zipRead(buf, pos, disk_number);                         // 16
    zipRead(buf, pos, disk_number);                         // 16
    zipRead(buf, pos, central_directory_entries);           // 16
    zipRead(buf, pos, central_directory_total_entries);     // 16
    zipRead(buf, pos, central_directory_size);              // 32
    zipRead(buf, pos, central_directory_offset);            // 32
    zipRead(buf, pos, comment_len);                         // 16
    zipRead(buf, pos, m_zip_comment, comment_len);          // string

    // note that if disk_number is defined, then these following two
    // numbers should differ too
    if(central_directory_entries != central_directory_total_entries)
    {
        throw FileCollectionException("ZipEndOfCentralDirectory with a number of entries and total entries that differ is not supported, spanned zip files are not supported");
    }

    m_central_directory_entries = central_directory_entries;
    m_central_directory_size    = central_directory_size;
    m_central_directory_offset  = central_directory_offset;

    return true;
}


void ZipEndOfCentralDirectory::write(std::ostream & os)
{
    if(m_zip_comment.length() > 65535)
    {
        throw InvalidStateException("the Zip archive comment is too large");
    }
    if(m_central_directory_entries > 65535)
    {
        throw InvalidStateException("the number of entries in the Zip archive is too large");
    }
// Solaris defines _ILP32 for 32 bit platforms
#if INTPTR_MAX != INT32_MAX
    if(m_central_directory_size   >= 0x100000000UL
    || m_central_directory_offset >= 0x100000000L)
    {
        throw FileCollectionException("the Zip archive size or offset are too large"); // LCOV_EXCL_LINE
    }
#endif

    uint16_t const disk_number(0);
    uint16_t const central_directory_entries(m_central_directory_entries);
    uint32_t const central_directory_size(m_central_directory_size);
    uint32_t const central_directory_offset(m_central_directory_offset);
    uint16_t const comment_len(m_zip_comment.length());

    // the total number of entries, across all disks is the same in our
    // case so we use one number for both fields

    zipWrite(os, g_signature);                      // 32
    zipWrite(os, disk_number);                      // 16
    zipWrite(os, disk_number);                      // 16
    zipWrite(os, central_directory_entries);        // 16
    zipWrite(os, central_directory_entries);        // 16
    zipWrite(os, central_directory_size);           // 32
    zipWrite(os, central_directory_offset);         // 32
    zipWrite(os, comment_len);                      // 16
    zipWrite(os, m_zip_comment);                    // string
}


} // zipios namespace

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