gzipoutputstreambuf.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 "gzipoutputstreambuf.hpp"

#include "zipios/zipiosexceptions.hpp"


namespace zipios
{

GZIPOutputStreambuf::GZIPOutputStreambuf(std::streambuf * outbuf, FileEntry::CompressionLevel compression_level)
    : DeflateOutputStreambuf(outbuf)
{
    if(!init(compression_level))
    {
        throw InvalidStateException("GZIPOutputStreambuf::GZIPOutputStreambuf() failed initializing zlib.");
    }
}


GZIPOutputStreambuf::~GZIPOutputStreambuf()
{
    finish();
}


void GZIPOutputStreambuf::setFilename(std::string const & filename)
{
    m_filename = filename;
}


void GZIPOutputStreambuf::setComment(std::string const & comment)
{
    m_comment = comment;
}


void GZIPOutputStreambuf::close()
{
    finish();
}


void GZIPOutputStreambuf::finish()
{
    if(!m_open)
    {
        return;
    }
    m_open = false;

    closeStream();
    writeTrailer();
}


int GZIPOutputStreambuf::overflow(int c)
{
    if(!m_open)
    {
        writeHeader();
        m_open = true;
    }

    return DeflateOutputStreambuf::overflow(c);
}


int GZIPOutputStreambuf::sync()
{
    return DeflateOutputStreambuf::sync();
}


void GZIPOutputStreambuf::writeHeader()
{
    unsigned char const flg(
                  (m_filename.empty() ? 0x00 : 0x08)
                | (m_comment.empty()  ? 0x00 : 0x10)
            );

    std::ostream os(m_outbuf);
    os << static_cast<unsigned char>(0x1f);  // Magic #
    os << static_cast<unsigned char>(0x8b);  // Magic #
    os << static_cast<unsigned char>(0x08);  // Deflater.DEFLATED
    os << flg;                               // FLG
    os << static_cast<unsigned char>(0x00);  // MTIME
    os << static_cast<unsigned char>(0x00);  // MTIME
    os << static_cast<unsigned char>(0x00);  // MTIME
    os << static_cast<unsigned char>(0x00);  // MTIME
    os << static_cast<unsigned char>(0x00);  // XFLG
    os << static_cast<unsigned char>(0x00);  // OS

    if(!m_filename.empty())
    {
        os << m_filename.c_str();             // Filename
        os << static_cast<unsigned char>(0x00);
    }

    if(!m_comment.empty())
    {
        os << m_comment.c_str();              // Comment
        os << static_cast<unsigned char>(0x00);
    }
}


void GZIPOutputStreambuf::writeTrailer()
{
    // write the CRC32 and Size at the end of the file
    writeInt(getCrc32());
    writeInt(getSize());
}


void GZIPOutputStreambuf::writeInt(uint32_t i)
{
    std::ostream os(m_outbuf);
    os << static_cast<unsigned char>( i        & 0xFF);
    os << static_cast<unsigned char>((i >>  8) & 0xFF);
    os << static_cast<unsigned char>((i >> 16) & 0xFF);
    os << static_cast<unsigned char>((i >> 24) & 0xFF);
}


} // zipios namespace

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// mode: cpp
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// c-basic-offset: 4
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// End:

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