gzip_encoding.h

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// Copyright (c) 2006-2013, Andrey N. Sabelnikov, www.sabelnikov.net
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of the Andrey N. Sabelnikov nor the
// names of its contributors may be used to endorse or promote products
// derived from this software without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER  BE LIABLE FOR ANY
// DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// 
 
 
 
 
#ifndef _GZIP_ENCODING_H_
#define _GZIP_ENCODING_H_
#include "net/http_client_base.h"
#include "zlib/zlib.h"
//#include "http.h"
 
 
namespace epee
{
namespace net_utils
{
 
 
 
    class content_encoding_gzip: public i_sub_handler
    {
    public:
        inline 
        content_encoding_gzip(i_target_handler* powner_filter, bool is_deflate_mode = false):m_powner_filter(powner_filter), 
            m_is_stream_ended(false), 
            m_is_deflate_mode(is_deflate_mode),
            m_is_first_update_in(true)
        {
            memset(&m_zstream_in, 0, sizeof(m_zstream_in));
            memset(&m_zstream_out, 0, sizeof(m_zstream_out));
            int ret = 0;
            if(is_deflate_mode)
            {
                ret = inflateInit(&m_zstream_in);   
                ret = deflateInit(&m_zstream_out, Z_DEFAULT_COMPRESSION);
            }else
            {
                ret = inflateInit2(&m_zstream_in, 0x1F);
                ret = deflateInit2(&m_zstream_out, Z_DEFAULT_COMPRESSION, Z_DEFLATED, 0x1F, 8, Z_DEFAULT_STRATEGY);
            }   
        }

        inline 
        ~content_encoding_gzip()
        {
            inflateEnd(& m_zstream_in );
            deflateEnd(& m_zstream_out );
        }

        inline 
        virtual bool update_in( std::string& piece_of_transfer)
        {   
 
            bool is_first_time_here = m_is_first_update_in;
            m_is_first_update_in = false;
 
            if(m_pre_decode.size())
                m_pre_decode += piece_of_transfer;
            else
                m_pre_decode.swap(piece_of_transfer);
            piece_of_transfer.clear();
 
            std::string decode_summary_buff;
 
            size_t  ungzip_size = m_pre_decode.size() * 0x30;
            std::string current_decode_buff(ungzip_size, 'X');
 
            //Here the cycle is introduced where we unpack the buffer, the cycle is required
            //because of the case where if after unpacking the data will exceed the awaited size, we will not halt with error
            bool continue_unpacking = true;
            bool first_step = true;
            while(m_pre_decode.size() && continue_unpacking)
            {
 
                //fill buffers
                m_zstream_in.next_in = (Bytef*)m_pre_decode.data();
                m_zstream_in.avail_in = (uInt)m_pre_decode.size();
                m_zstream_in.next_out = (Bytef*)current_decode_buff.data();
                m_zstream_in.avail_out = (uInt)ungzip_size;
 
                int flag = Z_SYNC_FLUSH;
                int ret = inflate(&m_zstream_in, flag);
                CHECK_AND_ASSERT_MES(ret>=0 || m_zstream_in.avail_out ||m_is_deflate_mode, false, "content_encoding_gzip::update_in() Failed to inflate. err = " << ret);
 
                if(Z_STREAM_END == ret)
                    m_is_stream_ended = true;
                else if(Z_DATA_ERROR == ret && is_first_time_here && m_is_deflate_mode&& first_step)
                {
                    // some servers (notably Apache with mod_deflate) don't generate zlib headers
                    // insert a dummy header and try again
                    static char dummy_head[2] =
                    {
                        0x8 + 0x7 * 0x10,
                        (((0x8 + 0x7 * 0x10) * 0x100 + 30) / 31 * 31) & 0xFF,
                    };
                    inflateReset(&m_zstream_in);
                    m_zstream_in.next_in = (Bytef*) dummy_head;
                    m_zstream_in.avail_in = sizeof(dummy_head);
 
                    ret = inflate(&m_zstream_in, Z_NO_FLUSH);
                    if (ret != Z_OK)
                    {
                        LOCAL_ASSERT(0);
                        m_pre_decode.swap(piece_of_transfer);
                        return false;
                    }
                    m_zstream_in.next_in = (Bytef*)m_pre_decode.data();
                    m_zstream_in.avail_in = (uInt)m_pre_decode.size();
 
                    ret = inflate(&m_zstream_in, Z_NO_FLUSH);
                    if (ret != Z_OK)
                    {
                        LOCAL_ASSERT(0);
                        m_pre_decode.swap(piece_of_transfer);
                        return false;
                    }
                }
 
 
                //leave only unpacked part in the output buffer to start with it the next time
                m_pre_decode.erase(0, m_pre_decode.size()-m_zstream_in.avail_in);
                //if decoder gave nothing to return, then everything is ahead, now simply break
                if(ungzip_size == m_zstream_in.avail_out)
                    break;
 
                //decode_buff currently stores data parts that were unpacked, fix this size
                current_decode_buff.resize(ungzip_size - m_zstream_in.avail_out);
                if(decode_summary_buff.size())
                    decode_summary_buff += current_decode_buff;
                else
                    current_decode_buff.swap(decode_summary_buff);
 
                current_decode_buff.resize(ungzip_size);
                first_step = false;
            }
 
            //Process these data if required
            bool res = true;
 
            res = m_powner_filter->handle_target_data(decode_summary_buff);
 
            return true;
 
        }

        inline 
        virtual void stop(std::string& OUT collect_remains)
        {
        }
    protected:
    private:
        i_target_handler* m_powner_filter;
        z_stream    m_zstream_in;
        z_stream    m_zstream_out;
        std::string m_pre_decode;
        std::string m_pre_encode;
        bool        m_is_stream_ended;
        bool        m_is_deflate_mode;
        bool        m_is_first_update_in;
    };
}
}
 
 
 
#endif //_GZIP_ENCODING_H_