cpipedeflate.cpp

研读AxCrypt对加解密的处理方法

/*! \file
    \brief Implementation of AxPipe::Stock::CPipeDeflate

    @(#) $Id$

    AxPipe - Binary Stream Framework

    Copyright (C) 2005 Svante Seleborg/Axon Data, All rights reserved.

    This program is free software; you can redistribute it and/or modify it under the terms
    of the GNU General Public License as published by the Free Software Foundation;
    either version 2 of the License, or (at your option) any later version.

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License along with this program;
    if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
    Boston, MA 02111-1307 USA

    The author may be reached at mailto:[e-mail] and http://axpipe.sourceforge.net

    Why is this framework released as GPL and not LGPL? See http://www.gnu.org/philosophy/why-not-lgpl.html

----
\verbatim
    E-mail                          YYYY-MM-DD              Reason
    [e-mail]              2005-11-04              Initial
\endverbatim
*/
#include "stdafx.h"
#include "CPipeDeflate.h"
#include "AxAssert.h"
#define AXLIB_ASSERT_FILE "CPipeDeflate.cpp"

// Can't use this for convenient notation below:
// using AxPipe::Stock::CPipeInflate;
// because the Doxygen get's confused.

namespace AxPipe {
    namespace Stock {
        static voidpf zalloc OF((voidpf opaque, uInt items, uInt size)) {
            // The semantics of zalloc are a bit unclear, so we always zero the memory...
            return memset(new unsigned char[items * size], 0, items * size);
        }

        static void zfree OF((voidpf opaque, voidpf address)) {
            delete[] static_cast<unsigned char *>(address);
        }

        /// \brief Initialize member variables
        CPipeDeflate::CPipeDeflate() {
            m_cbChunkSize = 0;
            m_cbFlushInterval = 0;
            m_pOutSeg = NULL;
            m_cbIn = 0;
            m_cbOut = 0;
            ZeroMemory(&m_Zstream, sizeof m_Zstream);
        }

        ///< \brief Initialize the flush interval
        /// \param cbChunkSize The size we output in. Collect this much before outputting.
        /// \param cbFlushInterval The frequence with which we make resync possible at decompression time. 0 means never.
        CPipeDeflate *CPipeDeflate::Init(int nSaveRatioForCompress, size_t cbChunkSize, size_t cbFlushInterval) {
            m_nSaveRatioForCompress = nSaveRatioForCompress;
            m_cbChunkSize = cbChunkSize;
            m_cbFlushInterval = cbFlushInterval;
            return this;
        }

        /// Clean up if necessary, should only need
        /// work to be done on error.
        CPipeDeflate::~CPipeDeflate() {
            if (m_pOutSeg) {
                m_pOutSeg->Release();
            }
        }

        /// Private helper to send the current segment onwards. m_pOutSeg is
        /// always NULL at return.
        void
        CPipeDeflate::SendOut() {
            if (m_pOutSeg) {
                // Update statistics
                m_cbOut += m_Zstream.total_out;
                m_Zstream.total_out = 0;

                m_pOutSeg->Len(m_pOutSeg->Len() - m_Zstream.avail_out);
                Pump(m_pOutSeg);
                m_pOutSeg = NULL;
            }
        }

        /// Allocate a new segment to deflate to, and update the z_stream structure accordingly
        void
        CPipeDeflate::AllocNew() {
            // Get a new segment, either of the chunk size, or the available in plus 6 (see zlib docs)
            m_pOutSeg = new AxPipe::CSeg(m_cbChunkSize ? m_cbChunkSize : (m_Zstream.avail_in/2 + 6));
            ASSPTR(m_pOutSeg);

            m_Zstream.next_out = m_pOutSeg->PtrWr();
            m_Zstream.avail_out = static_cast<UINT>(m_pOutSeg->Size());
        }

        /// Initialize the z_stream structure, including memory allocation functions
        /// \param pZstream Pointer to a z_stream structure
        void
        CPipeDeflate::InitZstream(z_stream *pZstream) {
            memset(pZstream, 0, sizeof *pZstream);
            pZstream->zalloc = zalloc;      // Use our custom alloc()
            pZstream->zfree = zfree;        // Use our custom free()

            if (deflateInit(pZstream, Z_DEFAULT_COMPRESSION) != Z_OK) {
                SetError(ERROR_CODE_STOCK, _T("ZLIB initialization error"));
            }
        }

        longlong CPipeDeflate::GetOutputSize() {
            return m_cbOut;
        }

        longlong CPipeDeflate::GetInputSize() {
            return m_cbIn;
        }

        int CPipeDeflate::TryDeflateLoop(AxPipe::CSeg *pSeg, z_stream *pZstream) {
            int iZerror;
            do {
                // We now have updated available input, so we call deflate and check the result...
                iZerror = deflate(pZstream, Z_FINISH);
                switch (iZerror) {
                    case Z_OK:
                        // re-use the buffer - we're not really interested in the data as such
                        pZstream->next_out = const_cast<unsigned char *>(pSeg->PtrRd());
                        pZstream->avail_out = static_cast<uInt>(pSeg->Len());
                        break;
                    case Z_STREAM_END:
                        break;
                    case Z_BUF_ERROR:
                    case Z_STREAM_ERROR:
                    default:
                        SetError(ERROR_CODE_STOCK, _T("ZLIB sequence error in CPipeDeflate::TryDeflate()"));
                        return iZerror;
                }
            } while (iZerror != Z_STREAM_END);
            return iZerror;
        }

        /// Try deflation of a memory buffer and return the resulting size
        /// \param p Pointer to data to try to deflate
        /// \param cb The number of bytes in the data buffer
        /// \return The total number of bytes necessary, including overhead
        size_t
        CPipeDeflate::TryDeflate(const void *p, size_t cb) {
            z_stream Zstream;
            InitZstream(&Zstream);

            // Allocate a reasonable buffer, at least 6 bytes large (to make room for header)
            AxPipe::CSeg *pSeg = new AxPipe::CSeg(cb/2+6);
            Zstream.next_in = const_cast<unsigned char *>(static_cast<const unsigned char *>(p));
            Zstream.avail_in = static_cast<uInt>(cb);
            Zstream.next_out = const_cast<unsigned char *>(pSeg->PtrRd());
            Zstream.avail_out = static_cast<uInt>(pSeg->Len());

            int iZerror = TryDeflateLoop(pSeg, &Zstream);
            pSeg->Release();

            // Clean up memory allocations etc
            if (deflateEnd(&Zstream) != Z_OK) {
                SetError(ERROR_CODE_DERIVED, _T("ZLIB error in deflateEnd error"));
                return 0;
            }

            if (iZerror != Z_STREAM_END) {
                return 0;
            }
            return Zstream.total_out;
        }

        bool
        CPipeDeflate::IsDeflatable(AxPipe::CSeg *pSeg, int nSaveRatioForCompress) {
            size_t nDeflatedForPercent = TryDeflate(pSeg->PtrRd(), pSeg->Len());
            size_t nOriginalForPercent = pSeg->Len();
            if (nDeflatedForPercent < (~size_t(0))/size_t(100)) {
                nDeflatedForPercent *= 100;
            } else {
                nOriginalForPercent /= 100;
                if (nOriginalForPercent == 0) {
                    // Avoid division by zero
                    nOriginalForPercent = 1;
                }
            }
            int nSaveRatio = 100 - static_cast<int>(nDeflatedForPercent/nOriginalForPercent);
            if (nSaveRatio < 0) {
                nSaveRatio = 0;
            }
            return nSaveRatio >= m_nSaveRatioForCompress;
        }

        bool 
        CPipeDeflate::IsDeflating() {
            return m_fDeflate;
        }

        /// Initialize zlib for this deflation.
        /// \return true to continue cascading of Open()
        bool
        CPipeDeflate::OutOpen() {
            bool fReturn = CPipe::OutOpen();        // Open base first, like constructor
            m_cbOut = 0;                            // Total output bytes counter
            m_cbIn = 0;                             // Total input bytes counter
            m_cbRemainBeforeFlush = 0;
            m_fDeflate = true;                      // Default is to deflate
            InitZstream(&m_Zstream);                // Since we're assuming we're actually to deflate...
            AllocNew();
            ASSPTR(m_pOutSeg);

            return fReturn;                         // Return the saved return code.
        }

        /// Compress output as it arrives. We also produce Z_FULL_FLUSH periodically to
        /// ensure that there is a certain redundancy. We always consume all data that is
        /// input, but it may be sent onwards in multiple segments.
        /// \param pSeg A segment with compressed data, and no trailing if last
        void
        CPipeDeflate::Out(AxPipe::CSeg *pSeg) {
            // If we're asked to try before compression, test once
            if (m_nSaveRatioForCompress) {
                m_fDeflate = IsDeflatable(pSeg, m_nSaveRatioForCompress);
                m_nSaveRatioForCompress = 0;
            }

            // If we're not deflating, just pass the segment onwards.
            if (!m_fDeflate) {
                m_cbIn = m_cbOut += pSeg->Len();
                Pump(pSeg);
                return;
            }

            size_t cb = pSeg->Len();
            unsigned char *p = const_cast<unsigned char *>(pSeg->PtrRd());
            while (cb) {
                m_Zstream.next_in = p;
                size_t cbThisCall = cb;
                if (m_cbFlushInterval) {
                    if (m_cbRemainBeforeFlush == 0) {
                        m_cbRemainBeforeFlush = m_cbFlushInterval;
                    }
                    cbThisCall = cb > m_cbRemainBeforeFlush ? m_cbRemainBeforeFlush : cb;
                    m_cbRemainBeforeFlush -= cbThisCall;
                }

                // The amount to consume is determined by how much is available, and the flush interval
                m_Zstream.avail_in = static_cast<uInt>(cbThisCall);
                p += cbThisCall;
                cb -= cbThisCall;

                while (m_Zstream.avail_in) {
                    do {
                        if (m_Zstream.avail_out == 0) {
                            SendOut();
                            AllocNew();
                        }

                        // We now have updated available input, so we call deflate and check the result...
                        int iZerror = deflate(&m_Zstream, (m_cbFlushInterval && (m_cbRemainBeforeFlush == 0)) ? Z_FULL_FLUSH : 0);
                        switch (iZerror) {
                            case Z_OK:
                                break;
                            case Z_BUF_ERROR:
                            case Z_STREAM_END:
                            case Z_STREAM_ERROR:
                            default:
                                SetError(ERROR_CODE_STOCK, _T("ZLIB sequence error in CPipeDeflate::Out()"));
                                return;
                        }
                    } while (m_Zstream.avail_out == 0);
                    m_cbIn += m_Zstream.total_in;
                    m_Zstream.total_in = 0;
                }
            }
        }

        /// Flush all data and end the deflation run.
        /// \return true to cascade the closing of the stream
        bool
        CPipeDeflate::OutClose() {
            if (!GetErrorCode() && m_fDeflate) {
                int iZerror;
                do {
                    iZerror = deflate(&m_Zstream, Z_FINISH);
                    switch (iZerror) {
                        case Z_OK:
                            SendOut();
                            AllocNew();
                            break;
                        case Z_STREAM_END:
                            break;
                        case Z_BUF_ERROR:
                        case Z_STREAM_ERROR:
                        default:
                            SetError(ERROR_CODE_STOCK, _T("ZLIB sequence error in CPipeDeflate::OutClose()"));
                            return false;
                    }
                } while (iZerror != Z_STREAM_END);

                // Final output
                SendOut();
            }

            // Clean up memory allocations etc
            if (deflateEnd(&m_Zstream) != Z_OK) {
                SetError(ERROR_CODE_DERIVED, _T("ZLIB error in deflateEnd error"));
            }

            return base::OutClose();
        }
    }
}