zdeflate.cpp

// zdeflate.cpp - originally written and placed in the public domain by Wei Dai

// Many of the algorithms and tables used here came from the deflate implementation
// by Jean-loup Gailly, which was included in Crypto++ 4.0 and earlier. I completely
// rewrote it in order to fix a bug that I could not figure out. This code
// is less clever, but hopefully more understandable and maintainable.

#include "pch.h"
#include "zdeflate.h"
#include "stdcpp.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

#if (defined(_MSC_VER) && (_MSC_VER < 1400)) && !defined(__MWERKS__)
    // VC60 and VC7 workaround: built-in std::reverse_iterator has two template parameters, Dinkumware only has one
    typedef std::reverse_bidirectional_iterator<unsigned int *, unsigned int> RevIt;
#elif defined(_RWSTD_NO_CLASS_PARTIAL_SPEC)
    typedef std::reverse_iterator<unsigned int *, std::random_access_iterator_tag, unsigned int> RevIt;
#else
    typedef std::reverse_iterator<unsigned int *> RevIt;
#endif

LowFirstBitWriter::LowFirstBitWriter(BufferedTransformation *attachment)
    : Filter(attachment), m_counting(false), m_bitCount(0), m_buffer(0)
    , m_bitsBuffered(0), m_bytesBuffered(0)
{
}

void LowFirstBitWriter::StartCounting()
{
    CRYPTOPP_ASSERT(!m_counting);
    m_counting = true;
    m_bitCount = 0;
}

unsigned long LowFirstBitWriter::FinishCounting()
{
    CRYPTOPP_ASSERT(m_counting);
    m_counting = false;
    return m_bitCount;
}

void LowFirstBitWriter::PutBits(unsigned long value, unsigned int length)
{
    if (m_counting)
        m_bitCount += length;
    else
    {
        m_buffer |= value << m_bitsBuffered;
        m_bitsBuffered += length;
        CRYPTOPP_ASSERT(m_bitsBuffered <= sizeof(unsigned long)*8);
        while (m_bitsBuffered >= 8)
        {
            m_outputBuffer[m_bytesBuffered++] = (byte)m_buffer;
            if (m_bytesBuffered == m_outputBuffer.size())
            {
                AttachedTransformation()->PutModifiable(m_outputBuffer, m_bytesBuffered);
                m_bytesBuffered = 0;
            }
            m_buffer >>= 8;
            m_bitsBuffered -= 8;
        }
    }
}

void LowFirstBitWriter::FlushBitBuffer()
{
    if (m_counting)
        m_bitCount += 8*(m_bitsBuffered > 0);
    else
    {
        if (m_bytesBuffered > 0)
        {
            AttachedTransformation()->PutModifiable(m_outputBuffer, m_bytesBuffered);
            m_bytesBuffered = 0;
        }
        if (m_bitsBuffered > 0)
        {
            AttachedTransformation()->Put((byte)m_buffer);
            m_buffer = 0;
            m_bitsBuffered = 0;
        }
    }
}

void LowFirstBitWriter::ClearBitBuffer()
{
    m_buffer = 0;
    m_bytesBuffered = 0;
    m_bitsBuffered = 0;
}

HuffmanEncoder::HuffmanEncoder(const unsigned int *codeBits, unsigned int nCodes)
{
    Initialize(codeBits, nCodes);
}

struct HuffmanNode
{
    // Coverity finding on uninitialized 'symbol' member
    HuffmanNode()
        : symbol(0), parent(0) {}
    HuffmanNode(const HuffmanNode& rhs)
        : symbol(rhs.symbol), parent(rhs.parent) {}

    size_t symbol;
    union {size_t parent; unsigned depth, freq;};
};

struct FreqLessThan
{
    inline bool operator()(unsigned int lhs, const HuffmanNode &rhs) {return lhs < rhs.freq;}
    inline bool operator()(const HuffmanNode &lhs, const HuffmanNode &rhs) const {return lhs.freq < rhs.freq;}
    // needed for MSVC .NET 2005
    inline bool operator()(const HuffmanNode &lhs, unsigned int rhs) {return lhs.freq < rhs;}
};

void HuffmanEncoder::GenerateCodeLengths(unsigned int *codeBits, unsigned int maxCodeBits, const unsigned int *codeCounts, size_t nCodes)
{
    CRYPTOPP_ASSERT(nCodes > 0);
    CRYPTOPP_ASSERT(nCodes <= ((size_t)1 << maxCodeBits));

    size_t i;
    SecBlockWithHint<HuffmanNode, 2*286> tree(nCodes);
    for (i=0; i<nCodes; i++)
    {
        tree[i].symbol = i;
        tree[i].freq = codeCounts[i];
    }
    std::sort(tree.begin(), tree.end(), FreqLessThan());
    size_t treeBegin = std::upper_bound(tree.begin(), tree.end(), 0, FreqLessThan()) - tree.begin();
    if (treeBegin == nCodes)
    {   // special case for no codes
        std::fill(codeBits, codeBits+nCodes, 0);
        return;
    }
    tree.resize(nCodes + nCodes - treeBegin - 1);

    size_t leastLeaf = treeBegin, leastInterior = nCodes;
    for (i=nCodes; i<tree.size(); i++)
    {
        size_t least;
        least = (leastLeaf == nCodes || (leastInterior < i && tree[leastInterior].freq < tree[leastLeaf].freq)) ? leastInterior++ : leastLeaf++;
        tree[i].freq = tree[least].freq;
        tree[least].parent = i;
        least = (leastLeaf == nCodes || (leastInterior < i && tree[leastInterior].freq < tree[leastLeaf].freq)) ? leastInterior++ : leastLeaf++;
        tree[i].freq += tree[least].freq;
        tree[least].parent = i;
    }

    tree[tree.size()-1].depth = 0;
    if (tree.size() >= 2)
        for (i=tree.size()-2; i>=nCodes; i--)
            tree[i].depth = tree[tree[i].parent].depth + 1;
    unsigned int sum = 0;
    SecBlockWithHint<unsigned int, 15+1> blCount(maxCodeBits+1);
    std::fill(blCount.begin(), blCount.end(), 0);
    for (i=treeBegin; i<nCodes; i++)
    {
        const size_t n = tree[i].parent;
        const size_t depth = STDMIN(maxCodeBits, tree[n].depth + 1);
        blCount[depth]++;
        sum += 1 << (maxCodeBits - depth);
    }

    unsigned int overflow = sum > (unsigned int)(1 << maxCodeBits) ? sum - (1 << maxCodeBits) : 0;

    while (overflow--)
    {
        unsigned int bits = maxCodeBits-1;
        while (blCount[bits] == 0)
            bits--;
        blCount[bits]--;
        blCount[bits+1] += 2;
        CRYPTOPP_ASSERT(blCount[maxCodeBits] > 0);
        blCount[maxCodeBits]--;
    }

    for (i=0; i<treeBegin; i++)
        codeBits[tree[i].symbol] = 0;
    unsigned int bits = maxCodeBits;
    for (i=treeBegin; i<nCodes; i++)
    {
        while (blCount[bits] == 0)
            bits--;
        codeBits[tree[i].symbol] = bits;
        blCount[bits]--;
    }
    CRYPTOPP_ASSERT(blCount[bits] == 0);
}

void HuffmanEncoder::Initialize(const unsigned int *codeBits, unsigned int nCodes)
{
    CRYPTOPP_ASSERT(nCodes > 0);
    unsigned int maxCodeBits = *std::max_element(codeBits, codeBits+nCodes);
    if (maxCodeBits == 0)
        return;     // assume this object won't be used

    SecBlockWithHint<unsigned int, 15+1> blCount(maxCodeBits+1);
    std::fill(blCount.begin(), blCount.end(), 0);
    unsigned int i;
    for (i=0; i<nCodes; i++)
        blCount[codeBits[i]]++;

    code_t code = 0;
    SecBlockWithHint<code_t, 15+1> nextCode(maxCodeBits+1);
    nextCode[1] = 0;
    for (i=2; i<=maxCodeBits; i++)
    {
        code = (code + blCount[i-1]) << 1;
        nextCode[i] = code;
    }
    CRYPTOPP_ASSERT(maxCodeBits == 1 || code == (1 << maxCodeBits) - blCount[maxCodeBits]);

    m_valueToCode.resize(nCodes);
    for (i=0; i<nCodes; i++)
    {
        unsigned int len = m_valueToCode[i].len = codeBits[i];
        if (len != 0)
            m_valueToCode[i].code = BitReverse(nextCode[len]++) >> (8*sizeof(code_t)-len);
    }
}

inline void HuffmanEncoder::Encode(LowFirstBitWriter &writer, value_t value) const
{
    CRYPTOPP_ASSERT(m_valueToCode[value].len > 0);
    writer.PutBits(m_valueToCode[value].code, m_valueToCode[value].len);
}

Deflator::Deflator(BufferedTransformation *attachment, int deflateLevel, int log2WindowSize, bool detectUncompressible)
    : LowFirstBitWriter(attachment)
    , m_deflateLevel(-1)
{
    InitializeStaticEncoders();
    IsolatedInitialize(MakeParameters("DeflateLevel", deflateLevel)("Log2WindowSize", log2WindowSize)("DetectUncompressible", detectUncompressible));
}

Deflator::Deflator(const NameValuePairs &parameters, BufferedTransformation *attachment)
    : LowFirstBitWriter(attachment)
    , m_deflateLevel(-1)
{
    InitializeStaticEncoders();
    IsolatedInitialize(parameters);
}

void Deflator::InitializeStaticEncoders()
{
    unsigned int codeLengths[288];
    std::fill(codeLengths + 0, codeLengths + 144, 8);
    std::fill(codeLengths + 144, codeLengths + 256, 9);
    std::fill(codeLengths + 256, codeLengths + 280, 7);
    std::fill(codeLengths + 280, codeLengths + 288, 8);
    m_staticLiteralEncoder.Initialize(codeLengths, 288);
    std::fill(codeLengths + 0, codeLengths + 32, 5);
    m_staticDistanceEncoder.Initialize(codeLengths, 32);
}

void Deflator::IsolatedInitialize(const NameValuePairs &parameters)
{
    int log2WindowSize = parameters.GetIntValueWithDefault("Log2WindowSize", DEFAULT_LOG2_WINDOW_SIZE);
    if (!(MIN_LOG2_WINDOW_SIZE <= log2WindowSize && log2WindowSize <= MAX_LOG2_WINDOW_SIZE))
        throw InvalidArgument("Deflator: " + IntToString(log2WindowSize) + " is an invalid window size");

    m_log2WindowSize = log2WindowSize;
    DSIZE = 1 << m_log2WindowSize;
    DMASK = DSIZE - 1;
    HSIZE = 1 << m_log2WindowSize;
    HMASK = HSIZE - 1;
    m_byteBuffer.New(2*DSIZE);
    m_head.New(HSIZE);
    m_prev.New(DSIZE);
    m_matchBuffer.New(DSIZE/2);
    Reset(true);

    const int deflateLevel = parameters.GetIntValueWithDefault("DeflateLevel", DEFAULT_DEFLATE_LEVEL);
    CRYPTOPP_ASSERT(deflateLevel >= MIN_DEFLATE_LEVEL /*0*/ && deflateLevel <= MAX_DEFLATE_LEVEL /*9*/);
    SetDeflateLevel(deflateLevel);
    bool detectUncompressible = parameters.GetValueWithDefault("DetectUncompressible", true);
    m_compressibleDeflateLevel = detectUncompressible ? m_deflateLevel : 0;
}

void Deflator::Reset(bool forceReset)
{
    if (forceReset)
        ClearBitBuffer();
    else
        CRYPTOPP_ASSERT(m_bitsBuffered == 0);

    m_headerWritten = false;
    m_matchAvailable = false;
    m_dictionaryEnd = 0;
    m_stringStart = 0;
    m_lookahead = 0;
    m_minLookahead = MAX_MATCH;
    m_matchBufferEnd = 0;
    m_blockStart = 0;
    m_blockLength = 0;

    m_detectCount = 1;
    m_detectSkip = 0;

    // m_prev will be initialized automatically in InsertString
    std::fill(m_head.begin(), m_head.end(), byte(0));

    std::fill(m_literalCounts.begin(), m_literalCounts.end(), byte(0));
    std::fill(m_distanceCounts.begin(), m_distanceCounts.end(), byte(0));
}

void Deflator::SetDeflateLevel(int deflateLevel)
{
    if (!(MIN_DEFLATE_LEVEL <= deflateLevel && deflateLevel <= MAX_DEFLATE_LEVEL))
        throw InvalidArgument("Deflator: " + IntToString(deflateLevel) + " is an invalid deflate level");

    if (deflateLevel == m_deflateLevel)
        return;

    EndBlock(false);

    static const unsigned int configurationTable[10][4] = {
        /*      good lazy nice chain */
        /* 0 */ {0,    0,  0,    0},  /* store only */
        /* 1 */ {4,    3,  8,    4},  /* maximum speed, no lazy matches */
        /* 2 */ {4,    3, 16,    8},
        /* 3 */ {4,    3, 32,   32},
        /* 4 */ {4,    4, 16,   16},  /* lazy matches */
        /* 5 */ {8,   16, 32,   32},
        /* 6 */ {8,   16, 128, 128},
        /* 7 */ {8,   32, 128, 256},
        /* 8 */ {32, 128, 258, 1024},
        /* 9 */ {32, 258, 258, 4096}}; /* maximum compression */

    GOOD_MATCH = configurationTable[deflateLevel][0];
    MAX_LAZYLENGTH = configurationTable[deflateLevel][1];
    MAX_CHAIN_LENGTH = configurationTable[deflateLevel][3];

    m_deflateLevel = deflateLevel;
}

unsigned int Deflator::FillWindow(const byte *str, size_t length)
{
    unsigned int maxBlockSize = (unsigned int)STDMIN(2UL*DSIZE, 0xffffUL);

    if (m_stringStart >= maxBlockSize - MAX_MATCH)
    {
        if (m_blockStart < DSIZE)
            EndBlock(false);

        memcpy(m_byteBuffer, m_byteBuffer + DSIZE, DSIZE);

        m_dictionaryEnd = m_dictionaryEnd < DSIZE ? 0 : m_dictionaryEnd-DSIZE;
        CRYPTOPP_ASSERT(m_stringStart >= DSIZE);
        m_stringStart -= DSIZE;
        CRYPTOPP_ASSERT(!m_matchAvailable || m_previousMatch >= DSIZE);
        m_previousMatch -= DSIZE;
        CRYPTOPP_ASSERT(m_blockStart >= DSIZE);
        m_blockStart -= DSIZE;

        // These are set to the same value in IsolatedInitialize(). If they
        //   are the same, then we can clear a Coverity false alarm.
        CRYPTOPP_ASSERT(DSIZE == HSIZE);

        unsigned int i;
        for (i=0; i<HSIZE; i++)
            m_head[i] = SaturatingSubtract(m_head[i], HSIZE); // was DSIZE???

        for (i=0; i<DSIZE; i++)
            m_prev[i] = SaturatingSubtract(m_prev[i], DSIZE);
    }

    CRYPTOPP_ASSERT(maxBlockSize > m_stringStart+m_lookahead);
    unsigned int accepted = UnsignedMin(maxBlockSize-(m_stringStart+m_lookahead), length);
    CRYPTOPP_ASSERT(accepted > 0);
    memcpy(m_byteBuffer + m_stringStart + m_lookahead, str, accepted);
    m_lookahead += accepted;
    return accepted;
}

inline unsigned int Deflator::ComputeHash(const byte *str) const
{
    CRYPTOPP_ASSERT(str+3 <= m_byteBuffer + m_stringStart + m_lookahead);
    return ((str[0] << 10) ^ (str[1] << 5) ^ str[2]) & HMASK;
}

unsigned int Deflator::LongestMatch(unsigned int &bestMatch) const
{
    CRYPTOPP_ASSERT(m_previousLength < MAX_MATCH);

    bestMatch = 0;
    unsigned int bestLength = STDMAX(m_previousLength, (unsigned int)MIN_MATCH-1);
    if (m_lookahead <= bestLength)
        return 0;

    const byte *scan = m_byteBuffer + m_stringStart, *scanEnd = scan + STDMIN((unsigned int)MAX_MATCH, m_lookahead);
    unsigned int limit = m_stringStart > (DSIZE-MAX_MATCH) ? m_stringStart - (DSIZE-MAX_MATCH) : 0;
    unsigned int current = m_head[ComputeHash(scan)];

    unsigned int chainLength = MAX_CHAIN_LENGTH;
    if (m_previousLength >= GOOD_MATCH)
        chainLength >>= 2;

    while (current > limit && --chainLength > 0)
    {
        const byte *match = m_byteBuffer + current;
        CRYPTOPP_ASSERT(scan + bestLength < m_byteBuffer + m_stringStart + m_lookahead);
        if (scan[bestLength-1] == match[bestLength-1] && scan[bestLength] == match[bestLength] && scan[0] == match[0] && scan[1] == match[1])
        {
            CRYPTOPP_ASSERT(scan[2] == match[2]);
            unsigned int len = (unsigned int)(
#if defined(_STDEXT_BEGIN) && !(defined(_MSC_VER) && (_MSC_VER < 1400 || _MSC_VER >= 1600)) && !defined(_STLPORT_VERSION)
                stdext::unchecked_mismatch
#else
                std::mismatch
#endif
#if _MSC_VER >= 1600
                (stdext::make_unchecked_array_iterator(scan)+3, stdext::make_unchecked_array_iterator(scanEnd), stdext::make_unchecked_array_iterator(match)+3).first - stdext::make_unchecked_array_iterator(scan));
#else
                (scan+3, scanEnd, match+3).first - scan);
#endif
            CRYPTOPP_ASSERT(len != bestLength);
            if (len > bestLength)
            {
                bestLength = len;
                bestMatch = current;

                CRYPTOPP_ASSERT(scanEnd >= scan);
                if (len == (unsigned int)(scanEnd - scan))
                    break;
            }
        }
        current = m_prev[current & DMASK];
    }
    return (bestMatch > 0) ? bestLength : 0;
}

inline void Deflator::InsertString(unsigned int start)
{
    CRYPTOPP_ASSERT(start <= 0xffff);
    unsigned int hash = ComputeHash(m_byteBuffer + start);
    m_prev[start & DMASK] = m_head[hash];
    m_head[hash] = word16(start);
}

void Deflator::ProcessBuffer()
{
    if (!m_headerWritten)
    {
        WritePrestreamHeader();
        m_headerWritten = true;
    }

    if (m_deflateLevel == 0)
    {
        m_stringStart += m_lookahead;
        m_lookahead = 0;
        m_blockLength = m_stringStart - m_blockStart;
        m_matchAvailable = false;
        return;
    }

    while (m_lookahead > m_minLookahead)
    {
        while (m_dictionaryEnd < m_stringStart && m_dictionaryEnd+3 <= m_stringStart+m_lookahead)
            InsertString(m_dictionaryEnd++);

        if (m_matchAvailable)
        {
            unsigned int matchPosition = 0, matchLength = 0;
            bool usePreviousMatch;
            if (m_previousLength >= MAX_LAZYLENGTH)
                usePreviousMatch = true;
            else
            {
                matchLength = LongestMatch(matchPosition);
                usePreviousMatch = (matchLength == 0);
            }
            if (usePreviousMatch)
            {
                MatchFound(m_stringStart-1-m_previousMatch, m_previousLength);
                m_stringStart += m_previousLength-1;
                m_lookahead -= m_previousLength-1;
                m_matchAvailable = false;
            }
            else
            {
                m_previousLength = matchLength;
                m_previousMatch = matchPosition;
                LiteralByte(m_byteBuffer[m_stringStart-1]);
                m_stringStart++;
                m_lookahead--;
            }
        }
        else
        {
            m_previousLength = 0;
            m_previousLength = LongestMatch(m_previousMatch);
            if (m_previousLength)
                m_matchAvailable = true;
            else
                LiteralByte(m_byteBuffer[m_stringStart]);
            m_stringStart++;
            m_lookahead--;
        }

        CRYPTOPP_ASSERT(m_stringStart - (m_blockStart+m_blockLength) == (unsigned int)m_matchAvailable);
    }

    if (m_minLookahead == 0 && m_matchAvailable)
    {
        LiteralByte(m_byteBuffer[m_stringStart-1]);
        m_matchAvailable = false;
    }
}

size_t Deflator::Put2(const byte *str, size_t length, int messageEnd, bool blocking)
{
    if (!blocking)
        throw BlockingInputOnly("Deflator");

    size_t accepted = 0;
    while (accepted < length)
    {
        unsigned int newAccepted = FillWindow(str+accepted, length-accepted);
        ProcessBuffer();
        // call ProcessUncompressedData() after WritePrestreamHeader()
        ProcessUncompressedData(str+accepted, newAccepted);
        accepted += newAccepted;
    }
    CRYPTOPP_ASSERT(accepted == length);

    if (messageEnd)
    {
        m_minLookahead = 0;
        ProcessBuffer();
        EndBlock(true);
        FlushBitBuffer();
        WritePoststreamTail();
        Reset();
    }

    Output(0, NULLPTR, 0, messageEnd, blocking);
    return 0;
}

bool Deflator::IsolatedFlush(bool hardFlush, bool blocking)
{
    if (!blocking)
        throw BlockingInputOnly("Deflator");

    m_minLookahead = 0;
    ProcessBuffer();
    m_minLookahead = MAX_MATCH;
    EndBlock(false);
    if (hardFlush)
        EncodeBlock(false, STORED);
    return false;
}

void Deflator::LiteralByte(byte b)
{
    if (m_matchBufferEnd == m_matchBuffer.size())
        EndBlock(false);

    m_matchBuffer[m_matchBufferEnd++].literalCode = b;
    m_literalCounts[b]++;
    m_blockLength++;
}

void Deflator::MatchFound(unsigned int distance, unsigned int length)
{
    if (m_matchBufferEnd == m_matchBuffer.size())
        EndBlock(false);

    static const unsigned int lengthCodes[] = {
        257, 258, 259, 260, 261, 262, 263, 264, 265, 265, 266, 266, 267, 267, 268, 268,
        269, 269, 269, 269, 270, 270, 270, 270, 271, 271, 271, 271, 272, 272, 272, 272,
        273, 273, 273, 273, 273, 273, 273, 273, 274, 274, 274, 274, 274, 274, 274, 274,
        275, 275, 275, 275, 275, 275, 275, 275, 276, 276, 276, 276, 276, 276, 276, 276,
        277, 277, 277, 277, 277, 277, 277, 277, 277, 277, 277, 277, 277, 277, 277, 277,
        278, 278, 278, 278, 278, 278, 278, 278, 278, 278, 278, 278, 278, 278, 278, 278,
        279, 279, 279, 279, 279, 279, 279, 279, 279, 279, 279, 279, 279, 279, 279, 279,
        280, 280, 280, 280, 280, 280, 280, 280, 280, 280, 280, 280, 280, 280, 280, 280,
        281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281,
        281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281, 281,
        282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282,
        282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282, 282,
        283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283,
        283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283, 283,
        284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284,
        284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 284, 285};
    static const unsigned int lengthBases[] =
        {3,4,5,6,7,8,9,10,11,13,15,17,19,23,27,31,35,43,51,59,67,83,99,115,131,163,195,
         227,258};
    static const unsigned int distanceBases[30] =
        {1,2,3,4,5,7,9,13,17,25,33,49,65,97,129,193,257,385,513,769,1025,1537,2049,3073,
         4097,6145,8193,12289,16385,24577};

    CRYPTOPP_ASSERT(m_matchBufferEnd < m_matchBuffer.size());
    EncodedMatch &m = m_matchBuffer[m_matchBufferEnd++];
    CRYPTOPP_ASSERT((length >= 3) && (length-3 < COUNTOF(lengthCodes)));
    unsigned int lengthCode = lengthCodes[length-3];
    m.literalCode = lengthCode;
    m.literalExtra = length - lengthBases[lengthCode-257];
    unsigned int distanceCode = (unsigned int)(std::upper_bound(distanceBases, distanceBases+30, distance) - distanceBases - 1);
    m.distanceCode = distanceCode;
    m.distanceExtra = distance - distanceBases[distanceCode];

    m_literalCounts[lengthCode]++;
    m_distanceCounts[distanceCode]++;
    m_blockLength += length;
}

inline unsigned int CodeLengthEncode(const unsigned int *begin,
                                     const unsigned int *end,
                                     const unsigned int *& p,
                                     unsigned int &extraBits,
                                     unsigned int &extraBitsLength)
{
    unsigned int v = *p;
    if ((end-p) >= 3)
    {
        const unsigned int *oldp = p;
        if (v==0 && p[1]==0 && p[2]==0)
        {
            for (p=p+3; p!=end && *p==0 && p!=oldp+138; p++) {}
            unsigned int repeat = (unsigned int)(p - oldp);
            if (repeat <= 10)
            {
                extraBits = repeat-3;
                extraBitsLength = 3;
                return 17;
            }
            else
            {
                extraBits = repeat-11;
                extraBitsLength = 7;
                return 18;
            }
        }
        else if (p!=begin && v==p[-1] && v==p[1] && v==p[2])
        {
            for (p=p+3; p!=end && *p==v && p!=oldp+6; p++) {}
            unsigned int repeat = (unsigned int)(p - oldp);
            extraBits = repeat-3;
            extraBitsLength = 2;
            return 16;
        }
    }
    p++;
    extraBits = 0;
    extraBitsLength = 0;
    return v;
}

void Deflator::EncodeBlock(bool eof, unsigned int blockType)
{
    PutBits(eof, 1);
    PutBits(blockType, 2);

    if (blockType == STORED)
    {
        CRYPTOPP_ASSERT(m_blockStart + m_blockLength <= m_byteBuffer.size());
        CRYPTOPP_ASSERT(m_blockLength <= 0xffff);
        FlushBitBuffer();
        AttachedTransformation()->PutWord16(word16(m_blockLength), LITTLE_ENDIAN_ORDER);
        AttachedTransformation()->PutWord16(word16(~m_blockLength), LITTLE_ENDIAN_ORDER);
        AttachedTransformation()->Put(m_byteBuffer + m_blockStart, m_blockLength);
    }
    else
    {
        if (blockType == DYNAMIC)
        {
            FixedSizeSecBlock<unsigned int, 286> literalCodeLengths;
            FixedSizeSecBlock<unsigned int, 30> distanceCodeLengths;

            m_literalCounts[256] = 1;
            HuffmanEncoder::GenerateCodeLengths(literalCodeLengths, 15, m_literalCounts, 286);
            m_dynamicLiteralEncoder.Initialize(literalCodeLengths, 286);
            unsigned int hlit = (unsigned int)(FindIfNot(RevIt(literalCodeLengths.end()), RevIt(literalCodeLengths.begin()+257), 0).base() - (literalCodeLengths.begin()+257));

            HuffmanEncoder::GenerateCodeLengths(distanceCodeLengths, 15, m_distanceCounts, 30);
            m_dynamicDistanceEncoder.Initialize(distanceCodeLengths, 30);
            unsigned int hdist = (unsigned int)(FindIfNot(RevIt(distanceCodeLengths.end()), RevIt(distanceCodeLengths.begin()+1), 0).base() - (distanceCodeLengths.begin()+1));

            SecBlockWithHint<unsigned int, 286+30> combinedLengths(hlit+257+hdist+1);
            memcpy(combinedLengths, literalCodeLengths, (hlit+257)*sizeof(unsigned int));
            memcpy(combinedLengths+hlit+257, distanceCodeLengths, (hdist+1)*sizeof(unsigned int));

            FixedSizeSecBlock<unsigned int, 19> codeLengthCodeCounts, codeLengthCodeLengths;
            std::fill(codeLengthCodeCounts.begin(), codeLengthCodeCounts.end(), 0);
            const unsigned int *p = combinedLengths.begin(), *begin = combinedLengths.begin(), *end = combinedLengths.end();
            while (p != end)
            {
                unsigned int code=0, extraBits=0, extraBitsLength=0;
                code = CodeLengthEncode(begin, end, p, extraBits, extraBitsLength);
                codeLengthCodeCounts[code]++;
            }
            HuffmanEncoder::GenerateCodeLengths(codeLengthCodeLengths, 7, codeLengthCodeCounts, 19);
            HuffmanEncoder codeLengthEncoder(codeLengthCodeLengths, 19);
            static const unsigned int border[] = {    // Order of the bit length code lengths
                16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
            unsigned int hclen = 19;
            while (hclen > 4 && codeLengthCodeLengths[border[hclen-1]] == 0)
                hclen--;
            hclen -= 4;

            PutBits(hlit, 5);
            PutBits(hdist, 5);
            PutBits(hclen, 4);

            for (unsigned int i=0; i<hclen+4; i++)
                PutBits(codeLengthCodeLengths[border[i]], 3);

            p = combinedLengths.begin();
            while (p != end)
            {
                unsigned int code=0, extraBits=0, extraBitsLength=0;
                code = CodeLengthEncode(begin, end, p, extraBits, extraBitsLength);
                codeLengthEncoder.Encode(*this, code);
                PutBits(extraBits, extraBitsLength);
            }
        }

        static const unsigned int lengthExtraBits[] = {
            0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
            3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0};
        static const unsigned int distanceExtraBits[] = {
            0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
            7, 7, 8, 8, 9, 9, 10, 10, 11, 11,
            12, 12, 13, 13};

        const HuffmanEncoder &literalEncoder = (blockType == STATIC) ? m_staticLiteralEncoder : m_dynamicLiteralEncoder;
        const HuffmanEncoder &distanceEncoder = (blockType == STATIC) ? m_staticDistanceEncoder : m_dynamicDistanceEncoder;

        for (unsigned int i=0; i<m_matchBufferEnd; i++)
        {
            unsigned int literalCode = m_matchBuffer[i].literalCode;
            literalEncoder.Encode(*this, literalCode);
            if (literalCode >= 257)
            {
                CRYPTOPP_ASSERT(literalCode <= 285);
                PutBits(m_matchBuffer[i].literalExtra, lengthExtraBits[literalCode-257]);
                unsigned int distanceCode = m_matchBuffer[i].distanceCode;
                distanceEncoder.Encode(*this, distanceCode);
                PutBits(m_matchBuffer[i].distanceExtra, distanceExtraBits[distanceCode]);
            }
        }
        literalEncoder.Encode(*this, 256);  // end of block
    }
}

void Deflator::EndBlock(bool eof)
{
    if (m_blockLength == 0 && !eof)
        return;

    if (m_deflateLevel == 0)
    {
        EncodeBlock(eof, STORED);

        if (m_compressibleDeflateLevel > 0 && ++m_detectCount == m_detectSkip)
        {
            m_deflateLevel = m_compressibleDeflateLevel;
            m_detectCount = 1;
        }
    }
    else
    {
        unsigned long storedLen = 8*((unsigned long)m_blockLength+4) + RoundUpToMultipleOf(m_bitsBuffered+3, 8U)-m_bitsBuffered;

        StartCounting();
        EncodeBlock(eof, STATIC);
        unsigned long staticLen = FinishCounting();

        unsigned long dynamicLen;
        if (m_blockLength < 128 && m_deflateLevel < 8)
            dynamicLen = ULONG_MAX;
        else
        {
            StartCounting();
            EncodeBlock(eof, DYNAMIC);
            dynamicLen = FinishCounting();
        }

        if (storedLen <= staticLen && storedLen <= dynamicLen)
        {
            EncodeBlock(eof, STORED);

            if (m_compressibleDeflateLevel > 0)
            {
                if (m_detectSkip)
                    m_deflateLevel = 0;
                m_detectSkip = m_detectSkip ? STDMIN(2*m_detectSkip, 128U) : 1;
            }
        }
        else
        {
            if (staticLen <= dynamicLen)
                EncodeBlock(eof, STATIC);
            else
                EncodeBlock(eof, DYNAMIC);

            if (m_compressibleDeflateLevel > 0)
                m_detectSkip = 0;
        }
    }

    m_matchBufferEnd = 0;
    m_blockStart += m_blockLength;
    m_blockLength = 0;
    std::fill(m_literalCounts.begin(), m_literalCounts.end(), 0);
    std::fill(m_distanceCounts.begin(), m_distanceCounts.end(), 0);
}

NAMESPACE_END