zdeflate.h

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

//! \file zdeflate.h
//! \brief DEFLATE compression and decompression (RFC 1951)

#ifndef CRYPTOPP_ZDEFLATE_H
#define CRYPTOPP_ZDEFLATE_H

#include "cryptlib.h"
#include "filters.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

//! \class LowFirstBitWriter
//! \brief Encoding table writer
//! \since Crypto++ 1.0
class LowFirstBitWriter : public Filter
{
public:
    //! \brief Construct a LowFirstBitWriter
    //! \param attachment an attached transformation
    LowFirstBitWriter(BufferedTransformation *attachment);

    void PutBits(unsigned long value, unsigned int length);
    void FlushBitBuffer();
    void ClearBitBuffer();

    void StartCounting();
    unsigned long FinishCounting();

protected:
    bool m_counting;
    unsigned long m_bitCount;
    unsigned long m_buffer;
    unsigned int m_bitsBuffered, m_bytesBuffered;
    FixedSizeSecBlock<byte, 256> m_outputBuffer;
};

//! \class HuffmanEncoder
//! \brief Huffman Encoder
//! \since Crypto++ 1.0
class HuffmanEncoder
{
public:
    typedef unsigned int code_t;
    typedef unsigned int value_t;

    //! \brief Construct a HuffmanEncoder
    HuffmanEncoder() {}

    //! \brief Construct a HuffmanEncoder
    //! \param codeBits a table of code bits
    //! \param nCodes the number of codes in the table
    HuffmanEncoder(const unsigned int *codeBits, unsigned int nCodes);

    //! \brief Initialize or reinitialize this object
    //! \param codeBits a table of code bits
    //! \param nCodes the number of codes in the table
    void Initialize(const unsigned int *codeBits, unsigned int nCodes);

    static void GenerateCodeLengths(unsigned int *codeBits, unsigned int maxCodeBits, const unsigned int *codeCounts, size_t nCodes);

    void Encode(LowFirstBitWriter &writer, value_t value) const;

    struct Code
    {
        unsigned int code;
        unsigned int len;
    };

    SecBlock<Code> m_valueToCode;
};

//! \class Deflator
//! \brief DEFLATE compressor (RFC 1951)
//! \since Crypto++ 1.0
class Deflator : public LowFirstBitWriter
{
public:
    //! \brief Deflate level as enumerated values.
    enum {
        //! \brief Minimum deflation level, fastest speed (0)
        MIN_DEFLATE_LEVEL = 0,
        //! \brief Default deflation level, compromise between speed (6)
        DEFAULT_DEFLATE_LEVEL = 6,
        //! \brief Minimum deflation level, slowest speed (9)
        MAX_DEFLATE_LEVEL = 9};

    //! \brief Windows size as enumerated values.
    enum {
        //! \brief Minimum window size, smallest table (9)
        MIN_LOG2_WINDOW_SIZE = 9,
        //! \brief Default window size (15)
        DEFAULT_LOG2_WINDOW_SIZE = 15,
        //! \brief Maximum window size, largest table (15)
        MAX_LOG2_WINDOW_SIZE = 15};

    //! \brief Construct a Deflator compressor
    //! \param attachment an attached transformation
    //! \param deflateLevel the deflate level
    //! \param log2WindowSize the window size
    //! \param detectUncompressible flag to detect if data is compressible
    //! \details detectUncompressible makes it faster to process uncompressible files, but
    //!   if a file has both compressible and uncompressible parts, it may fail to compress
    //!   some of the compressible parts.
    Deflator(BufferedTransformation *attachment=NULLPTR, int deflateLevel=DEFAULT_DEFLATE_LEVEL, int log2WindowSize=DEFAULT_LOG2_WINDOW_SIZE, bool detectUncompressible=true);
    //! \brief Construct a Deflator compressor
    //! \param parameters a set of NameValuePairs to initialize this object
    //! \param attachment an attached transformation
    //! \details Possible parameter names: Log2WindowSize, DeflateLevel, DetectUncompressible
    Deflator(const NameValuePairs &parameters, BufferedTransformation *attachment=NULLPTR);

    //! \brief Sets the deflation level
    //! \param deflateLevel the level of deflation
    //! \details SetDeflateLevel can be used to set the deflate level in the middle of compression
    void SetDeflateLevel(int deflateLevel);

    //! \brief Retrieves the deflation level
    //! \returns the level of deflation
    int GetDeflateLevel() const {return m_deflateLevel;}

    //! \brief Retrieves the window size
    //! \returns the windows size
    int GetLog2WindowSize() const {return m_log2WindowSize;}

    void IsolatedInitialize(const NameValuePairs &parameters);
    size_t Put2(const byte *inString, size_t length, int messageEnd, bool blocking);
    bool IsolatedFlush(bool hardFlush, bool blocking);

protected:
    virtual void WritePrestreamHeader() {}
    virtual void ProcessUncompressedData(const byte *string, size_t length)
        {CRYPTOPP_UNUSED(string), CRYPTOPP_UNUSED(length);}
    virtual void WritePoststreamTail() {}

    enum {STORED = 0, STATIC = 1, DYNAMIC = 2};
    enum {MIN_MATCH = 3, MAX_MATCH = 258};

    void InitializeStaticEncoders();
    void Reset(bool forceReset = false);
    unsigned int FillWindow(const byte *str, size_t length);
    unsigned int ComputeHash(const byte *str) const;
    unsigned int LongestMatch(unsigned int &bestMatch) const;
    void InsertString(unsigned int start);
    void ProcessBuffer();

    void LiteralByte(byte b);
    void MatchFound(unsigned int distance, unsigned int length);
    void EncodeBlock(bool eof, unsigned int blockType);
    void EndBlock(bool eof);

    struct EncodedMatch
    {
        unsigned literalCode : 9;
        unsigned literalExtra : 5;
        unsigned distanceCode : 5;
        unsigned distanceExtra : 13;
    };

    int m_deflateLevel, m_log2WindowSize, m_compressibleDeflateLevel;
    unsigned int m_detectSkip, m_detectCount;
    unsigned int DSIZE, DMASK, HSIZE, HMASK, GOOD_MATCH, MAX_LAZYLENGTH, MAX_CHAIN_LENGTH;
    bool m_headerWritten, m_matchAvailable;
    unsigned int m_dictionaryEnd, m_stringStart, m_lookahead, m_minLookahead, m_previousMatch, m_previousLength;
    HuffmanEncoder m_staticLiteralEncoder, m_staticDistanceEncoder, m_dynamicLiteralEncoder, m_dynamicDistanceEncoder;
    SecByteBlock m_byteBuffer;
    SecBlock<word16> m_head, m_prev;
    FixedSizeSecBlock<unsigned int, 286> m_literalCounts;
    FixedSizeSecBlock<unsigned int, 30> m_distanceCounts;
    SecBlock<EncodedMatch> m_matchBuffer;
    unsigned int m_matchBufferEnd, m_blockStart, m_blockLength;
};

NAMESPACE_END

#endif