compress.h

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*
*                            Open Watcom Project
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*    Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
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*    This file contains Original Code and/or Modifications of Original
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//
//  compress.h  --Classes to support WinHelp-style LZ77 compression.
//
//
#include <watcom.h> // for uint_8, etc.
#include "myfile.h"
#include "hcmem.h"


//
//  CompWriter  --Base class to accept characters & codes and
//        do something with them.
//

class CompWriter
{
    // Assignment of CompWriter's is not permitted.
    CompWriter( CompWriter const & ){};
    CompWriter &    operator=( CompWriter const & ) { return *this; };

protected:
    uint_8  *_buffer;
    int     _numBytes;
    int     _numTokens;
    uint_8  _bitMask;
public:
    CompWriter();
    virtual ~CompWriter();

    virtual void    dump();
    int         putChr( uint_8 c );
    int         putCode( int distance, int length );
};


//
//  CompOutFile --Version of CompWriter to write to a file.
//

class CompOutFile : public CompWriter
{
    OutFile * _dest;
public:
    CompOutFile( OutFile * d_file ) : _dest(d_file) {};

    void    dump();
};


//
//  CompReader  --Class to compress text.
//

class CompReader
{
    Buffer<uint_8>  _buffer;    // Stores the text being compressed.

    Buffer<short>   _indices;   // Used to find patterns within
    Buffer<short>   _htable;    // the text.

    CompWriter  *_dest;
    short   _last, _first, _current;

    void    shuffle();  // Free space in the buffer.
public:
    CompReader( CompWriter *riter );

    int     compress( char const source[], int amount );

    // Add text to the compressed stream in a 'stupid' manner;
    // i.e. it pretends it's uncompressible.
    int     add( char const source[], int amount );
    int     skip( int amount );

    void    flush( int nodump = 0 );

    void    reset( CompWriter *riter, int nodump = 0 );
};