source: other-projects/trunk/7z-ant/src/SevenZip/Compression/LZ/InWindow.java@ 17387

// LZ.InWindow

package SevenZip.Compression.LZ;

import java.io.IOException;

public class InWindow
{
    public byte[] _bufferBase; // pointer to buffer with data
    java.io.InputStream _stream;
    int _posLimit;  // offset (from _buffer) of first byte when new block reading must be done
    boolean _streamEndWasReached; // if (true) then _streamPos shows real end of stream
    
    int _pointerToLastSafePosition;
    
    public int _bufferOffset;
    
    public int _blockSize;  // Size of Allocated memory block
    public int _pos;             // offset (from _buffer) of curent byte
    int _keepSizeBefore;  // how many BYTEs must be kept in buffer before _pos
    int _keepSizeAfter;   // how many BYTEs must be kept buffer after _pos
    public int _streamPos;   // offset (from _buffer) of first not read byte from Stream
    
    public void MoveBlock()
    {
        int offset = _bufferOffset + _pos - _keepSizeBefore;
        // we need one additional byte, since MovePos moves on 1 byte.
        if (offset > 0)
            offset--;

        int numBytes = _bufferOffset + _streamPos - offset;
        
        // check negative offset ????
        for (int i = 0; i < numBytes; i++)
            _bufferBase[i] = _bufferBase[offset + i];
        _bufferOffset -= offset;
    }
    
    public void ReadBlock() throws IOException
    {
        if (_streamEndWasReached)
            return;
        while (true)
        {
            int size = (0 - _bufferOffset) + _blockSize - _streamPos;
            if (size == 0)
                return;
            int numReadBytes = _stream.read(_bufferBase, _bufferOffset + _streamPos, size);
            if (numReadBytes == -1)
            {
                _posLimit = _streamPos;
                int pointerToPostion = _bufferOffset + _posLimit;
                if (pointerToPostion > _pointerToLastSafePosition)
                    _posLimit = _pointerToLastSafePosition - _bufferOffset;
                
                _streamEndWasReached = true;
                return;
            }
            _streamPos += numReadBytes;
            if (_streamPos >= _pos + _keepSizeAfter)
                _posLimit = _streamPos - _keepSizeAfter;
        }
    }
    
    void Free() { _bufferBase = null; }
    
    public void Create(int keepSizeBefore, int keepSizeAfter, int keepSizeReserv)
    {
        _keepSizeBefore = keepSizeBefore;
        _keepSizeAfter = keepSizeAfter;
        int blockSize = keepSizeBefore + keepSizeAfter + keepSizeReserv;
        if (_bufferBase == null || _blockSize != blockSize)
        {
            Free();
            _blockSize = blockSize;
            _bufferBase = new byte[_blockSize];
        }
        _pointerToLastSafePosition = _blockSize - keepSizeAfter;
    }
    
    public void SetStream(java.io.InputStream stream) { _stream = stream;   }
    public void ReleaseStream() { _stream = null; }

    public void Init() throws IOException
    {
        _bufferOffset = 0;
        _pos = 0;
        _streamPos = 0;
        _streamEndWasReached = false;
        ReadBlock();
    }
    
    public void MovePos() throws IOException
    {
        _pos++;
        if (_pos > _posLimit)
        {
            int pointerToPostion = _bufferOffset + _pos;
            if (pointerToPostion > _pointerToLastSafePosition)
                MoveBlock();
            ReadBlock();
        }
    }
    
    public byte GetIndexByte(int index) { return _bufferBase[_bufferOffset + _pos + index]; }
    
    // index + limit have not to exceed _keepSizeAfter;
    public int GetMatchLen(int index, int distance, int limit)
    {
        if (_streamEndWasReached)
            if ((_pos + index) + limit > _streamPos)
                limit = _streamPos - (_pos + index);
        distance++;
        // Byte *pby = _buffer + (size_t)_pos + index;
        int pby = _bufferOffset + _pos + index;
        
        int i;
        for (i = 0; i < limit && _bufferBase[pby + i] == _bufferBase[pby + i - distance]; i++);
        return i;
    }
    
    public int GetNumAvailableBytes()   { return _streamPos - _pos; }
    
    public void ReduceOffsets(int subValue)
    {
        _bufferOffset += subValue;
        _posLimit -= subValue;
        _pos -= subValue;
        _streamPos -= subValue;
    }
}