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      1 // LZ.InWindow
      2 
      3 package SevenZip.Compression.LZ;
      4 
      5 import java.io.IOException;
      6 
      7 public class InWindow
      8 {
      9 	public byte[] _bufferBase; // pointer to buffer with data
     10 	java.io.InputStream _stream;
     11 	int _posLimit;  // offset (from _buffer) of first byte when new block reading must be done
     12 	boolean _streamEndWasReached; // if (true) then _streamPos shows real end of stream
     13 
     14 	int _pointerToLastSafePosition;
     15 
     16 	public int _bufferOffset;
     17 
     18 	public int _blockSize;  // Size of Allocated memory block
     19 	public int _pos;             // offset (from _buffer) of curent byte
     20 	int _keepSizeBefore;  // how many BYTEs must be kept in buffer before _pos
     21 	int _keepSizeAfter;   // how many BYTEs must be kept buffer after _pos
     22 	public int _streamPos;   // offset (from _buffer) of first not read byte from Stream
     23 
     24 	public void MoveBlock()
     25 	{
     26 		int offset = _bufferOffset + _pos - _keepSizeBefore;
     27 		// we need one additional byte, since MovePos moves on 1 byte.
     28 		if (offset > 0)
     29 			offset--;
     30 
     31 		int numBytes = _bufferOffset + _streamPos - offset;
     32 
     33 		// check negative offset ????
     34 		for (int i = 0; i < numBytes; i++)
     35 			_bufferBase[i] = _bufferBase[offset + i];
     36 		_bufferOffset -= offset;
     37 	}
     38 
     39 	public void ReadBlock() throws IOException
     40 	{
     41 		if (_streamEndWasReached)
     42 			return;
     43 		while (true)
     44 		{
     45 			int size = (0 - _bufferOffset) + _blockSize - _streamPos;
     46 			if (size == 0)
     47 				return;
     48 			int numReadBytes = _stream.read(_bufferBase, _bufferOffset + _streamPos, size);
     49 			if (numReadBytes == -1)
     50 			{
     51 				_posLimit = _streamPos;
     52 				int pointerToPostion = _bufferOffset + _posLimit;
     53 				if (pointerToPostion > _pointerToLastSafePosition)
     54 					_posLimit = _pointerToLastSafePosition - _bufferOffset;
     55 
     56 				_streamEndWasReached = true;
     57 				return;
     58 			}
     59 			_streamPos += numReadBytes;
     60 			if (_streamPos >= _pos + _keepSizeAfter)
     61 				_posLimit = _streamPos - _keepSizeAfter;
     62 		}
     63 	}
     64 
     65 	void Free() { _bufferBase = null; }
     66 
     67 	public void Create(int keepSizeBefore, int keepSizeAfter, int keepSizeReserv)
     68 	{
     69 		_keepSizeBefore = keepSizeBefore;
     70 		_keepSizeAfter = keepSizeAfter;
     71 		int blockSize = keepSizeBefore + keepSizeAfter + keepSizeReserv;
     72 		if (_bufferBase == null || _blockSize != blockSize)
     73 		{
     74 			Free();
     75 			_blockSize = blockSize;
     76 			_bufferBase = new byte[_blockSize];
     77 		}
     78 		_pointerToLastSafePosition = _blockSize - keepSizeAfter;
     79 	}
     80 
     81 	public void SetStream(java.io.InputStream stream) { _stream = stream; 	}
     82 	public void ReleaseStream() { _stream = null; }
     83 
     84 	public void Init() throws IOException
     85 	{
     86 		_bufferOffset = 0;
     87 		_pos = 0;
     88 		_streamPos = 0;
     89 		_streamEndWasReached = false;
     90 		ReadBlock();
     91 	}
     92 
     93 	public void MovePos() throws IOException
     94 	{
     95 		_pos++;
     96 		if (_pos > _posLimit)
     97 		{
     98 			int pointerToPostion = _bufferOffset + _pos;
     99 			if (pointerToPostion > _pointerToLastSafePosition)
    100 				MoveBlock();
    101 			ReadBlock();
    102 		}
    103 	}
    104 
    105 	public byte GetIndexByte(int index)	{ return _bufferBase[_bufferOffset + _pos + index]; }
    106 
    107 	// index + limit have not to exceed _keepSizeAfter;
    108 	public int GetMatchLen(int index, int distance, int limit)
    109 	{
    110 		if (_streamEndWasReached)
    111 			if ((_pos + index) + limit > _streamPos)
    112 				limit = _streamPos - (_pos + index);
    113 		distance++;
    114 		// Byte *pby = _buffer + (size_t)_pos + index;
    115 		int pby = _bufferOffset + _pos + index;
    116 
    117 		int i;
    118 		for (i = 0; i < limit && _bufferBase[pby + i] == _bufferBase[pby + i - distance]; i++);
    119 		return i;
    120 	}
    121 
    122 	public int GetNumAvailableBytes()	{ return _streamPos - _pos; }
    123 
    124 	public void ReduceOffsets(int subValue)
    125 	{
    126 		_bufferOffset += subValue;
    127 		_posLimit -= subValue;
    128 		_pos -= subValue;
    129 		_streamPos -= subValue;
    130 	}
    131 }
    132