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 
MoveBlock()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 
ReadBlock()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 
Free()65 	void Free() { _bufferBase = null; }
66 
Create(int keepSizeBefore, int keepSizeAfter, int keepSizeReserv)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 
SetStream(java.io.InputStream stream)81 	public void SetStream(java.io.InputStream stream) { _stream = stream; 	}
ReleaseStream()82 	public void ReleaseStream() { _stream = null; }
83 
Init()84 	public void Init() throws IOException
85 	{
86 		_bufferOffset = 0;
87 		_pos = 0;
88 		_streamPos = 0;
89 		_streamEndWasReached = false;
90 		ReadBlock();
91 	}
92 
MovePos()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 
GetIndexByte(int index)105 	public byte GetIndexByte(int index)	{ return _bufferBase[_bufferOffset + _pos + index]; }
106 
107 	// index + limit have not to exceed _keepSizeAfter;
GetMatchLen(int index, int distance, int limit)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 
GetNumAvailableBytes()122 	public int GetNumAvailableBytes()	{ return _streamPos - _pos; }
123 
ReduceOffsets(int subValue)124 	public void ReduceOffsets(int subValue)
125 	{
126 		_bufferOffset += subValue;
127 		_posLimit -= subValue;
128 		_pos -= subValue;
129 		_streamPos -= subValue;
130 	}
131 }
132