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// LZ.InWindow

package com.badlogic.gdx.utils.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;
	}
}