sketcher2/src/com/jotuntech/sketcher/client/PackBitsOutputStream.java

package com.jotuntech.sketcher.client;

import java.io.DataOutput;
import java.io.IOException;
import java.io.OutputStream;

public class PackBitsOutputStream extends OutputStream {
	private DataOutput mdo;

	private final static int IN_BUFFER_SIZE = 2048;
	private final static int IN_BUFFER_MASK = IN_BUFFER_SIZE - 1;
	private final static int OUT_BUFFER_SIZE = 4096;

	private int[] inBuffer;
	private int inBufferWritePos, inBufferReadPos, inBufferMark;
	private byte[] outBuffer;
	private int outBufferWritePos;

	public PackBitsOutputStream(DataOutput mdo) {
		this.mdo = mdo;
		this.inBuffer = new int[IN_BUFFER_SIZE];
		this.inBufferWritePos = 0;
		this.inBufferReadPos = 0;
		this.inBufferMark = 0;
		this.outBuffer = new byte[OUT_BUFFER_SIZE];
		this.outBufferWritePos = 0;
	}

	public void write(int b) throws IOException {
		inBuffer[inBufferWritePos++ & IN_BUFFER_MASK] = b;

		if(inBufferWritePos - inBufferReadPos == IN_BUFFER_SIZE) {
			pack();
		}
	}

	public void write(byte[] b) throws IOException {
		for(int i = 0; i < b.length; i++) {
			inBuffer[inBufferWritePos++ & IN_BUFFER_MASK] = b[i];

			if(inBufferWritePos - inBufferReadPos == IN_BUFFER_SIZE) {
				pack();
			}
		}
	}

	public void write(byte[] b, int off, int len) throws IOException {
		for(int i = off; i < off + len; i++) {
			inBuffer[inBufferWritePos++ & IN_BUFFER_MASK] = b[i];

			if(inBufferWritePos - inBufferReadPos == IN_BUFFER_SIZE) {
				pack();
			}
		}
	}

	public void flush() throws IOException {
		pack();
	}

	private void output(int b) {
		outBuffer[outBufferWritePos++] = (byte) b;
	}

	private void pack() throws IOException {
		outBufferWritePos = 0;

		while(available() > 0) {
			int b = read();
			int repeat = 1;
			while(available() > 0 && peek() == b && repeat < 128) {
				++repeat;
				skip();
			}

			if(repeat == 1) {
				mark();
				int b2 = read();
				int literal = 0;
				while(available() > 0 && peek() != b2 && literal < 127) {
					b2 = read();
					++literal;
				}

				if(available() == 0 && literal < 127) {
					++literal;
				}

				if(literal == 0) {
					reset();
					output(0);
					output(b);
				} else {
					reset();
					output(literal);
					output(b);
					for(int i = 0; i < literal; i++) {
						output(read());
					}
				}
			} else if(repeat == 2) {
				output(1);
				output(b);
				output(b);
			} else  {
				output(1 - repeat);
				output(b);
			}
		}

		mdo.write(outBuffer, 0, outBufferWritePos);
	}

	public void close() throws IOException {
		pack();
	}

	private int available() {
		return inBufferWritePos - inBufferReadPos;
	}

	private int peek() {
		return inBuffer[inBufferReadPos & IN_BUFFER_MASK];
	}

	private int read() {
		return inBuffer[inBufferReadPos++ & IN_BUFFER_MASK];
	}

	private void skip() {
		++inBufferReadPos;
	}

	private void mark() {
		inBufferMark = inBufferReadPos;
	}

	private void reset() {
		inBufferReadPos = inBufferMark;
	}
}