sketcher2/src/com/jotuntech/sketcher/common/DiffUnpacker.java

package com.jotuntech.sketcher.common;

import java.util.zip.DataFormatException;
import java.util.zip.Inflater;

public class DiffUnpacker {
	Inflater inflater;
	private byte[] encodedDiff;

	public DiffUnpacker() {
		inflater = new Inflater(true);
	}

	public void unpack(byte[] input, int ofs, int len, short[] outputAlpha, short[] outputRed, short[] outputGreen, short[] outputBlue) {
		if(encodedDiff == null || encodedDiff.length < input.length * 8) {
			encodedDiff = new byte[outputAlpha.length * 8];
		}

		inflater.reset();
		inflater.setInput(input, ofs, len);

		int encodedLength = 0;
		try {
			while(!inflater.finished() && encodedLength < encodedDiff.length) {
				encodedLength += inflater.inflate(encodedDiff, encodedLength, encodedDiff.length - encodedLength);
			}
		} catch(DataFormatException e) {
			throw new RuntimeException(e);
		}

		if(encodedLength < outputAlpha.length * 8) {
			Log.error("needsInput = " + inflater.needsInput());
			throw new RuntimeException("Encoded length " + encodedLength + " is shorter than output length " + outputAlpha.length * 8 + ".");
		}

		short alpha = 0, red = 0, green = 0, blue = 0;
		for(int outputOffset = 0, alphaOffset = 0, redOffset = outputAlpha.length * 2, greenOffset = outputAlpha.length * 4, blueOffset = outputAlpha.length * 6; outputOffset < outputAlpha.length; outputOffset++, alphaOffset++, redOffset++, greenOffset++, blueOffset++) {
			alpha += (short) ((encodedDiff[alphaOffset++] << 8) | (encodedDiff[alphaOffset] & 0xff));
			red += (short) ((encodedDiff[redOffset++] << 8) | (encodedDiff[redOffset] & 0xff));
			green += (short) ((encodedDiff[greenOffset++] << 8) | (encodedDiff[greenOffset] & 0xff));
			blue += (short) ((encodedDiff[blueOffset++] << 8) | (encodedDiff[blueOffset] & 0xff));

			outputAlpha[outputOffset] = alpha;
			outputRed[outputOffset] = red;
			outputGreen[outputOffset] = green;
			outputBlue[outputOffset] = blue;
		}
	}
}