Class Decompress

ZezeJava/ZezeJava/src/main/java/Zeze/Net/Decompress.java:6–167

// RFC2118
public class Decompress implements Codec {
	protected final @NotNull Codec sink;
	protected int rem;
	protected int pos;
	protected int off = -1;
	private final byte[] hist = new byte[8192 * 3];
	private int hpos;

	public static class DecompressException extends CodecException {
	}

	public Decompress(@NotNull Codec sink) {
		this.sink = sink;
	}

	private void drain() {
		if (hpos >= 8192 * 2) {
			System.arraycopy(hist, hpos - 8192, hist, 0, 8192);
			hpos = 8192;
		}
	}

	private void copy(int dstPos, int srcPos, int length) {
		for (int i = 0; i < length; i++)
			hist[dstPos++] = hist[srcPos++];
	}

	private void output(byte c) throws CodecException {
		sink.update(hist[hpos++] = c);
		drain();
	}

	private void output(int off, int len) throws CodecException {
		if (hpos < off)
			throw new DecompressException();
		copy(hpos, hpos - off, len);
		sink.update(hist, hpos, len);
		hpos += len;
		drain();
	}

	private int bitCompute() {
		long val = ((long)rem << (32 - pos)) & 0xffff_ffffL;
		if (off < 0) {
			if (val < 0x8000_0000L)
				return 8;
			if (val < 0xc000_0000L)
				return 9;
			if (val < 0xe000_0000L)
				return 16;
			if (val < 0xf000_0000L)
				return 12;
			return 10;
		}
		if (val < 0x8000_0000L)
			return 1;
		if (val < 0xc000_0000L)
			return 4;