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Pure Java implementation of video/audio codecs and formats
There is a newer version: 0.2.5
package org.jcodec.codecs.common.biari;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * This class is part of JCodec ( www.jcodec.org )
 * This software is distributed under FreeBSD License
 * 
 * All the IO routines related to bits
 * 
 * @author Stanislav Vitvitskiy
 * 
 */
public class BitIO {

	public static interface InputBits {
		public int getBit() throws IOException;

	}

	public static interface OutputBits {
		public void putBit(int symbol) throws IOException;

		public void flush() throws IOException;
	}

	public static InputBits inputFromStream(InputStream is) {
		return new StreamInputBits(is);
	}

	public static OutputBits outputFromStream(OutputStream out) {
		return new StreamOutputBits(out);
	}

	public static InputBits inputFromArray(byte[] bytes) {
		return new StreamInputBits(new ByteArrayInputStream(bytes));
	}

	public static OutputBits outputFromArray(final byte[] bytes) {
		return new StreamOutputBits(new OutputStream() {
			int ptr;

			public void write(int b) throws IOException {
				if (ptr >= bytes.length)
					throw new IOException("Buffer is full");
				bytes[ptr++] = (byte) b;
			}
		});
	}

	public static byte[] compressBits(int[] decompressed) {
		byte[] compressed = new byte[(decompressed.length >> 3) + 1];
		OutputBits out = outputFromArray(compressed);
		try {
			for (int bit : decompressed) {
				out.putBit(bit);
			}
		} catch (IOException e) {
		}

		return compressed;
	}

	public static int[] decompressBits(byte[] compressed) {
		int[] decompressed = new int[compressed.length << 3];
		InputBits inputFromArray = inputFromArray(compressed);
		int read;
		try {
			for (int i = 0; (read = inputFromArray.getBit()) != -1; i++) {
				decompressed[i] = read;
			}
		} catch (IOException e) {
		}
		return decompressed;
	}

	public static class StreamInputBits implements InputBits {
		private InputStream in;
		private int cur;
		private int bit;

		public StreamInputBits(InputStream in) {
			this.in = in;
			this.bit = 8;
		}

		public int getBit() throws IOException {
			if (bit > 7) {
				cur = in.read();
				if (cur == -1)
					return -1;
				bit = 0;
			}
			return (cur >> (7 - bit++)) & 0x1;
		}
	}

	public static class StreamOutputBits implements OutputBits {
		private OutputStream out;
		private int cur;
		private int bit;

		public StreamOutputBits(OutputStream out) {
			this.out = out;
		}

		public void putBit(int symbol) throws IOException {
			if (bit > 7) {
				out.write(cur);
				cur = 0;
				bit = 0;
			}
			cur |= (symbol & 0x1) << (7 - bit++);
		}

		public void flush() throws IOException {
			if (bit > 0)
				out.write(cur);
		}
	}
}