Class BitInputStream

src/main/java/org/apache/sanselan/common/BitInputStream.java:22–123

import java.io.InputStream;

public class BitInputStream extends InputStream implements BinaryConstants
{
	// TODO should be byte order conscious, ie TIFF for reading 
	// samples size<8 - shuoldn't that effect their order within byte?
	private final InputStream is;

	public BitInputStream(InputStream is)
	{
		this.is = is;
		//			super(is);
	}

	public int read() throws IOException
	{
		if (cacheBitsRemaining > 0)
			throw new IOException("BitInputStream: incomplete bit read");
		return is.read();
	}

	private int cache;
	private int cacheBitsRemaining = 0;
	private long bytes_read = 0;

	public final int readBits(int count) throws IOException
	{
		if (count < 8)
		{
			if (cacheBitsRemaining == 0)
			{
				// fill cache
				cache = is.read();
				cacheBitsRemaining = 8;
				bytes_read++;
			}
			if (count > cacheBitsRemaining)
				throw new IOException(
						"BitInputStream: can't read bit fields across bytes");

			//				int bits_to_shift = cache_bits_remaining - count;
			cacheBitsRemaining -= count;
			int bits = cache >> cacheBitsRemaining;

			switch (count)
			{
				case 1 :
					return bits & 1;
				case 2 :
					return bits & 3;
				case 3 :
					return bits & 7;
				case 4 :
					return bits & 15;
				case 5 :
					return bits & 31;
				case 6 :
					return bits & 63;
				case 7 :
					return bits & 127;