import java.io.*;

public class BitInputStream extends FilterInputStream
{
	private int buffer = 0;
	private int bitsavail = 0;

	public BitInputStream(InputStream _in)
	{
		super(_in);
	}

	public boolean markSupported()
	{
		return false;
	}

	//read a single byte
	public int read() throws IOException
	{
		buffer = (buffer << 8) | in.read();
		return (buffer >> bitsavail) & 0xFF;

	}

	public int readBit() throws IOException
	{
		if(bitsavail == 0)
		{
			buffer = in.read();
			bitsavail = 8;
		}
		bitsavail--;
		return (buffer >> bitsavail) & 1;
	}

	public int read(byte b[], int off, int len) throws IOException
	{
		bitsavail = 0;
		return in.read(b, off, len);
	}

	public int read(int length) throws IOException
	{
		int l = length;
		while(l > bitsavail)
		{
			buffer = (buffer << 8) | in.read();
			bitsavail += 8;
		}
		bitsavail -= length;
		return (buffer >> bitsavail) & ((1 << length) - 1);
	}
}