/**
 ******************************************************************************
 *                    HOMEWORK     15-211      COMPRESSION
 ******************************************************************************
 *
 *  This class is for writing a sequence of bits in the stream
 *
 *
 *****************************************************************************/
 /*****************************************************************************

               There is no need to modify this file.

 *****************************************************************************/


import java.io.*;

public class BitWriter
{
	private OutputStream stream;

	private int bitCount = 0;
	private int currentByte = 0;

	/** Creates a OutputStreamBitWriter from an OutputStream */
	public BitWriter (OutputStream s)
	{
		stream = s;
	}

	/**
	 * Create a OutputStreamBitWriter
	 *
	 * @param filename
	 *            an absolute or relative filename
	 * @exception FileNotFoundException
	 *                thrown if the file is not writable
	 */
	public BitWriter (String filename)
	{
		try
		{
			stream = new BufferedOutputStream (new FileOutputStream (filename));
		}
		catch(FileNotFoundException e)
		{
			System.out.println(filename + " does not exist");
		}
	}


	public void writeBit (int bit)
	{
		if (bit != 0 && bit != 1)
			throw new IllegalArgumentException ("A bit must be 0 or 1");

		currentByte = currentByte << 1 | bit;
		bitCount++;
		if (bitCount == 8) {
			try{stream.write (currentByte);}catch(IOException e){}
			currentByte = 0;
			bitCount = 0;
		}

	}

	public void writeBits (int bits, int num)
	{
		if ((num < 0) || (num > 32))
			throw new IllegalArgumentException ("Number of bits is out of range");

		while (num > 0) {
			// write out byte by byte
			int cbit = Math.min (num, (8 - bitCount));

			currentByte = (currentByte << cbit) | ((bits >>> (num - cbit)) & ((1 << cbit) - 1));

			bitCount += cbit;
			num -= cbit;

			// flush to output
			if (bitCount == 8) {
				try{stream.write (currentByte);}catch(IOException e){}
				currentByte = 0;
				bitCount = 0;
			}
		}
	}

	public void writeByte (byte nextByte)
	{
		// fast path
		if (bitCount == 0)
			try{stream.write (nextByte);}catch(IOException e){}
		else
			writeBits (nextByte, 8);
	}

	public void writeBytes (byte [] bytes)
	{
		if (bitCount == 0)
			try{stream.write (bytes);}catch(IOException e){}
		else {
			for (byte b : bytes)
				writeByte (b);
		}
	}

	public void writeInt (int value)
	{
		// see http://msdn2.microsoft.com/en-US/library/system.io.binarywriter.write7bitencodedint.aspx
		// about the format. Code taken from Mono's BinaryWriter.
		do {
			int high = (value >>> 7) & 0x01ffffff;
			byte b = (byte)(value & 0x7f);

			if (high != 0) {
				b = (byte)(b | 0x80);
			}

			writeByte (b);
			value = high;
		} while(value != 0);
	}

	public void flush ()
	{
		while (bitCount > 0)
			writeBit (0);

		try{stream.flush ();}catch(IOException e){}
	}
}