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/**
 *
 *  Copyright © 2013 Nayuki Minase
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy of
 *  this software and associated documentation files (the "Software"), to deal in
 *  the Software without restriction, including without limitation the rights to
 *  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 *  the Software, and to permit persons to whom the Software is furnished to do so,
 *  subject to the following conditions:
 *
 *  * The above copyright notice and this permission notice shall be included in
 *    all copies or substantial portions of the Software.
 *
 *  * The Software is provided "as is", without warranty of any kind, express or
 *    implied, including but not limited to the warranties of merchantability,
 *    fitness for a particular purpose and noninfringement. In no event shall the
 *    authors or copyright holders be liable for any claim, damages or other
 *    liability, whether in an action of contract, tort or otherwise, arising from,
 *    out of or in connection with the Software or the use or other dealings in the
 *    Software.
 */

package nayuki.huffmancoding;

import java.io.IOException;
import java.io.OutputStream;


/**
 * A stream where bits can be written to. Because they are written to an underlying byte stream, the end of the stream is padded with 0's up to a multiple of 8 bits. The bits are written in big endian.
 */
public final class BitOutputStream {
	
	// Underlying byte stream to write to.
	private OutputStream output;
	
	// The accumulated bits for the current byte. Always in the range 0x00 to 0xFF.
	private int currentByte;
	
	// The number of accumulated bits in the current byte. Always between 0 and 7 (inclusive).
	private int numBitsInCurrentByte;
	
	
	
	// Creates a bit output stream based on the given byte output stream.
	public BitOutputStream(OutputStream out) {
		if (out == null)
			throw new NullPointerException("Argument is null");
		output = out;
		currentByte = 0;
		numBitsInCurrentByte = 0;
	}
	
	
	
	// Writes a bit to the stream. The specified bit must be 0 or 1.
	public void write(int b) throws IOException {
		if (!(b == 0 || b == 1))
			throw new IllegalArgumentException("Argument must be 0 or 1");
		currentByte = currentByte << 1 | b;
		numBitsInCurrentByte++;
		if (numBitsInCurrentByte == 8) {
			output.write(currentByte);
			numBitsInCurrentByte = 0;
		}
	}
	
	
	// Closes this stream and the underlying OutputStream. If called when this bit stream is not at a byte boundary,
	// then the minimum number of "0" bits (between 0 and 7 of them) are written as padding to reach the next byte boundary.
	public void close() throws IOException {
		while (numBitsInCurrentByte != 0)
			write(0);
		output.close();
	}
	
}