/**
 * CS 529 Sample bit-manipulation code
 * @author Michael Lee
 * Copyright (c)  2001
 */

import java.io.*;

public class CompressionExample {
	/**
	 * sets (turns on) the pos bit in byte b
	 */
	public static byte setBit (int pos, byte b) {
		b |= 1 << pos;
		return b;
	}

	/**
	 * unsets (turns off) the pos bit in byte b
	 */
	public static byte unsetBit (int pos, byte b) {
		/* not technically necessary, as byte arrays are automatically
		 * initialized to 0's in Java --- but used as a precaution */
		b &= ~( 1 << pos );
		return b;
	}

	/**
	 * compresses stuff in datain to dataout, and returns the size of the
	 * compressed data (in bits).
	 */
	public static int compressUnary (int[] datain, byte[] dataout) {
		int atByte 		= 0,
			atBit 		= 8,
			bitsLeft 	= 0;

		for (int i=0; i<datain.length; i++) {
			bitsLeft = datain[i];
			while (bitsLeft-- > 0) {
				if (atBit == 0)
					++atByte;
				atBit = (atBit-1 >= 0)? atBit-1 : 7;
				dataout[atByte] = setBit(atBit, dataout[atByte]);
			}
			if (atBit == 0)
				++atByte;
			atBit = (atBit-1 >= 0)? atBit-1 : 7;
			dataout[atByte] = unsetBit(atBit, dataout[atByte]);
		}
		return (atByte+1) * 8 + (8-atBit);
	}

	/**
	 * prints out the binary makeup of a byte
	 */
	public static void printByte (byte b) {
		for (int i=7; i>=0; i--) {
			System.out.print((b >>> i) & 1);
		}
	}

	public static void main (String[] args) {
		int[] intarr = { 0, 1, 2, 3, 10 };
		int complength = 0;
		byte[] bytearr;

		/* we can precalculate the amount of space needed for the
		 * compressed array */
		for (int i=0; i<intarr.length; i++) {
			complength+= intarr[i]+1;
		}
		bytearr = new byte[(int)Math.ceil(complength/8.0)];

		/* compress and print out the resulting bytes */
		compressUnary(intarr, bytearr);
		for (int i=0; i<bytearr.length; i++) {
			printByte(bytearr[i]);
		}
		System.out.println();
	}
}