BitOperation.java

public class BitOp {

    public static byte setBit(byte input, int pos) {
    	// this sets the bit of the input byte to be 1 at the position pos.
  		if (pos < 8) {
  		    byte output = (byte)(input | (1 << pos));
  		    return output;
  		} 
  		else {
  		    return input;
  		}
    }

    public static byte clearBit(byte input, int pos) {
  		// this sets the bit of the input byte to be 0 at the position pos.
  		if (pos < 8) {
  		    byte output = (byte)(input & ~(1 << pos));
  		    return output;
  		}
  		else {
  		    return input;
  		}
    }

    public static int readBit(byte input, int pos) {
  		// this reads the bit value of the input byte (either 1 or 0) at the position pos.
  		if (pos < 8) {
  		    byte output = (byte)(input & (1 << pos));
  		    return Byte.valueOf(output).intValue();
  		}
  		else {
  		    return -1;
  		}
    }


    public static byte[] setBit(byte[] input, int pos) {
  		/*
  		if (pos < 8) {
  		    input[0] = setBit(input[0], pos);
  		} else if ( pos < 16 ) {
  		    input[1] = setBit(input[1], pos - 8);
  		} else if ( pos < 24 ) {
  		    input[2] = setBit(input[2], pos - 16);
  		} 
  		*/
  
  		if (pos > 63) { 
  		    return input; 
  		} else {
  			int relPos = pos;
  			int counter = 0;
  		    while (relPos >= 8) {
  				counter ++;
  				relPos = relPos - 8;
  		    }
  		    input[counter] = setBit(input[counter], relPos);
  		    return input;
  		}
    }

    public static byte[] clearBit(byte[] input, int pos) {

  		if (pos > 63) { 
  		    return input; 
  		} else {
  		    int relPos = pos;
  		    int counter = 0;
  		    while (relPos >= 8) {
  				counter ++;
  				relPos = relPos - 8;
  		    }
  		    input[counter] = clearBit(input[counter], relPos);
  		    return input;
  		}
    }



    public static int readBit(byte[] input, int pos) {

  		if (pos > 63) { 
  		    return -1; 
  		} else {
  		    int relPos = pos;
  		    int counter = 0;
  		    while (relPos >= 8) {
  				counter ++;
  				relPos = relPos - 8;
  		    }
  		    return readBit(input[counter], relPos);
  		}
    }


    public static byte[] int64ToByteArray(int v) {
  		// we mod v with 8. 
  		// assumption: the most significant is having the larger index in the byte array
  		byte[] result = new byte[8];
  		int quotient = v;
  		int denom = 256; // (int)Math.pow(2,8);
  		for (int i = 0; i < 8; i ++) {
  		    int remainder = quotient % denom;
  		    quotient = quotient / denom;
  		    result[i] = (byte) remainder;
  		}
  		return result;
    }

}