Crc16Generator.java

package edu.cmu.sv.arinc838.crc;

public class Crc16Generator implements CrcGenerator {

	@Override
	public long calculateCrc(byte[] bytes) {
		int crc = 0xFFFF; // initial value
		int polynomial = 0x1021; // 0001 0000 0010 0001 (0, 5, 12)

		for (byte b : bytes) {
			for (int i = 0; i < 8; i++) {
				boolean bit = ((b >> (7 - i) & 1) == 1);
				boolean c15 = ((crc >> 15 & 1) == 1);
				crc <<= 1;
				if (c15 ^ bit)
					crc ^= polynomial;
			}
		}

		crc &= 0xffff;
		return crc;
	}

}