tinyos-main-master/tools/tinyos/java/net/tinyos/util/Crc.java
// $Id: Crc.java,v 1.5 2010-06-29 22:07:42 scipio Exp $

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package net.tinyos.util;

public class Crc {
    public static int calcByte(int crc, int b) {
      crc = crc ^ (int)b << 8;

      for (int i = 0; i < 8; i++) {
	if ((crc & 0x8000) == 0x8000)
	  crc = crc << 1 ^ 0x1021;
	else
	  crc = crc << 1;
      }

      return crc & 0xffff;
    }

    public static int calc(byte[] packet, int index, int count) {
	int crc = 0;
	
	while (count > 0) {
	    crc = calcByte(crc, packet[index++]);
	    count--;
	}
	return crc;
    }

    public static int calc(byte[] packet, int count) {
	return calc(packet, 0, count);
    }

    public static void set(byte[] packet) {
        int crc = Crc.calc(packet, packet.length - 2);

        packet[packet.length - 2] = (byte) (crc & 0xFF);
        packet[packet.length - 1] = (byte) ((crc >> 8) & 0xFF);
    }

    public static void main(String[] args) {
	byte[] ia = new byte[args.length];

	for (int i = 0; i < args.length; i++)
	    try {
		ia[i] = Integer.decode(args[i]).byteValue();
	    } catch (NumberFormatException e) { }
	System.out.println(Integer.toHexString(calc(ia, ia.length)));
    }
}
