crc.h

tinyos-2.x.rar

/* -*- mode:c++; indent-tabs-mode: nil -*- */
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/**
 * This CRC-16 function produces a 16-bit running CRC that adheres to the
 * ITU-T CRC standard.
 *
 * The ITU-T polynomial is: G_16(x) = x^16 + x^12 + x^5 + 1
 * @param crc Running CRC value
 * @param b Byte to "add" to the CRC
 * @return New CRC value
 *
 * @author Andreas Koepke <[e-mail]> 
 * @author Paul Curtis (pointed out this implementation, which is believed to be public domain)
 */
#ifndef CRC_H
#define CRC_H

uint16_t crcByte(uint16_t crc, uint8_t b) {
  crc = (uint8_t)(crc >> 8) | (crc << 8);
  crc ^= b;
  crc ^= (uint8_t)(crc & 0xff) >> 4;
  crc ^= crc << 12;
  crc ^= (crc & 0xff) << 5;
  return crc;
}

#endif