Contiki 2.6
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00001 /* 00002 * Copyright (c) 2005, Swedish Institute of Computer Science 00003 * All rights reserved. 00004 * 00005 * Redistribution and use in source and binary forms, with or without 00006 * modification, are permitted provided that the following conditions 00007 * are met: 00008 * 1. Redistributions of source code must retain the above copyright 00009 * notice, this list of conditions and the following disclaimer. 00010 * 2. Redistributions in binary form must reproduce the above copyright 00011 * notice, this list of conditions and the following disclaimer in the 00012 * documentation and/or other materials provided with the distribution. 00013 * 3. Neither the name of the Institute nor the names of its contributors 00014 * may be used to endorse or promote products derived from this software 00015 * without specific prior written permission. 00016 * 00017 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND 00018 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 00019 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 00020 * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE 00021 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 00022 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 00023 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 00024 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 00025 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 00026 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 00027 * SUCH DAMAGE. 00028 * 00029 * This file is part of the Contiki operating system. 00030 * 00031 * @(#)$Id: crc16.c,v 1.4 2009/05/14 12:05:04 nvt-se Exp $ 00032 */ 00033 00034 /** \addtogroup crc16 00035 * @{ */ 00036 00037 /** 00038 * \file 00039 * Implementation of the CRC16 calculcation 00040 * \author 00041 * Adam Dunkels <adam@sics.se> 00042 * 00043 */ 00044 00045 /* CITT CRC16 polynomial ^16 + ^12 + ^5 + 1 */ 00046 /*---------------------------------------------------------------------------*/ 00047 unsigned short 00048 crc16_add(unsigned char b, unsigned short acc) 00049 { 00050 /* 00051 acc = (unsigned char)(acc >> 8) | (acc << 8); 00052 acc ^= b; 00053 acc ^= (unsigned char)(acc & 0xff) >> 4; 00054 acc ^= (acc << 8) << 4; 00055 acc ^= ((acc & 0xff) << 4) << 1; 00056 */ 00057 00058 acc ^= b; 00059 acc = (acc >> 8) | (acc << 8); 00060 acc ^= (acc & 0xff00) << 4; 00061 acc ^= (acc >> 8) >> 4; 00062 acc ^= (acc & 0xff00) >> 5; 00063 return acc; 00064 } 00065 /*---------------------------------------------------------------------------*/ 00066 unsigned short 00067 crc16_data(const unsigned char *data, int len, unsigned short acc) 00068 { 00069 int i; 00070 00071 for(i = 0; i < len; ++i) { 00072 acc = crc16_add(*data, acc); 00073 ++data; 00074 } 00075 return acc; 00076 } 00077 /*---------------------------------------------------------------------------*/ 00078 00079 /** @} */