Added a function for computing the CRC16 over a portion of data
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adamdunkels
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/*
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* Copyright (c) 2005, Swedish Institute of Computer Science
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* All rights reserved.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*
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* @(#)$Id: crc16.c,v 1.1 2006/06/17 22:41:17 adamdunkels Exp $
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* @(#)$Id: crc16.c,v 1.2 2008/07/07 23:24:36 adamdunkels Exp $
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*/
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/** \addtogroup crc16
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@ -39,7 +39,7 @@
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* Implementation of the CRC16 calculcation
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* \author
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* Adam Dunkels <adam@sics.se>
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*
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*
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*/
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/* CITT CRC16 polynomial ^16 + ^12 + ^5 + 1 */
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@ -63,5 +63,18 @@ crc16_add(unsigned char b, unsigned short acc)
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return acc;
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}
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/*---------------------------------------------------------------------------*/
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unsigned short
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crc16_data(unsigned char *data, int len, unsigned short acc)
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{
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int i;
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unsigned short crc = 0;
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for(i = 0; i < len; ++i) {
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crc = crc16_add(*data, crc);
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++data;
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}
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return crc;
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}
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/*---------------------------------------------------------------------------*/
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/** @} */
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@ -50,7 +50,7 @@
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*
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* This file is part of the Contiki operating system.
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*
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* @(#)$Id: crc16.h,v 1.1 2006/06/17 22:41:17 adamdunkels Exp $
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* @(#)$Id: crc16.h,v 1.2 2008/07/07 23:24:36 adamdunkels Exp $
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*/
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#ifndef __CRC16_H__
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#define __CRC16_H__
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@ -73,6 +73,23 @@
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*/
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unsigned short crc16_add(unsigned char b, unsigned short crc);
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/**
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* \brief Calculate the CRC16 over a data area
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* \param data Pointer to the data
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* \param datalen The length of the data
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* \param crc The accumulated CRC that is to be updated (or zero).
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* \return The CRC16 checksum.
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*
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* This function calculates the CRC16 checksum of a data area.
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*
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* \note The algorithm used in this implementation is
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* tailored for a running checksum and does not perform as
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* well as a table-driven algorithm when checksumming an
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* entire data block.
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*/
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unsigned short crc16_data(unsigned char *data, int datalen,
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unsigned short acc);
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#endif /* __CRC16_H__ */
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/** @} */
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