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Added a function for computing the CRC16 over a portion of data

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adamdunkels 2008-07-07 23:24:36 +00:00
parent 9f08d7c6de
commit 35261f5208
2 changed files with 56 additions and 26 deletions
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63
core/lib/crc16.c
View File

@ -1,34 +1,34 @@
/*
* Copyright (c) 2005, Swedish Institute of Computer Science
* All rights reserved.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
* @(#)$Id: crc16.c,v 1.1 2006/06/17 22:41:17 adamdunkels Exp $
* @(#)$Id: crc16.c,v 1.2 2008/07/07 23:24:36 adamdunkels Exp $
*/
/** \addtogroup crc16
@ -39,7 +39,7 @@
* Implementation of the CRC16 calculcation
* \author
* Adam Dunkels <adam@sics.se>
*
*
*/
/* CITT CRC16 polynomial ^16 + ^12 + ^5 + 1 */
@ -63,5 +63,18 @@ crc16_add(unsigned char b, unsigned short acc)
return acc;
}
/*---------------------------------------------------------------------------*/
unsigned short
crc16_data(unsigned char *data, int len, unsigned short acc)
{
int i;
unsigned short crc = 0;
for(i = 0; i < len; ++i) {
crc = crc16_add(*data, crc);
++data;
}
return crc;
}
/*---------------------------------------------------------------------------*/
/** @} */

19
core/lib/crc16.h
View File

@ -50,7 +50,7 @@
*
* This file is part of the Contiki operating system.
*
* @(#)$Id: crc16.h,v 1.1 2006/06/17 22:41:17 adamdunkels Exp $
* @(#)$Id: crc16.h,v 1.2 2008/07/07 23:24:36 adamdunkels Exp $
*/
#ifndef __CRC16_H__
#define __CRC16_H__
@ -73,6 +73,23 @@
*/
unsigned short crc16_add(unsigned char b, unsigned short crc);
/**
* \brief Calculate the CRC16 over a data area
* \param data Pointer to the data
* \param datalen The length of the data
* \param crc The accumulated CRC that is to be updated (or zero).
* \return The CRC16 checksum.
*
* This function calculates the CRC16 checksum of a data area.
*
* \note The algorithm used in this implementation is
* tailored for a running checksum and does not perform as
* well as a table-driven algorithm when checksumming an
* entire data block.
*/
unsigned short crc16_data(unsigned char *data, int datalen,
unsigned short acc);
#endif /* __CRC16_H__ */
/** @} */