89 lines
2.9 KiB
C
89 lines
2.9 KiB
C
/**
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@file
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CRC Computations
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@defgroup util_crc16 "util/crc16.h": CRC Computations
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@code#include "util/crc16.h"@endcode
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This header file provides functions for calculating
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cyclic redundancy checks (CRC) using common polynomials.
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Modified by Doc Walker to be processor-independent (removed inline
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assembler to allow it to compile on SAM3X8E processors).
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@par References:
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Jack Crenshaw's "Implementing CRCs" article in the January 1992 issue of @e
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Embedded @e Systems @e Programming. This may be difficult to find, but it
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explains CRC's in very clear and concise terms. Well worth the effort to
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obtain a copy.
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*/
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/* Copyright (c) 2002, 2003, 2004 Marek Michalkiewicz
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Copyright (c) 2005, 2007 Joerg Wunsch
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Copyright (c) 2013 Dave Hylands
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Copyright (c) 2013 Frederic Nadeau
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Copyright (c) 2015 Doc Walker
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All rights reserved.
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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 are met:
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* 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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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of the copyright holders nor the names of
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND 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 COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE. */
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#ifndef _UTIL_CRC16_H_
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#define _UTIL_CRC16_H_
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#include <chip.h>
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/** @ingroup util_crc16
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Processor-independent CRC-16 calculation.
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Polynomial: x^16 + x^15 + x^2 + 1 (0xA001)<br>
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Initial value: 0xFFFF
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This CRC is normally used in disk-drive controllers.
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@param uint16_t crc (0x0000..0xFFFF)
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@param uint8_t a (0x00..0xFF)
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@return calculated CRC (0x0000..0xFFFF)
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*/
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static uint16_t crc16_update(uint16_t crc, uint8_t a)
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{
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int i;
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crc ^= a;
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for (i = 0; i < 8; ++i)
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{
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if (crc & 1)
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crc = (crc >> 1) ^ 0xA001;
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else
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crc = (crc >> 1);
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}
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return crc;
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}
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#endif /* _UTIL_CRC16_H_ */
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