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/*
* Ouroboros - Copyright (C) 2016 - 2026
*
* 8-bit Cyclic Redundancy Check (AUTOSAR variant)
*
* Dimitri Staessens <dimitri@ouroboros.rocks>
* Sander Vrijders <sander@ouroboros.rocks>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* version 2.1 as published by the Free Software Foundation.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., http://www.fsf.org/about/contact/.
*/
/*
* CRC-8/AUTOSAR (reveng catalog):
* poly = 0x2f
* init = 0xff
* refin = false
* refout = false
* xorout = 0xff
* check = crc8_autosar("123456789") == 0xdf
*/
#include "config.h"
#include <ouroboros/crc8.h>
/* Bit-by-bit MSB-first CRC. The expected use case is header check
* sequences of a handful of bytes; a 256-byte lookup table would not
* pay for the extra .rodata footprint at typical input sizes.
*/
void crc8_autosar(uint8_t * crc,
const void * buf,
size_t len)
{
const uint8_t * p;
uint8_t c;
size_t n;
int i;
p = (const uint8_t *) buf;
c = *crc ^ 0xff;
for (n = 0; n < len; n++) {
c ^= p[n];
for (i = 0; i < 8; i++) {
if (c & 0x80)
c = (uint8_t) ((c << 1) ^ 0x2f);
else
c = (uint8_t) (c << 1);
}
}
*crc = c ^ 0xff;
}
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