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Diffstat (limited to 'src/lib/crc8.c')
| -rw-r--r-- | src/lib/crc8.c | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/src/lib/crc8.c b/src/lib/crc8.c new file mode 100644 index 00000000..e8b9685a --- /dev/null +++ b/src/lib/crc8.c @@ -0,0 +1,64 @@ +/* + * 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; +} |