From 4cfc607ebbff840991d893a8c0fa3a004caeb416 Mon Sep 17 00:00:00 2001 From: Dimitri Staessens Date: Sun, 26 Apr 2026 07:56:38 +0200 Subject: lib: Move CRC implementations to a subfolder Signed-off-by: Dimitri Staessens Signed-off-by: Sander Vrijders --- src/lib/crc/crc16.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 src/lib/crc/crc16.c (limited to 'src/lib/crc/crc16.c') diff --git a/src/lib/crc/crc16.c b/src/lib/crc/crc16.c new file mode 100644 index 00000000..55af8647 --- /dev/null +++ b/src/lib/crc/crc16.c @@ -0,0 +1,64 @@ +/* + * Ouroboros - Copyright (C) 2016 - 2026 + * + * 16-bit Cyclic Redundancy Check (CCITT-FALSE variant) + * + * Dimitri Staessens + * Sander Vrijders + * + * 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-16/CCITT-FALSE (reveng catalog, alias CRC-16/IBM-3740): + * poly = 0x1021 + * init = 0xffff + * refin = false + * refout = false + * xorout = 0x0000 + * check = crc16_ccitt_false("123456789") == 0x29b1 + */ + +#include "config.h" + +#include + +/* Bit-by-bit MSB-first CRC. Header-check use case rarely exceeds a + * few hundred bytes; a 256-entry uint16_t table costs 512 B of + * .rodata and is easy to add later if profiling demands it. + */ +void crc16_ccitt_false(uint16_t * crc, + const void * buf, + size_t len) +{ + const uint8_t * p; + uint16_t c; + size_t n; + int i; + + p = (const uint8_t *) buf; + c = *crc ^ 0xffff; + + for (n = 0; n < len; n++) { + c ^= ((uint16_t) p[n]) << 8; + for (i = 0; i < 8; i++) { + if (c & 0x8000) + c = (uint16_t) ((c << 1) ^ 0x1021); + else + c = (uint16_t) (c << 1); + } + } + + *crc = c; +} -- cgit v1.2.3