blob: a0451b47358314eca618436cfed2037f076267f2 [file] [log] [blame]
/*
* Copyright (c) 2017 Intel Corporation.
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <crc.h>
u16_t crc16(const u8_t *src, size_t len, u16_t polynomial,
u16_t initial_value, bool pad)
{
u16_t crc = initial_value;
size_t padding = pad ? sizeof(crc) : 0;
size_t i, b;
/* src length + padding (if required) */
for (i = 0; i < len + padding; i++) {
for (b = 0; b < 8; b++) {
u16_t divide = crc & 0x8000;
crc = (crc << 1);
/* choose input bytes or implicit trailing zeros */
if (i < len) {
crc |= !!(src[i] & (0x80 >> b));
}
if (divide) {
crc = crc ^ polynomial;
}
}
}
return crc;
}
u16_t crc16_ccitt(u16_t seed, const u8_t *src, size_t len)
{
for (; len > 0; len--) {
u8_t e, f;
e = seed ^ *src++;
f = e ^ (e << 4);
seed = (seed >> 8) ^ (f << 8) ^ (f << 3) ^ (f >> 4);
}
return seed;
}
u16_t crc16_itu_t(u16_t seed, const u8_t *src, size_t len)
{
for (; len > 0; len--) {
seed = (seed >> 8) | (seed << 8);
seed ^= *src++;
seed ^= (seed & 0xff) >> 4;
seed ^= seed << 12;
seed ^= (seed & 0xff) << 5;
}
return seed;
}