ucrc16.c
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/*
* Copyright (C) 2016 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @{
*
* @file
* @author Martine Lenders <m.lenders@fu-berlin.de>
*/
#include <assert.h>
#include <inttypes.h>
#include "checksum/ucrc16.h"
#define UINT8_BIT_SIZE (8U)
#define UINT16_BIT_SIZE (16U)
#define LEFTMOST_BIT_SET(value) ((value) & 0x8000U)
#define RIGHTMOST_BIT_SET(value) ((value) & 0x0001U)
uint16_t ucrc16_calc_be(const uint8_t *buf, size_t len, uint16_t poly,
uint16_t seed)
{
assert(buf != NULL);
for (unsigned c = 0; c < len; c++, buf++) {
uint32_t tmp = seed ^ (*buf << (UINT16_BIT_SIZE - UINT8_BIT_SIZE));
for (unsigned i = 0; i < UINT8_BIT_SIZE; i++) {
tmp = LEFTMOST_BIT_SET(tmp) ? ((tmp << 1) ^ poly) : (tmp << 1);
}
seed = tmp & UINT16_MAX;
}
return seed;
}
uint16_t ucrc16_calc_le(const uint8_t *buf, size_t len, uint16_t poly,
uint16_t seed)
{
assert(buf != NULL);
for (unsigned c = 0; c < len; c++, buf++) {
seed ^= (*buf);
for (unsigned i = 0; i < UINT8_BIT_SIZE; i++) {
seed = RIGHTMOST_BIT_SET(seed) ? ((seed >> 1) ^ poly) : (seed >> 1);
}
}
return seed;
}
/** @} */