54 lines
1.0 KiB
C
54 lines
1.0 KiB
C
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/*
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* Copyright (c) 2023 Michal Morsisko
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <zephyr/sys/crc.h>
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uint8_t crc4(const uint8_t *src, size_t len, uint8_t polynomial, uint8_t initial_value,
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bool reversed)
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{
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uint8_t crc = initial_value;
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size_t i, j, k;
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for (i = 0; i < len; i++) {
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for (j = 0; j < 2; j++) {
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crc ^= ((src[i] >> (4 * (1 - j))) & 0xf);
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for (k = 0; k < 4; k++) {
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if (reversed) {
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if (crc & 0x01) {
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crc = (crc >> 1) ^ polynomial;
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} else {
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crc >>= 1;
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}
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} else {
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if (crc & 0x8) {
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crc = (crc << 1) ^ polynomial;
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} else {
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crc <<= 1;
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}
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}
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}
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}
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}
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return crc & 0xF;
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}
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uint8_t crc4_ti(uint8_t seed, const uint8_t *src, size_t len)
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{
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static const uint8_t lookup[8] = { 0x03, 0x65, 0xcf, 0xa9, 0xb8, 0xde, 0x74, 0x12 };
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uint8_t index;
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for (size_t i = 0; i < len; i++) {
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for (size_t j = 0U; j < 2U; j++) {
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index = seed ^ ((src[i] >> (4*(1-j))) & 0xf);
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seed = (lookup[index >> 1] >> (1 - (index & 1)) * 4) & 0xf;
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}
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}
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return seed;
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}
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