7f6524949a
As described in #42403, there was an issue with the existing crc16_ansi() implementation, since it was not calculating the CRC-16-ANSI (aka CRC-16-MODBUS). This is because the existing crc16() function only supported non-reflected input and output (and the CRC-16-ANSI requires reflection on both) and also it did not seem to support correctly inial seeds different from 0x0000 (and, again, the CRC-16-ANSI requires 0xffff as an initial seed). This commit replaces the existing crc16() with a functional pair, crc16() and crc16_reflect(), that also work with any poly, any initial seed and allow to select whether reflection is performed. It also adapts crc16_ansi() so that it actually returns the correct CRC. Fixes #42403. Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
77 lines
1.3 KiB
C
77 lines
1.3 KiB
C
/*
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* Copyright (c) 2017 Intel Corporation.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <sys/crc.h>
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uint16_t crc16(uint16_t poly, uint16_t seed, const uint8_t *src, size_t len)
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{
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uint16_t crc = seed;
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size_t i, j;
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for (i = 0; i < len; i++) {
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crc ^= (uint16_t)(src[i] << 8U);
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for (j = 0; j < 8; j++) {
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if (crc & 0x8000UL) {
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crc = (crc << 1U) ^ poly;
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} else {
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crc = crc << 1U;
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}
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}
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}
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return crc;
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}
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uint16_t crc16_reflect(uint16_t poly, uint16_t seed, const uint8_t *src, size_t len)
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{
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uint16_t crc = seed;
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size_t i, j;
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for (i = 0; i < len; i++) {
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crc ^= (uint16_t)src[i];
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for (j = 0; j < 8; j++) {
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if (crc & 0x0001UL) {
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crc = (crc >> 1U) ^ poly;
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} else {
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crc = crc >> 1U;
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}
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}
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}
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return crc;
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}
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uint16_t crc16_ccitt(uint16_t seed, const uint8_t *src, size_t len)
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{
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for (; len > 0; len--) {
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uint8_t e, f;
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e = seed ^ *src++;
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f = e ^ (e << 4);
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seed = (seed >> 8) ^ ((uint16_t)f << 8) ^ ((uint16_t)f << 3) ^ ((uint16_t)f >> 4);
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}
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return seed;
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}
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uint16_t crc16_itu_t(uint16_t seed, const uint8_t *src, size_t len)
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{
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for (; len > 0; len--) {
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seed = (seed >> 8U) | (seed << 8U);
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seed ^= *src++;
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seed ^= (seed & 0xffU) >> 4U;
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seed ^= seed << 12U;
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seed ^= (seed & 0xffU) << 5U;
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}
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return seed;
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}
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