63 lines
1.1 KiB
C
63 lines
1.1 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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u16_t crc16(const u8_t *src, size_t len, u16_t polynomial,
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u16_t initial_value, bool pad)
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{
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u16_t crc = initial_value;
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size_t padding = pad ? sizeof(crc) : 0;
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size_t i, b;
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/* src length + padding (if required) */
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for (i = 0; i < len + padding; i++) {
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for (b = 0; b < 8; b++) {
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u16_t divide = crc & 0x8000UL;
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crc = (crc << 1U);
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/* choose input bytes or implicit trailing zeros */
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if (i < len) {
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crc |= !!(src[i] & (0x80U >> b));
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}
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if (divide != 0U) {
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crc = crc ^ polynomial;
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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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u16_t crc16_ccitt(u16_t seed, const u8_t *src, size_t len)
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{
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for (; len > 0; len--) {
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u8_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) ^ (f << 8) ^ (f << 3) ^ (f >> 4);
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}
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return seed;
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}
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u16_t crc16_itu_t(u16_t seed, const u8_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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