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https://github.com/zephyrproject-rtos/zephyr
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5d8eadd7b1
'pad' parameter controls whether crc16() should add padding at the end of input bytes or not. This allows to compute CRC16 for data stored in non-contiguous buffers where CRC value is calculated using subsequent calls to crc16() with padding added only for last chunk. Signed-off-by: Andrzej Kaczmarek <andrzej.kaczmarek@codecoup.pl>
37 lines
646 B
C
37 lines
646 B
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 <crc16.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 & 0x8000;
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crc = (crc << 1);
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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] & (0x80 >> b));
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}
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if (divide) {
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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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