4e7b5769bd
Calculate crc32 4 bits at a time. The return value of the calculation is identical to the previous 1 bit at a time implementation. Results in a speed up of a factor 3 at the cost of using 64 bytes of flash for a crc table. Calculating crc32 of 128kB of flash on a 120MHz Kinetis MKE16F512 Cortex-M4 takes 99ms using the 1 bit at a time implementation, and 30ms using the 4 bits at a time implementation. The crc32 routine is used by subsys/canbus/canopen/canopen_program.c to calculate crc of flash images. Signed-off-by: Klaus H. Sorensen <khso@vestas.com>
35 lines
788 B
C
35 lines
788 B
C
/*
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* Copyright (c) 2018 Workaround GmbH.
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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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uint32_t crc32_ieee(const uint8_t *data, size_t len)
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{
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return crc32_ieee_update(0x0, data, len);
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}
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uint32_t crc32_ieee_update(uint32_t crc, const uint8_t *data, size_t len)
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{
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/* crc table generated from polynomial 0xedb88320 */
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static const uint32_t table[16] = {
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0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
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0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
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0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
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0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
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};
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crc = ~crc;
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for (size_t i = 0; i < len; i++) {
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uint8_t byte = data[i];
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crc = (crc >> 4) ^ table[(crc ^ byte) & 0x0f];
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crc = (crc >> 4) ^ table[(crc ^ (byte >> 4)) & 0x0f];
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}
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return (~crc);
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}
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