lib/os/crc32_sw.c

/*
 * Copyright (c) 2018 Workaround GmbH.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <sys/crc.h>

uint32_t crc32_ieee(const uint8_t *data, size_t len)
{
	return crc32_ieee_update(0x0, data, len);
}

uint32_t crc32_ieee_update(uint32_t crc, const uint8_t *data, size_t len)
{
	/* crc table generated from polynomial 0xedb88320 */
	static const uint32_t table[16] = {
		0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
		0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
		0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
		0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
	};

	crc = ~crc;

	for (size_t i = 0; i < len; i++) {
		uint8_t byte = data[i];

		crc = (crc >> 4) ^ table[(crc ^ byte) & 0x0f];
		crc = (crc >> 4) ^ table[(crc ^ ((uint32_t)byte >> 4)) & 0x0f];
	}

	return (~crc);
}