modules/littlefs/zephyr_lfs_crc.c

/*
 * lfs util functions
 *
 * Copyright (c) 2017, Arm Limited. All rights reserved.
 * SPDX-License-Identifier: BSD-3-Clause
 */
#include "lfs_util.h"

/* Use the LFS naive CRC implementation until it has been decided which CRC to
 * use for LittleFS.
 */

/* Software CRC implementation with small lookup table */
uint32_t lfs_crc(uint32_t crc, const void *buffer, size_t size)
{
	static const uint32_t rtable[16] = {
		0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
		0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
		0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
		0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
	};

	const uint8_t *data = buffer;

	for (size_t i = 0; i < size; i++) {
		crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 0)) & 0xf];
		crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 4)) & 0xf];
	}

	return crc;
}