1 /*
2 * lfs util functions
3 *
4 * Copyright (c) 2017, Arm Limited. All rights reserved.
5 * SPDX-License-Identifier: BSD-3-Clause
6 */
7 #include "lfs_util.h"
8
9 /* Use the LFS naive CRC implementation until it has been decided which CRC to
10 * use for LittleFS.
11 */
12
13 /* Software CRC implementation with small lookup table */
lfs_crc(uint32_t crc,const void * buffer,size_t size)14 uint32_t lfs_crc(uint32_t crc, const void *buffer, size_t size)
15 {
16 static const uint32_t rtable[16] = {
17 0x00000000, 0x1db71064, 0x3b6e20c8, 0x26d930ac,
18 0x76dc4190, 0x6b6b51f4, 0x4db26158, 0x5005713c,
19 0xedb88320, 0xf00f9344, 0xd6d6a3e8, 0xcb61b38c,
20 0x9b64c2b0, 0x86d3d2d4, 0xa00ae278, 0xbdbdf21c,
21 };
22
23 const uint8_t *data = buffer;
24
25 for (size_t i = 0; i < size; i++) {
26 crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 0)) & 0xf];
27 crc = (crc >> 4) ^ rtable[(crc ^ (data[i] >> 4)) & 0xf];
28 }
29
30 return crc;
31 }
32
