32 lines
831 B
C
32 lines
831 B
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;
|
||
|
|
}
|