1 /* Copyright 2014 The ChromiumOS Authors
2 * Use of this source code is governed by a BSD-style license that can be
3 * found in the LICENSE file.
4 *
5 * Very simple 8-bit CRC function.
6 */
7
8 #include "2crc8.h"
9 #include "2sysincludes.h"
10
11 /* Uses CRC-8 ITU version, with x^8 + x^2 + x + 1 polynomial.
12 Note that result will evaluate to zero for a buffer of all zeroes. */
vb2_crc8(const void * vptr,uint32_t size)13 uint8_t vb2_crc8(const void *vptr, uint32_t size)
14 {
15 const uint8_t *data = vptr;
16 unsigned crc = 0;
17 uint32_t i, j;
18
19 /* Calculate CRC-8 directly. A table-based algorithm would be faster,
20 but for only a few bytes it isn't worth the code size. */
21 for (j = size; j; j--, data++) {
22 crc ^= (*data << 8);
23 for (i = 8; i; i--) {
24 if (crc & 0x8000)
25 crc ^= (0x1070 << 3);
26 crc <<= 1;
27 }
28 }
29
30 return (uint8_t)(crc >> 8);
31 }
32