1 /*
2 * Little-endian CRC32 implementation.
3 *
4 * Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as
8 * published by the Free Software Foundation; either version 2 of the
9 * License, or any later version.
10 *
11 * This program is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 */
20
21 FILE_LICENCE ( GPL2_OR_LATER );
22
23 #include <gpxe/crc32.h>
24
25 #define CRCPOLY 0xedb88320
26
27 /**
28 * Calculate 32-bit little-endian CRC checksum
29 *
30 * @v seed Initial value
31 * @v data Data to checksum
32 * @v len Length of data
33 *
34 * Usually @a seed is initially zero or all one bits, depending on the
35 * protocol. To continue a CRC checksum over multiple calls, pass the
36 * return value from one call as the @a seed parameter to the next.
37 */
crc32_le(u32 seed,const void * data,size_t len)38 u32 crc32_le ( u32 seed, const void *data, size_t len )
39 {
40 u32 crc = seed;
41 const u8 *src = data;
42 u32 mult;
43 int i;
44
45 while ( len-- ) {
46 crc ^= *src++;
47 for ( i = 0; i < 8; i++ ) {
48 mult = ( crc & 1 ) ? CRCPOLY : 0;
49 crc = ( crc >> 1 ) ^ mult;
50 }
51 }
52
53 return crc;
54 }
55