crc16.h revision ca2634a46ab9da85a3a015a7772770d9dbe5848e 
1/*
2 *	crc16.h - CRC-16 routine
3 *
4 * Implements the standard CRC-16:
5 *   Width 16
6 *   Poly  0x8005 (x16 + x15 + x2 + 1)
7 *   Init  0
8 *
9 * Copyright (c) 2005 Ben Gardner <bgardner@wabtec.com>
10 *
11 * This source code is licensed under the GNU General Public License,
12 * Version 2. See the file COPYING for more details.
13 */
14
15#ifndef __CRC16_H
16#define __CRC16_H
17
18#include <ext2fs/ext2_types.h>
19
20extern __u16 const crc16_table[256];
21
22#ifdef WORDS_BIGENDIAN
23/* for an unknown reason, PPC treats __u16 as signed and keeps doing sign
24 * extension on the value.  Instead, use only the low 16 bits of an
25 * unsigned int for holding the CRC value to avoid this.
26 */
27typedef unsigned crc16_t;
28
29static inline crc16_t crc16_byte(crc16_t crc, const unsigned char data)
30{
31	return (((crc >> 8) & 0xffU) ^ crc16_table[(crc ^ data) & 0xffU]) &
32		0x0000ffffU;
33}
34#else
35typedef __u16 crc16_t;
36
37static inline crc16_t crc16_byte(crc16_t crc, const unsigned char data)
38{
39	return (crc >> 8) ^ crc16_table[(crc ^ data) & 0xff];
40}
41#endif
42
43extern crc16_t crc16(crc16_t crc, const void *buffer, unsigned int len);
44
45#endif /* __CRC16_H */
46