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Christoph Hellwigbc02e862012-11-16 09:20:37 +11001#ifndef _XFS_CKSUM_H
2#define _XFS_CKSUM_H 1
3
4#define XFS_CRC_SEED (~(__uint32_t)0)
5
6/*
7 * Calculate the intermediate checksum for a buffer that has the CRC field
8 * inside it. The offset of the 32bit crc fields is passed as the
9 * cksum_offset parameter.
10 */
11static inline __uint32_t
12xfs_start_cksum(char *buffer, size_t length, unsigned long cksum_offset)
13{
14 __uint32_t zero = 0;
15 __uint32_t crc;
16
17 /* Calculate CRC up to the checksum. */
18 crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset);
19
20 /* Skip checksum field */
21 crc = crc32c(crc, &zero, sizeof(__u32));
22
23 /* Calculate the rest of the CRC. */
24 return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)],
25 length - (cksum_offset + sizeof(__be32)));
26}
27
28/*
29 * Convert the intermediate checksum to the final ondisk format.
30 *
31 * The CRC32c calculation uses LE format even on BE machines, but returns the
32 * result in host endian format. Hence we need to byte swap it back to LE format
33 * so that it is consistent on disk.
34 */
35static inline __le32
36xfs_end_cksum(__uint32_t crc)
37{
38 return ~cpu_to_le32(crc);
39}
40
41/*
42 * Helper to generate the checksum for a buffer.
43 */
44static inline void
45xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)
46{
47 __uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset);
48
49 *(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);
50}
51
52/*
53 * Helper to verify the checksum for a buffer.
54 */
55static inline int
56xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset)
57{
58 __uint32_t crc = xfs_start_cksum(buffer, length, cksum_offset);
59
60 return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
61}
62
63#endif /* _XFS_CKSUM_H */