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#ifndef _XFS_CKSUM_H
#define _XFS_CKSUM_H 1
#define XFS_CRC_SEED (~(__uint32_t)0)
/*
* Calculate the intermediate checksum for a buffer that has the CRC field
* inside it. The offset of the 32bit crc fields is passed as the
* cksum_offset parameter. We do not modify the buffer during verification,
* hence we have to split the CRC calculation across the cksum_offset.
*/
static inline __uint32_t
xfs_start_cksum_safe(char *buffer, size_t length, unsigned long cksum_offset)
{
__uint32_t zero = 0;
__uint32_t crc;
/* Calculate CRC up to the checksum. */
crc = crc32c(XFS_CRC_SEED, buffer, cksum_offset);
/* Skip checksum field */
crc = crc32c(crc, &zero, sizeof(__u32));
/* Calculate the rest of the CRC. */
return crc32c(crc, &buffer[cksum_offset + sizeof(__be32)],
length - (cksum_offset + sizeof(__be32)));
}
/*
* Fast CRC method where the buffer is modified. Callers must have exclusive
* access to the buffer while the calculation takes place.
*/
static inline __uint32_t
xfs_start_cksum_update(char *buffer, size_t length, unsigned long cksum_offset)
{
/* zero the CRC field */
*(__le32 *)(buffer + cksum_offset) = 0;
/* single pass CRC calculation for the entire buffer */
return crc32c(XFS_CRC_SEED, buffer, length);
}
/*
* Convert the intermediate checksum to the final ondisk format.
*
* The CRC32c calculation uses LE format even on BE machines, but returns the
* result in host endian format. Hence we need to byte swap it back to LE format
* so that it is consistent on disk.
*/
static inline __le32
xfs_end_cksum(__uint32_t crc)
{
return ~cpu_to_le32(crc);
}
/*
* Helper to generate the checksum for a buffer.
*
* This modifies the buffer temporarily - callers must have exclusive
* access to the buffer while the calculation takes place.
*/
static inline void
xfs_update_cksum(char *buffer, size_t length, unsigned long cksum_offset)
{
__uint32_t crc = xfs_start_cksum_update(buffer, length, cksum_offset);
*(__le32 *)(buffer + cksum_offset) = xfs_end_cksum(crc);
}
/*
* Helper to verify the checksum for a buffer.
*/
static inline int
xfs_verify_cksum(char *buffer, size_t length, unsigned long cksum_offset)
{
__uint32_t crc = xfs_start_cksum_safe(buffer, length, cksum_offset);
return *(__le32 *)(buffer + cksum_offset) == xfs_end_cksum(crc);
}
#endif /* _XFS_CKSUM_H */
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