1 #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 */ 11 static inline __uint32_t 12 xfs_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 */ 35 static inline __le32 36 xfs_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 */ 44 static inline void 45 xfs_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 */ 55 static inline int 56 xfs_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 */ 64