On 11/07/12 07:37, Dave Chinner wrote:
+/*
+ * 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.
+ */
+static inline __uint32_t
+xfs_start_cksum(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)));
+}
Why not zero the cksum field and then calculate the crc on the whole buffer?
--Mark.
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