diff options
| author | Bob Pearson <rpearson@systemfabricworks.com> | 2012-03-23 15:02:23 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-03-23 16:58:37 -0700 |
| commit | 9a1dbf6a29694c9d81b498019f103aee0f8b5b6c (patch) | |
| tree | 1f331fa108ea29ccf06a7b5816da4dbcaa12bf2d /lib/crc32.c | |
| parent | ce4320ddda4c2520fe77194d3c801ad4e8a8aa11 (diff) | |
crc32: make CRC_*_BITS definition correspond to actual bit counts
crc32.c provides a choice of one of several algorithms for computing the
LSB and LSB versions of the CRC32 checksum based on the parameters
CRC_LE_BITS and CRC_BE_BITS.
In the original version the values 1, 2, 4 and 8 respectively selected
versions of the alrogithm that computed the crc 1, 2, 4 and 32 bits as a
time.
This patch series adds a new version that computes the CRC 64 bits at a
time. To make things easier to understand the parameter has been
reinterpreted to actually stand for the number of bits processed in each
step of the algorithm so that the old value 8 has been replaced with the
value 32.
This also allows us to add in a widely used crc algorithm that computes
the crc 8 bits at a time called the Sarwate algorithm.
[djwong@us.ibm.com: Minor changelog tweaks]
Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com>
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/crc32.c')
| -rw-r--r-- | lib/crc32.c | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/lib/crc32.c b/lib/crc32.c index 7394288c045..5971f2ad46d 100644 --- a/lib/crc32.c +++ b/lib/crc32.c @@ -27,13 +27,13 @@ #include <linux/types.h> #include "crc32defs.h" -#if CRC_LE_BITS == 8 +#if CRC_LE_BITS > 8 # define tole(x) ((__force u32) __constant_cpu_to_le32(x)) #else # define tole(x) (x) #endif -#if CRC_BE_BITS == 8 +#if CRC_BE_BITS > 8 # define tobe(x) ((__force u32) __constant_cpu_to_be32(x)) #else # define tobe(x) (x) @@ -45,7 +45,7 @@ MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>"); MODULE_DESCRIPTION("Ethernet CRC32 calculations"); MODULE_LICENSE("GPL"); -#if CRC_LE_BITS == 8 || CRC_BE_BITS == 8 +#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8 static inline u32 crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) @@ -126,6 +126,12 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) crc = (crc >> 4) ^ crc32table_le[0][crc & 15]; } # elif CRC_LE_BITS == 8 + /* aka Sarwate algorithm */ + while (len--) { + crc ^= *p++; + crc = (crc >> 8) ^ crc32table_le[0][crc & 255]; + } +# else const u32 (*tab)[] = crc32table_le; crc = (__force u32) __cpu_to_le32(crc); @@ -169,6 +175,11 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) crc = (crc << 4) ^ crc32table_be[0][crc >> 28]; } # elif CRC_BE_BITS == 8 + while (len--) { + crc ^= *p++ << 24; + crc = (crc << 8) ^ crc32table_be[0][crc >> 24]; + } +# else const u32 (*tab)[] = crc32table_be; crc = (__force u32) __cpu_to_be32(crc); |