ich777/linux_media
1
0
Fork 0
mirror of https://github.com/tbsdtv/linux_media.git synced 2025-07-23 12:43:29 +02:00
Code Issues Packages Projects Releases Wiki Activity

crc32: make CRC_*_BITS definition correspond to actual bit counts

Browse Source 
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>
This commit is contained in:
Bob Pearson
2012-03-23 15:02:23 -07:00
committed by Linus Torvalds
parent ce4320ddda
commit 9a1dbf6a29
3 changed files with 34 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
lib/crc32.c
View File

@@ -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);