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crc32: miscellaneous cleanups
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Misc cleanup of lib/crc32.c and related files.

- remove unnecessary header files.

- straighten out some convoluted ifdef's

- rewrite some references to 2 dimensional arrays as 1 dimensional
  arrays to make them correct.  I.e.  replace tab[i] with tab[0][i].

- a few trivial whitespace changes

- fix a warning in gen_crc32tables.c caused by a mismatch in the type of
  the pointer passed to output table.  Since the table is only used at
  kernel compile time, it is simpler to make the table big enough to hold
  the largest column size used.  One cannot make the column size smaller
  in output_table because it has to be used by both the le and be tables
  and they can have different column sizes.

[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>
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Bob Pearson authored and Linus Torvalds committed Mar 23, 2012
1 parent 3863ef3 commit 60e58d5
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Showing 2 changed files with 39 additions and 71 deletions.
104 changes: 36 additions & 68 deletions lib/crc32.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,13 +23,10 @@
/* see: Documentation/crc32.txt for a description of algorithms */

#include <linux/crc32.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/atomic.h>
#include "crc32defs.h"

#if CRC_LE_BITS == 8
# define tole(x) __constant_cpu_to_le32(x)
#else
Expand All @@ -41,6 +38,7 @@
#else
# define tobe(x) (x)
#endif

#include "crc32table.h"

MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>");
Expand Down Expand Up @@ -96,60 +94,47 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
#undef DO_CRC4
}
#endif

/**
* crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32
* @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for
* other uses, or the previous crc32 value if computing incrementally.
* @p: pointer to buffer over which CRC is run
* @len: length of buffer @p
*/
u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len);

#if CRC_LE_BITS == 1
/*
* In fact, the table-based code will work in this case, but it can be
* simplified by inlining the table in ?: form.
*/

u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
{
#if CRC_LE_BITS == 1
int i;
while (len--) {
crc ^= *p++;
for (i = 0; i < 8; i++)
crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
}
return crc;
}
#else /* Table-based approach */

u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
{
# if CRC_LE_BITS == 8
const u32 (*tab)[] = crc32table_le;

crc = __cpu_to_le32(crc);
crc = crc32_body(crc, p, len, tab);
return __le32_to_cpu(crc);
# elif CRC_LE_BITS == 4
# elif CRC_LE_BITS == 2
while (len--) {
crc ^= *p++;
crc = (crc >> 4) ^ crc32table_le[crc & 15];
crc = (crc >> 4) ^ crc32table_le[crc & 15];
crc = (crc >> 2) ^ crc32table_le[0][crc & 3];
crc = (crc >> 2) ^ crc32table_le[0][crc & 3];
crc = (crc >> 2) ^ crc32table_le[0][crc & 3];
crc = (crc >> 2) ^ crc32table_le[0][crc & 3];
}
return crc;
# elif CRC_LE_BITS == 2
# elif CRC_LE_BITS == 4
while (len--) {
crc ^= *p++;
crc = (crc >> 2) ^ crc32table_le[crc & 3];
crc = (crc >> 2) ^ crc32table_le[crc & 3];
crc = (crc >> 2) ^ crc32table_le[crc & 3];
crc = (crc >> 2) ^ crc32table_le[crc & 3];
crc = (crc >> 4) ^ crc32table_le[0][crc & 15];
crc = (crc >> 4) ^ crc32table_le[0][crc & 15];
}
# elif CRC_LE_BITS == 8
const u32 (*tab)[] = crc32table_le;

crc = __cpu_to_le32(crc);
crc = crc32_body(crc, p, len, tab);
crc = __le32_to_cpu(crc);
#endif
return crc;
# endif
}
#endif
EXPORT_SYMBOL(crc32_le);

/**
* crc32_be() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32
Expand All @@ -158,16 +143,9 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
* @p: pointer to buffer over which CRC is run
* @len: length of buffer @p
*/
u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len);

#if CRC_BE_BITS == 1
/*
* In fact, the table-based code will work in this case, but it can be
* simplified by inlining the table in ?: form.
*/

u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
{
#if CRC_BE_BITS == 1
int i;
while (len--) {
crc ^= *p++ << 24;
Expand All @@ -176,39 +154,29 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
(crc << 1) ^ ((crc & 0x80000000) ? CRCPOLY_BE :
0);
}
return crc;
}

#else /* Table-based approach */
u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
{
# if CRC_BE_BITS == 8
const u32 (*tab)[] = crc32table_be;

crc = __cpu_to_be32(crc);
crc = crc32_body(crc, p, len, tab);
return __be32_to_cpu(crc);
# elif CRC_BE_BITS == 4
# elif CRC_BE_BITS == 2
while (len--) {
crc ^= *p++ << 24;
crc = (crc << 4) ^ crc32table_be[crc >> 28];
crc = (crc << 4) ^ crc32table_be[crc >> 28];
crc = (crc << 2) ^ crc32table_be[0][crc >> 30];
crc = (crc << 2) ^ crc32table_be[0][crc >> 30];
crc = (crc << 2) ^ crc32table_be[0][crc >> 30];
crc = (crc << 2) ^ crc32table_be[0][crc >> 30];
}
return crc;
# elif CRC_BE_BITS == 2
# elif CRC_BE_BITS == 4
while (len--) {
crc ^= *p++ << 24;
crc = (crc << 2) ^ crc32table_be[crc >> 30];
crc = (crc << 2) ^ crc32table_be[crc >> 30];
crc = (crc << 2) ^ crc32table_be[crc >> 30];
crc = (crc << 2) ^ crc32table_be[crc >> 30];
crc = (crc << 4) ^ crc32table_be[0][crc >> 28];
crc = (crc << 4) ^ crc32table_be[0][crc >> 28];
}
return crc;
# elif CRC_BE_BITS == 8
const u32 (*tab)[] = crc32table_be;

crc = __cpu_to_be32(crc);
crc = crc32_body(crc, p, len, tab);
crc = __be32_to_cpu(crc);
# endif
return crc;
}
#endif

EXPORT_SYMBOL(crc32_le);
EXPORT_SYMBOL(crc32_be);

#ifdef CONFIG_CRC32_SELFTEST
Expand Down
6 changes: 3 additions & 3 deletions lib/gen_crc32table.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -7,8 +7,8 @@
#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
#define BE_TABLE_SIZE (1 << CRC_BE_BITS)

static uint32_t crc32table_le[4][LE_TABLE_SIZE];
static uint32_t crc32table_be[4][BE_TABLE_SIZE];
static uint32_t crc32table_le[4][256];
static uint32_t crc32table_be[4][256];

/**
* crc32init_le() - allocate and initialize LE table data
Expand Down Expand Up @@ -62,7 +62,7 @@ static void crc32init_be(void)
}
}

static void output_table(uint32_t table[4][256], int len, char *trans)
static void output_table(uint32_t (*table)[256], int len, char *trans)
{
int i, j;

Expand Down

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