[PATCH 04/13] crc32: Miscellaneous cleanups

From: Darrick J. Wong
Date: Wed Jan 18 2012 - 17:28:32 EST

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Misc cleanup of lib/crc32.c and related files
- removed unnecessary header files.
- straightened out some convoluted ifdef's
- rewrote some references to 2 dimensional arrays as 1 dimensional
arrays to make them correct. I.e. replaced tab[i] with tab[0][i].
- a few trivial whitespace changes
- fixed 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.

From: Bob Pearson <rpearson@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Bob Pearson <rpearson@xxxxxxxxxxxxxxxxxxxxx>
[djwong@xxxxxxxxxx: Minor changelog tweaks]
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
lib/crc32.c | 104 +++++++++++++++++---------------------------------
lib/gen_crc32table.c | 6 +--
2 files changed, 39 insertions(+), 71 deletions(-)

diff --git a/lib/crc32.c b/lib/crc32.c
index 996115d..bf03922 100644
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -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
@@ -41,6 +38,7 @@
#else
# define tobe(x) (x)
#endif
+
#include "crc32table.h"

MODULE_AUTHOR("Matt Domsch <Matt_Domsch@xxxxxxxx>");
@@ -96,6 +94,7 @@ 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
@@ -103,53 +102,39 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
* @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
@@ -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;
@@ -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
diff --git a/lib/gen_crc32table.c b/lib/gen_crc32table.c
index 85d0e41..eced769 100644
--- a/lib/gen_crc32table.c
+++ b/lib/gen_crc32table.c
@@ -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
@@ -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;

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Next message: Darrick J. Wong: "[PATCH 06/13] crc32: Make CRC_*_BITS definition correspond to actualbit counts"
Previous message: Darrick J. Wong: "[PATCH 03/13] crc32: Simplify unit test code"
In reply to: Darrick J. Wong: "[PATCH 03/13] crc32: Simplify unit test code"
Next in thread: Darrick J. Wong: "[PATCH 06/13] crc32: Make CRC_*_BITS definition correspond to actualbit counts"
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