[patch v3 5/7] crc32: add-real-8-bit.diff

Bob Pearson
2011-08-09T05:25:52Z

crc32.c encodes an algorithm that processes 32 bits at a time
with the value BITS = 8 and leaves out the most common 8 bit algorithm
for computing the crc. This patch reencodes the 32 bit algorithm
with the value 32 and adds back the 'standard' 8 bit algorithm.

Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com>

---
lib/crc32.c | 17 ++++++++++++++---
lib/crc32defs.h | 18 ++++++++++--------
lib/gen_crc32table.c | 27 ++++++++++++++++++---------
3 files changed, 42 insertions(+), 20 deletions(-)

Index: infiniband/lib/crc32.c
===================================================================
--- infiniband.orig/lib/crc32.c
+++ infiniband/lib/crc32.c
@@ -25,13 +25,13 @@
#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)
@@ -43,7 +43,7 @@ MODULE_AUTHOR("Matt Domsch <Matt_Domsch@
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])
@@ -123,6 +123,12 @@ u32 __pure crc32_le(u32 crc, unsigned ch
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);
@@ -166,6 +172,11 @@ u32 __pure crc32_be(u32 crc, unsigned ch
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);
Index: infiniband/lib/crc32defs.h
===================================================================
--- infiniband.orig/lib/crc32defs.h
+++ infiniband/lib/crc32defs.h
@@ -6,27 +6,29 @@
#define CRCPOLY_LE 0xedb88320
#define CRCPOLY_BE 0x04c11db7

-/* How many bits at a time to use. Requires a table of 4<<CRC_xx_BITS bytes. */
-/* For less performance-sensitive, use 4 */
+/* How many bits at a time to use. Valid values are 1, 2, 4, 8, and 32. */
+/* For less performance-sensitive, use 4 or 8 */
#ifndef CRC_LE_BITS
-# define CRC_LE_BITS 8
+# define CRC_LE_BITS 32
#endif
#ifndef CRC_BE_BITS
-# define CRC_BE_BITS 8
+# define CRC_BE_BITS 32
#endif

/*
* Little-endian CRC computation. Used with serial bit streams sent
* lsbit-first. Be sure to use cpu_to_le32() to append the computed CRC.
*/
-#if CRC_LE_BITS > 8 || CRC_LE_BITS < 1 || CRC_LE_BITS & CRC_LE_BITS-1
-# error CRC_LE_BITS must be a power of 2 between 1 and 8
+#if CRC_LE_BITS > 32 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
+ CRC_LE_BITS & CRC_LE_BITS-1
+# error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32}"
#endif

/*
* Big-endian CRC computation. Used with serial bit streams sent
* msbit-first. Be sure to use cpu_to_be32() to append the computed CRC.
*/
-#if CRC_BE_BITS > 8 || CRC_BE_BITS < 1 || CRC_BE_BITS & CRC_BE_BITS-1
-# error CRC_BE_BITS must be a power of 2 between 1 and 8
+#if CRC_BE_BITS > 32 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
+ CRC_BE_BITS & CRC_BE_BITS-1
+# error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32}"
#endif
Index: infiniband/lib/gen_crc32table.c
===================================================================
--- infiniband.orig/lib/gen_crc32table.c
+++ infiniband/lib/gen_crc32table.c
@@ -4,11 +4,20 @@

#define ENTRIES_PER_LINE 4

+#if CRC_LE_BITS <= 8
#define LE_TABLE_SIZE (1 << CRC_LE_BITS)
+#else
+#define LE_TABLE_SIZE 256
+#endif
+
+#if CRC_BE_BITS <= 8
#define BE_TABLE_SIZE (1 << CRC_BE_BITS)
+#else
+#define BE_TABLE_SIZE 256
+#endif

-static uint32_t crc32table_le[4][LE_TABLE_SIZE];
-static uint32_t crc32table_be[4][BE_TABLE_SIZE];
+static uint32_t crc32table_le[8][256];
+static uint32_t crc32table_be[8][256];

/**
* crc32init_le() - allocate and initialize LE table data
@@ -24,14 +33,14 @@ static void crc32init_le(void)

crc32table_le[0][0] = 0;

- for (i = 1 << (CRC_LE_BITS - 1); i; i >>= 1) {
+ for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) {
crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
for (j = 0; j < LE_TABLE_SIZE; j += 2 * i)
crc32table_le[0][i + j] = crc ^ crc32table_le[0][j];
}
for (i = 0; i < LE_TABLE_SIZE; i++) {
crc = crc32table_le[0][i];
- for (j = 1; j < 4; j++) {
+ for (j = 1; j < 8; j++) {
crc = crc32table_le[0][crc & 0xff] ^ (crc >> 8);
crc32table_le[j][i] = crc;
}
@@ -55,18 +64,18 @@ static void crc32init_be(void)
}
for (i = 0; i < BE_TABLE_SIZE; i++) {
crc = crc32table_be[0][i];
- for (j = 1; j < 4; j++) {
+ for (j = 1; j < 8; j++) {
crc = crc32table_be[0][(crc >> 24) & 0xff] ^ (crc << 8);
crc32table_be[j][i] = crc;
}
}
}

-static void output_table(uint32_t table[4][256], int len, char *trans)
+static void output_table(uint32_t table[8][256], int len, char *trans)
{
int i, j;

- for (j = 0 ; j < 4; j++) {
+ for (j = 0 ; j < 8; j++) {
printf("{");
for (i = 0; i < len - 1; i++) {
if (i % ENTRIES_PER_LINE == 0)
@@ -83,14 +92,14 @@ int main(int argc, char** argv)

if (CRC_LE_BITS > 1) {
crc32init_le();
- printf("static const u32 crc32table_le[4][256] = {");
+ printf("static const u32 crc32table_le[8][256] = {");
output_table(crc32table_le, LE_TABLE_SIZE, "tole");
printf("};\n");
}

if (CRC_BE_BITS > 1) {
crc32init_be();
- printf("static const u32 crc32table_be[4][256] = {");
+ printf("static const u32 crc32table_be[8][256] = {");
output_table(crc32table_be, BE_TABLE_SIZE, "tobe");
printf("};\n");
}