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crc32: minor optimizations and cleanup 

Move common crc body to new function crc32_body() cleaup and micro
optimize crc32_body for speed and less size.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Joakim Tjernlund 2009-12-14 18:01:33 -08:00 committed by Linus Torvalds
parent 14f1b75b1d
commit ddcaccbc17
1 changed files with 44 additions and 77 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

121
lib/crc32.c
View File

@ -42,6 +42,48 @@ 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
static inline u32
crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 *tab)
{
# ifdef __LITTLE_ENDIAN
# define DO_CRC(x) crc = tab[(crc ^ (x)) & 255 ] ^ (crc >> 8)
# else
# define DO_CRC(x) crc = tab[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)
# endif
const u32 *b = (const u32 *)buf;
size_t rem_len;
/* Align it */
if (unlikely((long)b & 3 && len)) {
u8 *p = (u8 *)b;
do {
DO_CRC(*p++);
} while ((--len) && ((long)p)&3);
b = (u32 *)p;
}
rem_len = len & 3;
/* load data 32 bits wide, xor data 32 bits wide. */
len = len >> 2;
for (--b; len; --len) {
crc ^= *++b; /* use pre increment for speed */
DO_CRC(0);
DO_CRC(0);
DO_CRC(0);
DO_CRC(0);
}
len = rem_len;
/* And the last few bytes */
if (len) {
u8 *p = (u8 *)(b + 1) - 1;
do {
DO_CRC(*++p); /* use pre increment for speed */
} while (--len);
}
return crc;
}
#endif
/**
* crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32
* @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for
@ -72,48 +114,10 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)
{
# if CRC_LE_BITS == 8
const u32 *b =(u32 *)p;
const u32 *tab = crc32table_le;
# ifdef __LITTLE_ENDIAN
# define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)
# else
# define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)
# endif
crc = __cpu_to_le32(crc);
/* Align it */
if(unlikely(((long)b)&3 && len)){
do {
u8 *p = (u8 *)b;
DO_CRC(*p++);
b = (void *)p;
} while ((--len) && ((long)b)&3 );
}
if(likely(len >= 4)){
/* load data 32 bits wide, xor data 32 bits wide. */
size_t save_len = len & 3;
len = len >> 2;
--b; /* use pre increment below(*++b) for speed */
do {
crc ^= *++b;
DO_CRC(0);
DO_CRC(0);
DO_CRC(0);
DO_CRC(0);
} while (--len);
b++; /* point to next byte(s) */
len = save_len;
}
/* And the last few bytes */
if(len){
do {
u8 *p = (u8 *)b;
DO_CRC(*p++);
b = (void *)p;
} while (--len);
}
crc = crc32_body(crc, p, len, tab);
return __le32_to_cpu(crc);
#undef ENDIAN_SHIFT
#undef DO_CRC
@ -170,47 +174,10 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)
{
# if CRC_BE_BITS == 8
const u32 *b =(u32 *)p;
const u32 *tab = crc32table_be;
# ifdef __LITTLE_ENDIAN
# define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)
# else
# define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)
# endif
crc = __cpu_to_be32(crc);
/* Align it */
if(unlikely(((long)b)&3 && len)){
do {
u8 *p = (u8 *)b;
DO_CRC(*p++);
b = (u32 *)p;
} while ((--len) && ((long)b)&3 );
}
if(likely(len >= 4)){
/* load data 32 bits wide, xor data 32 bits wide. */
size_t save_len = len & 3;
len = len >> 2;
--b; /* use pre increment below(*++b) for speed */
do {
crc ^= *++b;
DO_CRC(0);
DO_CRC(0);
DO_CRC(0);
DO_CRC(0);
} while (--len);
b++; /* point to next byte(s) */
len = save_len;
}
/* And the last few bytes */
if(len){
do {
u8 *p = (u8 *)b;
DO_CRC(*p++);
b = (void *)p;
} while (--len);
}
crc = crc32_body(crc, p, len, tab);
return __be32_to_cpu(crc);
#undef ENDIAN_SHIFT
#undef DO_CRC