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| author | Bob Pearson <rpearson@systemfabricworks.com> | 2012-03-23 15:02:24 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-03-23 16:58:37 -0700 |
| commit | 324eb0f17d9dcead3c60c133aa244f6b3631fec9 (patch) | |
| tree | 657c564269a0fc1921f4252dbf0184725f5c85fa /lib/crc32.c | |
| parent | 9a1dbf6a29694c9d81b498019f103aee0f8b5b6c (diff) | |
| download | lwn-324eb0f17d9dcead3c60c133aa244f6b3631fec9.tar.gz lwn-324eb0f17d9dcead3c60c133aa244f6b3631fec9.zip | |
crc32: add slice-by-8 algorithm to existing code
Add slicing-by-8 algorithm to the existing slicing-by-4 algorithm. This
consists of:
- extend largest BITS size from 32 to 64
- extend tables from tab[4][256] to up to tab[8][256]
- Add code for inner loop.
[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>
Diffstat (limited to 'lib/crc32.c')
| -rw-r--r-- | lib/crc32.c | 38 |
1 files changed, 27 insertions, 11 deletions
diff --git a/lib/crc32.c b/lib/crc32.c index 5971f2ad46d5..826e16352e0e 100644 --- a/lib/crc32.c +++ b/lib/crc32.c @@ -47,25 +47,28 @@ MODULE_LICENSE("GPL"); #if CRC_LE_BITS > 8 || CRC_BE_BITS > 8 +/* implements slicing-by-4 or slicing-by-8 algorithm */ static inline u32 crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) { # ifdef __LITTLE_ENDIAN # define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8) -# define DO_CRC4 crc = t3[(crc) & 255] ^ \ - t2[(crc >> 8) & 255] ^ \ - t1[(crc >> 16) & 255] ^ \ - t0[(crc >> 24) & 255] +# define DO_CRC4 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \ + t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255]) +# define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \ + t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255]) # else # define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8) -# define DO_CRC4 crc = t0[(crc) & 255] ^ \ - t1[(crc >> 8) & 255] ^ \ - t2[(crc >> 16) & 255] ^ \ - t3[(crc >> 24) & 255] +# define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \ + t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255]) +# define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \ + t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255]) # endif const u32 *b; size_t rem_len; const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3]; + const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7]; + u32 q; /* Align it */ if (unlikely((long)buf & 3 && len)) { @@ -73,13 +76,25 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) DO_CRC(*buf++); } while ((--len) && ((long)buf)&3); } + +# if CRC_LE_BITS == 32 rem_len = len & 3; - /* load data 32 bits wide, xor data 32 bits wide. */ len = len >> 2; +# else + rem_len = len & 7; + len = len >> 3; +# endif + b = (const u32 *)buf; for (--b; len; --len) { - crc ^= *++b; /* use pre increment for speed */ - DO_CRC4; + q = crc ^ *++b; /* use pre increment for speed */ +# if CRC_LE_BITS == 32 + crc = DO_CRC4; +# else + crc = DO_CRC8; + q = *++b; + crc ^= DO_CRC4; +# endif } len = rem_len; /* And the last few bytes */ @@ -92,6 +107,7 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) return crc; #undef DO_CRC #undef DO_CRC4 +#undef DO_CRC8 } #endif |