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diffcore-pickaxe: use memmem()

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Use memmem() instead of open-coding it.  The system libraries usually have a
much faster version than the memcmp()-loop here.  Even our own fall-back in
compat/, which is used on Windows, is slightly faster.

The following commands were run in a Linux kernel repository and timed, the
best of five results is shown:

  $ STRING='Ensure that the real time constraints are schedulable.'
  $ git log -S"$STRING" HEAD -- kernel/sched.c >/dev/null

On Ubuntu 8.10 x64, before (v1.6.2-rc2):

  8.09user 0.04system 0:08.14elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
  0inputs+0outputs (0major+30952minor)pagefaults 0swaps

And with the patch:

  1.50user 0.04system 0:01.54elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
  0inputs+0outputs (0major+30645minor)pagefaults 0swaps

On Fedora 10 x64, before:

  8.34user 0.05system 0:08.39elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
  0inputs+0outputs (0major+29268minor)pagefaults 0swaps

And with the patch:

  1.15user 0.05system 0:01.20elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
  0inputs+0outputs (0major+32253minor)pagefaults 0swaps

On Windows Vista x64, before:

  real    0m9.204s
  user    0m0.000s
  sys     0m0.000s

And with the patch:

  real    0m8.470s
  user    0m0.000s
  sys     0m0.000s

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
René Scharfe 2009-03-03 00:00:55 +01:00 committed by Junio C Hamano
parent f474c52661
commit ce163c793d
1 changed files with 8 additions and 10 deletions
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18
diffcore-pickaxe.c
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@ -10,7 +10,7 @@ static unsigned int contains(struct diff_filespec *one,
regex_t *regexp)
{
unsigned int cnt;
unsigned long offset, sz;
unsigned long sz;
const char *data;
if (diff_populate_filespec(one, 0))
return 0;
@ -33,15 +33,13 @@ static unsigned int contains(struct diff_filespec *one,
}
} else { /* Classic exact string match */
/* Yes, I've heard of strstr(), but the thing is *data may
* not be NUL terminated. Sue me.
*/
for (offset = 0; offset + len <= sz; offset++) {
/* we count non-overlapping occurrences of needle */
if (!memcmp(needle, data + offset, len)) {
offset += len - 1;
cnt++;
}
while (sz) {
const char *found = memmem(data, sz, needle, len);
if (!found)
break;
sz -= found - data + len;
data = found + len;
cnt++;
}
}
diff_free_filespec_data(one);