diffcore-pickaxe: use memmem()

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>

René Scharfe committed Mar 3, 2009 at 00:00 UTC ce163c793d2058056ccc57563c350fd6415397ca

1 file changed +8 -10

diffcore-pickaxe.c

+8 -10

@@ -10,7 +10,7 @@ static unsigned int contains(struct diff_filespec *one,

10 regex_t *regexp)

11 {

12 unsigned int cnt;

13 - unsigned long offset, sz;

13 + unsigned long sz;

14 const char *data;

15 if (diff_populate_filespec(one, 0))

16 return 0;

@@ -33,15 +33,13 @@ static unsigned int contains(struct diff_filespec *one,

33 }

35 } else { /* Classic exact string match */

36 - /* Yes, I've heard of strstr(), but the thing is *data may

37 - * not be NUL terminated. Sue me.

38 - */

39 - for (offset = 0; offset + len <= sz; offset++) {

40 - /* we count non-overlapping occurrences of needle */

41 - if (!memcmp(needle, data + offset, len)) {

42 - offset += len - 1;

43 - cnt++;

44 - }

36 + while (sz) {

37 + const char *found = memmem(data, sz, needle, len);

38 + if (!found)

39 + break;

40 + sz -= found - data + len;

41 + data = found + len;

42 + cnt++;

43 }

44 }

45 diff_free_filespec_data(one);