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@xxxxxxxxxxxxxx>
---
diffcore-pickaxe.c | 18 ++++++++----------
1 files changed, 8 insertions(+), 10 deletions(-)
diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index af9fffe..574b3e8 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -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);
--
1.6.2.rc2
--
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