BSD and glibc have an extension to regexec which takes a buffer + length pair
instead of a NUL-terminated string. Since we already have the length
computed this can save us a strlen call.
---
On 26.01.10 16:28, Linus Torvalds wrote:
> so it's sadly internal to regex. It would be nice if there was a
> non-string interface to regexec (ie a "buffer + length" instead of a
> NUL-terminated string).
BSD and glibc have an "REG_STARTEND" flag to do that. I made a small
PoC patch to use it if it's available but it didn't give any significant
speedup on my system.
grep.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/grep.c b/grep.c
index d281a02..60cce46 100644
--- a/grep.c
+++ b/grep.c
@@ -675,8 +675,15 @@ static int look_ahead(struct grep_opt *opt,
if (p->fixed)
hit = !fixmatch(p->pattern, bol, p->ignore_case, &m);
- else
+ else {
+#ifdef REG_STARTEND
+ m.rm_so = 0;
+ m.rm_eo = *left_p;
+ hit = !regexec(&p->regexp, bol, 1, &m, REG_STARTEND);
+#else
hit = !regexec(&p->regexp, bol, 1, &m, 0);
+#endif
+ }
if (!hit || m.rm_so < 0 || m.rm_eo < 0)
continue;
if (earliest < 0 || m.rm_so < earliest)
--
1.7.0.rc0.12.gc33c3
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