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grep -w: forward to next possible position after rejected match

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grep -w accepts matches between non-word characters, only.  If a match
from regexec() doesn't meet this criteria, grep continues its search
after the first character of that match.

We can be a bit smarter here and skip all positions that follow a word
character first, as they can't match our criteria.  This way we can
consume characters quite cheaply and don't need to special-case the
handling of the beginning of a line.

Here's a contrived example command on msysgit (best of five runs):

	$ time git grep -w ...... v1.6.1 >/dev/null

	real    0m1.611s
	user    0m0.000s
	sys     0m0.015s

With the patch it's quite a bit faster:

	$ time git grep -w ...... v1.6.1 >/dev/null

	real    0m1.179s
	user    0m0.000s
	sys     0m0.015s

More common search patterns will gain a lot less, but it's a nice clean
up anyway.

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 2009-01-10 00:08:40 +01:00 committed by Junio C Hamano
parent c123b7c5fb
commit fb62eb7fab
1 changed files with 7 additions and 4 deletions
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11
grep.c
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@ -294,7 +294,6 @@ static struct {
static int match_one_pattern(struct grep_opt *opt, struct grep_pat *p, char *bol, char *eol, enum grep_context ctx)
{
int hit = 0;
int at_true_bol = 1;
int saved_ch = 0;
regmatch_t pmatch[10];
@ -337,7 +336,7 @@ static int match_one_pattern(struct grep_opt *opt, struct grep_pat *p, char *bol
* either end of the line, or at word boundary
* (i.e. the next char must not be a word char).
*/
if ( ((pmatch[0].rm_so == 0 && at_true_bol) ||
if ( ((pmatch[0].rm_so == 0) ||
!word_char(bol[pmatch[0].rm_so-1])) &&
((pmatch[0].rm_eo == (eol-bol)) ||
!word_char(bol[pmatch[0].rm_eo])) )
@ -349,10 +348,14 @@ static int match_one_pattern(struct grep_opt *opt, struct grep_pat *p, char *bol
/* There could be more than one match on the
* line, and the first match might not be
* strict word match. But later ones could be!
* Forward to the next possible start, i.e. the
* next position following a non-word char.
*/
bol = pmatch[0].rm_so + bol + 1;
at_true_bol = 0;
goto again;
while (word_char(bol[-1]) && bol < eol)
bol++;
if (bol < eol)
goto again;
}
}
if (p->token == GREP_PATTERN_HEAD && saved_ch)