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

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>

René Scharfe committed Jan 10, 2009 at 00:08 UTC fb62eb7fab97cea880ea7fe4f341a4dfad14ab48

1 file changed +7 -4

grep.c

+7 -4

@@ -294,7 +294,6 @@ static struct {

294 static int match_one_pattern(struct grep_opt *opt, struct grep_pat *p, char *bol, char *eol, enum grep_context ctx)

295 {

296 int hit = 0;

297 - int at_true_bol = 1;

297 int saved_ch = 0;

298 regmatch_t pmatch[10];

299

@@ -337,7 +336,7 @@ static int match_one_pattern(struct grep_opt *opt, struct grep_pat *p, char *bol

336 * either end of the line, or at word boundary

337 * (i.e. the next char must not be a word char).

338 */

340 - if ( ((pmatch[0].rm_so == 0 && at_true_bol) ||

339 + if ( ((pmatch[0].rm_so == 0) ||

340 !word_char(bol[pmatch[0].rm_so-1])) &&

341 ((pmatch[0].rm_eo == (eol-bol)) ||

342 !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

348 /* There could be more than one match on the

349 * line, and the first match might not be

350 * strict word match. But later ones could be!

351 + * Forward to the next possible start, i.e. the

352 + * next position following a non-word char.

353 */

354 bol = pmatch[0].rm_so + bol + 1;

354 - at_true_bol = 0;

355 - goto again;

355 + while (word_char(bol[-1]) && bol < eol)

356 + bol++;

357 + if (bol < eol)

358 + goto again;

359 }

360 }

361 if (p->token == GREP_PATTERN_HEAD && saved_ch)