}
}
+static int should_lookahead(struct grep_opt *opt)
+{
+ struct grep_pat *p;
+
+ if (opt->extended)
+ return 0; /* punt for too complex stuff */
+ if (opt->invert)
+ return 0;
+ for (p = opt->pattern_list; p; p = p->next) {
+ if (p->token != GREP_PATTERN)
+ return 0; /* punt for "header only" and stuff */
+ }
+ return 1;
+}
+
+static int look_ahead(struct grep_opt *opt,
+ unsigned long *left_p,
+ unsigned *lno_p,
+ char **bol_p)
+{
+ unsigned lno = *lno_p;
+ char *bol = *bol_p;
+ struct grep_pat *p;
+ char *sp, *last_bol;
+ regoff_t earliest = -1;
+
+ for (p = opt->pattern_list; p; p = p->next) {
+ int hit;
+ regmatch_t m;
+
+ if (p->fixed)
+ hit = !fixmatch(p->pattern, bol, &m);
+ else
+ hit = !regexec(&p->regexp, bol, 1, &m, 0);
+ if (!hit || m.rm_so < 0 || m.rm_eo < 0)
+ continue;
+ if (earliest < 0 || m.rm_so < earliest)
+ earliest = m.rm_so;
+ }
+
+ if (earliest < 0) {
+ *bol_p = bol + *left_p;
+ *left_p = 0;
+ return 1;
+ }
+ for (sp = bol + earliest; bol < sp && sp[-1] != '\n'; sp--)
+ ; /* find the beginning of the line */
+ last_bol = sp;
+
+ for (sp = bol; sp < last_bol; sp++) {
+ if (*sp == '\n')
+ lno++;
+ }
+ *left_p -= last_bol - bol;
+ *bol_p = last_bol;
+ *lno_p = lno;
+ return 0;
+}
+
static int grep_buffer_1(struct grep_opt *opt, const char *name,
char *buf, unsigned long size, int collect_hits)
{
unsigned last_hit = 0;
int binary_match_only = 0;
unsigned count = 0;
+ int try_lookahead = 0;
enum grep_context ctx = GREP_CONTEXT_HEAD;
xdemitconf_t xecfg;
opt->priv = &xecfg;
}
}
+ try_lookahead = should_lookahead(opt);
while (left) {
char *eol, ch;
int hit;
+ /*
+ * look_ahead() skips quicly to the line that possibly
+ * has the next hit; don't call it if we need to do
+ * something more than just skipping the current line
+ * in response to an unmatch for the current line. E.g.
+ * inside a post-context window, we will show the current
+ * line as a context around the previous hit when it
+ * doesn't hit.
+ */
+ if (try_lookahead
+ && !(last_hit
+ && lno <= last_hit + opt->post_context)
+ && look_ahead(opt, &left, &lno, &bol))
+ break;
eol = end_of_line(bol, &left);
ch = *eol;
*eol = 0;