diff options
| -rw-r--r-- | grep.c | 75 |
1 files changed, 75 insertions, 0 deletions
@@ -608,6 +608,65 @@ static void show_pre_context(struct grep_opt *opt, const char *name, char *buf, } } +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) { @@ -617,6 +676,7 @@ static int grep_buffer_1(struct grep_opt *opt, const char *name, 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; @@ -645,11 +705,26 @@ static int grep_buffer_1(struct grep_opt *opt, const char *name, 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; |