Make ce_uptodate() trustworthy again

diff --git a/grep.c b/grep.c
index bdadf2c0ccfafc18011beee3bc05754860392523..8e1f7de7717da95e8954491f5205547f2091aa35 100644 (file)
--- a/grep.c
+++ b/grep.c
@@ -29,13 +29,6 @@ void append_grep_pattern(struct grep_opt *opt, const char *pat,
        p->next = NULL;
 }
 
-static int is_fixed(const char *s)
-{
-       while (*s && !is_regex_special(*s))
-               s++;
-       return !*s;
-}
-
 static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
 {
        int err;
@@ -43,7 +36,7 @@ static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
        p->word_regexp = opt->word_regexp;
        p->ignore_case = opt->ignore_case;
 
-       if (opt->fixed || is_fixed(p->pattern))
+       if (opt->fixed)
                p->fixed = 1;
        if (opt->regflags & REG_ICASE)
                p->fixed = 0;
@@ -615,6 +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, p->ignore_case, &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)
 {
@@ -624,6 +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;
 
@@ -652,11 +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;