Improve body color matching speed by caching future matches.

On a *very* long body (or header_partial) lines with multiple color
lines that match, performance can be degraded.  For instance if there
were moderately expensive regexp matches against "A" "B" and "C".  A
line with:

  A A A A A B A A C A A A B A A A C

The B and C regexps were scanned again after every "A" match, despite
that the result would be discarded again for the next A match.

Change the color matching to cache the location of each color line
match.  Discard the cache once the match offset passes that point.

1 files changed, 5 insertions, 0 deletions

diff --git a/mutt_curses.h b/mutt_curses.h
index d6f14d7c..e7c85b13 100644
--- a/mutt_curses.h
+++ b/mutt_curses.h
@@ -154,9 +154,14 @@ typedef struct color_line
   int pair;
   struct color_line *next;
 
+  regoff_t cached_rm_so;
+  regoff_t cached_rm_eo;
+
   unsigned int stop_matching : 1; /* used by the pager for body patterns,
                                      to prevent the color from being retried
                                      once it fails. */
+  unsigned int cached : 1; /* indicates cached_rm_so and cached_rm_eo
+                            * hold the last match location */
 } COLOR_LINE;
 
 #define MUTT_PROGRESS_SIZE      (1<<0)  /* traffic-based progress */