Add a pattern_cache_t to speed up a few repeated matches.

Vincent Lefèvre reported experiencing an index display performance
issue.  This occurred with messages containing many recipients.  He
had many index color lines containing ~l.  The ~l ended up being run
over and over on these messages, resulting in a noticable slowdown
displaying the index.

This patch adds caching for just a few of the pattern operations (~l,
~u, ~p, ~P) that are potentially expensive and also don't have
arguments.  The caching is only enabled for operations repeatedly
matching against the same message: color, hooks, scoring.

The caching is fairly targeted, but isn't that invasive or
complicated.

1 files changed, 11 insertions, 2 deletions

diff --git a/hook.c b/hook.c
index d8f678a8..0cb40344 100644
--- a/hook.c
+++ b/hook.c
@@ -360,6 +360,7 @@ void mutt_message_hook (CONTEXT *ctx, HEADER *hdr, int type)
 {
   BUFFER err, token;
   HOOK *hook;
+  pattern_cache_t cache;
 
   current_hook_type = type;
 
@@ -367,13 +368,15 @@ void mutt_message_hook (CONTEXT *ctx, HEADER *hdr, int type)
   err.dsize = STRING;
   err.data = safe_malloc (err.dsize);
   mutt_buffer_init (&token);
+  memset (&cache, 0, sizeof (cache));
   for (hook = Hooks; hook; hook = hook->next)
   {
     if(!hook->command)
       continue;
 
     if (hook->type & type)
-      if ((mutt_pattern_exec (hook->pattern, 0, ctx, hdr) > 0) ^ hook->rx.not)
+      if ((mutt_pattern_exec (hook->pattern, 0, ctx, hdr, &cache) > 0) ^ hook->rx.not)
+      {
 	if (mutt_parse_rc_line (hook->command, &token, &err) != 0)
 	{
 	  FREE (&token.data);
@@ -384,6 +387,10 @@ void mutt_message_hook (CONTEXT *ctx, HEADER *hdr, int type)
 
 	  return;
 	}
+        /* Executing arbitrary commands could affect the pattern results,
+         * so the cache has to be wiped */
+        memset (&cache, 0, sizeof (cache));
+      }
   }
   FREE (&token.data);
   FREE (&err.data);
@@ -395,7 +402,9 @@ static int
 mutt_addr_hook (char *path, size_t pathlen, int type, CONTEXT *ctx, HEADER *hdr)
 {
   HOOK *hook;
+  pattern_cache_t cache;
 
+  memset (&cache, 0, sizeof (cache));
   /* determine if a matching hook exists */
   for (hook = Hooks; hook; hook = hook->next)
   {
@@ -403,7 +412,7 @@ mutt_addr_hook (char *path, size_t pathlen, int type, CONTEXT *ctx, HEADER *hdr)
       continue;
 
     if (hook->type & type)
-      if ((mutt_pattern_exec (hook->pattern, 0, ctx, hdr) > 0) ^ hook->rx.not)
+      if ((mutt_pattern_exec (hook->pattern, 0, ctx, hdr, &cache) > 0) ^ hook->rx.not)
       {
 	mutt_make_string (path, pathlen, hook->command, ctx, hdr);
 	return 0;