Switch color chunk matching to use bsearch

Emails with extremely long lines, combined with a large number of
color matches, can cause a performance hit so severe that mutt appears
to have hung.

Switching out to using a binary search speeds things up noticably.

The for loops being replaced were a bit strange.  resolve_types()
ensures there are no overlaps, and that they are ordered.  A match is
defined by (first <= cnt < last).  I can't see any reason for the
strange comparison of (cnt > last) follow by (cnt != last).  Perhaps
at one time it made sense.

diff --git a/pager.c b/pager.c
index f24f6874a41af315290e3510f5de97b7397e66a9..6ac430ca7851a2a1c7e0d947ab55b27e478c203c 100644 (file)
--- a/pager.c
+++ b/pager.c
@@ -27,6 +27,7 @@
 #include <limits.h>
 #include <regex.h>
 #include <stdbool.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -246,6 +247,26 @@ static int check_sig(const char *s, struct Line *info, int n)
   return 0;
 }
 
+/**
+ * comp_syntax_t - Search for a Syntax using bsearch
+ * @param m1 Search key
+ * @param m2 Array member
+ * @retval -1 m1 precedes m2
+ * @retval  0 m1 matches m2
+ * @retval  1 m2 precedes m1
+ */
+static int comp_syntax_t(const void *m1, const void *m2)
+{
+  const int *cnt = (const int *) m1;
+  const struct Syntax *stx = (const struct Syntax *) m2;
+
+  if (*cnt < stx->first)
+    return -1;
+  if (*cnt >= stx->last)
+    return 1;
+  return 0;
+}
+
 /**
  * resolve_color - Set the colour for a line of text
  * @param line_info Line info array
@@ -263,6 +284,7 @@ static void resolve_color(struct Line *line_info, int n, int cnt, int flags,
   static int last_color; /* last color set */
   bool search = false;
   int m;
+  struct Syntax *matching_chunk = NULL;
 
   if (!cnt)
     last_color = -1; /* force attrset() */
@@ -308,39 +330,26 @@ static void resolve_color(struct Line *line_info, int n, int cnt, int flags,
   }
 
   color = def_color;
-  if (flags & MUTT_SHOWCOLOR)
+  if ((flags & MUTT_SHOWCOLOR) && line_info[m].chunks)
   {
-    for (int i = 0; i < line_info[m].chunks; i++)
+    matching_chunk = bsearch(&cnt, line_info[m].syntax, line_info[m].chunks,
+                             sizeof(struct Syntax), comp_syntax_t);
+    if (matching_chunk && (cnt >= matching_chunk->first) &&
+        (cnt < matching_chunk->last))
     {
-      /* we assume the chunks are sorted */
-      if (cnt > (line_info[m].syntax)[i].last)
-        continue;
-      if (cnt < (line_info[m].syntax)[i].first)
-        break;
-      if (cnt != (line_info[m].syntax)[i].last)
-      {
-        color = (line_info[m].syntax)[i].color;
-        break;
-      }
-      /* don't break here, as cnt might be
-       * in the next chunk as well */
+      color = matching_chunk->color;
     }
   }
 
-  if (flags & MUTT_SEARCH)
+  if ((flags & MUTT_SEARCH) && line_info[m].search_cnt)
   {
-    for (int i = 0; i < line_info[m].search_cnt; i++)
+    matching_chunk = bsearch(&cnt, line_info[m].search, line_info[m].search_cnt,
+                             sizeof(struct Syntax), comp_syntax_t);
+    if (matching_chunk && (cnt >= matching_chunk->first) &&
+        (cnt < matching_chunk->last))
     {
-      if (cnt > (line_info[m].search)[i].last)
-        continue;
-      if (cnt < (line_info[m].search)[i].first)
-        break;
-      if (cnt != (line_info[m].search)[i].last)
-      {
-        color = ColorDefs[MT_COLOR_SEARCH];
-        search = true;
-        break;
-      }
+      color = ColorDefs[MT_COLOR_SEARCH];
+      search = 1;
     }
   }