(memcoll): Optimize for the common case where the

arguments are bytewise equal.

diff --git a/lib/ChangeLog b/lib/ChangeLog
index 9fa61ac..2d2203e 100644 (file)
--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,3 +1,8 @@
+2006-08-14  Paul Eggert  <eggert@cs.ucla.edu>
+
+       * memcoll.c (memcoll): Optimize for the common case where the
+       arguments are bytewise equal.
+
 2006-08-11  Paul Eggert  <eggert@cs.ucla.edu>
 
        * pipe-safer.c (pipe_safer): Fix misspelling: HAVE_FUNC_PIPE ->

diff --git a/lib/memcoll.c b/lib/memcoll.c
index 82d889f..7f61a6b 100644 (file)
--- a/lib/memcoll.c
+++ b/lib/memcoll.c
@@ -38,39 +38,48 @@ memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
 
 #if HAVE_STRCOLL
 
-  char n1 = s1[s1len];
-  char n2 = s2[s2len];
+  /* strcoll is slow on many platforms, so check for the common case
+     where the arguments are bytewise equal.  Otherwise, walk through
+     the buffers using strcoll on each substring.  */
 
-  s1[s1len++] = '\0';
-  s2[s2len++] = '\0';
-
-  while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
+  if (s1len == s2len && memcmp (s1, s2, s1len) == 0)
+    diff = 0;
+  else
     {
-      /* strcoll found no difference, but perhaps it was fooled by NUL
-        characters in the data.  Work around this problem by advancing
-        past the NUL chars.  */
-      size_t size1 = strlen (s1) + 1;
-      size_t size2 = strlen (s2) + 1;
-      s1 += size1;
-      s2 += size2;
-      s1len -= size1;
-      s2len -= size2;
-
-      if (s1len == 0)
-       {
-         if (s2len != 0)
-           diff = -1;
-         break;
-       }
-      else if (s2len == 0)
+      char n1 = s1[s1len];
+      char n2 = s2[s2len];
+
+      s1[s1len++] = '\0';
+      s2[s2len++] = '\0';
+
+      while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
        {
-         diff = 1;
-         break;
+         /* strcoll found no difference, but perhaps it was fooled by NUL
+            characters in the data.  Work around this problem by advancing
+            past the NUL chars.  */
+         size_t size1 = strlen (s1) + 1;
+         size_t size2 = strlen (s2) + 1;
+         s1 += size1;
+         s2 += size2;
+         s1len -= size1;
+         s2len -= size2;
+
+         if (s1len == 0)
+           {
+             if (s2len != 0)
+               diff = -1;
+             break;
+           }
+         else if (s2len == 0)
+           {
+             diff = 1;
+             break;
+           }
        }
-    }
 
-  s1[s1len - 1] = n1;
-  s2[s2len - 1] = n2;
+      s1[s1len - 1] = n1;
+      s2[s2len - 1] = n2;
+    }
 
 #else