(x)memcoll: speedup when input is known to be NUL delimited

[pspp] / lib / memcoll.c

diff --git a/lib/memcoll.c b/lib/memcoll.c
index 457d1104a93c9093d67875e123fcff1a850b7273..8e4855135f12151a0fa93abe3c7751f4912c2c2e 100644 (file)
--- a/lib/memcoll.c
+++ b/lib/memcoll.c
@@ -1,10 +1,12 @@
 /* Locale-specific memory comparison.
-   Copyright (C) 1999, 2002, 2003, 2004 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   Copyright (C) 1999, 2002-2004, 2006, 2009-2010 Free Software Foundation,
+   Inc.
+
+   This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -12,32 +14,63 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software Foundation,
-   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 /* Contributed by Paul Eggert <eggert@twinsun.com>.  */
 
-#ifdef HAVE_CONFIG_H
-# include <config.h>
-#endif
+#include <config.h>
 
 #include "memcoll.h"
 
 #include <errno.h>
+#include <stdlib.h>
 #include <string.h>
 
+/* Ensure strcoll operates on the entire input strings, in case they contain
+   NUL bytes. */
+
+static inline int
+strcoll_loop (const char *s1, size_t s1len, const char *s2, size_t s2len)
+{
+  int diff;
+  while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
+    {
+      /* 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;
+        }
+    }
+  return diff;
+}
+
 /* Compare S1 (with length S1LEN) and S2 (with length S2LEN) according
    to the LC_COLLATE locale.  S1 and S2 do not overlap, and are not
    adjacent.  Perhaps temporarily modify the bytes after S1 and S2,
    but restore their original contents before returning.  Set errno to an
    error number if there is an error, and to zero otherwise.  */
+
 int
 memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
 {
   int diff;
 
-#if HAVE_STRCOLL
-
   /* 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.  */
@@ -55,43 +88,33 @@ memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
       s1[s1len++] = '\0';
       s2[s2len++] = '\0';
 
-      while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
-       {
-         /* 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;
-           }
-       }
+      diff = strcoll_loop (s1, s1len, s2, s2len);
 
       s1[s1len - 1] = n1;
       s2[s2len - 1] = n2;
     }
 
-#else
+  return diff;
+}
 
-  diff = memcmp (s1, s2, s1len < s2len ? s1len : s2len);
-  if (! diff)
-    diff = s1len < s2len ? -1 : s1len != s2len;
-  errno = 0;
+/* Like memcoll, but S1 and S2 are known to be NUL delimited, thus no
+   modification to S1 or S2 are needed. */
+int
+memcoll0 (const char *s1, size_t s1len, const char *s2, size_t s2len)
+{
+  int diff;
+  if (!(s1len > 0 && s1[s1len] == '\0'))
+    abort ();
+  if (!(s2len > 0 && s2[s2len] == '\0'))
+    abort ();
 
-#endif
+  if (s1len == s2len && memcmp (s1, s2, s1len) == 0)
+    {
+      errno = 0;
+      diff = 0;
+    }
+  else
+    diff = strcoll_loop (s1, s1len, s2, s2len);
 
   return diff;
 }