Make strstr() work in multibyte locales.

[gnulib.git] / lib / strstr.c

diff --git a/lib/strstr.c b/lib/strstr.c
index 6c67d9f..5bd7cb4 100644 (file)
--- a/lib/strstr.c
+++ b/lib/strstr.c
@@ -1,5 +1,6 @@
-/* strstr.c -- return the offset of one string within another
-   Copyright (C) 1989, 1990 Free Software Foundation, Inc.
+/* Searching in a string.
+   Copyright (C) 2005 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2005.
 
    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
@@ -12,38 +13,114 @@
    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., 675 Mass Ave, Cambridge, MA 02139, USA.  */
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
 
-/* Author:
-       Mike Rendell                    Department of Computer Science
-       michael@garfield.mun.edu        Memorial University of Newfoundland
-       ..!uunet!garfield!michael       St. John's, Nfld., Canada
-       (709) 737-4550                  A1C 5S7
-*/
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
 
-/* Return the starting address of string S2 in S1;
-   return 0 if it is not found. */
+/* Specification.  */
+#include "strstr.h"
 
+#if HAVE_MBRTOWC
+# include "mbuiter.h"
+#endif
+
+/* Find the first occurrence of NEEDLE in HAYSTACK.  */
 char *
-strstr (s1, s2)
-     char *s1;
-     char *s2;
+strstr (const char *haystack, const char *needle)
 {
-  int i;
-  char *p1;
-  char *p2;
-  char *s = s1;
-
-  for (p2 = s2, i = 0; *s; p2 = s2, i++, s++)
+  /* Be careful not to look at the entire extent of haystack or needle
+     until needed.  This is useful because of these two cases:
+       - haystack may be very long, and a match of needle found early,
+       - needle may be very long, and not even a short initial segment of
+         needle may be found in haystack.  */
+#if HAVE_MBRTOWC
+  if (MB_CUR_MAX > 1)
     {
-      for (p1 = s; *p1 && *p2 && *p1 == *p2; p1++, p2++)
-       ;
-      if (!*p2)
-       break;
+      mbui_iterator_t iter_needle;
+
+      mbui_init (iter_needle, needle);
+      if (mbui_avail (iter_needle))
+       {
+         mbui_iterator_t iter_haystack;
+
+         mbui_init (iter_haystack, haystack);
+         for (;; mbui_advance (iter_haystack))
+           {
+             if (!mbui_avail (iter_haystack))
+               /* No match.  */
+               return NULL;
+
+             if (mb_equal (mbui_cur (iter_haystack), mbui_cur (iter_needle)))
+               /* The first character matches.  */
+               {
+                 mbui_iterator_t rhaystack;
+                 mbui_iterator_t rneedle;
+
+                 memcpy (&rhaystack, &iter_haystack, sizeof (mbui_iterator_t));
+                 mbui_advance (rhaystack);
+
+                 mbui_init (rneedle, needle);
+                 if (!mbui_avail (rneedle))
+                   abort ();
+                 mbui_advance (rneedle);
+
+                 for (;; mbui_advance (rhaystack), mbui_advance (rneedle))
+                   {
+                     if (!mbui_avail (rneedle))
+                       /* Found a match.  */
+                       return (char *) haystack;
+                     if (!mbui_avail (rhaystack))
+                       /* No match.  */
+                       return NULL;
+                     if (!mb_equal (mbui_cur (rhaystack), mbui_cur (rneedle)))
+                       /* Nothing in this round.  */
+                       break;
+                   }
+               }
+           }
+       }
+      else
+       return (char *) haystack;
     }
-  if (!*p2)
-    return s1 + i;
+  else
+#endif
+    {
+      if (*needle != '\0')
+       {
+         /* Speed up the following searches of needle by caching its first
+            character.  */
+         char b = *needle++;
 
-  return 0;
+         for (;; haystack++)
+           {
+             if (*haystack == '\0')
+               /* No match.  */
+               return NULL;
+             if (*haystack == b)
+               /* The first character matches.  */
+               {
+                 const char *rhaystack = haystack + 1;
+                 const char *rneedle = needle;
+
+                 for (;; rhaystack++, rneedle++)
+                   {
+                     if (*rneedle == '\0')
+                       /* Found a match.  */
+                       return (char *) haystack;
+                     if (*rhaystack == '\0')
+                       /* No match.  */
+                       return NULL;
+                     if (*rhaystack != *rneedle)
+                       /* Nothing in this round.  */
+                       break;
+                   }
+               }
+           }
+       }
+      else
+       return (char *) haystack;
+    }
 }