Generic strstr.c.
authordrepper <drepper>
Wed, 14 Dec 2005 11:12:34 +0000 (11:12 +0000)
committerdrepper <drepper>
Wed, 14 Dec 2005 11:12:34 +0000 (11:12 +0000)
string/strstr.c [new file with mode: 0644]

diff --git a/string/strstr.c b/string/strstr.c
new file mode 100644 (file)
index 0000000..fce1f2a
--- /dev/null
@@ -0,0 +1,123 @@
+/* Return the offset of one string within another.
+   Copyright (C) 1994,1996,1997,2000,2001,2003 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+/*
+ * My personal strstr() implementation that beats most other algorithms.
+ * Until someone tells me otherwise, I assume that this is the
+ * fastest implementation of strstr() in C.
+ * I deliberately chose not to comment it.  You should have at least
+ * as much fun trying to understand it, as I had to write it :-).
+ *
+ * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de        */
+
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#if defined _LIBC || defined HAVE_STRING_H
+# include <string.h>
+#endif
+
+typedef unsigned chartype;
+
+#undef strstr
+
+char *
+strstr (phaystack, pneedle)
+     const char *phaystack;
+     const char *pneedle;
+{
+  const unsigned char *haystack, *needle;
+  chartype b;
+  const unsigned char *rneedle;
+
+  haystack = (const unsigned char *) phaystack;
+
+  if ((b = *(needle = (const unsigned char *) pneedle)))
+    {
+      chartype c;
+      haystack--;              /* possible ANSI violation */
+
+      {
+       chartype a;
+       do
+         if (!(a = *++haystack))
+           goto ret0;
+       while (a != b);
+      }
+
+      if (!(c = *++needle))
+       goto foundneedle;
+      ++needle;
+      goto jin;
+
+      for (;;)
+       {
+         {
+           chartype a;
+           if (0)
+           jin:{
+               if ((a = *++haystack) == c)
+                 goto crest;
+             }
+           else
+             a = *++haystack;
+           do
+             {
+               for (; a != b; a = *++haystack)
+                 {
+                   if (!a)
+                     goto ret0;
+                   if ((a = *++haystack) == b)
+                     break;
+                   if (!a)
+                     goto ret0;
+                 }
+             }
+           while ((a = *++haystack) != c);
+         }
+       crest:
+         {
+           chartype a;
+           {
+             const unsigned char *rhaystack;
+             if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
+               do
+                 {
+                   if (!a)
+                     goto foundneedle;
+                   if (*++rhaystack != (a = *++needle))
+                     break;
+                   if (!a)
+                     goto foundneedle;
+                 }
+               while (*++rhaystack == (a = *++needle));
+             needle = rneedle; /* took the register-poor aproach */
+           }
+           if (!a)
+             break;
+         }
+       }
+    }
+foundneedle:
+  return (char *) haystack;
+ret0:
+  return 0;
+}
+libc_hidden_builtin_def (strstr)