Commit yaboot 1.3.0

[tonyb-yaboot.git] / lib / strstr.c

diff --git a/lib/strstr.c b/lib/strstr.c
new file mode 100644 (file)
index 0000000..fbe7cfb
--- /dev/null
+++ b/lib/strstr.c
@@ -0,0 +1,119 @@
+/* Return the offset of one string within another.
+   Copyright (C) 1994, 1996, 1997 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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  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        */
+
+#include <string.h>
+
+typedef unsigned chartype;
+
+#undef strstr
+
+char *
+strstr (phaystack, pneedle)
+     const char *phaystack;
+     const char *pneedle;
+{
+  register const unsigned char *haystack, *needle;
+  register chartype b, c;
+
+  haystack = (const unsigned char *) phaystack;
+  needle = (const unsigned char *) pneedle;
+
+  b = *needle;
+  if (b != '\0')
+    {
+      haystack--;                              /* possible ANSI violation */
+      do
+       {
+         c = *++haystack;
+         if (c == '\0')
+           goto ret0;
+       }
+      while (c != b);
+
+      c = *++needle;
+      if (c == '\0')
+       goto foundneedle;
+      ++needle;
+      goto jin;
+
+      for (;;)
+        {
+          register chartype a;
+         register const unsigned char *rhaystack, *rneedle;
+
+         do
+           {
+             a = *++haystack;
+             if (a == '\0')
+               goto ret0;
+             if (a == b)
+               break;
+             a = *++haystack;
+             if (a == '\0')
+               goto ret0;
+shloop:            }
+          while (a != b);
+
+jin:     a = *++haystack;
+         if (a == '\0')
+           goto ret0;
+
+         if (a != c)
+           goto shloop;
+
+         rhaystack = haystack-- + 1;
+         rneedle = needle;
+         a = *rneedle;
+
+         if (*rhaystack == a)
+           do
+             {
+               if (a == '\0')
+                 goto foundneedle;
+               ++rhaystack;
+               a = *++needle;
+               if (*rhaystack != a)
+                 break;
+               if (a == '\0')
+                 goto foundneedle;
+               ++rhaystack;
+               a = *++needle;
+             }
+           while (*rhaystack == a);
+
+         needle = rneedle;             /* took the register-poor approach */
+
+         if (a == '\0')
+           break;
+        }
+    }
+foundneedle:
+  return (char*) haystack;
+ret0:
+  return 0;
+}