-/* strstr.c -- return the offset of one string within another
- Copyright (C) 1989, 1990 Free Software Foundation, Inc.
+/* Copyright (C) 1994, 1999, 2002-2003 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
- 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.
+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.
- This program 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 General Public License for more details.
+This program 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 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+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. */
-/* Written by Mike Rendell <michael@cs.mun.ca>. */
+/*
+ * 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 */
-/* Return the starting address of string S2 in S1;
- return 0 if it is not found. */
+#if HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <string.h>
+
+typedef unsigned chartype;
+
+#undef strstr
char *
-strstr (s1, s2)
- char *s1;
- char *s2;
+strstr (const char *phaystack, const char *pneedle)
{
- int i;
- char *p1;
- char *p2;
- char *s = s1;
+ register const unsigned char *haystack, *needle;
+ register chartype b, c;
+
+ haystack = (const unsigned char *) phaystack;
+ needle = (const unsigned char *) pneedle;
- for (p2 = s2, i = 0; *s; p2 = s2, i++, s++)
+ b = *needle;
+ if (b != '\0')
{
- for (p1 = s; *p1 && *p2 && *p1 == *p2; p1++, p2++)
- ;
- if (!*p2)
- break;
- }
- if (!*p2)
- return s1 + i;
+ 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;
}