1 /* Return the offset of one string within another.
2 Copyright (C) 1994,1996,1997,2000,2001,2003 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
21 * My personal strstr() implementation that beats most other algorithms.
22 * Until someone tells me otherwise, I assume that this is the
23 * fastest implementation of strstr() in C.
24 * I deliberately chose not to comment it. You should have at least
25 * as much fun trying to understand it, as I had to write it :-).
27 * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
33 #if defined _LIBC || defined HAVE_STRING_H
37 typedef unsigned chartype;
42 strstr (phaystack, pneedle)
43 const char *phaystack;
46 const unsigned char *haystack, *needle;
48 const unsigned char *rneedle;
50 haystack = (const unsigned char *) phaystack;
52 if ((b = *(needle = (const unsigned char *) pneedle)))
55 haystack--; /* possible ANSI violation */
60 if (!(a = *++haystack))
76 if ((a = *++haystack) == c)
83 for (; a != b; a = *++haystack)
87 if ((a = *++haystack) == b)
93 while ((a = *++haystack) != c);
99 const unsigned char *rhaystack;
100 if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
105 if (*++rhaystack != (a = *++needle))
110 while (*++rhaystack == (a = *++needle));
111 needle = rneedle; /* took the register-poor aproach */
119 return (char *) haystack;
123 libc_hidden_builtin_def (strstr)