1 /* Return the offset of one string within another.
2 Copyright (C) 1994, 1996-2000, 2004 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 */
35 #if defined _LIBC || defined HAVE_STRING_H
40 # include <locale/localeinfo.h>
41 # define TOLOWER(c) __tolower_l ((unsigned char) c, loc)
43 # define TOLOWER(c) _tolower (c)
46 typedef unsigned chartype;
52 __strcasestr (phaystack, pneedle)
53 const char *phaystack;
56 register const unsigned char *haystack, *needle;
57 register chartype b, c;
59 __locale_t loc = _NL_CURRENT_LOCALE;
62 haystack = (const unsigned char *) phaystack;
63 needle = (const unsigned char *) pneedle;
65 b = TOLOWER (*needle);
68 haystack--; /* possible ANSI violation */
75 while (TOLOWER (c) != (int) b);
77 c = TOLOWER (*++needle);
86 register const unsigned char *rhaystack, *rneedle;
93 if (TOLOWER (a) == (int) b)
101 while (TOLOWER (a) != (int) b);
103 jin: a = *++haystack;
107 if (TOLOWER (a) != (int) c)
110 rhaystack = haystack-- + 1;
112 a = TOLOWER (*rneedle);
114 if (TOLOWER (*rhaystack) == (int) a)
120 a = TOLOWER (*++needle);
121 if (TOLOWER (*rhaystack) != (int) a)
126 a = TOLOWER (*++needle);
128 while (TOLOWER (*rhaystack) == (int) a);
130 needle = rneedle; /* took the register-poor approach */
137 return (char*) haystack;
142 weak_alias (__strcasestr, strcasestr)