1 /* Return the offset of one string within another.
2 Copyright (C) 1994,1996,1997,1998,1999,2000 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
39 typedef unsigned chartype
;
45 __strcasestr (phaystack
, pneedle
)
46 const char *phaystack
;
49 register const unsigned char *haystack
, *needle
;
50 register chartype b
, c
;
52 haystack
= (const unsigned char *) phaystack
;
53 needle
= (const unsigned char *) pneedle
;
55 b
= _tolower (*needle
);
58 haystack
--; /* possible ANSI violation */
65 while (_tolower (c
) != (int) b
);
67 c
= _tolower (*++needle
);
76 register const unsigned char *rhaystack
, *rneedle
;
83 if (_tolower (a
) == (int) b
)
91 while (_tolower (a
) != (int) b
);
97 if (_tolower (a
) != (int) c
)
100 rhaystack
= haystack
-- + 1;
102 a
= _tolower (*rneedle
);
104 if (_tolower (*rhaystack
) == (int) a
)
110 a
= _tolower (*++needle
);
111 if (_tolower (*rhaystack
) != (int) a
)
116 a
= _tolower (*++needle
);
118 while (_tolower (*rhaystack
) == (int) a
);
120 needle
= rneedle
; /* took the register-poor approach */
127 return (char*) haystack
;
132 weak_alias (__strcasestr
, strcasestr
)