1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
/* 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 */
/* added strcasestr support, davidm@lineo.com */
#if HAVE_CONFIG_H
# include <config.h>
#endif
#if defined _LIBC || defined HAVE_STRING_H
# include <string.h>
#endif
typedef unsigned chartype;
#if defined(L_strstr)
#define VAL(x) (x)
#define FUNC strstr
#undef strstr
#elif defined(L_strcasestr)
#include <ctype.h>
#define VAL(x) tolower(x)
#define FUNC strcasestr
#undef strcasestr
#else
#error "No target function defined."
#endif
char * FUNC ( 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 (VAL(c) != VAL(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 (VAL(a) == VAL(b))
break;
a = *++haystack;
if (a == '\0')
goto ret0;
shloop:
;
}
while (VAL(a) != VAL(b));
jin:a = *++haystack;
if (a == '\0')
goto ret0;
if (VAL(a) != VAL(c))
goto shloop;
rhaystack = haystack-- + 1;
rneedle = needle;
a = *rneedle;
if (VAL(*rhaystack) == VAL(a))
do {
if (a == '\0')
goto foundneedle;
++rhaystack;
a = *++needle;
if (VAL(*rhaystack) != VAL(a))
break;
if (a == '\0')
goto foundneedle;
++rhaystack;
a = *++needle;
}
while (VAL(*rhaystack) == VAL(a));
needle = rneedle; /* took the register-poor approach */
if (a == '\0')
break;
}
}
foundneedle:
return (char *) haystack;
ret0:
return 0;
}
|
