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
|
/* Return the offset of one string within another.
Copyright (C) 1994, 1996, 1997, 2000, 2001 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 Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; 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 */
#if HAVE_CONFIG_H
# include <config.h>
#endif
#if defined _LIBC || defined HAVE_STRING_H
# include <string.h>
#endif
typedef unsigned chartype;
#undef strstr
char *
strstr (phaystack, pneedle)
const char *phaystack;
const char *pneedle;
{
const unsigned char *haystack, *needle;
chartype b;
const unsigned char *rneedle;
haystack = (const unsigned char *) phaystack;
if ((b = *(needle = (const unsigned char *) pneedle)))
{
chartype c;
haystack--; /* possible ANSI violation */
{
chartype a;
do
if (!(a = *++haystack))
goto ret0;
while (a != b);
}
if (!(c = *++needle))
goto foundneedle;
++needle;
goto jin;
for (;;)
{
{
chartype a;
if (0)
jin:{
if ((a = *++haystack) == c)
goto crest;
}
else
a = *++haystack;
do
{
for (; a != b; a = *++haystack)
{
if (!a)
goto ret0;
if ((a = *++haystack) == b)
break;
if (!a)
goto ret0;
}
}
while ((a = *++haystack) != c);
}
crest:
{
chartype a;
{
const unsigned char *rhaystack;
if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
do
{
if (!a)
goto foundneedle;
if (*++rhaystack != (a = *++needle))
break;
if (!a)
goto foundneedle;
}
while (*++rhaystack == (a = *++needle));
needle = rneedle; /* took the register-poor aproach */
}
if (!a)
break;
}
}
}
foundneedle:
return (char *) haystack;
ret0:
return 0;
}
|
