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Commit | Line | Data |
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c84142e8 | 1 | /* Return the offset of one string within another. |
85dd1003 | 2 | Copyright (C) 1994,1996,1997,2000,2001,2003 Free Software Foundation, Inc. |
6d52618b | 3 | This file is part of the GNU C Library. |
28f540f4 | 4 | |
6d52618b | 5 | The GNU C Library is free software; you can redistribute it and/or |
41bdb6e2 AJ |
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. | |
28f540f4 | 9 | |
6d52618b UD |
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 | |
41bdb6e2 | 13 | Lesser General Public License for more details. |
28f540f4 | 14 | |
41bdb6e2 AJ |
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 | |
18 | 02111-1307 USA. */ | |
28f540f4 | 19 | |
60478656 RM |
20 | /* |
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 :-). | |
26 | * | |
27 | * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */ | |
28 | ||
c84142e8 UD |
29 | #if HAVE_CONFIG_H |
30 | # include <config.h> | |
31 | #endif | |
32 | ||
33 | #if defined _LIBC || defined HAVE_STRING_H | |
34 | # include <string.h> | |
35 | #endif | |
60478656 RM |
36 | |
37 | typedef unsigned chartype; | |
28f540f4 | 38 | |
9a0a462c UD |
39 | #undef strstr |
40 | ||
28f540f4 | 41 | char * |
60478656 RM |
42 | strstr (phaystack, pneedle) |
43 | const char *phaystack; | |
44 | const char *pneedle; | |
28f540f4 | 45 | { |
638621af UD |
46 | const unsigned char *haystack, *needle; |
47 | chartype b; | |
48 | const unsigned char *rneedle; | |
60478656 RM |
49 | |
50 | haystack = (const unsigned char *) phaystack; | |
28f540f4 | 51 | |
a49d0179 | 52 | if ((b = *(needle = (const unsigned char *) pneedle))) |
60478656 | 53 | { |
638621af UD |
54 | chartype c; |
55 | haystack--; /* possible ANSI violation */ | |
56 | ||
57 | { | |
58 | chartype a; | |
59 | do | |
60 | if (!(a = *++haystack)) | |
60478656 | 61 | goto ret0; |
638621af UD |
62 | while (a != b); |
63 | } | |
28f540f4 | 64 | |
638621af | 65 | if (!(c = *++needle)) |
60478656 RM |
66 | goto foundneedle; |
67 | ++needle; | |
68 | goto jin; | |
28f540f4 | 69 | |
60478656 | 70 | for (;;) |
638621af UD |
71 | { |
72 | { | |
73 | chartype a; | |
74 | if (0) | |
75 | jin:{ | |
76 | if ((a = *++haystack) == c) | |
77 | goto crest; | |
78 | } | |
79 | else | |
60478656 | 80 | a = *++haystack; |
60478656 RM |
81 | do |
82 | { | |
638621af UD |
83 | for (; a != b; a = *++haystack) |
84 | { | |
85 | if (!a) | |
86 | goto ret0; | |
87 | if ((a = *++haystack) == b) | |
88 | break; | |
89 | if (!a) | |
90 | goto ret0; | |
91 | } | |
60478656 | 92 | } |
638621af UD |
93 | while ((a = *++haystack) != c); |
94 | } | |
95 | crest: | |
96 | { | |
97 | chartype a; | |
98 | { | |
99 | const unsigned char *rhaystack; | |
100 | if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle))) | |
101 | do | |
102 | { | |
103 | if (!a) | |
104 | goto foundneedle; | |
105 | if (*++rhaystack != (a = *++needle)) | |
106 | break; | |
107 | if (!a) | |
108 | goto foundneedle; | |
109 | } | |
110 | while (*++rhaystack == (a = *++needle)); | |
111 | needle = rneedle; /* took the register-poor aproach */ | |
112 | } | |
113 | if (!a) | |
114 | break; | |
115 | } | |
116 | } | |
60478656 RM |
117 | } |
118 | foundneedle: | |
638621af | 119 | return (char *) haystack; |
60478656 RM |
120 | ret0: |
121 | return 0; | |
28f540f4 | 122 | } |
85dd1003 | 123 | libc_hidden_builtin_def (strstr) |