1/* Copyright (C) 1995-2023 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18/*
19 * The original strstr() file contains the following comment:
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
29#include <wchar.h>
30
31wchar_t *
32wcsstr (const wchar_t *haystack, const wchar_t *needle)
33{
34 wchar_t b, c;
35
36 if ((b = *needle) != L'\0')
37 {
38 haystack--; /* possible ANSI violation */
39 do
40 if ((c = *++haystack) == L'\0')
41 goto ret0;
42 while (c != b);
43
44 if (!(c = *++needle))
45 goto foundneedle;
46 ++needle;
47 goto jin;
48
49 for (;;)
50 {
51 wchar_t a;
52 const wchar_t *rhaystack, *rneedle;
53
54 do
55 {
56 if (!(a = *++haystack))
57 goto ret0;
58 if (a == b)
59 break;
60 if ((a = *++haystack) == L'\0')
61 goto ret0;
62shloop: ;
63 }
64 while (a != b);
65
66jin: if (!(a = *++haystack))
67 goto ret0;
68
69 if (a != c)
70 goto shloop;
71
72 if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
73 do
74 {
75 if (a == L'\0')
76 goto foundneedle;
77 if (*++rhaystack != (a = *++needle))
78 break;
79 if (a == L'\0')
80 goto foundneedle;
81 }
82 while (*++rhaystack == (a = *++needle));
83
84 needle = rneedle; /* took the register-poor approach */
85
86 if (a == L'\0')
87 break;
88 }
89 }
90foundneedle:
91 return (wchar_t*) haystack;
92ret0:
93 return NULL;
94}
95/* This alias is for backward compatibility with drafts of the ISO C
96 standard. Unfortunately the Unix(TM) standard requires this name. */
97weak_alias (wcsstr, wcswcs)
98