aboutsummaryrefslogtreecommitdiff
path: root/sysdeps/generic/strcasestr.c
blob: 6ceb2d7d830e48d0efc991b9e840af102be4a680 (plain)
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
/* Return the offset of one string within another.
   Copyright (C) 1994,1996,1997,1998,1999,2000 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

#include <ctype.h>

#if defined _LIBC || defined HAVE_STRING_H
# include <string.h>
#endif

typedef unsigned chartype;

#undef strcasestr
#undef __strcasestr

char *
__strcasestr (phaystack, pneedle)
     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 = _tolower (*needle);
  if (b != '\0')
    {
      haystack--;				/* possible ANSI violation */
      do
	{
	  c = *++haystack;
	  if (c == '\0')
	    goto ret0;
	}
      while (_tolower (c) != (int) b);

      c = _tolower (*++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 (_tolower (a) == (int) b)
		break;
	      a = *++haystack;
	      if (a == '\0')
		goto ret0;
shloop:
	      ;
	    }
          while (_tolower (a) != (int) b);

jin:	  a = *++haystack;
	  if (a == '\0')
	    goto ret0;

	  if (_tolower (a) != (int) c)
	    goto shloop;

	  rhaystack = haystack-- + 1;
	  rneedle = needle;
	  a = _tolower (*rneedle);

	  if (_tolower (*rhaystack) == (int) a)
	    do
	      {
		if (a == '\0')
		  goto foundneedle;
		++rhaystack;
		a = _tolower (*++needle);
		if (_tolower (*rhaystack) != (int) a)
		  break;
		if (a == '\0')
		  goto foundneedle;
		++rhaystack;
		a = _tolower (*++needle);
	      }
	    while (_tolower (*rhaystack) == (int) a);

	  needle = rneedle;		/* took the register-poor approach */

	  if (a == '\0')
	    break;
        }
    }
foundneedle:
  return (char*) haystack;
ret0:
  return 0;
}

weak_alias (__strcasestr, strcasestr)