string/strcasestr.c

   1 /* Return the offset of one string within another.
   2    Copyright (C) 1994, 1996-2000, 2004 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   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.
   9
  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
  13    Lesser General Public License for more details.
  14
  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.  */
  19
  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 #if HAVE_CONFIG_H
  30 # include <config.h>
  31 #endif
  32
  33 #include <ctype.h>
  34
  35 #if defined _LIBC || defined HAVE_STRING_H
  36 # include <string.h>
  37 #endif
  38
  39 #ifdef _LIBC
  40 # include <locale/localeinfo.h>
  41 # define TOLOWER(c) __tolower_l ((unsigned char) c, loc)
  42 #else
  43 # define TOLOWER(c) _tolower (c)
  44 #endif
  45
  46 typedef unsigned chartype;
  47
  48 #undef strcasestr
  49 #undef __strcasestr
  50
  51 char *
  52 __strcasestr (phaystack, pneedle)
  53      const char *phaystack;
  54      const char *pneedle;
  55 {
  56   register const unsigned char *haystack, *needle;
  57   register chartype b, c;
  58 #ifdef _LIBC
  59   __locale_t loc = _NL_CURRENT_LOCALE;
  60 #endif
  61
  62   haystack = (const unsigned char *) phaystack;
  63   needle = (const unsigned char *) pneedle;
  64
  65   b = TOLOWER (*needle);
  66   if (b != '\0')
  67     {
  68       haystack--;                               /* possible ANSI violation */
  69       do
  70         {
  71           c = *++haystack;
  72           if (c == '\0')
  73             goto ret0;
  74         }
  75       while (TOLOWER (c) != (int) b);
  76
  77       c = TOLOWER (*++needle);
  78       if (c == '\0')
  79         goto foundneedle;
  80       ++needle;
  81       goto jin;
  82
  83       for (;;)
  84         {
  85           register chartype a;
  86           register const unsigned char *rhaystack, *rneedle;
  87
  88           do
  89             {
  90               a = *++haystack;
  91               if (a == '\0')
  92                 goto ret0;
  93               if (TOLOWER (a) == (int) b)
  94                 break;
  95               a = *++haystack;
  96               if (a == '\0')
  97                 goto ret0;
  98 shloop:
  99               ;
 100             }
 101           while (TOLOWER (a) != (int) b);
 102
 103 jin:      a = *++haystack;
 104           if (a == '\0')
 105             goto ret0;
 106
 107           if (TOLOWER (a) != (int) c)
 108             goto shloop;
 109
 110           rhaystack = haystack-- + 1;
 111           rneedle = needle;
 112           a = TOLOWER (*rneedle);
 113
 114           if (TOLOWER (*rhaystack) == (int) a)
 115             do
 116               {
 117                 if (a == '\0')
 118                   goto foundneedle;
 119                 ++rhaystack;
 120                 a = TOLOWER (*++needle);
 121                 if (TOLOWER (*rhaystack) != (int) a)
 122                   break;
 123                 if (a == '\0')
 124                   goto foundneedle;
 125                 ++rhaystack;
 126                 a = TOLOWER (*++needle);
 127               }
 128             while (TOLOWER (*rhaystack) == (int) a);
 129
 130           needle = rneedle;             /* took the register-poor approach */
 131
 132           if (a == '\0')
 133             break;
 134         }
 135     }
 136 foundneedle:
 137   return (char*) haystack;
 138 ret0:
 139   return 0;
 140 }
 141
 142 weak_alias (__strcasestr, strcasestr)