compiler/stdc/strcasestr.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     C extension function strcasestr().
   6 */
   7
   8 #include <ctype.h>
   9
  10 /*****************************************************************************
  11
  12     NAME */
  13 #include <string.h>
  14
  15         char * strcasestr (
  16
  17 /*  SYNOPSIS */
  18         const char * str,
  19         const char * search)
  20
  21 /*  FUNCTION
  22         Searches for a string in a string.
  23
  24     INPUTS
  25         str - Search this string
  26         search - Look for this string
  27
  28     RESULT
  29         A pointer to the first occurence of search in str or NULL if search
  30         is not found in str.
  31
  32     NOTES
  33
  34     EXAMPLE
  35         char buffer[64];
  36
  37         strcpy (buffer, "Hello ");
  38
  39         // This returns a pointer to the first l in buffer.
  40         strcasestr (buffer, "llo ");
  41
  42         // This returns NULL
  43         strcasestr (buffer, "llox");
  44
  45     BUGS
  46
  47     SEE ALSO
  48         strchr(), strrchr(), strpbrk()
  49
  50     INTERNALS
  51
  52 ******************************************************************************/
  53 {
  54     size_t       done;
  55     size_t       len_s = strlen (search);
  56     const char * t;
  57
  58     do
  59     {
  60         /* If the first character matches */
  61         if (tolower(*search) == tolower(*str))
  62         {
  63             /* How many characters to compare */
  64             done = len_s;
  65
  66             /* Skip the first char (we have checked this one already) */
  67             t = search + 1;
  68             str ++;
  69
  70             /*
  71                 Until all characters have been compared and the two
  72                 characters at the current position are equal ...
  73             */
  74             while ((--done) && (tolower(*t) == tolower(*str)))
  75             {
  76                 /* Next character */
  77                 t ++;
  78                 str ++;
  79             }
  80
  81             /* All character compared ? */
  82             if (!done)
  83             {
  84                 /*
  85                     Then we have found what we were looking for. str points
  86                     now to the last character of the string we look for.
  87                     Therefore we must move it backward to the beginning of
  88                     the string.
  89                 */
  90                 str -= len_s;
  91                 return ((char *)str);
  92             }
  93             else
  94             {
  95                 /*
  96                     The strings are the same upto this character. I must
  97                     go back since the pattern might be something like
  98                     "ccbba" and the string "cccbba".
  99                 */
 100                 str -= len_s - done;
 101             }
 102         }
 103     } while (*str++);
 104
 105     /* nothing found */
 106     return(0);
 107 } /* strcasestr */
 108
 109 #ifdef TEST
 110 #include <stdio.h>
 111 #include <string.h>
 112
 113 int main (int argc, char ** argv)
 114 {
 115     char * ptr;
 116
 117     if (argc != 3)
 118     {
 119         printf ("Usage: %s string search\n", argv[0]);
 120         return 10;
 121     }
 122
 123     ptr = strcasestr (argv[1], argv[2]);
 124
 125     if (!ptr)
 126         printf ("%s not found in %s\n", argv[2], argv[1]);
 127     else
 128         printf ("%s found in %s as %s\n", argv[2], argv[1], ptr);
 129
 130     return 0;
 131 }
 132 #endif /* TEST */