toolchain/gcc/newlib/libc/string/strstr.c

   1 /*
   2 FUNCTION
   3         <<strstr>>---find string segment
   4
   5 INDEX
   6         strstr
   7
   8 ANSI_SYNOPSIS
   9         #include <string.h>
  10         char *strstr(const char *<[s1]>, const char *<[s2]>);
  11
  12 TRAD_SYNOPSIS
  13         #include <string.h>
  14         char *strstr(<[s1]>, <[s2]>)
  15         char *<[s1]>;
  16         char *<[s2]>;
  17
  18 DESCRIPTION
  19         Locates the first occurence in the string pointed to by <[s1]> of
  20         the sequence of characters in the string pointed to by <[s2]>
  21         (excluding the terminating null  character).
  22
  23 RETURNS
  24         Returns a pointer to the located string segment, or a null
  25         pointer if the string <[s2]> is not found. If <[s2]> points to
  26         a string with zero length, the <[s1]> is returned.
  27
  28 PORTABILITY
  29 <<strstr>> is ANSI C.
  30
  31 <<strstr>> requires no supporting OS subroutines.
  32
  33 QUICKREF
  34         strstr ansi pure
  35 */
  36
  37 #include <string.h>
  38
  39 char *
  40 _DEFUN (strstr, (searchee, lookfor),
  41         _CONST char *searchee _AND
  42         _CONST char *lookfor)
  43 {
  44   if (*searchee == 0)
  45     {
  46       if (*lookfor)
  47         return (char *) NULL;
  48       return (char *) searchee;
  49     }
  50
  51   while (*searchee)
  52     {
  53       size_t i;
  54       i = 0;
  55
  56       while (1)
  57         {
  58           if (lookfor[i] == 0)
  59             {
  60               return (char *) searchee;
  61             }
  62
  63           if (lookfor[i] != searchee[i])
  64             {
  65               break;
  66             }
  67           i++;
  68         }
  69       searchee++;
  70     }
  71
  72   return (char *) NULL;
  73 }