libiberty/strstr.c

   1 /* Simple implementation of strstr for systems without it.
   2    This function is in the public domain.  */
   3
   4 /*
   5
   6 @deftypefn Supplemental char* strstr (const char *@var{string}, const char *@var{sub})
   7
   8 This function searches for the substring @var{sub} in the string
   9 @var{string}, not including the terminating null characters.  A pointer
  10 to the first occurrence of @var{sub} is returned, or @code{NULL} if the
  11 substring is absent.  If @var{sub} points to a string with zero
  12 length, the function returns @var{string}.
  13
  14 @end deftypefn
  15
  16
  17 */
  18
  19
  20 /* FIXME:  The above description is ANSI compiliant.  This routine has not
  21    been validated to comply with it.  -fnf */
  22
  23 #include <stddef.h>
  24
  25 extern char *strchr (const char *, int);
  26 extern int strncmp (const void *, const void *, size_t);
  27 extern size_t strlen (const char *);
  28
  29 char *
  30 strstr (const char *s1, const char *s2)
  31 {
  32   const char *p = s1;
  33   const size_t len = strlen (s2);
  34
  35   for (; (p = strchr (p, *s2)) != 0; p++)
  36     {
  37       if (strncmp (p, s2, len) == 0)
  38         return (char *)p;
  39     }
  40   return (0);
  41 }