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 #include <stddef.h>
  20
  21 extern char *strchr (const char *, int);
  22 extern int strncmp (const void *, const void *, size_t);
  23 extern size_t strlen (const char *);
  24
  25 char *
  26 strstr (const char *s1, const char *s2)
  27 {
  28   const char *p = s1;
  29   const size_t len = strlen (s2);
  30
  31   if (!len)
  32     return s1;
  33
  34   for (; (p = strchr (p, *s2)) != 0; p++)
  35     {
  36       if (strncmp (p, s2, len) == 0)
  37         return (char *)p;
  38     }
  39   return (0);
  40 }