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 *
strstr(const char * s1,const char * s2)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 }
42