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