1 #include <ctype.h> 2 #include <stddef.h> 3 4 char *strcasestr(const char *s1, const char *s2) 5 { 6 const char *s = s1; 7 const char *p = s2; 8 9 do { 10 if (!*p) 11 return (char *) s1; 12 if ((*p == *s) || 13 (tolower(*p) == tolower(*s))) { 14 ++p; 15 ++s; 16 } else { 17 p = s2; 18 if (!*s) 19 return NULL; 20 s = ++s1; 21 } 22 } while (1); 23 24 return *p ? NULL : (char *) s1; 25 } 26
