Are you always limited to a small alphabet, with a limited string length?
I doubt you'll get a unique function that will work on any length of string (lets say a DNA fragment).

One simple way would be to strcat() a copy of one string to itself, then use strstr() on the other.

Say
Code:
strcpy(temp,"cdeab");
strcat(temp,"cdeab");
// find cdeabcdeab
if ( strstr( temp, "abcde" ) ) {
  // match
}