"memmove" can safely handle the situation where the source
string overlaps the destination string 

an example
ptr = memmove( s1, s2, N );

"memmove" copies exactly N characters from the string "s2"
into the area of memory pointed to by "s1". Unlike the
function "strncpy", "memmove" does not check for the
terminating '\0' of string "s2"; it simply copies N
characters. It does not put a terminating '\0' on the end of
string "s1".