UniStrncat appends not more than n code elements (a null code element and code elements that follow it are not appended) from the code element array pointed to by ucs2 to the end of the code element string pointed to by ucs1. The initial code element of ucs2 overwrites the null code element at the end of ucs1. An ending null code element is always appended to the result. If copying takes place between objects that overlap, the results are unpredictable.