wchar_t *wmemccpy(wchar_t *s1, const wchar_t *s2, wchar_t c, size_t n);
wmemccpy copies at most n wide characters from the object pointed to by s2 into the object pointed to by s1. The copying stops as soon as n wide characters are copied or the wide character c is copied into the destination object pointed to by s1. The behavior of wmemccpy is undefined if copying takes place between objects that overlap.
wmemccpy returns a pointer to the wide character immediately following c in s1, or NULL if c was not found in the first n wide characters of s2.
wmemccpy conforms to POSIX.1-2008.