Make wchar_t upper case with LCMapString API

I'm curious about the LCMapString API for a Windows app. My goal is to capitalize a single wchar_t (or 2-byte character.) Am I safe to assume that it will always map it to a single wchar_t?

Or this:

wchar_t c1 = input_character;   //Say, L'd';
wchar_t c2 = 0;
if(LCMapString(LOCALE_INVARIANT, LCMAP_UPPERCASE, &c1, 1, &c2, 1))
{
    //Success, capitalized result is in `c2`
}

via Chebli Mohamed