Returns index of next character. If exact fit, returned index equals output slice length. Assumes there is enough space for the output.
pub fn wtf8ToWtf16Le(wtf16le: []u16, wtf8: []const u8) error
pub fn wtf8ToWtf16Le(wtf16le: []u16, wtf8: []const u8) error{InvalidWtf8}!usize {
return utf8ToUtf16LeImpl(wtf16le, wtf8, .can_encode_surrogate_half);
}