Function encoder_max_buffer_length_from_utf16_if_no_unmappables 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn encoder_max_buffer_length_from_utf16_if_no_unmappables(
    encoder: *const Encoder,
    u16_length: usize,
) -> usize

Query the worst-case output size when encoding from UTF-16 with replacement.

Returns the size of the output buffer in bytes that will not overflow given the current state of the encoder and u16_length number of additional input code units if there are no unmappable characters in the input or SIZE_MAX if size_t would overflow.