/*
 * call-seq:
 *
 *      io.kgio_trywritev(array)     -> nil, Array or :wait_writable
 *
 * Returns nil if the write was completed in full.
 *
 * Returns an Array of strings containing the unwritten portion
 * if EAGAIN was encountered, but some portion was successfully written.
 *
 * Returns :wait_writable if EAGAIN is encountered and nothing
 * was written.
 *
 * Note: it uses +Array()+ semantic for converting argument, so that
 * it will succeed if you pass something else.
 */
static VALUE kgio_trywritev(VALUE io, VALUE ary)
{
        return my_writev(io, ary, 0);
}