Function xcb::base::pack_bitfield

pub fn pack_bitfield<T, L>(bf: &mut Vec<(T, L)>) -> (T, Vec<L>) where
    T: Ord + Zero + Copy + BitAnd<Output = T> + BitOr<Output = T>,
    L: Copy, 

pack bitfields tuples into vector usable for FFI requests

    let values = [
        (xcb::CW_EVENT_MASK, xcb::EVENT_MASK_EXPOSURE | xcb::EVENT_MASK_KEY_PRESS),
        (xcb::CW_BACK_PIXEL, 0xffffffff),
    ];
    let ffi_values = (
        xcb::CW_BACK_PIXEL | xcb::CW_EVENT_MASK,
        [
            Oxffffffff,
            xcb::EVENT_MASK_EXPOSURE | xcb::EVENT_MASK_KEY_PRESS,
            0
        ]
    );
    assert_eq!(pack_bitfield(&mut values), ffi_values);