CompletionQueue

pub const CompletionQueue = struct {
    head: *u32,
    tail: *u32,
    mask: u32,
    overflow: *u32,
    cqes: []linux.io_uring_cqe,

    pub fn init(fd: linux.fd_t, p: linux.io_uring_params, sq: SubmissionQueue) !CompletionQueue {
        assert(fd >= 0);
        assert((p.features & linux.IORING_FEAT_SINGLE_MMAP) != 0);
        const mmap = sq.mmap;
        const cqes: [*]linux.io_uring_cqe = @ptrCast(@alignCast(&mmap[p.cq_off.cqes]));
        assert(p.cq_entries == @as(*u32, @ptrCast(@alignCast(&mmap[p.cq_off.ring_entries]))).*);
        return CompletionQueue{
            .head = @ptrCast(@alignCast(&mmap[p.cq_off.head])),
            .tail = @ptrCast(@alignCast(&mmap[p.cq_off.tail])),
            .mask = @as(*u32, @ptrCast(@alignCast(&mmap[p.cq_off.ring_mask]))).*,
            .overflow = @ptrCast(@alignCast(&mmap[p.cq_off.overflow])),
            .cqes = cqes[0..p.cq_entries],
        };
    }

    pub fn deinit(self: *CompletionQueue) void {
        _ = self;
        // A no-op since we now share the mmap with the submission queue.
        // Here for symmetry with the submission queue, and for any future feature support.
    }
}