Function copy_cqes [src]

Copies as many CQEs as are ready, and that can fit into the destination cqes slice. If none are available, enters into the kernel to wait for at most wait_nr CQEs. Returns the number of CQEs copied, advancing the CQ ring. Provides all the wait/peek methods found in liburing, but with batching and a single method. The rationale for copying CQEs rather than copying pointers is that pointers are 8 bytes whereas CQEs are not much more at only 16 bytes, and this provides a safer faster interface. Safer, because you no longer need to call cqe_seen(), avoiding idempotency bugs. Faster, because we can now amortize the atomic store release to cq.head across the batch. See https://github.com/axboe/liburing/issues/103#issuecomment-686665007. Matches the implementation of io_uring_peek_batch_cqe() in liburing, but supports waiting.

Prototype

pub fn copy_cqes(self: *IoUring, cqes: []linux.io_uring_cqe, wait_nr: u32) !u32

Parameters

self: *IoUringcqes: []linux.io_uring_cqewait_nr: u32

Source

  pub fn copy_cqes(self: *IoUring, cqes: []linux.io_uring_cqe, wait_nr: u32) !u32 {
    const count = self.copy_cqes_ready(cqes);
    if (count > 0) return count;
    if (self.cq_ring_needs_flush() or wait_nr > 0) {
        _ = try self.enter(0, wait_nr, linux.IORING_ENTER_GETEVENTS);
        return self.copy_cqes_ready(cqes);
    }
    return 0;
}  