copy_cqes_ready

fn copy_cqes_ready(self: *IoUring, cqes: []linux.io_uring_cqe) u32 {
    const ready = self.cq_ready();
    const count = @min(cqes.len, ready);
    const head = self.cq.head.* & self.cq.mask;

    // before wrapping
    const n = @min(self.cq.cqes.len - head, count);
    @memcpy(cqes[0..n], self.cq.cqes[head..][0..n]);

    if (count > n) {
        // wrap self.cq.cqes
        const w = count - n;
        @memcpy(cqes[n..][0..w], self.cq.cqes[0..w]);
    }

    self.cq_advance(count);
    return count;
}