spsc-queue/queue-relacy.h

   1 #include "eventcount-relacy.h"
   2
   3 template<typename T>
   4 class spsc_queue
   5 {
   6 public:
   7         spsc_queue()
   8         {
   9                 node* n = new node ();
  10                 head($) = n;
  11                 tail($) = n;
  12         }
  13
  14         ~spsc_queue()
  15         {
  16                 RL_ASSERT(head($) == tail($));
  17                 delete ((node*)head($));
  18         }
  19
  20         void enqueue(T data)
  21         {
  22                 node* n = new node (data);
  23                 head($)->next.store(n, std::memory_order_release);
  24                 head($) = n;
  25                 ec.signal_relaxed();
  26         }
  27
  28         T dequeue()
  29         {
  30                 T data = try_dequeue();
  31                 while (0 == data)
  32                 {
  33                         int cmp = ec.get();
  34                         data = try_dequeue();
  35                         if (data)
  36                                 break;
  37                         ec.wait(cmp);
  38                         data = try_dequeue();
  39                         if (data)
  40                                 break;
  41                 }
  42                 return data;
  43         }
  44
  45 private:
  46         struct node
  47         {
  48                 std::atomic<node*> next;
  49                 rl::var<T> data;
  50
  51                 node(T data = T())
  52                         : data(data)
  53                 {
  54                         next($) = 0;
  55                 }
  56         };
  57
  58         rl::var<node*> head;
  59         rl::var<node*> tail;
  60
  61         eventcount ec;
  62
  63         T try_dequeue()
  64         {
  65                 node* t = tail($);
  66                 node* n = t->next.load(std::memory_order_acquire);
  67                 if (0 == n)
  68                         return 0;
  69                 T data = n->data($);
  70                 delete (t);
  71                 tail($) = n;
  72                 return data;
  73         }
  74 };