spsc-queue/queue.h

   1 #include <unrelacy.h>
   2
   3 #include "eventcount.h"
   4
   5 template<typename T>
   6 class spsc_queue
   7 {
   8 public:
   9         spsc_queue()
  10         {
  11                 node* n = RL_NEW node ();
  12                 head = n;
  13                 tail = n;
  14         }
  15
  16         ~spsc_queue()
  17         {
  18                 RL_ASSERT(head == tail);
  19                 RL_DELETE((node*)head($));
  20         }
  21
  22         void enqueue(T data)
  23         {
  24                 node* n = RL_NEW node (data);
  25                 head($)->next.store(n, std::memory_order_release);
  26                 head = n;
  27                 ec.signal_relaxed();
  28         }
  29
  30         T dequeue()
  31         {
  32                 T data = try_dequeue();
  33                 while (0 == data)
  34                 {
  35                         int cmp = ec.get();
  36                         data = try_dequeue();
  37                         if (data)
  38                                 break;
  39                         ec.wait(cmp);
  40                         data = try_dequeue();
  41                         if (data)
  42                                 break;
  43                 }
  44                 return data;
  45         }
  46
  47 private:
  48         struct node
  49         {
  50                 std::atomic<node*> next;
  51                 rl::var<T> data;
  52
  53                 node(T data = T())
  54                         : next(0)
  55                         , data(data)
  56                 {}
  57         };
  58
  59         rl::var<node*> head;
  60         rl::var<node*> tail;
  61
  62         eventcount ec;
  63
  64         T try_dequeue()
  65         {
  66                 node* t = tail($);
  67                 node* n = t->next.load(std::memory_order_acquire);
  68                 if (0 == n)
  69                         return 0;
  70                 T data = n->data($);
  71                 RL_DELETE(t);
  72                 tail = n;
  73                 return data;
  74         }
  75 };