spsc-queue/queue.h

   1 #include "eventcount.h"
   2
   3 template<typename T>
   4 class spsc_queue
   5 {
   6 public:
   7         spsc_queue()
   8         {
   9                 node* n = RL_NEW node ();
  10                 head($) = n;
  11                 tail($) = n;
  12         }
  13
  14         ~spsc_queue()
  15         {
  16                 RL_ASSERT(head($) == tail($));
  17                 RL_DELETE((node*)head($));
  18         }
  19
  20         void enqueue(T data)
  21         {
  22                 node* n = RL_NEW node (data);
  23                 head($)->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                         : next(0)
  53                         , data(data)
  54                 {}
  55         };
  56
  57         rl::var<node*> head;
  58         rl::var<node*> tail;
  59
  60         eventcount ec;
  61
  62         T try_dequeue()
  63         {
  64                 node* t = tail($);
  65                 node* n = t->next($).load(std::memory_order_acquire);
  66                 if (0 == n)
  67                         return 0;
  68                 T data = n->data($);
  69                 RL_DELETE(t);
  70                 tail($) = n;
  71                 return data;
  72         }
  73 };