spsc-bugfix/queue.h

   1 #include <unrelacy.h>
   2 #include <atomic>
   3
   4 #include "eventcount.h"
   5
   6 template<typename T>
   7 class spsc_queue
   8 {
   9 public:
  10         spsc_queue()
  11         {
  12                 node* n = new node ();
  13                 head = n;
  14                 tail = n;
  15         }
  16
  17         ~spsc_queue()
  18         {
  19                 RL_ASSERT(head == tail);
  20                 delete ((node*)head($));
  21         }
  22
  23         void enqueue(T data)
  24         {
  25                 node* n = new node (data);
  26                 head($)->next.store(n, std::memory_order_release);
  27                 head = n;
  28                 ec.signal();
  29         }
  30
  31         T dequeue()
  32         {
  33                 T data = try_dequeue();
  34                 while (0 == data)
  35                 {
  36                         int cmp = ec.get();
  37                         data = try_dequeue();
  38                         if (data)
  39                                 break;
  40                         ec.wait(cmp);
  41                         data = try_dequeue();
  42                         if (data)
  43                                 break;
  44                 }
  45                 return data;
  46         }
  47
  48 private:
  49         struct node
  50         {
  51                 std::atomic<node*> next;
  52                 rl::var<T> data;
  53
  54                 node(T data = T())
  55                         : data(data)
  56                 {
  57                         next = 0;
  58                 }
  59         };
  60
  61         rl::var<node*> head;
  62         rl::var<node*> tail;
  63
  64         eventcount ec;
  65
  66         T try_dequeue()
  67         {
  68                 node* t = tail($);
  69                 node* n = t->next.load(std::memory_order_acquire);
  70                 if (0 == n)
  71                         return 0;
  72                 T data = n->data($);
  73                 delete (t);
  74                 tail = n;
  75                 return data;
  76         }
  77 };