mwsr_queue.h

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#ifndef ROSRT_DETAIL_MWSR_QUEUE_H
#define ROSRT_DETAIL_MWSR_QUEUE_H

#include "lockfree/object_pool.h"
#include <ros/atomic.h>

namespace rosrt
{
namespace detail
{

template<typename T>
class MWSRQueue
{
public:
  struct Node
  {
    T val;
    Node* next;
  };

  MWSRQueue(uint32_t size)
  : pool_(size, Node())
  , head_(0)
  {

  }

  bool push(const T& val)
  {
    Node* n = pool_.allocate();
    if (!n)
    {
      return false;
    }

    n->val = val;
    Node* stale_head = head_.load(ros::memory_order_relaxed);
    do
    {
      n->next = stale_head;
    } while(!head_.compare_exchange_weak(stale_head, n, ros::memory_order_release));

    return true;
  }

  Node* popAll()
  {
    Node* last = head_.exchange(0, ros::memory_order_consume);
    Node* first = 0;

    // Reverse the list to get it back in push() order
    while (last)
    {
      Node* tmp = last;
      last = last->next;
      tmp->next = first;
      first = tmp;
    }

    return first;
  }

  void free(Node* node)
  {
    pool_.free(node);
  }

private:
  lockfree::ObjectPool<Node> pool_;
  ros::atomic<Node*> head_;
};

} // namespace detail
} // namespace rosrt

#endif // ROSRT_DETAIL_MWSR_QUEUE_H