MemoryReclamationByReference.h

/*************************************************************************
 @Author: jiapeng.wen(jiapeng.wen@ele.me)
 @Created Time : Wed 11 Sep 2019 02:57:00 PM CST
 @File Name: MemoryReclamationByReference.h
 @brief:
************************************************************************/
#pragma once 
#include <atomic>
#include <cassert>

template<typename _Node>
class MemoryReclamationByReferenceCountingT
{
  std::atomic<size_t> counter_ = ATOMIC_VAR_INIT(0);
  std::atomic<_Node*> will_be_deleted_list_ = ATOMIC_VAR_INIT(nullptr);
  void InsertToList(_Node* first, _Node* last)
  {
    last->next = will_be_deleted_list_;
    while (!will_be_deleted_list_.compare_exchange_strong(last->next, first));
  }
  void InsertToList(_Node* head)
  {
    _Node* last = head;
    while (_Node* next = last->next) last = next;
    InsertToList(head, last);
  }
public:
  ~MemoryReclamationByReferenceCountingT()
  {
    // 如果线程正常退出，Reference Counting算法能删除所有数据
    assert(will_be_deleted_list_.load() == nullptr);
    assert(counter_.load() == 0);
    _Node* to_delete_list = will_be_deleted_list_.exchange(nullptr);
    while (to_delete_list) {
      _Node* node = to_delete_list;
      to_delete_list = node->next;
      delete node;
    }
  }
  inline void Addref()
  {
    ++counter_;
  }
  inline bool Store(_Node* node) { return true; }
  bool Release(_Node* node)
  {
    if (!node) return false;
    if (counter_ == 1)
    {
      _Node* to_delete_list = will_be_deleted_list_.exchange(nullptr);
      if (!--counter_) {
        while (to_delete_list) {
          _Node* node = to_delete_list;
          to_delete_list = node->next;
          delete node;
        }
      } else if (to_delete_list) {
        InsertToList(to_delete_list);
      }
      delete node;
    } else {
      if (node) InsertToList(node, node);
      --counter_;
    }
    return true;
  }
};