change-counter.hpp

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
#ifndef NDN_CHANGE_COUNTER_HPP
#define NDN_CHANGE_COUNTER_HPP

#include "../common.hpp"

namespace ndn {

template<class T>
class ChangeCounter {
public:
  ChangeCounter()
  {
    changeCount_ = target_.getChangeCount();
  }

  ChangeCounter(const T& target)
  : target_(target)
  {
    changeCount_ = target_.getChangeCount();
  }

  const T&
  get() const { return target_; }

  T&
  get() { return target_; }

  void
  set(const T& target)
  {
    target_ = target;
    changeCount_ = target_.getChangeCount();
  }

  bool
  checkChanged() const
  {
    uint64_t targetChangeCount = target_.getChangeCount();
    if (changeCount_ != targetChangeCount) {
      // This method can be called on a const object, but we want to be able to update the changeCount_.
      const_cast<ChangeCounter<T>*>(this)->changeCount_ = targetChangeCount;
      return true;
    }
    else
      return false;
  }

private:
  T target_;
  uint64_t changeCount_;
};

template<class T>
class SharedPointerChangeCounter {
public:
  SharedPointerChangeCounter()
  {
    changeCount_ = 0;
  }

  SharedPointerChangeCounter(T *target)
  : target_(target)
  {
    if (target_)
      changeCount_ = target_->getChangeCount();
    else
      changeCount_ = 0;
  }

  const T*
  get() const { return target_.get(); }

  T*
  get() { return target_.get(); }

  void
  set(const ptr_lib::shared_ptr<T>& target)
  {
    target_ = target;
    if (target_)
      changeCount_ = target_->getChangeCount();
    else
      changeCount_ = 0;
  }

  bool
  checkChanged() const
  {
    if (!target_)
      return false;

    uint64_t targetChangeCount = target_->getChangeCount();
    if (changeCount_ != targetChangeCount) {
      // This method can be called on a const object, but we want to be able to update the changeCount_.
      const_cast<SharedPointerChangeCounter<T>*>(this)->changeCount_ = targetChangeCount;
      return true;
    }
    else
      return false;
  }

private:
  ptr_lib::shared_ptr<T> target_;
  uint64_t changeCount_;
};

}

#endif