shareable.h

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#ifndef ION_BASE_SHAREABLE_H_
#define ION_BASE_SHAREABLE_H_

#include "base/macros.h"
#include "ion/base/logging.h"
#include "ion/port/atomic.h"

namespace ion {
namespace base {

class Shareable {
 public:
  int GetRefCount() const { return ref_count_; }

 protected:
  Shareable(): ref_count_(0) {}

  virtual ~Shareable() { DCHECK_EQ(ref_count_.load(), 0); }

 private:
  void IncrementRefCount() const { ++ref_count_; }
  void DecrementRefCount() const {
    const int new_count = --ref_count_;
    DCHECK_GE(new_count, 0);
    if (new_count == 0) {
      OnZeroRefCount();
    }
  }

  virtual void OnZeroRefCount() const { delete this; }

  mutable std::atomic<int> ref_count_;

  template <typename T> friend class SharedPtr;
  friend class WeakReferent;

  DISALLOW_COPY_AND_ASSIGN(Shareable);
};

}  // namespace base
}  // namespace ion

#endif  // ION_BASE_SHAREABLE_H_