services/service_manager/public/cpp/service_context_ref.h

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SERVICES_SERVICE_MANAGER_PUBLIC_CPP_SERVICE_CONTEXT_REF_H_
#define SERVICES_SERVICE_MANAGER_PUBLIC_CPP_SERVICE_CONTEXT_REF_H_

#include <memory>

#include "base/callback.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"

namespace service_manager {

class ServiceContextRefImpl;

// An interface implementation can keep this object as a member variable to
// hold a reference to the ServiceContext, keeping it alive as long as the
// bound implementation exists.
//
// This class is safe to use on any thread and instances may be passed to other
// threads. However, each instance should only be used on one thread at a time,
// otherwise there'll be races between the AddRef resulting from cloning and
// destruction.
class ServiceContextRef {
 public:
  virtual ~ServiceContextRef() {}

  virtual std::unique_ptr<ServiceContextRef> Clone() = 0;
};

class ServiceContextRefFactory {
 public:
  // |quit_closure| is called whenever the last ref is destroyed.
  explicit ServiceContextRefFactory(const base::Closure& quit_closure);
  ~ServiceContextRefFactory();

  std::unique_ptr<ServiceContextRef> CreateRef();

  bool HasNoRefs() const { return !ref_count_; }

 private:
  friend ServiceContextRefImpl;

  // Called from ServiceContextRefImpl.
  void AddRef();
  void Release();

  const base::Closure quit_closure_;
  int ref_count_ = 0;
  base::WeakPtrFactory<ServiceContextRefFactory> weak_factory_;

  DISALLOW_COPY_AND_ASSIGN(ServiceContextRefFactory);
};

}  // namespace service_manager

#endif  // SERVICES_SERVICE_MANAGER_PUBLIC_CPP_SERVICE_CONTEXT_REF_H_