revocable_store.h - mozsearch

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

// Copyright (c) 2006-2008 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 BASE_REVOCABLE_STORE_H_

#define BASE_REVOCABLE_STORE_H_

#include "base/basictypes.h"

#include "nsISupportsImpl.h"

// |RevocableStore| is a container of items that can be removed from the store.

class RevocableStore {

 public:

  // A |StoreRef| is used to link the |RevocableStore| to its items.  There is

  // one StoreRef per store, and each item holds a reference to it.  If the

  // store wishes to revoke its items, it sets |store_| to null.  Items are

  // permitted to release their reference to the |StoreRef| when they no longer

  // require the store.

  class StoreRef final {

   public:

    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(StoreRef)

    explicit StoreRef(RevocableStore* aStore) : store_(aStore) {}

    void set_store(RevocableStore* aStore) { store_ = aStore; }

    RevocableStore* store() const { return store_; }

   protected:

    ~StoreRef() {}

   private:

    RevocableStore* store_;

    DISALLOW_EVIL_CONSTRUCTORS(StoreRef);

};

  // An item in the store.  On construction, the object adds itself to the

  // store.

  class Revocable {

   public:

    explicit Revocable(RevocableStore* store);

    ~Revocable() = default;

    // This item has been revoked if it no longer has a pointer to the store.

    bool revoked() const { return !store_reference_->store(); }

   private:

    // We hold a reference to the store through this ref pointer.  We release

    // this reference on destruction.

    RefPtr<StoreRef> store_reference_;

    DISALLOW_EVIL_CONSTRUCTORS(Revocable);

};

  RevocableStore();

  ~RevocableStore();

  // Revokes all the items in the store.

  void RevokeAll();

 private:

  friend class Revocable;

  // Adds an item to the store.  To add an item to the store, construct it

  // with a pointer to the store.

  void Add(Revocable* item);

  // This is the reference the unrevoked items in the store hold.

  RefPtr<StoreRef> owning_reference_;

  DISALLOW_EVIL_CONSTRUCTORS(RevocableStore);

};

#endif  // BASE_REVOCABLE_STORE_H_