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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2             : /* vim: set ts=8 sts=2 et sw=2 tw=80: */
       3             : // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
       4             : // Use of this source code is governed by a BSD-style license that can be
       5             : // found in the LICENSE file.
       6             : 
       7             : #ifndef BASE_REVOCABLE_STORE_H_
       8             : #define BASE_REVOCABLE_STORE_H_
       9             : 
      10             : #include "base/basictypes.h"
      11             : #include "nsISupportsImpl.h"
      12             : #include "nsAutoPtr.h"
      13             : 
      14             : // |RevocableStore| is a container of items that can be removed from the store.
      15             : class RevocableStore {
      16             :  public:
      17             :   // A |StoreRef| is used to link the |RevocableStore| to its items.  There is
      18             :   // one StoreRef per store, and each item holds a reference to it.  If the
      19             :   // store wishes to revoke its items, it sets |store_| to null.  Items are
      20             :   // permitted to release their reference to the |StoreRef| when they no longer
      21             :   // require the store.
      22             :   class StoreRef final {
      23             :    public:
      24          70 :     NS_INLINE_DECL_THREADSAFE_REFCOUNTING(StoreRef)
      25          44 :     explicit StoreRef(RevocableStore* aStore) : store_(aStore) { }
      26             : 
      27          13 :     void set_store(RevocableStore* aStore) { store_ = aStore; }
      28           0 :     RevocableStore* store() const { return store_; }
      29             : 
      30             :    protected:
      31          13 :     ~StoreRef() {}
      32             :    private:
      33             :     RevocableStore* store_;
      34             : 
      35             :     DISALLOW_EVIL_CONSTRUCTORS(StoreRef);
      36             :   };
      37             : 
      38             :   // An item in the store.  On construction, the object adds itself to the
      39             :   // store.
      40             :   class Revocable {
      41             :    public:
      42             :     explicit Revocable(RevocableStore* store);
      43             :     ~Revocable();
      44             : 
      45             :     // This item has been revoked if it no longer has a pointer to the store.
      46           0 :     bool revoked() const { return !store_reference_->store(); }
      47             : 
      48             :   private:
      49             :     // We hold a reference to the store through this ref pointer.  We release
      50             :     // this reference on destruction.
      51             :     RefPtr<StoreRef> store_reference_;
      52             : 
      53             :     DISALLOW_EVIL_CONSTRUCTORS(Revocable);
      54             :   };
      55             : 
      56             :   RevocableStore();
      57             :   ~RevocableStore();
      58             : 
      59             :   // Revokes all the items in the store.
      60             :   void RevokeAll();
      61             : 
      62             :   // Returns true if there are no items in the store.
      63             :   bool empty() const { return count_ == 0; }
      64             : 
      65             :  private:
      66             :   friend class Revocable;
      67             : 
      68             :   // Adds an item to the store.  To add an item to the store, construct it
      69             :   // with a pointer to the store.
      70             :   void Add(Revocable* item);
      71             : 
      72             :   // This is the reference the unrevoked items in the store hold.
      73             :   RefPtr<StoreRef> owning_reference_;
      74             : 
      75             :   // The number of unrevoked items in the store.
      76             :   int count_;
      77             : 
      78             :   DISALLOW_EVIL_CONSTRUCTORS(RevocableStore);
      79             : };
      80             : 
      81             : #endif  // BASE_REVOCABLE_STORE_H_