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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"
+#include "nsAutoPtr.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();
+
+ // This item has been revoked if it no longer has a pointer to the store.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();
+
+ // Returns true if there are no items in the store.
+ bool empty() const { return count_ == 0; }
+
+ 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_;
+
+ // The number of unrevoked items in the store.
+ int count_;
+
+ DISALLOW_EVIL_CONSTRUCTORS(RevocableStore);
+};
+
+#endif // BASE_REVOCABLE_STORE_H_