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// Copyright 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef BASE_REVOCABLE_STORE_H__
#define BASE_REVOCABLE_STORE_H__
#include "base/basictypes.h"
#include "base/logging.h"
#include "base/ref_counted.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 : public base::RefCounted<StoreRef> {
public:
StoreRef(RevocableStore* store) : store_(store) { }
void set_store(RevocableStore* store) { store_ = store; }
RevocableStore* store() const { return store_; }
private:
RevocableStore* store_;
DISALLOW_EVIL_CONSTRUCTORS(StoreRef);
};
// An item in the store. On construction, the object adds itself to the
// store.
class Revocable {
public:
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.
scoped_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.
scoped_refptr<StoreRef> owning_reference_;
// The number of unrevoked items in the store.
int count_;
DISALLOW_EVIL_CONSTRUCTORS(RevocableStore);
};
#endif // BASE_REVOCABLE_STORE_H__
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