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The Tor Browser
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revocable_store.h (2287B)

      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 
     13 // |RevocableStore| is a container of items that can be removed from the store.
     14 class RevocableStore {
     15 public:
     16  // A |StoreRef| is used to link the |RevocableStore| to its items.  There is
     17  // one StoreRef per store, and each item holds a reference to it.  If the
     18  // store wishes to revoke its items, it sets |store_| to null.  Items are
     19  // permitted to release their reference to the |StoreRef| when they no longer
     20  // require the store.
     21  class StoreRef final {
     22   public:
     23    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(StoreRef)
     24    explicit StoreRef(RevocableStore* aStore) : store_(aStore) {}
     25 
     26    void set_store(RevocableStore* aStore) { store_ = aStore; }
     27    RevocableStore* store() const { return store_; }
     28 
     29   protected:
     30    ~StoreRef() {}
     31 
     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() = default;
     44 
     45    // This item has been revoked if it no longer has a pointer to the store.
     46    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 private:
     63  friend class Revocable;
     64 
     65  // Adds an item to the store.  To add an item to the store, construct it
     66  // with a pointer to the store.
     67  void Add(Revocable* item);
     68 
     69  // This is the reference the unrevoked items in the store hold.
     70  RefPtr<StoreRef> owning_reference_;
     71 
     72  DISALLOW_EVIL_CONSTRUCTORS(RevocableStore);
     73 };
     74 
     75 #endif  // BASE_REVOCABLE_STORE_H_