Add a CallbackRegistry class to base/ to manage callbacks

base/callback_list_internal.h

+// Copyright 2013 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_CALLBACK_LIST_INTERNAL_H_
+#define BASE_CALLBACK_LIST_INTERNAL_H_
+
+#include <limits>
+#include <vector>
+
+#include "base/base_export.h"
+#include "base/basictypes.h"
+#include "base/callback_internal.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+
+namespace base {
+
+namespace internal {
+
+// Holds the CallbackList methods that do not require specialization to reduce
+// template bloat.
+//
+// This class is meant as an implementation detail for CallbackList and
+// CallbackListWithDetails. Do not use it directly.
+
+class BASE_EXPORT CallbackListImpl {
+ public:
+  typedef std::vector<base::internal::CallbackBase*> ListType;

[awong, 2013/09/04 23:20:07]

This typedef can be private.

[Cait (Slow), 2013/09/06 18:41:46]

Done.

+
+  // An iterator class that can be used to access the list of callbacks.
+  class Iterator {
+   public:
+    explicit Iterator(const base::WeakPtr<CallbackListImpl>& list);
+
+    ~Iterator();
+
+    base::internal::CallbackBase* GetNext();
+
+   private:
+    base::WeakPtr<CallbackListImpl> list_;
+    size_t index_;
+  };
+
+  CallbackListImpl();
+  ~CallbackListImpl();
+
+  // Add a callback to the list, if it is not already in there. This method
+  // takes ownership of |cb|, and will handle deleting it upon removal from the
+  // list. The returned closure is used to remove the callback from the list.
+  base::Closure Add(base::internal::CallbackBase* cb);
+
+  // Delete all callbacks in the list.
+  void Clear();
+
+  // Assert that the list is empty and no iterators are active.
+  void AssertEmpty();

[awong, 2013/09/04 23:20:07]

This is missing an implementation.

[Cait (Slow), 2013/09/06 18:41:46]

Done.

+
+  // Get an iterator to the CallbackList.
+  scoped_ptr<CallbackListImpl::Iterator> GetIterator();

[awong, 2013/09/04 23:20:07]

What about returning the Iterator by copy like erikwright was saying?

I think you'd have to add a copy constructor that also incremented
active_iterator_count_.  With copy-ellision, it'll probably never get invoked so
there's no cost. The upside is you avoid a malloc.

[Cait (Slow), 2013/09/06 18:41:46]

Done.

+
+  // Compact the list (remove any elements which were nulled out during

[awong, 2013/09/04 23:20:07]

nulled -> NULLed

[Cait (Slow), 2013/09/06 18:41:46]

Done.

+  // iteration).
+  void Compact();
+
+ private:
+  // Remove a callback from the list if it is in the list.
+  void Remove(base::internal::CallbackBase* cb);
+
+  ListType callbacks_;
+  int active_iterator_count_;
+  base::WeakPtrFactory<CallbackListImpl> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(CallbackListImpl);
+};
+
+} // namespace internal
+} // namespace base
+
+#endif  // BASE_CALLBACK_LIST_INTERNAL_H_