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Diffstat (limited to 'ipc/chromium/src/base/observer_list.h')
| -rw-r--r-- | ipc/chromium/src/base/observer_list.h | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/ipc/chromium/src/base/observer_list.h b/ipc/chromium/src/base/observer_list.h new file mode 100644 index 0000000000..4dce7ae59b --- /dev/null +++ b/ipc/chromium/src/base/observer_list.h @@ -0,0 +1,186 @@ +/* -*- 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_OBSERVER_LIST_H__ +#define BASE_OBSERVER_LIST_H__ + +#include <algorithm> +#include <limits> +#include <vector> + +#include "base/basictypes.h" +#include "base/logging.h" + +#if defined(ANDROID) && defined(_STLP_STD_NAME) +using _STLP_STD_NAME::find; +#endif + +namespace base { + +/////////////////////////////////////////////////////////////////////////////// +// +// OVERVIEW: +// +// A container for a list of observers. Unlike a normal STL vector or list, +// this container can be modified during iteration without invalidating the +// iterator. So, it safely handles the case of an observer removing itself +// or other observers from the list while observers are being notified. +// +// TYPICAL USAGE: +// +// class MyWidget { +// public: +// ... +// +// class Observer { +// public: +// virtual void OnFoo(MyWidget* w) = 0; +// virtual void OnBar(MyWidget* w, int x, int y) = 0; +// }; +// +// void AddObserver(Observer* obs) { +// observer_list_.AddObserver(obs); +// } +// +// void RemoveObserver(Observer* obs) { +// observer_list_.RemoveObserver(obs); +// } +// +// void NotifyFoo() { +// FOR_EACH_OBSERVER(Observer, observer_list_, OnFoo(this)); +// } +// +// void NotifyBar(int x, int y) { +// FOR_EACH_OBSERVER(Observer, observer_list_, OnBar(this, x, y)); +// } +// +// private: +// ObserverList<Observer> observer_list_; +// }; +// +// +/////////////////////////////////////////////////////////////////////////////// + +template <class ObserverType, bool check_empty = false> +class ObserverList { + public: + // Enumeration of which observers are notified. + enum NotificationType { + // Specifies that any observers added during notification are notified. + // This is the default type if non type is provided to the constructor. + NOTIFY_ALL, + + // Specifies that observers added while sending out notification are not + // notified. + NOTIFY_EXISTING_ONLY + }; + + ObserverList() : notify_depth_(0), type_(NOTIFY_ALL) {} + explicit ObserverList(NotificationType type) : notify_depth_(0), type_(type) {} + ~ObserverList() { + // When check_empty is true, assert that the list is empty on destruction. + if (check_empty) { + Compact(); + DCHECK_EQ(observers_.size(), 0U); + } + } + + // Add an observer to the list. + void AddObserver(ObserverType* obs) { + DCHECK(find(observers_.begin(), observers_.end(), obs) == observers_.end()) + << "Observers can only be added once!"; + observers_.push_back(obs); + } + + // Remove an observer from the list. + void RemoveObserver(ObserverType* obs) { + typename ListType::iterator it = + std::find(observers_.begin(), observers_.end(), obs); + if (it != observers_.end()) { + if (notify_depth_) { + *it = 0; + } else { + observers_.erase(it); + } + } + } + + size_t size() const { + return observers_.size(); + } + + ObserverType* GetElementAt(int index) const { + return observers_[index]; + } + + // An iterator class that can be used to access the list of observers. See + // also the FOREACH_OBSERVER macro defined below. + class Iterator { + public: + explicit Iterator(const ObserverList<ObserverType>& list) + : list_(list), + index_(0), + max_index_(list.type_ == NOTIFY_ALL ? + std::numeric_limits<size_t>::max() : + list.observers_.size()) { + ++list_.notify_depth_; + } + + ~Iterator() { + if (--list_.notify_depth_ == 0) + list_.Compact(); + } + + ObserverType* GetNext() { + ListType& observers = list_.observers_; + // Advance if the current element is null + size_t max_index = std::min(max_index_, observers.size()); + while (index_ < max_index && !observers[index_]) + ++index_; + return index_ < max_index ? observers[index_++] : NULL; + } + + private: + const ObserverList<ObserverType>& list_; + size_t index_; + size_t max_index_; + }; + + private: + typedef std::vector<ObserverType*> ListType; + + void Compact() const { + typename ListType::iterator it = observers_.begin(); + while (it != observers_.end()) { + if (*it) { + ++it; + } else { + it = observers_.erase(it); + } + } + } + + // These are marked mutable to facilitate having NotifyAll be const. + mutable ListType observers_; + mutable int notify_depth_; + NotificationType type_; + + friend class ObserverList::Iterator; + + DISALLOW_EVIL_CONSTRUCTORS(ObserverList); +}; + +} // namespace base + +#define FOR_EACH_OBSERVER(ObserverType, observer_list, func) \ + do { \ + base::ObserverList<ObserverType>::Iterator it(observer_list); \ + ObserverType* obs; \ + while ((obs = it.GetNext()) != NULL) \ + obs->func; \ + } while (0) + +#endif // BASE_OBSERVER_LIST_H__ |