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// 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.
// This file describes a central switchboard for notifications that might
// happen in various parts of the application, and allows users to register
// observers for various classes of events that they're interested in.
#ifndef CHROME_COMMON_NOTIFICATION_SERVICE_H_
#define CHROME_COMMON_NOTIFICATION_SERVICE_H_
#include <map>
#include "base/observer_list.h"
#include "chrome/common/notification_details.h"
#include "chrome/common/notification_observer.h"
#include "chrome/common/notification_source.h"
#include "chrome/common/notification_type.h"
class NotificationObserver;
class NotificationService {
public:
// Returns the NotificationService object for the current thread, or NULL if
// none.
static NotificationService* current();
// Normally instantiated when the thread is created. Not all threads have
// a NotificationService. Only one instance should be created per thread.
NotificationService();
~NotificationService();
// Synchronously posts a notification to all interested observers.
// Source is a reference to a NotificationSource object representing
// the object originating the notification (can be
// NotificationService::AllSources(), in which case
// only observers interested in all sources will be notified).
// Details is a reference to an object containing additional data about
// the notification. If no additional data is needed, NoDetails() is used.
// There is no particular order in which the observers will be notified.
void Notify(NotificationType type,
const NotificationSource& source,
const NotificationDetails& details);
// Returns a NotificationSource that represents all notification sources
// (for the purpose of registering an observer for events from all sources).
static Source<void> AllSources() { return Source<void>(NULL); }
// Returns a NotificationDetails object that represents a lack of details
// associated with a notification. (This is effectively a null pointer.)
static Details<void> NoDetails() { return Details<void>(NULL); }
private:
friend class NotificationRegistrar;
typedef ObserverList<NotificationObserver> NotificationObserverList;
typedef std::map<uintptr_t, NotificationObserverList*> NotificationSourceMap;
// Convenience function to determine whether a source has a
// NotificationObserverList in the given map;
static bool HasKey(const NotificationSourceMap& map,
const NotificationSource& source);
// NOTE: Rather than using this directly, you should use a
// NotificationRegistrar.
//
// Registers a NotificationObserver to be called whenever a matching
// notification is posted. Observer is a pointer to an object subclassing
// NotificationObserver to be notified when an event matching the other two
// parameters is posted to this service. Type is the type of events to
// be notified about (or NOTIFY_ALL to receive events of all types).
// Source is a NotificationSource object (created using
// "Source<classname>(pointer)"), if this observer only wants to
// receive events from that object, or NotificationService::AllSources()
// to receive events from all sources.
//
// A given observer can be registered only once for each combination of
// type and source. If the same object is registered more than once,
// it must be removed for each of those combinations of type and source later.
//
// The caller retains ownership of the object pointed to by observer.
void AddObserver(NotificationObserver* observer,
NotificationType type, const NotificationSource& source);
// NOTE: Rather than using this directly, you should use a
// NotificationRegistrar.
//
// Removes the object pointed to by observer from receiving notifications
// that match type and source. If no object matching the parameters is
// currently registered, this method is a no-op.
void RemoveObserver(NotificationObserver* observer,
NotificationType type, const NotificationSource& source);
// Keeps track of the observers for each type of notification.
// Until we get a prohibitively large number of notification types,
// a simple array is probably the fastest way to dispatch.
NotificationSourceMap observers_[NotificationType::NOTIFICATION_TYPE_COUNT];
#ifndef NDEBUG
// Used to check to see that AddObserver and RemoveObserver calls are
// balanced.
int observer_counts_[NotificationType::NOTIFICATION_TYPE_COUNT];
#endif
DISALLOW_COPY_AND_ASSIGN(NotificationService);
};
#endif // CHROME_COMMON_NOTIFICATION_SERVICE_H_
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