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// 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 ASH_SHELF_SCOPED_OBSERVER_WITH_DUPLICATED_SOURCES_H_
#define ASH_SHELF_SCOPED_OBSERVER_WITH_DUPLICATED_SOURCES_H_
#include <map>
#include "base/basictypes.h"
#include "base/logging.h"
// ScopedObserverWithDuplicatedSources is used to keep track of the set of
// sources an object has attached itself to as an observer. When
// ScopedObserverWithDuplicatedSources is destroyed it removes the object as an
// observer from all sources it has been added to.
// ScopedObserverWithDuplicatedSources adds |observer| once for a particular
// source, no matter how many times Add() is invoked. Additionaly |observer| is
// only removed once Remove() is invoked the same number of times as Add().
template <class Source, class Observer>
class ScopedObserverWithDuplicatedSources {
public:
explicit ScopedObserverWithDuplicatedSources(Observer* observer)
: observer_(observer) {}
~ScopedObserverWithDuplicatedSources() {
typename SourceToAddCountMap::const_iterator iter =
counted_sources_.begin();
for (; iter != counted_sources_.end(); ++iter)
iter->first->RemoveObserver(observer_);
}
// Adds the object passed to the constructor only once as an observer on
// |source|.
void Add(Source* source) {
if (counted_sources_.find(source) == counted_sources_.end())
source->AddObserver(observer_);
counted_sources_[source]++;
}
// Only remove the object passed to the constructor as an observer from
// |source| when Remove() is invoked the same number of times as Add().
void Remove(Source* source) {
typename SourceToAddCountMap::iterator iter =
counted_sources_.find(source);
DCHECK(iter != counted_sources_.end() && iter->second > 0);
if (--iter->second == 0) {
counted_sources_.erase(source);
source->RemoveObserver(observer_);
}
}
bool IsObserving(Source* source) const {
return counted_sources_.find(source) != counted_sources_.end();
}
private:
typedef std::map<Source*, int> SourceToAddCountMap;
Observer* observer_;
// Map Source and its adding count.
std::map<Source*, int> counted_sources_;
DISALLOW_COPY_AND_ASSIGN(ScopedObserverWithDuplicatedSources);
};
#endif // ASH_SHELF_SCOPED_OBSERVER_WITH_DUPLICATED_SOURCES_H_
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