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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 BASE_CALLBACK_REGISTRY_H_
#define BASE_CALLBACK_REGISTRY_H_
#include <list>
#include "base/basictypes.h"
#include "base/callback.h"
#include "base/compiler_specific.h"
#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
// OVERVIEW:
//
// A container for a list of callbacks. Unlike a normal STL vector or list,
// this container can be modified during iteration without invalidating the
// iterator. It safely handles the case of a callback removing itself
// or another callback from the list while callbacks are being run.
//
// TYPICAL USAGE:
//
// class MyWidget {
// public:
// ...
//
// typedef base::Callback<void(const Foo&)> OnFooCallback;
//
// scoped_ptr<base::CallbackRegistry<Foo>::Subscription> RegisterCallback(
// const OnFooCallback& cb) {
// return callback_registry_.Add(cb);
// }
//
// private:
// void NotifyFoo(const Foo& foo) {
// callback_registry_.Notify(foo);
// }
//
// base::CallbackRegistry<Foo> callback_registry_;
// };
//
//
// class MyWidgetListener {
// public:
// MyWidgetListener::MyWidgetListener() {
// foo_subscription_ = MyWidget::GetCurrent()->RegisterCallback(
// base::Bind(&MyWidgetListener::OnFoo, this)));
// }
//
// MyWidgetListener::~MyWidgetListener() {
// // Subscription gets deleted automatically and will deregister
// // the callback in the process.
// }
//
// private:
// void OnFoo(const Foo& foo) {
// // Do something.
// }
//
// scoped_ptr<base::CallbackRegistry<Foo>::Subscription> foo_subscription_;
// };
namespace base {
namespace internal {
template <typename CallbackType>
class CallbackRegistryBase {
public:
class Subscription {
public:
Subscription(CallbackRegistryBase<CallbackType>* list,
typename std::list<CallbackType>::iterator iter)
: list_(list),
iter_(iter) {}
~Subscription() {
if (list_->active_iterator_count_)
(*iter_).Reset();
else
list_->callbacks_.erase(iter_);
}
private:
CallbackRegistryBase<CallbackType>* list_;
typename std::list<CallbackType>::iterator iter_;
DISALLOW_COPY_AND_ASSIGN(Subscription);
};
// Add a callback to the list. The callback will remain registered until the
// returned Subscription is destroyed, which must occur before the
// CallbackRegistry is destroyed.
scoped_ptr<Subscription> Add(const CallbackType& cb) {
DCHECK(!cb.is_null());
return scoped_ptr<Subscription>(
new Subscription(this, callbacks_.insert(callbacks_.end(), cb)));
}
protected:
// An iterator class that can be used to access the list of callbacks.
class Iterator {
public:
explicit Iterator(CallbackRegistryBase<CallbackType>* list)
: list_(list),
list_iter_(list_->callbacks_.begin()) {
++list_->active_iterator_count_;
}
Iterator(const Iterator& iter)
: list_(iter.list_),
list_iter_(iter.list_iter_) {
++list_->active_iterator_count_;
}
~Iterator() {
if (list_ && --list_->active_iterator_count_ == 0) {
list_->Compact();
}
}
CallbackType* GetNext() {
while ((list_iter_ != list_->callbacks_.end()) && list_iter_->is_null())
++list_iter_;
CallbackType* cb = NULL;
if (list_iter_ != list_->callbacks_.end()) {
cb = &(*list_iter_);
++list_iter_;
}
return cb;
}
private:
CallbackRegistryBase<CallbackType>* list_;
typename std::list<CallbackType>::iterator list_iter_;
};
CallbackRegistryBase()
: active_iterator_count_(0) {}
~CallbackRegistryBase() {
DCHECK_EQ(0, active_iterator_count_);
DCHECK_EQ(0U, callbacks_.size());
}
// Returns an instance of a CallbackRegistryBase::Iterator which can be used
// to run callbacks.
Iterator GetIterator() {
return Iterator(this);
}
// Compact the list: remove any entries which were NULLed out during
// iteration.
void Compact() {
typename std::list<CallbackType>::iterator it = callbacks_.begin();
while (it != callbacks_.end()) {
if ((*it).is_null())
it = callbacks_.erase(it);
else
++it;
}
}
private:
std::list<CallbackType> callbacks_;
int active_iterator_count_;
DISALLOW_COPY_AND_ASSIGN(CallbackRegistryBase);
};
} // namespace internal
template <typename Details>
class CallbackRegistry
: public internal::CallbackRegistryBase<Callback<void(const Details&)> > {
public:
CallbackRegistry() {}
// Execute all active callbacks with |details| parameter.
void Notify(const Details& details) {
typename internal::CallbackRegistryBase<
Callback<void(const Details&)> >::Iterator it = this->GetIterator();
Callback<void(const Details&)>* cb;
while((cb = it.GetNext()) != NULL) {
cb->Run(details);
}
}
private:
DISALLOW_COPY_AND_ASSIGN(CallbackRegistry);
};
template <> class CallbackRegistry<void>
: public internal::CallbackRegistryBase<Closure> {
public:
CallbackRegistry() {}
// Execute all active callbacks.
void Notify() {
Iterator it = this->GetIterator();
Closure* cb;
while((cb = it.GetNext()) != NULL) {
cb->Run();
}
}
private:
DISALLOW_COPY_AND_ASSIGN(CallbackRegistry);
};
} // namespace base
#endif // BASE_CALLBACK_REGISTRY_H_
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