132 lines
3.1 KiB
C
132 lines
3.1 KiB
C
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/*
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* Copyright (c) 2021 Huawei Device Co., Ltd.
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef UTILS_BASE_OBSERVER_H
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#define UTILS_BASE_OBSERVER_H
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#include <memory>
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#include <vector>
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#include <set>
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#include <mutex>
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namespace OHOS {
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/**
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* @brief Provides the parameters and data required to call the update method.
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*/
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struct ObserverArg {
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public:
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virtual ~ObserverArg() = default;
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};
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/**
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* @brief Implements the <b>Observer</b> class.
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*/
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class Observer;
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/**
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* @brief Implements the observed class.
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*/
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class Observable {
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public:
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virtual ~Observable() = default;
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/**
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* @brief Adds the specified observer to the set of observers.
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*
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* If `o` is valid and does not exist in the observer set, the observer
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* will be added; otherwise, this function will return directly.
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*/
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void AddObserver(const std::shared_ptr<Observer>& o);
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/**
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* @brief Removes the specified observer.
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*/
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void RemoveObserver(const std::shared_ptr<Observer>& o);
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/**
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* @brief Removes all observers.
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*/
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void RemoveAllObservers();
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/**
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* @brief Notifies all observers with no data passed.
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*
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* This function is equivalent to <b>NotifyObservers(nullptr)</b>.
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*/
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void NotifyObservers();
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/**
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* @brief Notifies all observers, with the data 'arg' passed to
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* the observers.
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*
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* If `changed_` is true, call the `Update()` function to notify all
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* observers to respond.
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*
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* @param arg Indicates the parameters and data to be used for
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* <b>Observer::Update()</b>.
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* @see ObserverArg.
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*/
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void NotifyObservers(const ObserverArg* arg);
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/**
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* @brief Obtains the number of observers.
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*/
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int GetObserversCount();
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protected:
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/**
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* @brief Obtains the state of this <b>Observable</b> object.
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*
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* @return Returns the value of `changed_`.
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*/
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bool HasChanged();
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/**
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* @brief Sets the state of this <b>Observable</b> object to true.
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*/
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void SetChanged();
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/**
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* @brief Set the state of this <b>Observable</b> object to false.
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*/
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void ClearChanged();
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protected:
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std::set<std::shared_ptr<Observer>> obs; // A collection of observers.
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std::mutex mutex_;
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private:
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bool changed_ = false; // The state of this Observable object.
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};
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class Observer {
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public:
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virtual ~Observer() = default;
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/**
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* @brief Updates this observer.
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*
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* It will be called when this observer is notified by an
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* <b>Observable</b> object.
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*/
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virtual void Update(const Observable* o, const ObserverArg* arg) = 0;
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};
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}
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#endif
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