TaskQueue.h

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/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
 
#ifndef META_OCEAN_BASE_TASK_QUEUE_H
#define META_OCEAN_BASE_TASK_QUEUE_H
 
#include "ocean/base/Base.h"
#include "ocean/base/Caller.h"
#include "ocean/base/Singleton.h"
#include "ocean/base/Thread.h"
 
#include <queue>
 
namespace Ocean
{
 
/**
 * This class implements a queue for tasks.
 * The queue is based on a single thread so that all tasks will be processes sequential in a normal FIFO queue order.<br>
 * In contrast to the Scheduler the TaskQueue invokes a function only once.<br>
 * @see Scheduler, ThreadPool.
 * @ingroup base
 */
class OCEAN_BASE_EXPORT TaskQueue :
    public Singleton<TaskQueue>,
    protected Thread
{
    friend class Singleton<TaskQueue>;
 
    public:
 
        /**
         * Definition of a task as caller function.
         */
        typedef Caller<void> Task;
 
    protected:
 
        /**
         * Definition of a queue holding tasks.
         */
        typedef std::queue<Task> Tasks;
 
    public:
 
        /**
         * Adds a new tasks to the queue which will be invoked after all previous task have been invoked.
         * @param task The new task to add
         */
        void pushTask(const Task& task);
 
        /**
         * Returns the number of tasks currently in the queue (not counting an currently invoked task).
         * @return The number of pending tasks.
         */
        size_t pendingTasks();
 
        /**
         * Removes all pending tasks from this queue.
         * A currently invoked task will not be stopped.
         */
        void clear();
 
    protected:
 
        /**
         * Creates a new task queue object.
         */
        TaskQueue();
 
        /**
         * Destructs a task queue object.
         */
        ~TaskQueue();
 
        /**
         * The thread run function.
         */
        virtual void threadRun();
 
    protected:
 
        /// The tasks if this queue.
        Tasks queueTasks;
 
        /// True, if at least one task has been added to this queue before.
        bool queueHadTask;
 
        /// The lock of this queue.
        Lock queueLock;
};
 
}
 
#endif // META_OCEAN_BASE_TASK_QUEUE_H