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 /* -*- C++ -*-
     This file declares the Job class.
 
     SPDX-FileCopyrightText: 2004-2013 Mirko Boehm <mirko@kde.org>
 
     SPDX-License-Identifier: LGPL-2.0-or-later
 
     $Id: Job.h 32 2005-08-17 08:38:01Z mirko $
 */
 
 #ifndef THREADWEAVER_JOB_H
 #define THREADWEAVER_JOB_H
 
 #include "jobinterface.h"
 #include "jobpointer.h"
 #include "threadweaver_export.h"
 
 class QMutex;
 class QWaitCondition;
 
 namespace ThreadWeaver
 {
 namespace Private
 {
 class Job_Private;
 }
 
 class Thread;
 class QueuePolicy;
 class QueueAPI;
 class Executor;
 
 /** @brief A Job is a simple abstraction of an action that is to be executed in a thread context.
  *
  * It is essential for the ThreadWeaver library that as a kind of convention, the different creators of Job objects do not touch
  * the protected data members of the Job until somehow notified by the Job.
  *
  * Jobs may not be executed twice. Create two different objects to perform two consecutive or parallel runs.
  * (Note: this rule is being reconsidered.)
  *
  * Jobs may declare dependencies. If Job B depends on Job A, B may not be executed before A is finished. To learn about
  * dependencies, see DependencyPolicy.
  *
  * Job objects do not inherit QObject. To connect to signals when jobs are started or finished, see QObjectDecorator.
  */
 class THREADWEAVER_EXPORT Job : public JobInterface
 {
 public:
     /** Construct a Job. */
     Job();
     Job(Private::Job_Private *d);
 
     /** Destructor. */
     ~Job() override;
 
     /** Perform the job. The thread in which this job is executed is given as a parameter.
      *
      * Do not overload this method to create your own Job implementation, overload run().
      * Whenever the currently executed job is communicated to the outside world, use the supplied job pointer
      * to keep the reference count correct.
      *
      * job is the Job that the queue is executing. It is not necessarily equal to this. For example, Jobs that are
      * decorated expose the decorator's address, not the address of the decorated object.
      */
     void execute(const JobPointer &job, Thread *) override;
 
     /** Perform the job synchronously in the current thread. */
     void blockingExecute() override;
 
     /** Set the Executor object that is supposed to run the job.
      *
      * Returns the previously set executor. The executor can never be unset. If zero is passed in as the new executor, the Job
      * will internally reset to a default executor that only invokes run().
      */
     Executor *setExecutor(Executor *executor) override;
 
     /** Returns the executor currently set on the Job. */
     Executor *executor() const override;
 
     /** The queueing priority of the job.
      * Jobs will be sorted by their queueing priority when enqueued. A higher queueing priority will place the job in front of all
      * lower-priority jobs in the queue.
      *
      * Note: A higher or lower priority does not influence queue policies. For example, a high-priority job that has an unresolved
      * dependency will not be executed, which means an available lower-priority job will take precedence.
      *
      * The default implementation returns zero. Only if this method is overloaded for some job classes, priorities will influence
      * the execution order of jobs. */
     int priority() const override;
 
     /** @brief Set the status of the Job.
      *
      * Do not call this method unless you know what you are doing, please :-) */
     void setStatus(Status) override;
 
     /** @brief The status of the job.
      *
      * The status will be changed to Status_Success if the run() method exits normally.
      */
     Status status() const override;
 
     /** Return whether the Job finished successfully or not.
      * The default implementation simply returns true. Overload in derived classes if the derived Job class can fail.
      *
      * If a job fails (success() returns false), it will *NOT* resolve its dependencies when it finishes. This will make sure that
      * Jobs that depend on the failed job will not be started.
      *
      * There is an important gotcha: When a Job object it deleted, it will always resolve its dependencies. If dependent jobs should
      * not be executed after a failure, it is important to dequeue those before deleting the failed Job. A Sequence may be
      * helpful for that purpose.
      */
     bool success() const override;
 
     /** Abort the execution of the job.
      *
      * Call this method to ask the Job to abort if it is currently executed. Please note that the default implementation of
      * the method does nothing (!). This is due to the fact that there is no generic method to abort a processing Job. Not even a
      * default boolean flag makes sense, as Job could, for example, be in an event loop and will need to create an exit event. You
      * have to reimplement the method to actually initiate an abort action.
      *
      * The method is not pure virtual because users are not supposed to be forced to always implement requestAbort(). Also, this
      * method is supposed to return immediately, not after the abort has completed. It requests the abort, the Job has to act on
      * the request. */
     void requestAbort() override
     {
     }
 
     /** The job is about to be added to the weaver's job queue.
      *
      * The job will be added right after this method finished. The default implementation does nothing. Use this method to, for
      * example, queue sub-operations as jobs before the job itself is queued.
      *
      * Note: When this method is called, the associated Weaver object's thread holds a lock on the weaver's queue. Therefore, it
      * is save to assume that recursive queueing is atomic from the queues perspective.
      *
      * @param api the QueueAPI object the job will be queued in */
     void aboutToBeQueued(QueueAPI *api) override;
 
     /** Called from aboutToBeQueued() while the mutex is being held. */
     void aboutToBeQueued_locked(QueueAPI *api) override;
 
     /** This Job is about the be dequeued from the weaver's job queue.
      *
      * The job will be removed from the queue right after this method returns. Use this method to dequeue, if necessary,
      * sub-operations (jobs) that this job has enqueued.
      *
      * Note: When this method is called, the associated Weaver object's thread does hold a lock on the weaver's queue.
      * Note: The default implementation does nothing.
      *
      * @param weaver the Weaver object from which the job will be dequeued */
     void aboutToBeDequeued(QueueAPI *api) override;
 
     /** Called from aboutToBeDequeued() while the mutex is being held. */
     void aboutToBeDequeued_locked(QueueAPI *api) override;
 
     /** Returns true if the jobs's execute method finished. */
     bool isFinished() const override;
 
     /** Assign a queue policy.
      *
      * Queue Policies customize the queueing (running) behaviour of sets of jobs. Examples for queue policies are dependencies
      * and resource restrictions. Every queue policy object can only be assigned once to a job, multiple assignments will be
      * IGNORED. */
     void assignQueuePolicy(QueuePolicy *) override;
 
     /** Remove a queue policy from this job. */
     void removeQueuePolicy(QueuePolicy *) override;
 
     /** @brief Return the queue policies assigned to this Job. */
     QList<QueuePolicy *> queuePolicies() const override;
 
     /** The mutex used to protect this job. */
     QMutex *mutex() const override;
 
 private:
     Private::Job_Private *d_;
 
 protected:
     Private::Job_Private *d();
     const Private::Job_Private *d() const;
 
     friend class Executor;
     /** The method that actually performs the job.
      *
      * It is called from execute(). This method is the one to overload it with the job's task.
      *
      * The Job will be executed in the specified thread. thread may be zero, indicating that the job is being executed some
      * other way (for example, synchronously by some other job). self specifies the job as the queue sees it. Whenever publishing
      * information about the job to the outside world, for example by emitting signals, use self, not this. self is the reference
      * counted object handled by the queue. Using it as signal parameters will amongst other things prevent thejob from being
      * memory managed and deleted.
      */
     virtual void run(JobPointer self, Thread *thread) override = 0;
 
     /** @brief Perform standard tasks before starting the execution of a job.
      *
      * The default implementation is empty.
      * job is the Job that the queue is executing. It is not necessarily equal to this. For example, Jobs that are
      * decorated expose the decorator's address, not the address of the decorated object. */
     void defaultBegin(const JobPointer &job, Thread *thread) override;
 
     /** @brief Perform standard task after the execution of a job.
      *
      * The default implementation is empty.
      * job is the Job that the queue is executing. It is not necessarily equal to this. For example, Jobs that are
      * decorated expose the decorator's address, not the address of the decorated object. */
     void defaultEnd(const JobPointer &job, Thread *thread) override;
 };
 
 }
 
 #endif // THREADWEAVER_JOB_H