ThreadWeaver::QueueInterface Class

Member Function Documentation

[virtual noexcept] QueueInterface::~QueueInterface()

[pure virtual] int QueueInterface::currentNumberOfThreads() const

Returns the current number of threads in the inventory.

[pure virtual] void QueueInterface::dequeue()

Remove all queued jobs.

All waiting jobs will be dequeued. The semantics are the same as for dequeue(JobInterface).

See also dequeue(JobInterface).

[pure virtual] bool QueueInterface::dequeue(const ThreadWeaver::JobPointer &job)

Remove a job from the queue.

If the job was queued but not started so far, it is removed from the queue.

You can always call dequeue, it will return true if the job was dequeued. However if the job is not in the queue anymore, it is already being executed, it is too late to dequeue, and dequeue will return false. The return value is thread-safe - if true is returned, the job was still waiting, and has been dequeued. If not, the job was not waiting in the queue.

Modifying queued jobs is best done on a suspended queue. Often, for example at the end of an application, it is sufficient to dequeue all jobs (which leaves only the ones mid-air in threads), call finish (that will wait for all the mid air jobs to complete), and then exit. Without dequeue(), all jobs in the queue would be executed during finish().

See requestAbort for aborting jobs during execution

Returns true if the job was waiting and has been dequeued

Returns false if the job was not found waiting in the queue

[pure virtual] void QueueInterface::enqueue(const QList<ThreadWeaver::JobPointer> &jobs)

Queue a vector of jobs.

It depends on the state if execution of the job will be attempted immediately. In suspended state, jobs can be added to the queue, but the threads remain suspended. In WorkongHard state, an idle thread may immediately execute the job, or it might be queued if all threads are busy.

JobPointer is a shared pointer. This means the object pointed to will be deleted if this object is the last remaining reference to it. Keep a JobPointer to the job to avoid automatic deletion.

[pure virtual] void QueueInterface::finish()

Finish all queued operations, then return.

This method is used in imperative (not event driven) programs that cannot react on events to have the controlling (main) thread wait wait for the jobs to finish. The call will block the calling thread and return when all queued jobs have been processed.

Warning: This will suspend your thread! Warning: If one of your jobs enters an infinite loop, this will never return!

[pure virtual] bool QueueInterface::isEmpty() const

Is the queue empty? The queue is empty if no more jobs are queued.

[pure virtual] bool QueueInterface::isIdle() const

Is the weaver idle? The weaver is idle if no jobs are queued and no jobs are processed by the threads.

[pure virtual] int QueueInterface::maximumNumberOfThreads() const

Get the maximum number of threads this Weaver may start.

See also setMaximumNumberOfThreads().

[pure virtual] int QueueInterface::queueLength() const

Returns the number of pending jobs. This will return the number of queued jobs. Jobs that are currently being executed are not part of the queue. All jobs in the queue are waiting to be executed.

[pure virtual] void QueueInterface::requestAbort()

Request aborts of the currently executed jobs. It is important to understand that aborts are requested, but cannot be guaranteed, as not all Job classes support it. It is up to the application to decide if and how job aborts are necessary.

[pure virtual] void QueueInterface::reschedule()

Reschedule the jobs in the queue. This method triggers a scheduling attempt to perform jobs. It will schedule enqueued jobs to be executed by idle threads. It should only be necessary to call it if the canRun() status of a job changed spontaneously due to external reasons.

[pure virtual] void QueueInterface::resume()

Resume job queueing.

See also suspend.

[pure virtual] void QueueInterface::setMaximumNumberOfThreads(int cap)

Set the maximum number of threads this Weaver object may start.

See also maximumNumberOfThreads().

[pure virtual] void QueueInterface::shutDown()

Shut down the queue. Tells all threads to exit, and changes to Destructed state. It is safe to destroy the queue once this method returns.

[pure virtual] const ThreadWeaver::State *QueueInterface::state() const

Return the state of the weaver object.

[pure virtual] void QueueInterface::suspend()

Suspend job execution. When suspending, all threads are allowed to finish the currently assigned job but will not receive a new assignment. When all threads are done processing the assigned job, the signal suspended will() be emitted. If you call suspend() and there are no jobs left to be done, you will immediately receive the suspended() signal.