How to: Creating a manual task queue
Example
You might want to explicitly control the threads that are used for task queue work and completions. In these cases, create a manual task queue and dispatch the calls yourself. If you're using manual task queues, you must ensure that they also pump the Windows message queue.
The following example shows how to create a manually pumped task queue. It creates two STL threads that dispatch calls for both the work port and the completion port.
void CreatingTaskQueueWithManualThreads()
{
// Create a manual task queue.
XTaskQueueHandle queue;
HRESULT hr = XTaskQueueCreate(
XTaskQueueDispatchMode::Manual,
XTaskQueueDispatchMode::Manual,
&queue);
if (FAILED(hr))
{
printf("Creating queue failed: 0x%x\r\n", hr);
return;
}
// We create threads to pump the queue: one thread for the work port
// and one thread for the completion port.
std::thread workThread([queue]
{
// XTaskQueueDispatch returns false when there's nothing to
// dispatch. Here, we wait forever for something new to come
// in. This will return false only if the queue is being
// terminated.
while (XTaskQueueDispatch(queue, XTaskQueuePort::Work, INFINITE));
});
std::thread completionThread([queue]
{
// XTaskQueueDispatch returns false when there's nothing to
// dispatch. Here, we wait forever for something new to come
// in. This will return false only if the queue is being
// terminated.
while (XTaskQueueDispatch(queue, XTaskQueuePort::Completion, INFINITE));
});
SubmitCallbacks(queue);
// Wait a while for the callbacks to run.
Sleep(1000);
// Terminating the queue will cause a waiting XTaskQueueDispatch to return
// false.
XTaskQueueTerminate(queue, true, nullptr, nullptr);
workThread.join();
completionThread.join();
}