/// <summary>Queues a user work item to the thread pool.</summary>
/// <param name="callback">
/// A WaitCallback representing the delegate to invoke when the thread in the
/// thread pool picks up the work item.
/// </param>
/// <param name="state">
/// The object that is passed to the delegate when serviced from the thread pool.
/// </param>
/// <param name="priority">The priority for this callback.</param>
public void QueueUserWorkItem(WaitCallback callback, object state, int priority)
{
// Create a waiting callback that contains the delegate and its state.
// At it to the processing queue, and signal that data is waiting.
PriorityThreadPool.WaitingCallback waiting = new PriorityThreadPool.WaitingCallback(callback, state);
lock (_waitingCallbacks.SyncRoot) { _waitingCallbacks.Enqueue(priority, waiting); }
_workerThreadNeeded.AddOne();
}
/// <summary>A thread worker function that processes items from the work queue.</summary>
private void ProcessQueuedItems()
{
// Process indefinitely
while (true)
{
// Get the next item in the queue. If there is nothing there, go to sleep
// for a while until we're woken up when a callback is waiting.
PriorityThreadPool.WaitingCallback callback = null;
while (callback == null)
{
// Try to get the next callback available. We need to lock on the
// queue in order to make our count check and retrieval atomic.
lock (_waitingCallbacks.SyncRoot) {
if (_waitingCallbacks.Count > 0)
{
callback = (PriorityThreadPool.WaitingCallback)_waitingCallbacks.Dequeue();
}
}
// If we can't get one, go to sleep.
if (callback == null)
{
_workerThreadNeeded.WaitOne();
}
}
// We now have a callback. Execute it. Make sure to accurately
// record how many callbacks are currently executing.
try {
Interlocked.Increment(ref _inUseThreads);
callback.Callback(callback.State);
}
catch (System.Exception)
{
// Ignore any errors; not our problem.
}
finally {
Interlocked.Decrement(ref _inUseThreads);
}
}
}