/// <summary>
/// Raises the AfterWorkItem event
/// </summary>
void OnAfterWorkItem(ThreadPoolWorkItem workItem)
{
AfterWorkItemHandler delegateToFire;
lock (eventLock)
{
delegateToFire = afterWorkItem;
}
if (delegateToFire != null)
{
delegateToFire(this, workItem);
}
}
/// <summary>
/// Adds a work item to the queue and potentially start a new thread.
/// A thread is started if there are no idle threads or if there is already
/// something on the queue - but in each case, only if the total number of
/// threads is less than the maximum.
/// </summary>
/// <param name="workItem">The actual work item to add to the queue.</param>
public void AddWorkItem(ThreadPoolWorkItem workItem)
{
if (workItem == null)
{
throw new ArgumentNullException("workItem");
}
bool startNewThread;
lock (stateLock)
{
lock (queueLock)
{
if (queue.Count == 0)
{
queue.Enqueue(workItem);
}
else
{
// Work out where in the queue the item should go
// Common case: it belongs at the end
if (((ThreadPoolWorkItem)queue[queue.Count - 1]).Priority >= workItem.Priority)
{
queue.Enqueue(workItem);
}
else
{
// This will find the complement of the correct position, due to the
// "interesting" nature of PriorityComparer.
int position = queue.BinarySearch(workItem, PriorityComparer.Instance);
queue.Enqueue(workItem, ~position);
}
}
startNewThread = (WorkingThreads + queue.Count > TotalThreads) &&
(TotalThreads < MaxThreads);
// Always pulse the queueLock, whether there's something waiting or not.
// This is easier than trying to work out for sure whether or not it's
// worth pulsing, and errs on the side of caution.
Monitor.Pulse(queueLock);
}
}
if (startNewThread)
{
StartWorkerThread();
}
}
/// <summary>
/// Cancels the first work item with the specified ID, if there is one.
/// Note that items which have been taken off the queue and are running
/// or about to be started cannot be cancelled.
/// </summary>
/// <param name="id">The ID of the work item to cancel</param>
public bool CancelWorkItem(object id)
{
if (id == null)
{
throw new ArgumentNullException("id");
}
lock (queueLock)
{
for (int i = 0; i < queue.Count; i++)
{
ThreadPoolWorkItem item = (ThreadPoolWorkItem)queue[i];
object otherID = item.ID;
if (otherID != null && id.Equals(otherID))
{
queue.RemoveAt(i);
return(true);
}
}
}
return(false);
}
/// <summary>
/// Main worker thread loop. This picks jobs off the queue and executes
/// them, until it's time to die.
/// </summary>
void WorkerThreadLoop()
{
// Big try/finally block just to decrement the number of threads whatever happens.
try
{
DateTime lastJob = DateTime.UtcNow;
while (true)
{
lock (stateLock)
{
if (TotalThreads > MaxThreads)
{
return;
}
}
int waitPeriod = CalculateWaitPeriod(lastJob);
ThreadPoolWorkItem job = GetNextWorkItem(waitPeriod);
// No job? Check whether or not we should die
if (job == null)
{
if (CheckIfThreadShouldQuit(lastJob))
{
return;
}
}
else
{
ExecuteWorkItem(job);
lastJob = DateTime.UtcNow;
}
}
}
finally
{
OnWorkerThreadExit();
}
}
/// <summary>
/// Raises the BeforeWorkItem event
/// </summary>
/// <param name="workItem">The work item which is about to execute</param>
/// <param name="cancel">Whether or not the work item was cancelled by an event handler</param>
void OnBeforeWorkItem(ThreadPoolWorkItem workItem, out bool cancel)
{
cancel = false;
BeforeWorkItemHandler delegateToFire;
lock (eventLock)
{
delegateToFire = beforeWorkItem;
}
if (delegateToFire != null)
{
Delegate[] delegates = delegateToFire.GetInvocationList();
foreach (BeforeWorkItemHandler d in delegates)
{
d(this, workItem, ref cancel);
if (cancel)
{
return;
}
}
}
}
/// <summary>
/// Raises the WorkerException event.
/// TODO: Write to the event log if no exception handlers are attached?
/// </summary>
void OnException(ThreadPoolWorkItem workItem, Exception e)
{
ThreadPoolExceptionHandler eh;
lock (eventLock)
{
eh = exceptionHandler;
}
if (eh != null)
{
Delegate[] delegates = eh.GetInvocationList();
bool handled = false;
foreach (ThreadPoolExceptionHandler d in delegates)
{
d(this, workItem, e, ref handled);
if (handled)
{
return;
}
}
}
}
/// <summary>
/// Executes the given work item, firing the BeforeWorkItem and AfterWorkItem events,
/// and incrementing and decrementing the number of working threads.
/// </summary>
/// <param name="job">The work item to execute</param>
void ExecuteWorkItem(ThreadPoolWorkItem job)
{
lock (stateLock)
{
workingThreads++;
Thread.CurrentThread.Priority = workerThreadPriority;
Thread.CurrentThread.IsBackground = workerThreadsAreBackground;
}
try
{
bool cancel;
OnBeforeWorkItem(job, out cancel);
if (cancel)
{
return;
}
try
{
job.Invoke();
}
catch (Exception e)
{
OnException(job, e);
return;
}
OnAfterWorkItem(job);
}
finally
{
lock (stateLock)
{
Thread.CurrentThread.Priority = workerThreadPriority;
Thread.CurrentThread.IsBackground = workerThreadsAreBackground;
workingThreads--;
}
}
}
