/// <summary>
/// Waits until evaluation gets cancelled or a value is set
/// </summary>
public void Wait(ICycleDetector cycleDetector = null)
{
lock (this)
{
if (m_result != EvaluationStatus.None)
{
return;
}
m_eventWaiters++;
if (m_event == null)
{
m_event = new ManualResetEvent(false);
}
}
if (cycleDetector == null)
{
m_event.WaitOne();
}
else
{
// wait for evaluation in separate thread to finish
m_event.WaitOne(m_startupDelay);
// at first, wait for a reasonable amount of time without actually starting up cycle detector
bool hasResult;
lock (this)
{
hasResult = m_result != EvaluationStatus.None;
}
if (!hasResult)
{
// after the first delay, evaluation is still neither canceled nor finished; let's make sure the cycle detector is actually started up
cycleDetector.EnsureStarted();
m_event.WaitOne(m_increasePriorityDelay);
// second, wait for a reasonable amount of time without tinkering with priorities
lock (this)
{
hasResult = m_result != EvaluationStatus.None;
}
if (!hasResult)
{
// after the second delay, evaluation is still neither canceled nor finished; let's raise priority of cycle detector while we keep waiting
using (cycleDetector.IncreasePriority())
{
m_event.WaitOne();
// third, just keep waiting until signaled, because of cancellation of because evaluation finishes
}
}
}
}
lock (this)
{
Contract.Assume(m_result != EvaluationStatus.None);
if (--m_eventWaiters == 0)
{
m_event.Dispose();
m_event = null;
}
}
}
