public void Acquire()
{
// Fast path.
if (Interlocked.CompareExchange(ref _value, 1, 0) == 0)
{
return;
}
// Slow path 1 - spin for a while.
/*
* if (SpinEnabled)
* {
* for (int i = 0; i < SpinCount; i++)
* {
* if (Interlocked.CompareExchange(ref _value, 1, 0) == 0)
* return;
* }
* }
*/
// Slow path 2 - wait on the event.
// Note: see FastEvent.cs for a more detailed explanation of this
// technique.
CEvent newEvent = Interlocked.CompareExchange(ref _event, null, null);
if (newEvent == null)
{
newEvent = new CEvent(true, false);
if (Interlocked.CompareExchange(ref _event, newEvent, null) != null)
{
newEvent.Close();
}
}
// Loop trying to acquire the lock. Note that after we
// get woken up another thread might have acquired the lock,
// and that's why we need a loop.
while (true)
{
if (Interlocked.CompareExchange(ref _value, 1, 0) == 0)
{
break;
}
if (!_event.Wait(Timeout.Infinite))
{
Break("Failed to wait indefinitely on an object.");
}
}
}
/// <summary>
/// Dereferences the event, closing it if necessary.
/// </summary>
private void DerefEvent()
{
if ((InterlockedEx.Add(ref _value, -EventRefCountIncrement) >> EventRefCountShift) == 0)
{
if (_event != null)
{
_event.Close();
_event = null;
}
}
}
public override void Close()
{
#if USE_FAST_EVENT
m_isClosed = true;
#else
CEvent oldGate = Interlocked.CompareExchange(ref m_gate, null, m_gate);
if (oldGate != null)
{
oldGate.Close();
}
#endif
base.Close();
}
private void TestEventCmd(string parameters)
{
switch (parameters.ToUpper())
{
case "SET":
myEvent.Set();
break;
case "RESET":
myEvent.Reset();
break;
case "CLOSE":
myEvent.Close();
break;
case "CREATE":
killThreads();
myEvent = new CEvent();
createTestCEventThreads();
break;
case "CREATE FALSE FALSE":
killThreads();
myEvent = new CEvent(false, false);
createTestCEventThreads();
break;
case "CREATE FALSE TRUE":
killThreads();
myEvent = new CEvent(false, true);
createTestCEventThreads();
break;
case "CREATE TRUE FALSE":
killThreads();
myEvent = new CEvent(true, false);
createTestCEventThreads();
break;
case "CREATE TRUE TRUE":
killThreads();
myEvent = new CEvent(true, true);
createTestCEventThreads();
break;
default:
break;
}
}
/// <summary>
/// Waits for the event to be set.
/// </summary>
/// <param name="millisecondsTimeout">The number of milliseconds to wait.</param>
/// <returns>Whether the event was set before the timeout period elapsed.</returns>
public bool Wait(int millisecondsTimeout)
{
// 1. [Optional] If Value = 1, Return.
// 2. [Optional] If Timeout = 0 And Value = 0, Return.
// 3. [Optional] Reference the Global Event.
// 4. [Optional] If Global Event is present, skip Step 5.
// 5. Create Event.
// 6. Global Event = Event only if Global Event is not present.
// 7. If Value = 1, Return (rather, go to Step 9).
// 8. Wait for Global Event.
// 9. [Optional] Dereference the Global Event.
int result = _autoReset ? InterlockedEx.And(ref _value, ~EventSet) : _value;
// Shortcut: return immediately if the event is set.
if ((result & EventSet) != 0)
{
return(true);
}
// Shortcut: if the timeout is 0, return immediately if
// the event isn't set.
if (millisecondsTimeout == 0)
{
return(false);
}
// Prevent the event from being closed or invalidated.
RefEvent();
// Shortcut: don't bother creating an event if we already have one.
CEvent newEvent = _event;
// If we don't have an event, create one and try to set it.
if (newEvent == null)
{
// Create an event. We might not need it, though.
newEvent = new CEvent(_autoReset, false);
// Atomically use the event only if we don't already
// have one.
if (Interlocked.CompareExchange(ref _event, newEvent, null) != null)
{
// Someone else set the event before we did.
newEvent.Close();
}
}
try
{
// Check the value to see if we are meant to wait. This step
// is essential, because if someone set the event before we
// created the event (previous step), we would be waiting
// on an event no one knows about.
if ((_value & EventSet) != 0)
{
return(true);
}
return(_event.Wait(millisecondsTimeout));
}
finally
{
// We don't need the event anymore.
DerefEvent();
}
}
