/// <summary>V the semaphore (add 1 unit to it).</summary>
public void V()
{
// Lock so we can work in peace. This works because lock is actually
// built around Monitor.
using (TimedLock.Lock(this))
{
// Release our hold on the unit of control. Then tell everyone
// waiting on this object that there is a unit available.
_count++;
Monitor.Pulse(this);
}
}
/// <summary>
/// Attempts to obtain a lock on the specified object for up to
/// the specified timeout.
/// </summary>
/// <param name="o"></param>
/// <param name="timeout"></param>
/// <returns></returns>
public static TimedLock Lock(object o, TimeSpan timeout)
{
Thread.BeginCriticalRegion();
TimedLock tl = new TimedLock(o);
if (!Monitor.TryEnter(o, timeout))
{
// Failed to acquire lock.
#if DEBUG
GC.SuppressFinalize(tl.leakDetector);
throw new LockTimeoutException(o);
#else
throw new LockTimeoutException();
#endif
}
return(tl);
}
/// <summary>P the semaphore (take out 1 unit from it).</summary>
public void P()
{
// Lock so we can work in peace. This works because lock is actually
// built around Monitor.
using (TimedLock.Lock(this))
{
// Wait until a unit becomes available. We need to wait
// in a loop in case someone else wakes up before us. This could
// happen if the Monitor.Pulse statements were changed to Monitor.PulseAll
// statements in order to introduce some randomness into the order
// in which threads are woken.
while (_count <= 0)
{
Monitor.Wait(this, Timeout.Infinite);
}
_count--;
}
}
/// <summary>A thread worker function that processes items from the work queue.</summary>
private static 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.
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.
using (TimedLock.Lock(_waitingCallbacks.SyncRoot))
{
if (_waitingCallbacks.Count > 0)
{
try { callback = (WaitingCallback)_waitingCallbacks.Dequeue(); }
catch { } // make sure not to fail here
}
}
// 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 (Exception)
{
}
finally
{
Interlocked.Decrement(ref _inUseThreads);
}
}
}
/// <summary>Resets the semaphore to the specified count. Should be used cautiously.</summary>
public void Reset(int count)
{
using (TimedLock.Lock(this)) { _count = count; }
}
/// <summary>
/// Attempts to obtain a lock on the specified object for up to
/// the specified timeout.
/// </summary>
/// <param name="o"></param>
/// <param name="timeout"></param>
/// <returns></returns>
public static TimedLock Lock(object o, TimeSpan timeout)
{
Thread.BeginCriticalRegion();
TimedLock tl = new TimedLock(o);
if (!Monitor.TryEnter(o, timeout))
{
// Failed to acquire lock.
#if DEBUG
GC.SuppressFinalize(tl.leakDetector);
throw new LockTimeoutException(o);
#else
throw new LockTimeoutException();
#endif
}
return tl;
}
