void ITaskTimerOwner.AddToPending(TaskTimer timer, TaskEnv env, TaskTimerStatus next)
{
env.Acquire();
if(timer.Env != null) {
timer.Env.Release();
}
if(_running) {
lock(_pending) {
timer.Env = env;
timer.SetStatus(next);
_pending[timer] = null;
}
} else {
env.Release();
timer.Env = null;
timer.SetStatus(TaskTimerStatus.Done);
}
}
void ITaskTimerOwner.AddToQueue(TaskTimer timer, TaskEnv env, TaskTimerStatus next)
{
env.Acquire();
if(timer.Env != null) {
timer.Env.Release();
}
if(_running) {
lock(_queue) {
timer.Env = env;
timer.SetStatus(next);
_queue.Enqueue(timer);
}
} else {
env.Release();
timer.Env = null;
timer.SetStatus(TaskTimerStatus.Done);
}
}
/// <summary>
/// Change when the timer will execute.
/// </summary>
/// <param name="when">The absolute time.</param>
/// <param name="env">The environment to use for invocation.</param>
public void Change(DateTime when, TaskEnv env)
{
DateTime now = DateTime.UtcNow;
// determine new status
int next;
if (when <= now.AddSeconds(QUEUE_CUTOFF))
{
next = (int)TaskTimerStatus.Queued;
}
else if (when < DateTime.MaxValue)
{
next = (int)TaskTimerStatus.Pending;
}
else
{
next = (int)TaskTimerStatus.Done;
}
// ensure we have a behavior if we need one and we don't if we do not
if (next != (int)TaskTimerStatus.Done)
{
if (env == null)
{
throw new ArgumentNullException("env");
}
}
else
{
env = null;
}
// attempt to change current status
retry:
int current;
switch (_status)
{
case (int)TaskTimerStatus.Done:
// nothing to do
break;
case (int)TaskTimerStatus.Pending:
// attempt to remove timer from pending list
current = Interlocked.CompareExchange(ref _status, (int)TaskTimerStatus.Done, (int)TaskTimerStatus.Pending);
switch (current)
{
case (int)TaskTimerStatus.Done:
// nothing to do
break;
case (int)TaskTimerStatus.Pending:
// remove timer from pending list
_owner.RemoveFromPending(this);
break;
case (int)TaskTimerStatus.Queued:
// we changed states; retry
Interlocked.Increment(ref _retries);
goto retry;
case (int)TaskTimerStatus.Locked:
// somebody else is already changing the timer; no need to compete
return;
}
break;
case (int)TaskTimerStatus.Queued:
// attempto remove timer from queue
current = Interlocked.CompareExchange(ref _status, (int)TaskTimerStatus.Done, (int)TaskTimerStatus.Queued);
switch (current)
{
case (int)TaskTimerStatus.Done:
// nothing to do
break;
case (int)TaskTimerStatus.Pending:
// we changed states; retry
Interlocked.Increment(ref _retries);
goto retry;
case (int)TaskTimerStatus.Queued:
// remove timer from queue
_owner.RemoveFromQueue(this);
break;
case (int)TaskTimerStatus.Locked:
// somebody else is already changing the timer; no need to compete
return;
}
break;
case (int)TaskTimerStatus.Locked:
// somebody else is already changing the timer; no need to compete
return;
}
// register timer according to new status
if (Interlocked.CompareExchange(ref _status, (int)TaskTimerStatus.Locked, (int)TaskTimerStatus.Done) == (int)TaskTimerStatus.Done)
{
_when = when;
switch (next)
{
case (int)TaskTimerStatus.Done:
// release Task Environment
if (Env != null)
{
Env.Release();
}
Env = null;
Interlocked.Exchange(ref _status, next);
return;
case (int)TaskTimerStatus.Pending:
// add timer to pending list
_owner.AddToPending(this, env, (TaskTimerStatus)next);
break;
case (int)TaskTimerStatus.Queued:
// add timer to active queue
_owner.AddToQueue(this, env, (TaskTimerStatus)next);
break;
case (int)TaskTimerStatus.Locked:
Interlocked.Exchange(ref _status, (int)TaskTimerStatus.Done);
throw new InvalidOperationException("should never happen");
}
}
}