public WorkItem(WorkQueueOperation operation, TKey key, TValue value)
{
this.operation = operation;
this.key = key;
this.value = value;
this.consumed = false;
}
public bool TryChange(WorkQueueOperation newOperation, TValue newValue)
{
lock (lockObject)
{
if (consumed)
{
return(false);
}
// can't change existing add to add or existing delete to delete
if (newOperation == operation && operation != WorkQueueOperation.Update)
{
throw new InvalidOperationException();
}
// change existing update or add to use new value on update
else if (newOperation == WorkQueueOperation.Update && (operation == WorkQueueOperation.Add || operation == WorkQueueOperation.Update))
{
value = newValue;
}
// change an existing delete to an update on add
else if (newOperation == WorkQueueOperation.Add && operation == WorkQueueOperation.Remove)
{
operation = WorkQueueOperation.Update;
value = newValue;
}
// remove an existing add on delete
else if (newOperation == WorkQueueOperation.Remove && operation == WorkQueueOperation.Add)
{
operation = WorkQueueOperation.Nothing;
value = default(TValue);
}
// remove an existing update on delete
else if (newOperation == WorkQueueOperation.Remove && operation == WorkQueueOperation.Update)
{
operation = WorkQueueOperation.Remove;
value = default(TValue);
}
// the remaining conditions are all invalid:
// - change an existing add to an update
// - change an existing delete to an update
else
{
throw new InvalidOperationException();
}
return(true);
}
}
private void QueueWork(WorkQueueOperation operation, TKey key, TValue value)
{
bool alreadyExists;
WorkItem workItem;
if (!(alreadyExists = workByKey.TryGetValue(key, out workItem)) || !workItem.TryChange(operation, value))
{
workItem = new WorkItem(operation, key, value);
workByKey[key] = workItem;
if (!workQueue.Post(workItem))
{
throw new InvalidOperationException();
}
}
else if (alreadyExists)
{
WorkChangeCount++;
}
}
