// Base Enqueue() is protected to allow specialized implementations to
// hide the concept of priority (e.g. PunisherQueue).
//
protected void Enqueue(T item, TPriority priority)
{
if (item == null)
{
throw new InvalidOperationException("Item cannot be null.");
}
lock (CriticalSection) {
if (ItemsByPriority.TryGetValue(priority, out T oldItem) && !item.Equals(oldItem))
{
throw new InvalidOperationException("An item with the same priority exists.");
}
if (ItemPriority.TryGetValue(GetItemKey(item), out TPriority oldPriority))
{
ItemsByPriority.Remove(oldPriority);
--Count;
}
ItemPriority[GetItemKey(item)] = priority;
ItemsByPriority[priority] = item;
Head = ItemsByPriority.First().Value;
++Count;
}
}
public void Remove(T item)
{
lock (CriticalSection) {
object key = GetItemKey(item);
if (key == null)
{
return;
}
ItemsByPriority.Remove(ItemPriority[key]);
ItemPriority.Remove(key);
--Count;
if (key == GetItemKey(Head))
{
if (IsEmpty)
{
Head = default(T);
}
else
{
Head = ItemsByPriority.First().Value;
}
}
}
}