network: The Queue class holds a list of packets

This patch modifies the Queue class to allow subclasses to perform additional enqueue/dequeue/peek/remove operations which can manipulate any element in the queue (as required by WifiMacQueue). Now, the Queue class:

- defines a std::list<Ptr<Item>> (subclasses no longer define their own containers)

- has virtual public Enqueue/Dequeue/Peek/Remove methods that are undefined and must be defined by every subclass

- the only way subclasses have to manipulate the queue is through the following methods:
   + bool Queue<Item>::DoEnqueue (ConstIterator pos, Ptr<Item> item)
   + Ptr<Item> Queue<Item>::DoDequeue (ConstIterator pos)
   + Ptr<const Item> Queue<Item>::DoPeek (ConstIterator pos) const
   + Ptr<Item> Queue<Item>::DoRemove (ConstIterator pos)

Two protected methods (ConstIterator Head (void) const e ConstIterator Tail (void) const) are provided to allow subclasses to access any item in the queue. As an example:

template <typename Item>
bool
DropTailQueue<Item>::Enqueue (Ptr<Item> item)
{
  NsLog (LOG_DEBUG, "Enqueue ", this, item);
  return DoEnqueue (Tail (), item);
}

- subclasses can define additional public methods, as an example:

bool
WifiMacQueue::PushFront (Ptr<WifiMacQueueItem> item)
{
  [...]
  return DoEnqueue (Head (), item);
}

[Mohit P. Tahiliani, 2017-01-21 17:39:39]

On 2017/01/19 23:26:35, Stefano Avallone wrote:

The patch looks good to me.

Thanks,
Mohit P. Tahiliani

[Stefano Avallone, 2017-01-24 17:19:46]

Changes with respect to the first version:

- removed the PendingPacket method

- updated the models documentation