// AddObject- Add an object to the list after a particular node.
public LLNode AddObject(LLNode previousNode, object toAdd)
{
// Create a new node with the object attached.
LLNode newNode = new LLNode(toAdd);
// Start with the easiest case:
// If the list is empty then...
if (_head == null && _tail == null)
{
// ...start off with just the one node in the list.
_head = newNode;
_tail = newNode;
return newNode;
}
// OK, are we adding the new node to the middle of the list?
if (previousNode != null && previousNode._forward != null)
{
// Just switch the pointers around and we're done.
LLNode nextNode = previousNode._forward;
// First, store the forward pointers.
newNode._forward = nextNode;
previousNode._forward = newNode;
// Now the backward pointers.
nextNode._backward = newNode;
newNode._backward = previousNode;
return newNode;
}
// Are we adding it to the beginning?
if (previousNode == null)
{
// Make this the head man.
LLNode nextNode = _head;
newNode._forward = nextNode;
nextNode._backward = newNode;
_head = newNode;
return newNode;
}
// Must be the end of the list.
newNode._backward = previousNode;
previousNode._forward = newNode;
_tail = newNode;
return newNode;
}
// Reset - move the iterator back to immediately prior
// to the first node in the list
public void Reset()
{
currentNode = null;
nextNode = linkedList.head;
}
// MoveNext - Move to the next item in the list unless we
// have already reached the end.
public bool MoveNext()
{
_currentNode = _nextNode;
if (_currentNode == null)
{
return false;
}
_nextNode = _nextNode._forward;
return true;
}
// Reset - Move the iterator back to immediately prior
// to the first node in the list.
public void Reset()
{
_currentNode = null;
_nextNode = _linkedList._head;
}
// RemoveObject - Remove an object from the list.
public void RemoveObject(LLNode currentNode)
{
// Get the current node's neighbors.
LLNode previousNode = currentNode._backward;
LLNode nextNode = currentNode._forward;
// Remove the current object's pointers.
currentNode._forward = currentNode._backward = null;
// Now... if this was the last element in the list.
if (_head == currentNode && _tail == currentNode)
{
_head = _tail = null;
return;
}
// Ok, if this node is in the middle...
if (_head != currentNode && _tail != currentNode)
{
previousNode._forward = nextNode;
nextNode._backward = previousNode;
return;
}
// At the front of the list?
if (_head == currentNode && _tail != currentNode)
{
_head = nextNode;
nextNode._backward = null;
return;
}
// Must be at the end of the list.
_tail = previousNode;
previousNode._forward = null;
}
// Reset - Move the iterator back to immediately prior
// to the first node in the list.
public void Reset()
{
_currentNode = null;
_nextNode = _linkedList._head;
}