/// <summary>
/// Enqueues the specified item.
/// </summary>
/// <param name="item">The item.</param>
public void Enqueue(T item)
{
SingleLinkedNode <T> oldTail = null;
var node = new SingleLinkedNode <T>
{
Item = item
};
// Loop until we have managed to update the tail's Next link to point to our new node.
var updatedNewLink = false;
while (!updatedNewLink)
{
// Make local copies of the tail and its Next link, but in getting the latter use the local copy of
// the tail since another thread may have changed the value of tail.
oldTail = tail;
var oldNext = oldTail.Next;
// Providing that the tail field has not changed...
if (tail == oldTail)
{
// ...and its Next field is null...
if (oldNext == null)
{
// ...try to update the tail's Next field.
updatedNewLink = null == Interlocked.CompareExchange(ref tail.Next, node, null);
}
else
{
// If the tail's Next field was non-null, another thread is in the middle of enqueuing a new node, so try and
// advance the tail to point to its Next node.
Interlocked.CompareExchange(ref tail, oldNext, oldTail);
}
}
}
// Try and update the tail field to point to our node; Don't worry if we can't, another thread will update it for us on
// the next call to Enqueue().
Interlocked.CompareExchange(ref tail, node, oldTail);
Interlocked.Increment(ref count);
}
/// <summary>
/// Initializes a new instance of the <see cref="LockFreeQueue<T>" /> class.
/// </summary>
public LockFreeQueue()
{
head = new SingleLinkedNode <T>();
tail = head;
}