C# LockFreeStack类
单链表实现的LockFreeStack
using System;
using System.Collections;
using System.Threading;
namespace Rocky.Stored
{
public class LockFreeStack : IEnumerable
{
private class SingleLinkedNode
{
public object Value;
public SingleLinkedNode Next;
}
private SingleLinkedNode m_head;
private int count;
public int Count
{
get { return count; }
}
public void Push(object item)
{
SingleLinkedNode node = new SingleLinkedNode();
node.Value = item;
SingleLinkedNode head;
do
{
head = m_head;
node.Next = head;
}
while (m_head != head || Interlocked.CompareExchange(ref m_head, node, head) != head);
Interlocked.Increment(ref count);
}
public object Peek()
{
SingleLinkedNode head = m_head;
if (head == null)
{
throw new InvalidOperationException("Stack Empty!");
}
return head.Value;
}
public object Pop()
{
object result;
if (TryPop(out result))
{
return result;
}
throw new InvalidOperationException("Stack Empty!");
}
/// <summary>
/// 考虑到在多线程环境中,这里不抛出异常。我们需要人为判断其是否为空,即 !TryPop() or result != null
/// </summary>
/// <returns></returns>
public bool TryPop(out object item)
{
SingleLinkedNode head;
SingleLinkedNode next;
do
{
head = m_head;
if (head == null)
{
item = null;
return false;
}
next = m_head.Next;
}
while (Interlocked.CompareExchange(ref m_head, next, head) != head);
Interlocked.Decrement(ref count);
item = head.Value;
return true;
}
public object SpinPop()
{
SingleLinkedNode head;
SpinWait spin = new SpinWait();
while (true)
{
SingleLinkedNode next;
do
{
head = m_head;
if (head == null)
{
goto emptySpin;
}
next = head.Next;
}
while (m_head != head || Interlocked.CompareExchange(ref m_head, next, head) != head);
break;
emptySpin:
spin.Spin();
}
Interlocked.Decrement(ref count);
return head.Value;
}
public bool Contains(object item)
{
SingleLinkedNode head = m_head;
while (m_head != null && head != null)
{
if (head.Value.Equals(item))
{
return true;
}
head = head.Next;
}
return false;
}
public void Clear()
{
Interlocked.Exchange(ref m_head, null);
Interlocked.Exchange(ref count, 0);
}
public IEnumerator GetEnumerator()
{
SingleLinkedNode head = m_head;
while (m_head != null && head != null)
{
yield return head.Value;
head = head.Next;
}
}
}
}