1 files changed, 156 insertions, 0 deletions

diff --git a/Src/nu/LockFreeStack.h b/Src/nu/LockFreeStack.h
new file mode 100644
index 00000000..7c1d1b1e
--- /dev/null
+++ b/Src/nu/LockFreeStack.h
@@ -0,0 +1,156 @@
+#pragma once
+#include <windows.h>
+
+/* lock free stack object 
+multiple threads can push and pop without locking
+note that order is not guaranteed.  that is, if Thread 1 calls Insert before Thread 2, Thread 2's item might still make it in before.
+
+since it uses malloc/free for the linked list nodes, it might not be considered truely lock-free.
+
+use LockFreeStack2 if you can assure that you have a 'next' pointer in your class/struct
+*/
+template <class value_t>
+class LockFreeStackNode
+{
+public:
+	LockFreeStackNode(value_t _data)
+	{
+		data = _data;
+		next = 0;
+	}
+	value_t data;
+
+	LockFreeStackNode *next;
+};
+
+template <class value_t>
+class LockFreeStack
+{
+public:
+	LockFreeStack()
+	{
+		head = 0;
+	}
+
+	void push(value_t data)
+	{
+		LockFreeStackNode<value_t> *new_head = new LockFreeStackNode<value_t>(data);
+		LockFreeStackNode<value_t> *old_head = 0;
+		do
+		{
+			old_head = (LockFreeStackNode<value_t> *)head;
+			new_head->next = old_head;
+		} while (InterlockedCompareExchangePointer((volatile PVOID *)&head, new_head, old_head) != old_head);
+	}
+
+	value_t pop()
+	{
+		LockFreeStackNode<value_t> *new_head = 0, *old_head = 0;
+		do
+		{
+			old_head = (LockFreeStackNode<value_t> *)head;
+			if (old_head)
+			{
+				new_head = old_head->next;
+			}	
+			else
+			{
+				new_head = 0;
+			}
+		} while (InterlockedCompareExchangePointer((volatile PVOID *)&head, new_head, old_head) != old_head);
+		value_t ret = old_head?old_head->data:0;
+		delete old_head;
+		return ret;
+	}
+
+	bool pop_ref(value_t *val)
+	{
+		LockFreeStackNode<value_t> *new_head = 0, *old_head = 0;
+		do
+		{
+			old_head = (LockFreeStackNode<value_t> *)head;
+			if (old_head)
+			{
+				new_head = old_head->next;
+			}			
+			else
+			{
+				new_head = 0;
+			}
+		} while (InterlockedCompareExchangePointer((volatile PVOID *)&head, new_head, old_head) != old_head);
+		if (old_head)
+		{
+			*val = old_head->data;
+			delete old_head;
+			return true;
+		}
+
+		return false;
+	}
+
+	volatile LockFreeStackNode<value_t> *head;
+};
+
+template <class value_t>
+class LockFreeStack2
+{
+public:
+	LockFreeStack()
+	{
+		head = 0;
+	}
+
+	void push(value_t *data)
+	{
+		value_t *old_head = 0;
+		do
+		{
+			old_head = head;
+			data->next = old_head;
+		} while (InterlockedCompareExchangePointer((volatile PVOID *)&head, data, old_head) != old_head);
+	}
+
+	value_t *pop()
+	{
+		value_t *new_head = 0, *old_head = 0;
+		do
+		{
+			old_head = head;
+			if (old_head)
+			{
+				new_head = old_head->next;
+			}
+			else
+			{
+				new_head = 0;
+			}
+		} while (InterlockedCompareExchangePointer((volatile PVOID *)&head, new_head, old_head) != old_head);
+		return old_head;
+	}
+
+	bool pop_ref(value_t **val)
+	{
+		value_t *new_head = 0, *old_head = 0;
+		do
+		{
+			old_head = head;
+			if (old_head)
+			{
+				new_head = old_head->next;
+			}
+			else
+			{
+				new_head = 0;
+			}
+		} while (InterlockedCompareExchangePointer((volatile PVOID *)&head, new_head, old_head) != old_head);
+		if (old_head)
+		{
+			*val = old_head;
+			return true;
+		}
+
+		return false;
+	}
+
+	volatile value_t *head;
+};
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