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deps/include/Box2D/Common/b2IntrusiveList.h

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+/*
+* Copyright (c) 2014 Google, Inc.
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+#ifndef B2_INTRUSIVE_LIST
+#define B2_INTRUSIVE_LIST
+
+#include <Box2D/Common/b2Settings.h>
+
+// Whether to enable b2IntrusiveList::ValidateList().
+// Be careful when enabling this since this changes the size of
+// b2IntrusiveListNode so make sure *all* projects that include Box2D.h
+// also define this value in the same way to avoid data corruption.
+#ifndef B2_INTRUSIVE_LIST_VALIDATE
+#define B2_INTRUSIVE_LIST_VALIDATE 0
+#endif  // B2_INTRUSIVE_LIST_VALIDATE
+
+/// b2IntrusiveListNode is used to implement an intrusive doubly-linked
+/// list.
+///
+/// For example:
+///
+/// class MyClass {
+/// public:
+/// 	MyClass(const char *msg) : m_msg(msg) {}
+/// 	const char* GetMessage() const { return m_msg; }
+/// 	B2_INTRUSIVE_LIST_GET_NODE(m_node);
+/// 	B2_INTRUSIVE_LIST_NODE_GET_CLASS(MyClass, m_node);
+/// private:
+/// 	b2IntrusiveListNode m_node;
+/// 	const char *m_msg;
+/// };
+///
+/// int main(int argc, char *argv[]) {
+/// 	b2IntrusiveListNode list; // NOTE: type is NOT MyClass
+/// 	MyClass a("this");
+/// 	MyClass b("is");
+/// 	MyClass c("a");
+/// 	MyClass d("test");
+/// 	list.InsertBefore(a.GetListNode());
+/// 	list.InsertBefore(b.GetListNode());
+/// 	list.InsertBefore(c.GetListNode());
+/// 	list.InsertBefore(d.GetListNode());
+/// 	for (b2IntrusiveListNode* node = list.GetNext();
+/// 		 node != list.GetTerminator(); node = node->GetNext()) {
+/// 		MyClass *cls = MyClass::GetInstanceFromListNode(node);
+/// 		printf("%s\n", cls->GetMessage());
+/// 	}
+/// 	return 0;
+/// }
+class b2IntrusiveListNode
+{
+public:
+	/// Initialize the node.
+	b2IntrusiveListNode()
+	{
+		Initialize();
+#if B2_INTRUSIVE_LIST_VALIDATE
+		m_magic = k_magic;
+#endif // B2_INTRUSIVE_LIST_VALIDATE
+	}
+
+	/// If the node is in a list, remove it from the list.
+	~b2IntrusiveListNode()
+	{
+		Remove();
+#if B2_INTRUSIVE_LIST_VALIDATE
+		m_magic = 0;
+#endif // B2_INTRUSIVE_LIST_VALIDATE
+	}
+
+	/// Insert this node after the specified node.
+	void InsertAfter(b2IntrusiveListNode* const node)
+	{
+		b2Assert(!node->InList());
+		node->m_next = m_next;
+		node->m_prev = this;
+		m_next->m_prev = node;
+		m_next = node;
+	}
+
+	/// Insert this node before the specified node.
+	void InsertBefore(b2IntrusiveListNode* const node)
+	{
+		b2Assert(!node->InList());
+		node->m_next = this;
+		node->m_prev = m_prev;
+		m_prev->m_next = node;
+		m_prev = node;
+	}
+
+	/// Get the terminator of the list.
+	const b2IntrusiveListNode* GetTerminator() const
+	{
+		return this;
+	}
+
+	/// Remove this node from the list it's currently in.
+	b2IntrusiveListNode* Remove()
+	{
+		m_prev->m_next = m_next;
+		m_next->m_prev = m_prev;
+		Initialize();
+		return this;
+	}
+
+	/// Determine whether this list is empty or the node isn't in a list.
+	bool IsEmpty() const
+	{
+	  return GetNext() == this;
+	}
+
+	/// Determine whether this node is in a list or the list contains nodes.
+	bool InList() const
+	{
+	  return !IsEmpty();
+	}
+
+	/// Calculate the length of the list.
+	uint32 GetLength() const
+	{
+		uint32 length = 0;
+		const b2IntrusiveListNode * const terminator = GetTerminator();
+		for (const b2IntrusiveListNode* node = GetNext();
+			 node != terminator; node = node->GetNext())
+		{
+			length++;
+		}
+		return length;
+	}
+
+	/// Get the next node in the list.
+	b2IntrusiveListNode* GetNext() const
+	{
+		return m_next;
+	}
+
+	/// Get the previous node in the list.
+	b2IntrusiveListNode* GetPrevious() const
+	{
+		return m_prev;
+	}
+
+	/// If B2_INTRUSIVE_LIST_VALIDATE is 1 perform a very rough validation
+	/// of all nodes in the list.
+	bool ValidateList() const
+	{
+#if B2_INTRUSIVE_LIST_VALIDATE
+	  if (m_magic != k_magic) return false;
+	  const b2IntrusiveListNode * const terminator = GetTerminator();
+	  for (b2IntrusiveListNode *node = GetNext(); node != terminator;
+		   node = node->GetNext()) {
+		if (node->m_magic != k_magic) return false;
+	  }
+#endif  // B2_INTRUSIVE_LIST_VALIDATE
+	  return true;
+	}
+
+	/// Determine whether the specified node is present in this list.
+	bool FindNodeInList(b2IntrusiveListNode* const nodeToFind) const
+	{
+		const b2IntrusiveListNode * const terminator = GetTerminator();
+		for (b2IntrusiveListNode *node = GetNext(); node != terminator;
+			 node = node->GetNext())
+		{
+			if (nodeToFind == node) return true;
+		}
+		return false;
+	}
+
+private:
+	/// Initialize the list node.
+	void Initialize()
+	{
+		m_next = this;
+		m_prev = this;
+	}
+
+private:
+#if B2_INTRUSIVE_LIST_VALIDATE
+	uint32 m_magic;
+#endif  // B2_INTRUSIVE_LIST_VALIDATE
+	/// The next node in the list.
+	b2IntrusiveListNode *m_prev;
+	/// The previous node in the list.
+	b2IntrusiveListNode *m_next;
+
+private:
+#if B2_INTRUSIVE_LIST_VALIDATE
+	static const uint32 k_magic = 0x7157ac01;
+#endif  // B2_INTRUSIVE_LIST_VALIDATE
+};
+
+/// Declares the member function GetListNode() of Class to retrieve a pointer
+/// to NodeMemberName.
+/// See #B2_INTRUSIVE_LIST_NODE_GET_CLASS_ACCESSOR()
+#define B2_INTRUSIVE_LIST_GET_NODE(NodeMemberName) \
+	b2IntrusiveListNode* GetListNode() { return &NodeMemberName; } \
+	const b2IntrusiveListNode* GetListNode() const { return &NodeMemberName; }
+
+/// Declares the member function FunctionName of Class to retrieve a pointer
+/// to a Class instance from a list node pointer.   NodeMemberName references
+/// the name of the b2IntrusiveListNode member of Class.
+#define B2_INTRUSIVE_LIST_NODE_GET_CLASS_ACCESSOR( \
+	Class, NodeMemberName, FunctionName) \
+	static Class* FunctionName(b2IntrusiveListNode *node) \
+	{ \
+		Class *cls = NULL; \
+		/* This effectively performs offsetof(Class, NodeMemberName) */ \
+		/* which ends up in the undefined behavior realm of C++ but in */ \
+		/* practice this works with most compilers. */ \
+		return reinterpret_cast<Class*>((uint8*)(node) - \
+										(uint8*)(&cls->NodeMemberName)); \
+	} \
+	\
+	static const Class* FunctionName(const b2IntrusiveListNode *node) \
+	{ \
+		return FunctionName(const_cast<b2IntrusiveListNode*>(node)); \
+	}
+
+/// Declares the member function GetInstanceFromListNode() of Class to retrieve
+/// a pointer to a Class instance from a list node pointer.  NodeMemberName
+/// reference the name of the b2IntrusiveListNode member of Class.
+#define B2_INTRUSIVE_LIST_NODE_GET_CLASS(Class, NodeMemberName) \
+	B2_INTRUSIVE_LIST_NODE_GET_CLASS_ACCESSOR(Class, NodeMemberName, \
+											  GetInstanceFromListNode)
+
+/// b2TypedIntrusiveListNode which supports inserting an object into a single
+/// doubly linked list.  For objects that need to be inserted in multiple
+/// doubly linked lists, use b2IntrusiveListNode.
+///
+/// For example:
+///
+/// class IntegerItem : public b2TypedIntrusiveListNode<IntegerItem>
+/// {
+/// public:
+/// 	IntegerItem(int32 value) : m_value(value) { }
+/// 	~IntegerItem() { }
+/// 	int32 GetValue() const { return m_value; }
+/// private:
+/// 	int32 m_value;
+/// };
+///
+/// int main(int argc, const char *arvg[]) {
+/// 	b2TypedIntrusiveListNode<IntegerItem> list;
+/// 	IntegerItem a(1);
+/// 	IntegerItem b(2);
+/// 	IntegerItem c(3);
+/// 	list.InsertBefore(&a);
+/// 	list.InsertBefore(&b);
+/// 	list.InsertBefore(&c);
+/// 	for (IntegerItem* item = list.GetNext();
+/// 		 item != list.GetTerminator(); item = item->GetNext())
+/// 	{
+/// 		printf("%d\n", item->GetValue());
+/// 	}
+/// }
+template<typename T>
+class b2TypedIntrusiveListNode
+{
+public:
+	b2TypedIntrusiveListNode() { }
+	~b2TypedIntrusiveListNode() { }
+
+	/// Insert this object after the specified object.
+	void InsertAfter(T* const obj)
+	{
+		b2Assert(obj);
+		GetListNode()->InsertAfter(obj->GetListNode());
+	}
+
+	/// Insert this object before the specified object.
+	void InsertBefore(T* const obj)
+	{
+		b2Assert(obj);
+		GetListNode()->InsertBefore(obj->GetListNode());
+	}
+
+	/// Get the next object in the list.
+	/// Check against GetTerminator() before deferencing the object.
+	T* GetNext() const
+	{
+		return GetInstanceFromListNode(GetListNode()->GetNext());
+	}
+
+	/// Get the previous object in the list.
+	/// Check against GetTerminator() before deferencing the object.
+	T* GetPrevious() const
+	{
+		return GetInstanceFromListNode(GetListNode()->GetPrevious());
+	}
+
+	/// Get the terminator of the list.
+	/// This should not be dereferenced as it is a pointer to
+	/// b2TypedIntrusiveListNode<T> *not* T.
+	T* GetTerminator() const
+	{
+		return (T*)GetListNode();
+	}
+
+	/// Remove this object from the list it's currently in.
+	T* Remove()
+	{
+		GetListNode()->Remove();
+		return GetInstanceFromListNode(GetListNode());
+	}
+
+	/// Determine whether this object is in a list.
+	bool InList() const
+	{
+		return GetListNode()->InList();
+	}
+
+	// Determine whether this list is empty.
+	bool IsEmpty() const
+	{
+		return GetListNode()->IsEmpty();
+	}
+
+	/// Calculate the length of the list.
+	uint32 GetLength() const
+	{
+		return GetListNode()->GetLength();
+	}
+
+	B2_INTRUSIVE_LIST_GET_NODE(m_node);
+
+private:
+	// Node within an intrusive list.
+	b2IntrusiveListNode m_node;
+
+public:
+	/// Get a pointer to the instance of T that contains "node".
+	static T* GetInstanceFromListNode(b2IntrusiveListNode* const node)
+	{
+		b2Assert(node);
+		// Calculate the pointer to T from the offset.
+		return (T*)((uint8*)node - GetNodeOffset(node));
+	}
+
+private:
+	// Get the offset of m_node within this class.
+	static int32 GetNodeOffset(b2IntrusiveListNode* const node)
+	{
+		b2Assert(node);
+		// Perform some type punning to calculate the offset of m_node in T.
+		// WARNING: This could result in undefined behavior with some C++
+		// compilers.
+		T* obj = (T*)node;
+		int32 nodeOffset = (int32)((uint8*)&obj->m_node - (uint8*)obj);
+		return nodeOffset;
+	}
+};
+
+#endif // B2_INTRUSIVE_LIST
+