Object tracker list refactor; add object tracker to audio system

lib/Common.hpp

@@ -0,0 +1,65 @@
+#ifndef BOO_INTERNAL_COMMON_HPP
+#define BOO_INTERNAL_COMMON_HPP
+
+#include "boo/BooObject.hpp"
+#include <iterator>
+
+namespace boo
+{
+
+/** Linked-list iterator shareable by data container types */
+template<class T>
+class DataIterator : public std::iterator<std::bidirectional_iterator_tag, T>
+{
+    T* m_node;
+public:
+    explicit DataIterator(T* node) : m_node(node) {}
+    T& operator*() const { return *m_node; }
+    bool operator!=(const DataIterator& other) const { return m_node != other.m_node; }
+    DataIterator& operator++() { m_node = m_node->m_next; return *this; }
+    DataIterator& operator--() { m_node = m_node->m_prev; return *this; }
+};
+
+/** Linked-list IObj node made part of objects participating in list
+ *  Subclasses must implement static methods _getHeadPtr() and _getHeadLock()
+ *  to support the common list-management functionality.
+ */
+template <class N, class H, class P = IObj>
+struct ListNode : P
+{
+    using iterator = DataIterator<N>;
+    iterator begin() { return iterator(static_cast<N*>(this)); }
+    iterator end() { return iterator(nullptr); }
+
+    H m_head;
+    N* m_next;
+    N* m_prev = nullptr;
+    ListNode(H head) : m_head(head)
+    {
+        auto lk = N::_getHeadLock(head);
+        m_next = N::_getHeadPtr(head);
+        if (m_next)
+            m_next->m_prev = static_cast<N*>(this);
+        N::_getHeadPtr(head) = static_cast<N*>(this);
+    }
+protected:
+    ~ListNode()
+    {
+        if (m_prev)
+        {
+            if (m_next)
+                m_next->m_prev = m_prev;
+            m_prev->m_next = m_next;
+        }
+        else
+        {
+            if (m_next)
+                m_next->m_prev = nullptr;
+            N::_getHeadPtr(m_head) = m_next;
+        }
+    }
+};
+
+}
+
+#endif // BOO_INTERNAL_COMMON_HPP