flatten 20260225

tjp/core/singleton/ThreadSafeSingleton.hpp

@@ -0,0 +1,112 @@
+// TJP COPYRIGHT HEADER
+
+/**
+ * legal header 
+ *
+ * ============================================================================
+ * TJP	10/11/01		Got rid of the constructed singleton, it was essentially
+ *		a pointer!
+ *
+ * @author	Timothy Prepscius
+ * @created 3/../01
+ */
+
+#pragma once
+
+#include "ThreadSafeSingleton.h"
+#include "../threads/Monitor.h"
+
+namespace timprepscius {
+namespace core {
+
+/**
+ * a Singleton container, whose contained instance is constructed on its
+ * first request
+ *
+ * T defines the class pointer type
+ * X defines the allocation class type
+ */
+
+template<class T>
+class ThreadSafeSingletonNoConstruct : public Monitor<T>
+{
+	public:
+		typedef Monitor<T> Super;
+		typedef typename Super::Writer Accessor;
+
+	protected:
+		// only called by reader/writer after lock
+		virtual T *access() const
+		{
+			return this->object;
+		}
+
+	public:
+		ThreadSafeSingletonNoConstruct () :
+			Super(NULL)
+		{
+		}
+	
+		virtual ~ThreadSafeSingletonNoConstruct()
+		{
+			deleteInstance();
+		}
+	
+		virtual void setInstance (T *instance)
+		{
+			Accessor w(*this);
+			{
+				this->object = instance;
+			}
+		}
+
+		void deleteInstance()
+		{
+			Accessor w(*this);
+
+			if (this->object)
+				delete this->object;
+
+			this->object = NULL;
+		}
+} ;
+
+template<class T, class X=T>
+class ThreadSafeSingleton : public ThreadSafeSingletonNoConstruct<T>
+{
+	public:
+		typedef ThreadSafeSingletonNoConstruct<T> Super;
+		typedef typename Super::Writer Accessor;
+
+	protected:
+		// only called by reader/writer after lock
+		virtual T *access() const
+		{
+			if (!this->object)
+			{
+				const_cast<ThreadSafeSingleton<T> *>(this)->setInstance(new T());
+			}
+			
+			return this->object;
+		}
+
+	public:
+		virtual ~ThreadSafeSingleton()
+		{
+			Super::deleteInstance();
+		}
+		
+		virtual void setInstance (T *instance)
+		{
+			Accessor a(*this);
+			
+			if (this->object)
+				delete this->object;
+		
+			this->object = instance;
+		}
+} ;
+
+} // namespace utilities 
+} // namespace
+