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filesystem/filesystem_stdio/ThreadSafeRefCountedObject.h

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+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: 
+//
+//=============================================================================
+
+#ifndef THREADSAFEREFCOUNTEDOBJECT_H
+#define THREADSAFEREFCOUNTEDOBJECT_H
+#ifdef _WIN32
+#pragma once
+#endif
+
+
+// This class can be used for fast access to an object from multiple threads,
+// and the main thread can wait until the threads are done using the object before it frees the object.
+template< class T >
+class CThreadSafeRefCountedObject
+{
+public:
+	CThreadSafeRefCountedObject( T initVal )
+	{
+		m_RefCount = 0;
+		m_pObject = initVal;
+		m_RefCount = 0;
+	}
+	
+	void Init( T pObj )
+	{
+		Assert( ThreadInMainThread() );
+		Assert( !m_pObject );
+		m_RefCount = 0;
+		m_pObject = pObj;
+		m_RefCount = 1;
+	}
+	
+	// Threads that access the object need to use AddRef/Release to access it.
+	T AddRef()
+	{
+		if ( ++m_RefCount > 1 )
+		{
+			return m_pObject;
+		}
+		else
+		{
+			// If the refcount was 0 when we called this, then the whitelist is about to be freed.
+			--m_RefCount;
+			return NULL;
+		}
+	}
+	void ReleaseRef( T pObj )
+	{
+		if ( --m_RefCount >= 1 )
+		{
+			Assert( m_pObject == pObj );
+		}
+	}
+
+	// The main thread can use this to access the object, since only it can Init() and Free() the object.
+	T GetInMainThread()
+	{
+		Assert( ThreadInMainThread() );
+		return m_pObject;
+	}
+
+	// The main thread calls this after it has released its last reference to the object.
+	void ResetWhenNoRemainingReferences( T newValue )
+	{
+		Assert( ThreadInMainThread() );
+		
+		// Wait until we can free it.
+		while ( m_RefCount > 0 )
+		{
+			CThread::Sleep( 20 );
+		}
+		
+		m_pObject = newValue;
+	}
+
+private:	
+	CInterlockedIntT<long>	m_RefCount;
+	T						m_pObject;
+};
+
+
+#endif // THREADSAFEREFCOUNTEDOBJECT_H