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public/appframework/iappsystem.h

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+//===== Copyright <20> 1996-2005, Valve Corporation, All rights reserved. ======//
+//
+// Purpose: An application framework 
+//
+// $Revision: $
+// $NoKeywords: $
+//===========================================================================//
+
+#ifndef IAPPSYSTEM_H
+#define IAPPSYSTEM_H
+
+#ifdef COMPILER_MSVC
+#pragma once
+#endif
+
+#include "tier1/interface.h"
+#include "interfaces/interfaces.h"
+
+
+//-----------------------------------------------------------------------------
+// Specifies a module + interface name for initialization
+//-----------------------------------------------------------------------------
+struct AppSystemInfo_t
+{
+	const char *m_pModuleName;
+	const char *m_pInterfaceName;
+};
+
+
+//-----------------------------------------------------------------------------
+// Client systems are singleton objects in the client codebase responsible for
+// various tasks
+// The order in which the client systems appear in this list are the
+// order in which they are initialized and updated. They are shut down in
+// reverse order from which they are initialized.
+//-----------------------------------------------------------------------------
+enum InitReturnVal_t
+{
+	INIT_FAILED = 0,
+	INIT_OK,
+
+	INIT_LAST_VAL,
+};
+
+enum AppSystemTier_t
+{
+	APP_SYSTEM_TIER0 = 0,
+	APP_SYSTEM_TIER1,
+	APP_SYSTEM_TIER2,
+	APP_SYSTEM_TIER3,
+
+	APP_SYSTEM_TIER_OTHER,
+};
+
+
+abstract_class IAppSystem
+{
+public:
+	// Here's where the app systems get to learn about each other 
+	virtual bool Connect( CreateInterfaceFn factory ) = 0;
+	virtual void Disconnect() = 0;
+
+	// Here's where systems can access other interfaces implemented by this object
+	// Returns NULL if it doesn't implement the requested interface
+	virtual void *QueryInterface( const char *pInterfaceName ) = 0;
+
+	// Init, shutdown
+	virtual InitReturnVal_t Init() = 0;
+	virtual void Shutdown() = 0;
+
+	// Returns all dependent libraries
+	virtual const AppSystemInfo_t* GetDependencies() {return NULL;}
+
+	// Returns the tier
+	virtual AppSystemTier_t GetTier() {return APP_SYSTEM_TIER_OTHER;}
+
+	// Reconnect to a particular interface
+	virtual void Reconnect( CreateInterfaceFn factory, const char *pInterfaceName ) {}
+	// Is this appsystem a singleton? (returns false if there can be multiple instances of this interface)
+	virtual bool IsSingleton() { return true; }
+};
+
+
+//-----------------------------------------------------------------------------
+// Helper empty implementation of an IAppSystem
+//-----------------------------------------------------------------------------
+template< class IInterface > 
+class CBaseAppSystem : public IInterface
+{
+public:
+	// Here's where the app systems get to learn about each other 
+	virtual bool Connect( CreateInterfaceFn factory ) { return true; }
+	virtual void Disconnect() {}
+
+	// Here's where systems can access other interfaces implemented by this object
+	// Returns NULL if it doesn't implement the requested interface
+	virtual void *QueryInterface( const char *pInterfaceName ) { return NULL; }
+
+	// Init, shutdown
+	virtual InitReturnVal_t Init() { return INIT_OK; }
+	virtual void Shutdown() {}
+
+	virtual const AppSystemInfo_t* GetDependencies() { return NULL; }
+	virtual AppSystemTier_t GetTier() { return APP_SYSTEM_TIER_OTHER; }
+
+	virtual void Reconnect( CreateInterfaceFn factory, const char *pInterfaceName )
+	{
+		ReconnectInterface( factory, pInterfaceName );
+	}
+};
+
+
+//-----------------------------------------------------------------------------
+// Helper implementation of an IAppSystem for tier0
+//-----------------------------------------------------------------------------
+template< class IInterface > 
+class CTier0AppSystem : public CBaseAppSystem< IInterface >
+{
+};
+
+
+#endif // IAPPSYSTEM_H
+