Function Binding. Special thanks to: John Edwards. Randy Gaul

Transcription

1 Function Binding Special thanks to: John Edwards Randy Gaul

2 Introspection Generic Variable Function Binding Simple Case Uses Demo Overview Function Binding

3 Introspection Run-time knows little about types Introspection saves compile-time data Generic code

4 Introspection Questions we can Answer What methods does this class have What members are in this struct What type of data is this Can I convert type A to type B How can I send this type to script How can I send this type to a file How can I create this type from file What sort of messaging can I achieve

5 Introspection Register your Data We want tables of data Type Name - "int" Size - 4 bytes Members - none Methods - none Inherits from - none

6 Introspection Register your Data Store data in a struct struct TypeInfo { const char *name; int size; TypeInfo *inheritsfrom; Method *methods; Members *members; };

7 Introspection Register your Data Use a macro to register info into your tables void RegisterSomeData( void ) { REGISTER_TYPE( int ); REGISTER_TYPE( SomeStruct ); REGISTER_MEMBER( SomeStruct, x ); }

8 Magic Macros! Introspection Register your Data #define REGISTER_TYPE( T ) \ Introspection::Get( )->RegisterType<T>( sizeof( T ), #T )

9 Introspection Register your Data Introspection singleton struct IntrospectionManager { static IntrospectionManager *Get( void ) { static IntrospectionManager instance; return &instance; } template <typename T> TypeInfo *RegisterType( int size, char *name ) { static TypeInfo instance; TypeInfo *typeinfo = &instance; m_typemap.add( name, typeinfo ); return typeinfo; } private: HashTable<const char *, TypeInfo *> m_typemap; };

10 Introspection Retrieve Data Retrieve data from Singleton Make single Get for a type Wrap this in a GET_TYPE( T ) macro template <typename T> const TypeInfo *IntrospectionManager::GetType( void ) const { static TypeInfo instance; return &instance; }

11 Introspection The Macros Might want something like these #define REGISTER( T ) #define TYPE( T ) #define TYPE_OF( OBJECT ) #define TYPE_OF_MEMBER( T, MEMBER ) #define STR_TYPE( STR ) #define ADD_MEMBER( T, MEMBER ) #define SET_SERIALIZER( T, SERIALIZER ) #define SET_DESERIALIZER( T, DESERIALIZER )

12 Variable Generic Variable needed for generic code We want to do this: Variable v; int x = 5; v = x; v.tolua( ); // Send 5 to Lua v.serialize( file ); // write 5 in a file // Valid SomeStruct s; v = s;

13 TypeInfo * Void * Variable

14 Variable GetValue template <typename T> T& Variable::GetValue( void ) { return *((T *)m_data )); }

15 Function Binding Lets create generic Function Lets pass it Variables as arguments

16 Function Binding Step 1: Lets create generic Function Store function pointer as template type template <typename FunctionType, FunctionType FunctionPtr> Function BuildFunction( void (*fn)( void ) ) { return Function; // Not finished! }

17 Function Binding Function needs function pointer template type Pass address of Call Helper template <typename FunctionType, FunctionType FunctionPtr> Function BuildFunction( void (*fn)( void ) ) { return Function( &Call<FunctionType, FunctionPtr> ); }

18 Function Binding Call helper calls the real function pointer template <typename FunctionType, FunctionType FunctionPtr> void Call( Variable *ret, Variable *args, unsigned argcount ) { assert( argcount == 0 ); } (*FunctionPtr)( );

19 Can now call void (*)( void ) Function Binding Function f = BuildFunction<decltype( &Func ), &Func>( &Func ); f( ); // calls Func

20 What about arguments? Make some overloads Function Binding template <typename FunctionType, FunctionType FunctionPtr, typename Arg1> Function BuildFunction( void (*fn)( Arg1 ) ) { return Function( &Call<FunctionType, FunctionPtr, Arg1> ); } template <typename FunctionType, FunctionType FunctionPtr, typename Arg1> void Call( Variable *ret, Variable *args, unsigned argcount ) { assert( argcount == 0 ); } (*FunctionPtr)( args[0].getvalue<arg1>( ) );

21 What about more arguments? Make some more overloads Function Binding

22 What about non-void return? Function Binding

23 What about non-void return? MAKE SOME MORE OVERLOADS Function Binding

24 Function Binding My final function binding: 1783 lines in header Screenshot is about 1/10 th of file

25 Properties!! Function for Get/Set methods Function Binding - Uses

26 Function Binding - Uses Visual scripting Attach and pass around Function objects

27 Bind functions to call from script Function Binding - Uses REGISTER_FUNCTION( glbegin ); REGISTER_FUNCTION( glend ); // in script glbegin( blah );... // Render a beautiful scene glend( );

28 Messaging omg Function Binding - Uses void Object::SendMessage( Variable v1 ); void Object::SendMessage( Variable v1, Variable v2 ); void Object::SendMessage( Variable v1, Variable v2, Variable v3 );

29 Function Binding - Uses Listeners Messaging even better super omg void Object::Subscribe( Function& f ); void Object::PostMSG( MSG_ID id ); void Object::PostMSG( MSG_ID id, Variable v1 ); void Object::PostMSG( MSG_ID id, Variable v1, Variable v2 );

30 And more..? Function Binding - Uses

31 Demo

32 Questions?

33 Resources Template Metaprogramming John Edwards My website Sean middleditche s website Engine Arch online files (Sean made some demos)