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Marshal.GetFunctionPointerForDelegateI try to get a function pointer from a delegate with
Marshal.GetFunctionPointerForDelegate() Doesn't works with Action<AManagedC++ type> is there any reason why :-( ?! -- Regards, Lloyd Dupont NovaMind development team NovaMind Software Mind Mapping Software <www.nova-mind.com>
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"Lloyd Dupont" <net.galador@ld> wrote in message You must use delegates with isomorphic types for news:uWzhoRLyFHA.1856@TK2MSFTNGP12.phx.gbl... >I try to get a function pointer from a delegate with > Marshal.GetFunctionPointerForDelegate() > > Doesn't works with Action<AManagedC++ type> > is there any reason why :-( ?! > > -- > Regards, > Lloyd Dupont > > NovaMind development team > NovaMind Software > Mind Mapping Software > <www.nova-mind.com> Marshal.GetFunctionPointerForDelete. > You must use delegates with isomorphic types for What is an isomorphic type by the way?> Marshal.GetFunctionPointerForDelete. Ha, right. An isomorpic type is a type for that an equivalent type in both worlds
exist: Int32 is isomorphic because there is (are) 32 bit signed integer types is the native world, too. All in all I guess, this does probalby not really answer your initial question about Marshal.GetFunctionPointerForDelegate, which is an interesting one: Marshal.GetFunctionPointerForDelegate creates a umnanaged/managed thunk that forwards to a given delegate and returns a pointer to that thunk, so that native functions can call this delegate. Next question: What is an unmanaged/managed thunk? An unmanaged/managed thunk is a runtime generated function, that can be called from native code and forwards to a managed function. Thunks are created in different scenarions: * When a thunk is explicitly requested via Marshal::GetFunctionPointerForDelegate * When a P/Invoke function has a delegate as an argument * When a manged function has a native calling convention (C++/CLI only) Next question: Why should Marshal::GetFunctionPointerForDelegate be used? Whenever you want to pass a pointer to a managed function to the native world. This usually happens via a function pointer argument (e.g. EnumWindows) or via a function pointer field of a native struct that is passed as a method argument (WNDCLASS, RegisterWindowClass). Next question: Do I really have to care about this? In most cases not: Even if you have to call functions that expect a native function pointer as an argument, there is another option: You can use a delegate for your P/Invoke function, because the default P/Invoke marshaling of delegates does the same as Marshal::GetFunctionPointerForDelegate would do: It creates an unmanaged/managed thunk that forwards to a managed function. Maybe you would never have asked these questions and thought about something different. But maybe someone found this useful. Marcus Heege DevelopMentor Show quote "Lloyd Dupont" <net.galador@ld> wrote in message news:%23nly1OgyFHA.2652@TK2MSFTNGP14.phx.gbl... >> You must use delegates with isomorphic types for >> Marshal.GetFunctionPointerForDelete. > Ha, right. > What is an isomorphic type by the way? > Thanks Marcus for your long and detail answer.
Anyway finally I used Action<IntPtr> and marshal the IntPtr <=> MyCustomeClass myself and it work beautifully... Show quote "Marcus Heege" <NOSPAM@heege.net> wrote in message news:OVajwg4yFHA.1264@tk2msftngp13.phx.gbl... > An isomorpic type is a type for that an equivalent type in both worlds > exist: Int32 is isomorphic because there is (are) 32 bit signed integer > types is the native world, too. > > All in all I guess, this does probalby not really answer your initial > question about Marshal.GetFunctionPointerForDelegate, which is an > interesting one: > > Marshal.GetFunctionPointerForDelegate creates a umnanaged/managed thunk > that forwards to a given delegate and returns a pointer to that thunk, so > that native functions can call this delegate. > > Next question: What is an unmanaged/managed thunk? > An unmanaged/managed thunk is a runtime generated function, that can be > called from native code and forwards to a managed function. Thunks are > created in different scenarions: > * When a thunk is explicitly requested via > Marshal::GetFunctionPointerForDelegate > * When a P/Invoke function has a delegate as an argument > * When a manged function has a native calling convention (C++/CLI only) > > Next question: Why should Marshal::GetFunctionPointerForDelegate be used? > Whenever you want to pass a pointer to a managed function to the native > world. This usually happens via a function pointer argument (e.g. > EnumWindows) or via a function pointer field of a native struct that is > passed as a method argument (WNDCLASS, RegisterWindowClass). > > Next question: Do I really have to care about this? > In most cases not: Even if you have to call functions that expect a native > function pointer as an argument, there is another option: You can use a > delegate for your P/Invoke function, because the default P/Invoke > marshaling of delegates does the same as > Marshal::GetFunctionPointerForDelegate would do: It creates an > unmanaged/managed thunk that forwards to a managed function. > > Maybe you would never have asked these questions and thought about > something different. But maybe someone found this useful. > > Marcus Heege > DevelopMentor > > > "Lloyd Dupont" <net.galador@ld> wrote in message > news:%23nly1OgyFHA.2652@TK2MSFTNGP14.phx.gbl... >>> You must use delegates with isomorphic types for >>> Marshal.GetFunctionPointerForDelete. >> Ha, right. >> What is an isomorphic type by the way? >> > >  |
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