WMI MI_ApplicationFT struct is hard to use

[riverar]

Related: microsoft/windows-rs#1572

WMI APIs such as MI_Application_NewSession are header-only. (Nearly all of them are.) That's not a problem per se but in this case, after calling MI_Application_InitializeV1 you get back a function table defined as such:

typedef struct _MI_ApplicationFT
{
    MI_Result (MI_CALL *Close)(
        _Inout_     MI_Application *application);

    MI_Result (MI_CALL *NewSession)(
        _In_     MI_Application *application,
        _In_opt_z_ const MI_Char *protocol,
        _In_opt_z_ const MI_Char *destination,
        _In_opt_ MI_DestinationOptions *options,
        _In_opt_ MI_SessionCallbacks *callbacks,
        _Outptr_opt_result_maybenull_ MI_Instance **extendedError,
        _Out_    MI_Session *session);

    MI_Result (MI_CALL *NewHostedProvider)(
        _In_     MI_Application *application,
        _In_z_     const MI_Char *namespaceName,
        _In_z_     const MI_Char *providerName,
        _In_     MI_MainFunction mi_Main,
        _Outptr_opt_result_maybenull_ MI_Instance **extendedError,
        _Out_    MI_HostedProvider *provider
        );

   // ...
}

Metadata currently houses a table of difficult to use bare IntPtrs.

public struct MI_ApplicationFT
{
	public IntPtr Close;
	public IntPtr NewSession;
	public IntPtr NewHostedProvider;
	public IntPtr NewInstance;
	public IntPtr NewDestinationOptions;
	public IntPtr NewOperationOptions;
	public IntPtr NewSubscriptionDeliveryOptions;
	public IntPtr NewSerializer;
	public IntPtr NewDeserializer;
	public IntPtr NewInstanceFromClass;
	public IntPtr NewClass;
}

[mikebattista]

What change would you like to see here?

[riverar]

@mikebattista I think parsing the typedef blob into a delegate would be ideal. Maybe we can short term do this manually?

[vpopescu]

Any further thoughts/decisions on this?

[mikebattista]

The scraped C# is below. Seems like yet another case of not honoring the NativeTypeName like #1006 and #983.

    public partial struct MI_ApplicationFT
    {
        [NativeTypeName("MI_Result (*)(MI_Application *) __attribute__((stdcall))")]
        public IntPtr Close;

        [NativeTypeName("MI_Result (*)(MI_Application *, const MI_Char *, const MI_Char *, MI_DestinationOptions *, MI_SessionCallbacks *, MI_Instance **, MI_Session *) __attribute__((stdcall))")]
        public IntPtr NewSession;

        [NativeTypeName("MI_Result (*)(MI_Application *, const MI_Char *, const MI_Char *, MI_MainFunction, MI_Instance **, MI_HostedProvider *) __attribute__((stdcall))")]
        public IntPtr NewHostedProvider;

        [NativeTypeName("MI_Result (*)(MI_Application *, const MI_Char *, const MI_ClassDecl *, MI_Instance **) __attribute__((stdcall))")]
        public IntPtr NewInstance;

        [NativeTypeName("MI_Result (*)(MI_Application *, MI_DestinationOptions *) __attribute__((stdcall))")]
        public IntPtr NewDestinationOptions;

        [NativeTypeName("MI_Result (*)(MI_Application *, MI_Boolean, MI_OperationOptions *) __attribute__((stdcall))")]
        public IntPtr NewOperationOptions;

        [NativeTypeName("MI_Result (*)(MI_Application *, MI_SubscriptionDeliveryType, MI_SubscriptionDeliveryOptions *) __attribute__((stdcall))")]
        public IntPtr NewSubscriptionDeliveryOptions;

        [NativeTypeName("MI_Result (*)(MI_Application *, MI_Uint32, MI_Char *, MI_Serializer *) __attribute__((stdcall))")]
        public IntPtr NewSerializer;

        [NativeTypeName("MI_Result (*)(MI_Application *, MI_Uint32, MI_Char *, MI_Deserializer *) __attribute__((stdcall))")]
        public IntPtr NewDeserializer;

        [NativeTypeName("MI_Result (*)(MI_Application *, const MI_Char *, const MI_Class *, MI_Instance **) __attribute__((stdcall))")]
        public IntPtr NewInstanceFromClass;

        [NativeTypeName("MI_Result (*)(MI_Application *, const MI_ClassDecl *, const MI_Char *, const MI_Char *, MI_Class **) __attribute__((stdcall))")]
        public IntPtr NewClass;
    }

[mikebattista]

Delegates will need to be manually defined as with #796 and #983.

[jterry75]

Can someone point me to what the work would be as an example to make this better? I'm new to this crate but would like to see the MI headers become usable so we could use this newer application style beyond the CIM* style WMI.

[mikebattista]

The fix for #796 demonstrates the pattern. Manually define the delegates in https://github.com/microsoft/win32metadata/blob/main/generation/WinSDK/manual/Wmi.cs, then remap the APIs to use the delegates in https://github.com/microsoft/win32metadata/blob/main/generation/WinSDK/emitter.settings.rsp.

Assigning to you per our offline conversation.