[cffi-devel] Passing address of pointer

[Frank Goenninger]

Hi all,

I have a C struct as follows:

(defcstruct MyPrivateData
  (notification       io_object_t)
  (deviceInterface    :pointer) ;; void pointer 
  (deviceName         CFStringRef)
  (locationID         UInt32))

of which the deviceInterface slot is the one I'm interested in. I need to pass the address of the deviceInterface pointer to a function that sets the pointer to valid device interface struct.

So...

In the sample code from Apple the C function is called like this:

typedef struct MyPrivateData {
    io_object_t		   notification;
    IOUSBDeviceInterface   **deviceInterface;
    CFStringRef		   deviceName;
    UInt32		   locationID;
} MyPrivateData;

IOCFPlugInInterface	**plugInInterface = NULL;
SInt32	 	        score;
HRESULT 		res;

res = (*plugInInterface)->QueryInterface( plugInInterface, 
                                          CFUUIDGetUUIDBytes( kIOUSBDeviceInterfaceID ),
                                          (LPVOID*) &privateDataRef->deviceInterface );

How would I translate this call into a valid CFFI equivalent ?

I have so far:

(let ((query-interface-ptr
	 (foreign-slot-value plugInInterface
                             'IOCFPlugInInterface
                             'ccag.osx.iokit::QueryInterface)))

   (format *debug-io* "~%DEVICE-ADDED: query-interface-ptr = ~s."
           query-interface-ptr)
                
   (setq res (foreign-funcall-pointer
                query-interface-ptr
                ()
                :pointer plugInInterface
                CFUUIDBytes (cf-uuid-get-uuid-bytes
                               kIOUSBDeviceInterfaceID)
                :pointer (foreign-slot-pointer privateDataRef
                                               'MyPrivateData
                                               'deviceInterface)))

   (format *debug-io* "~%DEVICE-ADDED: deviceInterface = ~s."
           (foreign-slot-value privateDataRef 'MyPrivateData 'deviceInterface))

...

This code "crashes" with signal 100 as reported by AllegroCL in the call to foreign-funcall-pointer ...

Any hints or advice really appreciated!

TIA!

Best wishes
  Frank