how to pass a non static-member function as a callback?

Question

 
io_iterator_t enumerator;
kern_return_t   result;
result = IOServiceAddMatchingNotification(
             mNotifyPort,
             kIOMatchedNotification,
             IOServiceMatching( "IOFireWireLocalNode" ),
             serviceMatchingCallback, 
             (void *)0x1234,
             & enumerator );

serviceMatchingCallback((void *)0x1234, enumerator);

if i declare serviceMatchinCallback as static then it works, but i do not want it to be static. Is there a way to pass it a non-static callback function?

Thank you

Answer 1

The prototype for IOServiceMatchingCallback is not compatible with a non-static class method (and technically is not compatible with a static class method either), so you are not going to be able to use that.

But luckily IOServiceAddMatchingNotification supports a context pointer (or as they call it, a refCon) which will allow you to create a thunk that does not rely on global data.

You need to define a callback with compatible linkage (i.e. extern "C"). This function will cast your refCon to your object pointer and then forward the call to your instance method:

extern "C"
void io_callback(void *refcon, io_iterator_t iterator)
{
    myclass *c = static_cast<myclass *>(refcon);
    c->real_callback(iterator);
}

Then, when you call IOServiceAddMatchingNotification, make sure to pass a pointer to your object for refCon (here I'm assuming you call IOServiceAddMatchingNotification from a member function and you have a this pointer):

result = IOServiceAddMatchingNotification(
             mNotifyPort,
             kIOMatchedNotification,
             IOServiceMatching( "IOFireWireLocalNode" ),
             serviceMatchingCallback, 
             this,
             &enumerator );