Need help with pointers to class methods being used as callbacks...

[SpreadTooThin]

I have a C routine that wants to call a method of its user.
In this case the method is a method inside a class.
The C routine is passed a void * which can be used by the user any way
they like.
I use that parameter and pass the actual instance of the C++ class
that performed the call.
The C callback handler then uses the instance of the class and calls
the appropriate method.

Here is the code but it doesn't work. What am I doing wrong?

void DeviceFoundCallBack(void * userRefCon,
IOBluetoothDeviceInquiryRef inquiryRef, IOBluetoothDeviceRef
deviceRef)
{
userRefCon->DeviceFoundCallBack(inquiryRef, deviceRef);
}
 
void CompleteCallback(void * userRefCon, IOBluetoothDeviceInquiryRef
inquiryRef, IOBluetoothDeviceRef deviceRef)
{
userRefCon->CompleteCallBack(inquiryRef, deviceRef);
}
 
void BlueTooth::startSearch(void)
{
_inquiry =
IOBluetoothDeviceInquiryCreateWithCallbackRefCon(this);  // This will
be passed back to us to let us know the instance.
IOBluetoothDeviceInquirySetDeviceFoundCallback(_inquiry,
&DeviceFoundCallBack);
}
 

[Victor Bazarov]

SpreadTooThin wrote:

I have a C routine that wants to call a method of its user.
In this case the method is a method inside a class.
The C routine is passed a void * which can be used by the user any way
they like.
I use that parameter and pass the actual instance of the C++ class
that performed the call.
The C callback handler then uses the instance of the class and calls
the appropriate method.

Here is the code but it doesn't work. What am I doing wrong?

void DeviceFoundCallBack(void * userRefCon,
IOBluetoothDeviceInquiryRef inquiryRef, IOBluetoothDeviceRef
deviceRef)
{
userRefCon->DeviceFoundCallBack(inquiryRef, deviceRef);

 
'userRefCon' has to be of a class type or pointer to a class to use
the -syntax.  You have a void*, which is not a class.  You need to
convert your 'void*' into a pointer to the class:
 
someclasstype* pObj = static_cast<someclasstype*>(userRefCon);
 
only then you will be alble to call your member function.
 
        
                }

void CompleteCallback(void * userRefCon, IOBluetoothDeviceInquiryRef
inquiryRef, IOBluetoothDeviceRef deviceRef)
{
userRefCon->CompleteCallBack(inquiryRef, deviceRef);
}

void BlueTooth::startSearch(void)
{
_inquiry =
IOBluetoothDeviceInquiryCreateWithCallbackRefCon(this);  // This will
be passed back to us to let us know the instance.
IOBluetoothDeviceInquirySetDeviceFoundCallback(_inquiry,
&DeviceFoundCallBack);
 
 
You may have problems with the second argument here.  See the FAQ about
the callbacks and member functions.
 
        
                }
 
 
 

V
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[Andre Kostur]

SpreadTooThin <bj********@gmail.comwrote in
news:11*********************@x40g2000prg.googlegro ups.com:

I have a C routine that wants to call a method of its user.

Uh.. then it's not really a C routine is it? C routines would have no
concept of "method"s. (It may be a C++ routine with C linkage....)

In this case the method is a method inside a class.
The C routine is passed a void * which can be used by the user any way
they like.
I use that parameter and pass the actual instance of the C++ class
that performed the call.
The C callback handler then uses the instance of the class and calls
the appropriate method.

Here is the code but it doesn't work. What am I doing wrong?

void DeviceFoundCallBack(void * userRefCon,
IOBluetoothDeviceInquiryRef inquiryRef, IOBluetoothDeviceRef
deviceRef)
{
     userRefCon->DeviceFoundCallBack(inquiryRef, deviceRef);
}

 
userRefCon is a void*.  voids don't have methods.  You need to cast that
pointer back to the appropriate type first.
 
        
                >
void CompleteCallback(void * userRefCon, IOBluetoothDeviceInquiryRef
inquiryRef, IOBluetoothDeviceRef deviceRef)
{
     userRefCon->CompleteCallBack(inquiryRef, deviceRef);
}
 
 
Same as above.
 
        
                void BlueTooth::startSearch(void)
{
     _inquiry =
IOBluetoothDeviceInquiryCreateWithCallbackRefCon(this);  // This will
be passed back to us to let us know the instance.
     IOBluetoothDeviceInquirySetDeviceFoundCallback(_inquiry,
&DeviceFoundCallBack);
}
 
 
 

[Bart van Ingen Schenau]

SpreadTooThin wrote:

I have a C routine that wants to call a method of its user.
In this case the method is a method inside a class.
The C routine is passed a void * which can be used by the user any way
they like.
I use that parameter and pass the actual instance of the C++ class
that performed the call.
The C callback handler then uses the instance of the class and calls
the appropriate method.

Here is the code but it doesn't work. What am I doing wrong?

void DeviceFoundCallBack(void * userRefCon,
IOBluetoothDeviceInquiryRef inquiryRef, IOBluetoothDeviceRef
deviceRef)
{
userRefCon->DeviceFoundCallBack(inquiryRef, deviceRef);

 
userRefCon is a void* and does not have a member called
DeviceFoundCallBack.
You must use a cast in this situation to tell the compiler what type of
object userRefCon actually points to.
 
static_cast<BlueTotth>(userRefCon)->DeviceFoundCallBack(inquiryRef,
deviceRef);
 
        
                }

void CompleteCallback(void * userRefCon, IOBluetoothDeviceInquiryRef
inquiryRef, IOBluetoothDeviceRef deviceRef)
{
userRefCon->CompleteCallBack(inquiryRef, deviceRef);
 
 
Same problem here.
 
        
                }

void BlueTooth::startSearch(void)
{
_inquiry =
IOBluetoothDeviceInquiryCreateWithCallbackRefCon(this);  // This will
be passed back to us to let us know the instance.
IOBluetoothDeviceInquirySetDeviceFoundCallback(_inquiry,
&DeviceFoundCallBack);
}
 
 
 

Bart v Ingen Schenau
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