Completion Function15

When client programs schedule asynchronous read or write operations (by calling your component's DataHScheduleData or DataHWrite functions), they furnish your component a data-handler completion function. Your component must call this function when it completes the read or write operation, whether the operation was a success or a failure.

Data handler Completion Function

The client program's completion function must present the following interface:



 
pascal void DHCompleteProc (Ptr request, long refcon, OSErr err);

request: Specifies a pointer to the data that was associated with the read (DataHScheduleData ) or write (DataHWrite ) request. The client program uses this pointer to determine which request has completed.
refcon: Contains a reference constant that the client program supplied to your data handler component when it made the original request.
err: Indicates the success or failure of the operation. If the operation succeeded, set this parameter to 0. Otherwise, specify an appropriate error code.