Accessing a stream in your UDR

To access a stream in your UDR:

Open the stream with the appropriate type-specific stream-open function.
The stream-open function is the stream I/O function that opens the stream, making the data available for a read or write operation. It returns a pointer to a stream descriptor, which the C UDR uses to access the stream. For more information, see The stream-open function.
Access the opened stream with the appropriate generic stream I/O function.
After a particular stream is open, a UDR can use the generic functions of the stream I/O interface to access the associated I/O object. Each of the generic stream I/O functions requires a stream descriptor for the stream on which the function is to operate. The usual sequence of access is to seek to the desired location in the stream, read or write the desired number of bytes, and close the stream.