Native Streams

A special class of native objects are native streams. These are subclasses of class NativeStream, declared in NativeStream.h. Once created, instances of native streams are accessed by module io.

When subclassing NativeStream, you must implement the following abstract virtual functions:

virtual TBool ReadL(TDes8 &buf, TRequestStatus &status);
The raw read method. If the read occurs at EOF, buf.Length() must be set to zero. Returns ETrue if the call was asynchronous, EFalse if the data was already available.
virtual TBool WriteL(const TDesC8 &buf, TRequestStatus &status);
The raw write method. All buf.Length() bytes must be written (not necessarily in a single call). Returns ETrue if the call was asynchronous, EFalse if the data was already written.

If the above methods ever return ETrue, the following method must also be overridden:

virtual void Cancel();
Cancel an asynchronous I/O operation.

In addition, the class can override the virtual functions SeekL(), Close(), SizeL(), AvailL(), HandleError().

Here is a sample implementation of a native stream subclass reading from and writing to a socket:

class MyStream : public NativeStream { RSocket *socket; // owned by this class TSockXfrLength xfrLength; ~MyStream() { // garbage collecting the stream should also delete the socket delete socket; }

Next: Native Icons