typedef
  struct GB_STREAM {
    GB_STREAM_DESC *desc;
    long _reserved;
    long _free[6];
    }
  GB_STREAM;

If you create a class that inherits the Stream class, then you must declare your class structure this way:

typedef
  struct {
    GB_BASE object;
    GB_STREAM stream;
    }
  MyClass;

The _free array is a space where you can store data associated with the stream, like the opened file descriptor for example.

Do not use this structure directly, but declares a specific stream structure having the same size and beginning with the GB_STREAM_DESC field and the _reserved field.

The desc field must points at a structure that points at the implementation functions of your stream.

Streams of the same type should share the same description structure. See GB_STREAM_DESC for more details.