Each instance of a stream has an abstract data pointer that can hold
underlying resource handle(s) and other stateful data required by your
stream.
Lets see how to write a very simple file based stream, using
POSIX IO.
1: struct my_stream_data {
2: int filedes;
3: }
When we create our stream, we will store a pointer to the above structure
in the abstract field of the stream structure.
We can now move on and write the core operations for our stream...
