This section contains an example of how to create and install a set of user-streams.
The hook is set by calling SP_set_user_stream_hook() in the
main program like this:
     SP_set_user_stream_hook(user_strhook);
     
   Remember: SP_set_user_stream_hook() and
SP_set_user_stream_post_hook() must be called before
SP_initialize().
   
The hook user_strhook() is defined like this:
     SP_stream *user_strhook(int which)
     {
       SP_stream *s;
     
       SP_make_stream(NULL, my_getc, my_putc, my_flush, my_eof, my_clrerr,
                      NULL, &s);
     
       return s;
     }
     
   See Installing a New Stream for a description on the parameters to
SP_make_stream().