typedef struct { ... } SilcStreamOps;

    SILC Stream operations structure.  This structure includes callback
    functions to the actual stream implementation.  Any stream that
    use SILC Stream abstraction must fill this structure with the actual
    stream implementation.

    Each stream implementation MUST set this structure as the first field
    in their stream structure.  As it is that structure that is passed
    to the silc_stream_* routines, the SILC Stream API expects that the
    SilcStream context starts with this structure.

    typedef struct {
      const SilcStreamOps *ops;
      ... other stuff ...
    } *SilcFooStream;

    SilcFooStream foo;
    silc_stream_write(foo, data, data_len);

    typedef struct {
      /* This is called to read data from the stream.  This is called when
         silc_stream_read function was called. */
      int (*read)(SilcStream stream, unsigned char *buf, SilcUInt32 buf_len);
    
      /* This is called when writing data to the stream.  This is called when
         silc_stream_write function was called. */
      int (*write)(SilcStream stream, const unsigned char *data,
                   SilcUInt32 data_len);
    
      /* This is called to close the stream.  This is called when the
         silc_stream_close function was called. */
      SilcBool (*close)(SilcStream stream);
    
      /* This is called to destroy the stream.  This is called when the
         silc_stream_destroy function was called. */
      void (*destroy)(SilcStream stream);
    
      /* This is called to set a notifier callback to the stream and schedule
         the stream.  Stream should not be scheduled before calling this
         function.  If stream does not need scheduler then the scheduler can
         be ignored.  This is called when silc_stream_set_notifier was called.
         Returns FALSE if the stream could not be scheduled. */
      SilcBool (*notifier)(SilcStream stream, SilcSchedule schedule,
                           SilcStreamNotifier callback, void *context);
    
      /* This is called to return the associated scheduler, if set.  This is
         called when silc_stream_get_schedule was called. */
      SilcSchedule (*get_schedule)(SilcStream stream);
    } SilcStreamOps;