int silc_stream_read(SilcStream stream, unsigned char *buf,
                         SilcUInt32 buf_len);

    Reads data from the stream indicated by `stream' into the data buffer
    indicated by `buf' which is size of `buf_len'.  This returns the amount
    of data read, zero (0) if end of stream occurred, -1 if data could
    not be read at this moment, or -2 if error occurred.  If -1 is returned
    the notifier callback will later be called with SILC_STREAM_CAN_READ
    status when stream is again ready for reading.