SilcBuffer silc_attribute_payload_encode(SilcBuffer attrs,
                                             SilcAttribute attribute,
                                             SilcAttributeFlags flags,
                                             void *object,
                                             SilcUInt32 object_size);

    Encodes one attribute payload into the `attrs' buffer and returns
    pointer to the buffer, which may be different in case the buffer
    was reallocated.  If `attrs' is NULL for first attribute this
    allocates the buffer and returns it.  This can be called multiple
    times to add multiple attributes to the `attrs' buffer.  The `flags'
    indicates the validity of the added attribute.  Returns NULL on
    error.

    The `object' must always be the same data type as defined with
    SilcAttribute (see the comments) for all attributes.