slen = strlen (uris) + 1;
  idlen = strlen (identifier);
  if (NULL != update)
    nidlen = strlen (update) + 1;
  else
    nidlen = 1;
  mdsize = GNUNET_CONTAINER_meta_data_get_serialized_size (mmeta);
  size = sizeof (struct SBlock) + slen + nidlen + mdsize;
  if (size > MAX_SBLOCK_SIZE)
  {
    size = MAX_SBLOCK_SIZE;
    mdsize = size - (sizeof (struct SBlock) + slen + nidlen);
  }
  sb = GNUNET_malloc (sizeof (struct SBlock) + size);
  dest = (char *) &sb[1];
  if (update != NULL)
    memcpy (dest, update, nidlen);
  else
    memset (dest, 0, 1);