Size of full userdata

["Dan East" <dan@...>]

  I cannot find a formal method to determine the size of a full userdata
memory block.  I have found by looking at the lua source that I can cast the
value returned by lua_touserdata to an int pointer, subtract one from it,
and dereference it to get the size.  Is there a better way?

void *pData=lua_touserdata(L);
int nSize=*(((int *)pData)-1);

  Dan East