stream_element array contiguity

[ian_leroux@fastmail.fm (Ian Leroux)]

From reading previous posts, I gather that a common approach to
dealing with bitwise input is to use Unchecked_Conversion to transform
to packed arrays of Boolean from arrays of Stream_Element, obtained
from an appropriate Stream package. Given that Stream_Element'Size is
not guaranteed to be a multiple or factor of Storage_Element'Size, is
there any way of being sure that the elements of a Stream_Element
array will be contiguous? If not, is there any standard way of
avoiding the problem whereby padding bits in the Stream_Element array
corrupt the resulting boolean array?

I realize that on most compilers and platforms this is unlikely to be
a real issue, but I'm wondering if there is any way to be sure (since
being sure about this sort of thing is one of the features I find
appealing about Ada).

I am a newcomer to the language, and would be glad to be called on any
factual errors in this post.

Ian Leroux