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From: Ted Dennison <dennison@telepath.com>
Subject: Re: Decoding an octet stream
Date: 1999/12/02
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In article <87bt8a2uvr.fsf@deneb.cygnus.argh.org>,
  " "@deneb.cygnus.argh.org (Florian Weimer) wrote:
> swhalen@netcom.com writes:

> Perhaps I may ask again: Is it reasonable to assume that
> Storage_Element'Size equals 8 (although the standard doesn't
> require this, of course)?  And, looking at David's code, does

I don't. My code figures it out by doing the following:
   Bytes_Per_Element : constant := (Ada.Streams.Stream_Element'Size + 7)
/ 8;


It only really comes up when you need to convert between stream elements
and bytes for some reason though. I suppose if you are writing your own
'Write routine using Unchecked_Conversion instead of other 'Write's it
also would be an issue. Then you would need to do something
like this ("Instance" is the type you are converting):

   Bytes_Per_Element  : constant := (Ada.Streams.Stream_Element'Size +
7) / 8;
   Bytes_Per_Instance : constant Natural := (Instance'Size + 7) / 8;
   Elements_Per_Instance : constant Ada.Streams.Stream_Element_Offset :=
     Ada.Streams.Stream_Element_Offset(
       (Bytes_Per_Instance + (Bytes_Per_Element - 1)) /
Bytes_Per_Element);
   subtype Instance_Array is Ada.Streams.Stream_Element_Array (1 ..
Elements_Per_Instance);

   function From_Instance is new Unchecked_Conversion
     (Source => Instance,
      Target => Instance_Array);

   function To_Instance is new Unchecked_Conversion
     (Source => Instance_Array,
      Target => Instance);


Otherwise you will be working entirely in stream_element_array's anyway.

--
T.E.D.


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