Re: Base64-Encoding

[Stefan Bellon <sbellon@sbellon.de>]

On Fr, 19 Okt, anon wrote:

>   function To_Base64 is new Ada.Unchecked_Conversion 
>                              ( Source => Unsigned_8, 
>                                Target => base64_descriptor ) ;
> 
>   function From_Base64 is new Ada.Unchecked_Conversion 
>                              ( Target => Unsigned_8, 
>                                Source => base64_descriptor ) ;

But this only converts one whole byte (aka Unsigned_8) into a Six_Bits
by ignoring the two top-bits. This does not help with my original idea
of overlaying a packed array of 6-bit elements over an array of 8-bit
characters and then looping over the 6-bit elements to do the
conversion in a simple loop, character by character.

> In 2001 Tom Moran created a Ada BASE64 package which is archived at 
> 
> http://www.adapower.com/index.php?Command=Class&ClassID=Algorithms&CID=257
> 
> have a look at it. I a quick look it kind of suggest that the endian
> for Six_Bits is not important.

Yes, I know this package. But it handles three bytes in the original in
one go and always encodes three bytes into four 6-bits.

As I mentioned in my first posting, I am aware of the solutions to do
the actual conversion that exist (and already have been discussed a
few times here in the group). I was just wondering whether my idea
of overlaying the two arrays could be easily "fixed" so that it works.

But thanks for your ideas!

-- 
Stefan Bellon