Re: [ietf-smtp] quoted-unprintable ?

[Tony Finch <[e-mail]>]

Ned Freed <[e-mail]> wrote:
>
> > The advantage of BINARYMIME over base64 is that base64 is 33% bigger
> > since it encodes six bits per octet rather than 8.  It occurs to me
> > that since everone these days supports 8BITMIME, one could invent a
> > quoted-unprintable encoding that encodes only the characters that are
> > special, CR LF NUL.  (To play it safe I'd also encode 0xff). This gets
> > you about a 2% size increase and stays compatible with 8BITMIME.
>
> It's actually kind of tricky if you want to avoid pathological cases.
> Combining the encoding with compression is the simplest way to avoid
> that, since it's unlikely in the extreme that the compression scheme
> will spit out a high percentage of any specific character.

Stuart Cheshire and Mary Baker have a super elegant binary escaping scheme
called "consistent overhead byte stuffing" (COBS) that has a guaranteed
overhead of less than 1%.

http://www.stuartcheshire.org/papers/COBSforToN.pdf

Tony.
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