07-Nov-2001

yEncode - additional specs (after discussions) 
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The maximum line length for a yEncoded file should be: 254 bytes.
This permits Pascal implementations to handle one line in one string.
(The line size will then be 254 or 255 - which is the maximum length for Pascal).

However a yEnc decoder should be able to deal with smaller numbers
until we are sure that such long lines do not cause trouble.

Another proposal was to use only 63/64 bytes per line to stay within the 
'usual' line size for Usenet messages.


Some yEncoders might encode additional characters. So the decoders should be
prepared to decode ALL escaped combinations with the 'default method':
(subtract 64) from the character follwing the '=' (and then 42).


It is _highly_ recommended to start the subject line with a dash followed
by the filename (and the size + yEnc keyword). Comments should be
added only _behind_ this block - and again seperated by a dash.


It might be possible to avoid encoding of the TAB (dec. 9) character.
However it is still included into the source code example.

It might be possible to encode the DOT '.' character only in the first
column. Another method would be to duplicate the DOT when the article
is transmitted by NNTP. The dot is still encoded in the source code
example. I love the straight forward conception. No dot can occur
in the first column.





Additional ideas of the author (some implemented into MyNews)
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It might be a nice idea to add the CRC of posted files to the Subject-Line.
This permits advanced news-readers to find out that a specific file
is already locally available (and just a repost).


It might be a nice idea to add additional database info about posted binaries.
This would allow to store binaries as streams - together with additonal
info - and not in the original format which never contains related context data.

=ydata <database keyword> ': ' <description>
=ydata title: "The stonehenge miracle"
=ydata artist: "John Carpenter"
=ydata creation: 20 Jun 1983
=ydata newsgroup=alt.binaries.artpics
=ydata url: http://www.carpenter.pers.uk
=ybegin ...
<data>
=yend


The "Lines:" header for yEncoded messages is still calculated as if
UUencode would be used - and does NOT represent the real number of lines.
It is difficlut to calculate the number of lines for a message in ahead.
And it might be confusing for newsgroup-users if they see very small messages
which are then very huge for download.
So the number of lines is still calculated as:  "binary size / 45".
(Plus a few preface text lines and management lines)


to be continued...