[NNTP] Article Numbers Becoming Invalid (RFC 3977)

[Clive D.W. Feather]

I wrote:
> The basic model here is:
> 
> * Articles are numbered from 1 to some limit X - the next arriving article
> will be given a number Y greater than X, after which the limit will become
> Y.
> * There are two other numbers called LWM and HWM. HWM can increase or
> decrease; LWM can increase but never decrease.
> * All existing article numbers lie between LWM and HWMN inclusive.
> * Articles can be removed and/or reinstated at any time, and LWM and HWM
> changed at any time, providing that the above rules are obeyed.
> * The GROUP command returns LWM and HWM, and sets the "current article
> number" ("CAN") to LWM.

This was wrong. It sets CAN to the lowest number which corresponds to an
existing article at that moment, which might be greater than LWM or equal
to LWM.

> Similarly, because article LWM might have been removed, GROUP might not
> leave CAN referring to a valid article.

That's wrong. If the group is not empty, GROUP, NEXT, and LAST must all
leave CAN referring to a valid article.

-- 
Clive D.W. Feather          | If you lie to the compiler,
Email: clive at davros.org     | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
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