GNU bug report logs - #35880
[PATCH 0/7] Lzip support for 'guix publish' and 'guix substitute'

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From: Ludovic Courtès <ludo <at> gnu.org>
To: Pierre Neidhardt <mail <at> ambrevar.xyz>
Cc: 35880-done <at> debbugs.gnu.org
Subject: [bug#35880] [PATCH 1/7] lzlib: Add 'make-lzip-input-port/compressed'.
Date: Sat, 01 Jun 2019 11:41:59 +0200

Hi!

Pierre Neidhardt <mail <at> ambrevar.xyz> skribis:

> Ludovic Courtès <ludo <at> gnu.org> writes:
>
>> I think the ‘lzread!’ loop should look like this (the tests still pass
>> with this):
>>
>> --8<---------------cut here---------------start------------->8---
>>   (let loop ((read 0)
>>              (start start))
>>     (cond ((< read count)
>>            (match (lz-decompress-read decoder bv start (- count read))
>>              (0 (cond ((lz-decompress-finished? decoder)
>>                        read)
>>                       ((eof-object? (feed-decoder! decoder))
>>                        (lz-decompress-finish decoder)
>>                        (loop read start))
>>                       (else                       ;read again
>>                        (loop read start))))
>>              (n (loop (+ read n) (+ start n)))))
>>           (else
>>            read)))
>> --8<---------------cut here---------------end--------------->8---
>
> Looks good to me!

OK, committed!

>>>            (match (lz-decompress-read decoder bv start (- count read))
>>>              (0 (if (eof-object? (feed-decoder! decoder))
>>>                     read
>>>                     (loop read start)))
>>>
>>> I'm not sure I understand the above: if we read nothing, then we try
>>> again?
>>
>> No: if we read *something*, we try again; if we read nothing, we return.
>
> If we read nothing _and_ it is not an EOF (it can be an empty vector),
> then we loop indefinitely, no?

‘feed-decoder!’ cannot return an empty bytevector because
‘lz-decompress-write-size’ necessarily returns a strictly positive
integer at this point.

(Imperative programming is hard! :-))

Thanks,
Ludo’.

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