From: "Ludovic Courtès" <ludo@gnu.org>
To: Pierre Neidhardt <mail@ambrevar.xyz>
Cc: 35880@debbugs.gnu.org
Subject: [bug#35880] [PATCH 1/7] lzlib: Add 'make-lzip-input-port/compressed'.
Date: Sun, 26 May 2019 21:51:41 +0200 [thread overview]
Message-ID: <87ftp1m1te.fsf@gnu.org> (raw)
In-Reply-To: <87d0k6o3am.fsf@ambrevar.xyz> (Pierre Neidhardt's message of "Sat, 25 May 2019 19:24:33 +0200")
Hi!
Pierre Neidhardt <mail@ambrevar.xyz> skribis:
> As an Lzip enthusiast, I have some questions ;)
>
> I see you are using make-lzip-input-port/compressed in a subsequent
> patch, but this does not map how it's done for gzip et al., the latter
> being invoked via it's system command "gzip -c ...". Why did you decide
> to do it differently for lzip?
>
> Much of the code induced by make-lzip-input-port/compressed seems to
> repeat the lzread! / lzwrite business, maybe there is a way to factor
> some of it?
Actually, ‘make-lzip-input-port/compressed’ exists solely so we can have
‘compressed-port’ for lzip, which in turn allows us to write tests.
It uses (guix lzlib) instead of invoking the ‘lzip’ command because we
can. :-) Invoking commands is not as nice, because it’s more
expensive, requires us to spawn an additional process when the input is
not a file port (e.g., it’s a string port), and it’s forking is not
possible in multi-threaded programs like ‘guix publish’.
>> +(define (lzwrite! encoder source source-offset source-count
>> + target target-offset target-count)
>> + "Write up to SOURCE-COUNT bytes from SOURCE to ENCODER, and read up to
>> +TARGET-COUNT bytes into TARGET at TARGET-OFFSET. Return two values: the
>> +number of bytes read from SOURCE, and the number of bytes written to TARGET."
>> + (define read
>> + (if (< 0 (lz-compress-write-size encoder))
>> + (match (lz-compress-write encoder source source-offset source-count)
>> + (0 (lz-compress-finish encoder) 0)
>> + (n n))
>> + 0))
>> +
>> + (let loop ()
>> + (match (lz-compress-read encoder target target-offset target-count)
>> + (0 (loop))
>> + (written (values read written)))))
>
> Why looping on 0? If there is no byte to read, wouldn't this loop indefinitely?
Hmm, good point. The idea is that ‘lzwrite!’ should return 0 only on
end-of-file, but then the loop should include reading more from SOURCE.
I’ll follow up on this one.
Thanks!
Ludo’.
next prev parent reply other threads:[~2019-05-26 19:52 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-24 13:31 [bug#35880] [PATCH 0/7] Lzip support for 'guix publish' and 'guix substitute' Ludovic Courtès
2019-05-24 13:42 ` [bug#35880] [PATCH 1/7] lzlib: Add 'make-lzip-input-port/compressed' Ludovic Courtès
2019-05-24 13:42 ` [bug#35880] [PATCH 2/7] utils: Test 'compressed-port' and 'decompressed-port' for both gzip and xz Ludovic Courtès
2019-05-24 13:42 ` [bug#35880] [PATCH 3/7] utils: Support compression and decompression with lzip Ludovic Courtès
2019-05-25 17:27 ` Pierre Neidhardt
2019-05-26 19:52 ` Ludovic Courtès
2019-05-24 13:42 ` [bug#35880] [PATCH 4/7] publish: Add support for lzip Ludovic Courtès
2019-05-24 13:42 ` [bug#35880] [PATCH 5/7] self: Add dependency on lzlib Ludovic Courtès
2019-05-24 13:42 ` [bug#35880] [PATCH 6/7] gnu: guix: " Ludovic Courtès
2019-05-24 13:42 ` [bug#35880] [PATCH 7/7] lzlib: 'lzread!' never returns more than it was asked for Ludovic Courtès
2019-05-25 17:31 ` Pierre Neidhardt
2019-05-26 19:54 ` Ludovic Courtès
2019-05-26 20:57 ` Pierre Neidhardt
2019-05-26 21:28 ` Ludovic Courtès
2019-05-27 7:00 ` Pierre Neidhardt
2019-05-27 10:00 ` Ludovic Courtès
2019-05-25 17:24 ` [bug#35880] [PATCH 1/7] lzlib: Add 'make-lzip-input-port/compressed' Pierre Neidhardt
2019-05-26 19:51 ` Ludovic Courtès [this message]
2019-05-27 15:45 ` Ludovic Courtès
2019-05-27 16:24 ` Pierre Neidhardt
2019-05-27 20:53 ` bug#35880: " Ludovic Courtès
2019-05-27 21:12 ` [bug#35880] " Pierre Neidhardt
2019-05-28 7:52 ` Ludovic Courtès
2019-05-28 8:46 ` Pierre Neidhardt
2019-05-28 13:47 ` Ludovic Courtès
2019-05-29 14:57 ` Pierre Neidhardt
2019-05-31 20:54 ` Ludovic Courtès
2019-06-01 6:02 ` Pierre Neidhardt
2019-06-01 9:41 ` Ludovic Courtès
2019-06-01 9:58 ` Pierre Neidhardt
2019-06-01 12:21 ` Ludovic Courtès
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