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	for guix-patches@gnu.org; Mon, 27 May 2019 06:02:03 -0400
Subject: [bug#35880] [PATCH 7/7] lzlib: 'lzread!' never returns more than it
	was asked for.
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From: Ludovic =?UTF-8?Q?Court=C3=A8s?= <ludo@gnu.org>
References: <20190524134238.22802-1-ludo@gnu.org>
	<20190524134238.22802-7-ludo@gnu.org> <877eaeo2zr.fsf@ambrevar.xyz>
	<87zhn9kn3p.fsf@gnu.org> <87r28llyr4.fsf@ambrevar.xyz>
	<87a7f8kird.fsf@gnu.org> <87a7f8mlfw.fsf@ambrevar.xyz>
Date: Mon, 27 May 2019 12:00:54 +0200
In-Reply-To: <87a7f8mlfw.fsf@ambrevar.xyz> (Pierre Neidhardt's message of
	"Mon, 27 May 2019 09:00:03 +0200")
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To: Pierre Neidhardt <mail@ambrevar.xyz>
Cc: 35880@debbugs.gnu.org

Hi Pierre,

Pierre Neidhardt <mail@ambrevar.xyz> skribis:

> It does make sense, but then don't we have the same issue with zlib.scm:

Which issue?

> (define gzread!
>   (let ((proc (zlib-procedure int "gzread" (list '* '* unsigned-int))))
>     (lambda* (gzfile bv #:optional (start 0) (count (bytevector-length bv=
)))
>       "Read up to COUNT bytes from GZFILE into BV at offset START.  Retur=
n the
> number of uncompressed bytes actually read; it is zero if COUNT is zero o=
r if
> the end-of-stream has been reached."
>  ...
>
> I initially tried to mimic zlib.scm and this part confused me a lot back =
then.

There=E2=80=99s a key difference: the =E2=80=98gzread=E2=80=99 etc. API is =
high-level and easy
to use, but it wants a file descriptor to read from (thus a file port in
Scheme land.)

That=E2=80=99s enough for =E2=80=98guix publish=E2=80=99, which writes gzip=
ped data to files,
but that=E2=80=99s not enough for =E2=80=98guix substitute=E2=80=99, which =
can read data from
non-file ports (e.g., chunked-encoding ports or TLS ports from the HTTP
client.)

HTH,
Ludo=E2=80=99.