Re: Switch buffile.c/h to use pgoff_t

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com>
Cc: Postgres hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Bryan Green <dbryan(dot)green(at)gmail(dot)com>
Subject: Re: Switch buffile.c/h to use pgoff_t
Date: 2025-12-24 23:42:04
Message-ID: aUx6TMczfmwyv_h3@paquier.xyz
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On Wed, Dec 24, 2025 at 05:01:57PM +0800, Chao Li wrote:
> Make sense, bytestowrite is not a file offset. So, in the current code,
> availbytes is not a file offset either, but it is defined as pgoff_t, which
> has the same confusion, right? Also bytestowrite is casted to pgoff_t, it's
> the same confusion again.

Yeah, actually this suggestion makes more sense. availbytes is a
computation made of a maximal size and an offset, so defining it as an
offset from the start is kind of weird.

Now I don't think that your suggested set of changes could become more
consistent with a few more changes. For example, what about pos and
nbytes in BufFile? While ssize_t is more consistent with FileRead()
and FileWrite(), this code is written to care about signedness while
ssize_t has a stricter range per posix, hence could int64 be a better
choice for the whole interface? int64 is already what we use for
BufFileSize(), which is due to the limit of MAX_PHYSICAL_FILESIZE of
course.
--
Michael

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