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Re: how to reading 0 byte files properly
From: |
Andreas Schwab |
Subject: |
Re: how to reading 0 byte files properly |
Date: |
Thu, 17 Nov 2022 11:15:50 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) |
On Nov 17 2022, Binbin YE wrote:
> /* emacs/src/fileio.c:4587 */
>
> if (seekable || !NILP (end))
> total = end_offset - beg_offset;
> else
> /* For a special file, all we can do is guess. */
> total = READ_BUF_SIZE;
> ```
> Judging from the code, it assume the total size would be READ_BUF_SIZE
For a non-seekable file this is just a buffer size, see the read loop
later in the function (how_much stays zero then).
If the file is seekable, the important part is this:
/* The file size returned from fstat may be zero, but data
may be readable nonetheless, for example when this is a
file in the /proc filesystem. */
if (end_offset == 0)
end_offset = READ_BUF_SIZE;
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."