From: Paul Eggert <eggert@cs.ucla.edu>
To: Florian Weimer <fweimer@redhat.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH] stdio-common: Add the fgetln function
Date: Tue, 3 May 2022 17:40:04 -0700 [thread overview]
Message-ID: <577d0656-8b38-07d8-7b48-01870d3730c7@cs.ucla.edu> (raw)
In-Reply-To: <871qxbxe2i.fsf@oldenburg.str.redhat.com>
If the stream is not already oriented, FreeBSD getln sets the stream to
byte-orientation. Should glibc getln do the same?
On 5/3/22 00:36, Florian Weimer via Libc-alpha wrote:
> + /* Discard the old buffer. This optimizes for a buffered stream,
> + with multiple lines in each buffer. */
> + if (fp->_fgetln_buf != NULL)
> + {
> + free (fp->_fgetln_buf);
> + fp->_fgetln_buf = NULL;
> + }
Hope you don't mind a bit of bikeshedding here....
Why free the fgetln buffer eagerly? Instead, free it only when closing.
That would lessen pressure on the memory allocator and would save a few
insns in fgetln's usual case.
Come to think of it, how about if we restrict fgetln to streams for
which either (1) the user has not called setvbuf with a nonnull buffer,
or (2) the input line fits in the user-supplied setvbuf buffer. Then we
wouldn't need to worry about adding a _fgetln_buf slot, as fgetln could
always return a pointer into the already-existing stdio buffer, possibly
by enlarging the buffer in case (1). (In case (2) fgetln could fail with
ENOMEM if the input line is longer than the user-supplied buffer.) This
would suffice for 99.9% of applications and would be more efficient than
what FreeBSD does, and the whole point of fgetln is low-level efficiency
right?
next prev parent reply other threads:[~2022-05-04 0:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-03 7:36 Florian Weimer
2022-05-03 8:06 ` Andreas Schwab
2022-05-03 8:31 ` Florian Weimer
2022-05-03 8:46 ` Andreas Schwab
2022-05-03 9:01 ` Florian Weimer
2022-05-03 9:10 ` Andreas Schwab
2022-05-03 10:45 ` Cristian Rodríguez
2022-05-04 0:40 ` Paul Eggert [this message]
2022-06-09 7:37 ` Florian Weimer
2022-06-09 20:08 ` Paul Eggert
2022-06-24 11:01 ` Florian Weimer
2022-06-24 20:35 ` Paul Eggert
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