[stgt] [PATCH 1/4] struct concat_buf and concat_printf() for printing to buffers

FUJITA Tomonori fujita.tomonori at lab.ntt.co.jp
Sun Dec 4 04:20:02 CET 2011

On Sun, 27 Nov 2011 08:12:31 +0000
Alexander Nezhinsky <alexandern at mellanox.com> wrote:

> On Sat, Nov 26, 2011 at 1:43 PM, Fubo Chen <fubo.chen at gmail.com> wrote:
> > On Sat, Nov 26, 2011 at 12:21 PM, Alexander Nezhinsky
> > <alexandern at mellanox.com> wrote:
> > > Text queries issued through tgtadm use a fixed-size buffer that is filled,
> > > step by step, typically by a few calls to snprintf() or an equivalent.
> > > This requires tracking the current position within the buffer and guarding
> > > against overflows.
> >
> > Looks like a duplicate of asprintf() ? See also
> > http://www.gnu.org/s/libc/manual/html_node/Dynamic-Output.html.
> As far as i understand asprintf() always allocates a new buffer to accommodate the
> printed string. This would have been an ideal solution if we had called snprintf
> always only once not knowing the output length in advance. But we regularly
> call it few times and concatenate the output strings.
> If anything, we could use another mechanism appearing on the same manual page
> that you sent: obstack. 
> But i guess that even a better option would be a string stream opened by 
> open_memstream():
> http://www.gnu.org/s/hello/manual/libc/String-Streams.html#String-Streams
> I thought to defer this for a later stage, as concat_buf can encapsulate whatever
> mechanism we choose, probably with some changes to its init function (no buffer
> and size supplied by user in case we use a stream stream or a like and do not
> realloc by ourselves). 
> Tomo, what do you think? I can rewrite the patches to use a stream - or we can
> decide later and do it in two leaps. 

I'll review and comment on this series next week. Sorry for the delay.
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