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From: Pierre Habouzit <madcoder@debian•org>
To: "René Scharfe" <rene.scharfe@lsrfire•ath.cx>,
	"Junio C Hamano" <gitster@pobox•com>,
	"Johannes Schindelin" <Johannes.Schindelin@gmx•de>,
	git@vger•kernel.org
Subject: Re: [PATCH 3/3] pretty=format: Avoid some expensive calculations  when not needed
Date: Wed, 07 Nov 2007 01:14:58 +0100	[thread overview]
Message-ID: <20071107001458.GE4382@artemis.corp> (raw)
In-Reply-To: <20071107001112.GD4382@artemis.corp>

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On Wed, Nov 07, 2007 at 12:11:12AM +0000, Pierre Habouzit wrote:
> On Tue, Nov 06, 2007 at 11:17:14PM +0000, René Scharfe wrote:
> > I haven't seen any comments on strbuf_expand.  Is it too far out?
> > Here it is again, adjusted for current master and with the changes
> > to strbuf.[ch] coming first:
> 
>   I have one.
> 
> >  strbuf.c |   22 +++++
> >  strbuf.h |    3 
> >  pretty.c |  276 ++++++++++++++++++++++++++++++++++-----------------------------
> >  3 files changed, 178 insertions(+), 123 deletions(-)
> > 
> > diff --git a/strbuf.c b/strbuf.c
> > index f4201e1..b71da99 100644
> > --- a/strbuf.c
> > +++ b/strbuf.c
> > @@ -129,6 +129,28 @@ void strbuf_addf(struct strbuf *sb, const char *fmt, ...)
> >  	strbuf_setlen(sb, sb->len + len);
> >  }
> >  
> > +void strbuf_expand(struct strbuf *sb, const char *fmt,
> > +                   const char **placeholders, expand_fn_t fn, void *context)
> > +{
> > +	char c;
> > +	const char **p;
> > +
> > +	while ((c = *fmt++)) {
> > +		if (c != '%') {
> > +			strbuf_addch(sb, c);
> > +			continue;
> > +		}
> 
> strbuf_addch is pretty inneficient as it puts NULs each time. rather
> do that (sketchy) :
> 
> {
>     for (;;) {
>         const char *percent = strchr(fmt, '%');
>         if (!percent)
>             break;
>         strbuf_add(sb, fmt, percent - fmt);
>         fmt = percent + 1;
> 
>         /* do your stuff */
>     }
>     strbuf_addstr(sb, fmt);
> }


Or if we are at this level of micro-optimization:

{
    const char *percent = strchrnul(fmt, '%');
    while (*percent) {
        strbuf_add(sb, fmt, percent - fmt);
        fmt = percent + 1;

        /* do your stuff */

        percent = strchrnul(fmt, '%');
    }
    strbuf_add(sb, fmt, percent - fmt);
}


Which would require strchrnul, but it's trivial compat/ material for sure.


-- 
·O·  Pierre Habouzit
··O                                                madcoder@debian•org
OOO                                                http://www.madism.org

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  reply	other threads:[~2007-11-07  0:15 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-11-04 19:14 [PATCH 0/3] Make user formatted commit listing less expensive Johannes Schindelin
2007-11-04 19:15 ` [PATCH 1/3] Split off the pretty print stuff into its own file Johannes Schindelin
2007-11-05 21:16   ` Junio C Hamano
2007-11-04 19:15 ` [PATCH 2/3] interpolate.[ch]: Add a function to find which interpolations are active Johannes Schindelin
2007-11-04 19:15 ` [PATCH 3/3] pretty=format: Avoid some expensive calculations when not needed Johannes Schindelin
2007-11-05 19:51   ` Junio C Hamano
2007-11-05 20:21     ` René Scharfe
2007-11-05 20:25       ` Jon Loeliger
2007-11-05 23:53       ` Johannes Schindelin
2007-11-06  1:06       ` Junio C Hamano
2007-11-06 22:31         ` René Scharfe
2007-11-06 23:17           ` René Scharfe
2007-11-06 23:45             ` Johannes Schindelin
2007-11-07 23:19               ` René Scharfe
2007-11-08  0:14                 ` Johannes Schindelin
2007-11-07  0:11             ` Pierre Habouzit
2007-11-07  0:14               ` Pierre Habouzit [this message]
2007-11-07 23:21                 ` René Scharfe
2007-11-07 23:31                   ` Pierre Habouzit
2007-11-07 20:43             ` Junio C Hamano
2007-11-09  0:49               ` René Scharfe
2007-11-06 23:36           ` Johannes Schindelin
2007-11-06 23:38             ` [PATCH 1/2] interpolate.[ch]: Add a function to find which interpolations are active Johannes Schindelin
2007-11-06 23:38             ` [PATCH 2/2] pretty=format: Avoid some expensive calculations when not needed Johannes Schindelin

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