On 08/21/13 at 06:58pm, Kay Sievers wrote: > On Wed, Aug 21, 2013 at 6:53 PM, WANG Chao <chaow...@redhat.com> wrote: > > On 08/21/13 at 12:05pm, Kay Sievers wrote: > >> On Wed, Aug 21, 2013 at 8:36 AM, WANG Chao <chaow...@redhat.com> wrote: > >> > >> > --- a/TODO > >> > +++ b/TODO > >> > @@ -96,8 +96,6 @@ Features: > >> > > >> > -* do we really need both hasprefix() and startswith()? > >> > >> It needs a little bit more: > >> - the open-coded startswith seems really slow, it should not get more > >> users > >> - hasprefix can no longer be compile-time optimized, which is not good > > > > Apart from the overflow issue hasprefix has, may I ask why hasprefix > > can't be complile-time optimized now? What changed? > > Your patch replaced hasprefix with startswith. hasprefix was just a > define, it operated on static strings with static length, which the > compiler can optimize away. startswith is an open-coded function with > a counter, which has to be called and cannot really be optimized-away > by the compiler.
Thanks for clarify, I'll send two patches, one for macro startswith, another for the replacement. Thanks > > >> We might want something like this: > >> http://lists.freedesktop.org/archives/systemd-devel/2013-July/011860.html > > > > It looks like Lennart has already figured out an optimized startswith: > > > > #define startswith(s, prefix) ({ \ > > size_t _l; \ > > _l = strlen(prefix); \ > > strncmp(s, prefix, _l) == 0 ? s + _l : NULL; \ > > }) > > > > IMHO, using strncmp() is fast enough. What do you think? > > strncmp sounds fine instead of the open-coded loop in hasprefix, yes. > > Kay _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/systemd-devel
