Messages in this thread | | | Date | Tue, 17 Nov 2020 20:33:13 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 06/24] perf tools: Add build_id__is_defined function |
| |
Em Tue, Nov 17, 2020 at 09:53:59PM +0100, Jiri Olsa escreveu: > On Tue, Nov 17, 2020 at 11:00:37AM -0800, Ian Rogers wrote: > > On Tue, Nov 17, 2020 at 3:01 AM Jiri Olsa <jolsa@kernel.org> wrote: > > > > > Adding build_id__is_defined helper to check build id > > > is defined and is != zero build id. > > > > > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > > > --- > > > tools/perf/util/build-id.c | 7 +++++++ > > > tools/perf/util/build-id.h | 1 + > > > 2 files changed, 8 insertions(+) > > > > > > diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c > > > index 6b410c3d52dc..7d9ecc37849c 100644 > > > --- a/tools/perf/util/build-id.c > > > +++ b/tools/perf/util/build-id.c > > > @@ -912,3 +912,10 @@ void build_id__init(struct build_id *bid, const u8 > > > *data, size_t size) > > > memcpy(bid->data, data, size); > > > bid->size = size; > > > } > > > + > > > +bool build_id__is_defined(const struct build_id *bid) > > > +{ > > > + static u8 zero[BUILD_ID_SIZE]; > > > + > > > + return bid && bid->size ? memcmp(bid->data, &zero, bid->size) : > > > false;
> > Fwiw, I find this method to test for zero a little hard to parse - I'm > > heh, it's controversial one, Namhyung commented > on this one in previous version, so I changed it ;-) > https://lore.kernel.org/lkml/CAM9d7cjjGjTN8sDgLZ1PoQZ-sUXWjnVaNdyOVE1yHxq46PrPkw@mail.gmail.com/
So, the kernel has an idiom for this in lib/string.c:
/** * memchr_inv - Find an unmatching character in an area of memory. * @start: The memory area * @c: Find a character other than c * @bytes: The size of the area. * * returns the address of the first character other than @c, or %NULL * if the whole buffer contains just @c. */ void *memchr_inv(const void *start, int c, size_t bytes)
No need for any array of some particular size :-)
Its been there for a while:
commit 798248206b59acc6e1238c778281419c041891a7 Author: Akinobu Mita <akinobu.mita@gmail.com> Date: Mon Oct 31 17:08:07 2011 -0700
lib/string.c: introduce memchr_inv()
memchr_inv() is mainly used to check whether the whole buffer is filled with just a specified byte.
- Arnaldo > > > failing as a C programmer :-) Nit, should zero be const? > > right, should be const, will change
| |