From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37500) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d8IMS-0000xG-NP for qemu-devel@nongnu.org; Tue, 09 May 2017 23:32:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d8IMO-0005lO-PH for qemu-devel@nongnu.org; Tue, 09 May 2017 23:32:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52988) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d8IMO-0005lJ-Gg for qemu-devel@nongnu.org; Tue, 09 May 2017 23:32:20 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 41F9E83F3E for ; Wed, 10 May 2017 03:32:19 +0000 (UTC) Date: Wed, 10 May 2017 11:32:12 +0800 From: Peter Xu Message-ID: <20170510033212.GP2820@pxdev.xzpeter.org> References: <1494329105-4411-1-git-send-email-peterx@redhat.com> <1494329105-4411-3-git-send-email-peterx@redhat.com> <87a86mhyod.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87a86mhyod.fsf@dusky.pond.sub.org> Subject: Re: [Qemu-devel] [PATCH v5 2/3] utils: provide size_to_str() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: qemu-devel@nongnu.org, Paolo Bonzini , "Dr. David Alan Gilbert" On Tue, May 09, 2017 at 04:50:26PM +0200, Markus Armbruster wrote: > Peter Xu writes: > > > I stole the algorithm from print_type_size(). I didn't generalize it > > since that's using [KM...]iB while here we need [KM...]B to finally > > be able to stands for page sizes (and even more general). > > Can you explain why we need units without the 'i' here? Oops. I misunderstood XiB... My fault. Page sizes needs exactly "i". > > > > > Signed-off-by: Peter Xu > > --- > > include/qemu-common.h | 1 + > > util/cutils.c | 26 ++++++++++++++++++++++++++ > > 2 files changed, 27 insertions(+) > > > > diff --git a/include/qemu-common.h b/include/qemu-common.h > > index d218821..d7d0448 100644 > > --- a/include/qemu-common.h > > +++ b/include/qemu-common.h > > @@ -145,6 +145,7 @@ void qemu_hexdump(const char *buf, FILE *fp, const char *prefix, size_t size); > > int parse_debug_env(const char *name, int max, int initial); > > > > const char *qemu_ether_ntoa(const MACAddr *mac); > > +char *size_to_str(double val); > > void page_size_init(void); > > > > /* returns non-zero if dump is in progress, otherwise zero is > > diff --git a/util/cutils.c b/util/cutils.c > > index 50ad179..5aaf370 100644 > > --- a/util/cutils.c > > +++ b/util/cutils.c > > @@ -619,3 +619,29 @@ const char *qemu_ether_ntoa(const MACAddr *mac) > > > > return ret; > > } > > + > > +/* > > + * Sample output: > > + * > > + * 1 -> "1 B" > > + * 528 -> "0.516 KB" > > + * 4096 -> "4 KB" > > + * 2402958 -> "2.29 MB" > > + * 1073741824 -> "1 GB" > > + * > > + * Please free the buffer after use. > > + */ > > +char *size_to_str(double val) > > +{ > > + static const char suffixes[] = { 'B', 'K', 'M', 'G', 'T', 'P', 'E' }; > > + unsigned long div; > > + int i; > > + > > + frexp(val, &i); > > The ignored return value is in [0.5,1), and multiplying it by 2^i yields > val. i is close to the binary logarithm. > > > + i /= 10; > > Now it's close to base-1024 logarithm. > > Figuring this out requires too much thought for comfort. Recommend > steal the comment from print_type_size(), too. Let me do it even simpler - I'll just move the whole logic in print_type_size() into size_to_str(), then I'll refactor print_type_size(). > > > + assert(i < sizeof(suffixes)); > > + div = 1ULL << (i * 10); > > + > > + return g_strdup_printf("%0.3g %c%s", val / div, > > + suffixes[i], i ? "B" : ""); > > The conditional is a bit confusing. To avoid it, we could make > suffixes[] an array of strings, with suffixes[0] = "". I can fix this. Thanks reviewing! -- Peter Xu