From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46157) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZWvbK-000703-2f for qemu-devel@nongnu.org; Tue, 01 Sep 2015 20:08:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZWvbJ-0002Eu-3O for qemu-devel@nongnu.org; Tue, 01 Sep 2015 20:08:29 -0400 Date: Tue, 1 Sep 2015 20:08:21 -0400 From: Jeff Cody Message-ID: <20150902000821.GH2669@localhost.localdomain> References: <45295c490f1d7c2c2209a19fba8c656967d03d5b.1441140367.git.jcody@redhat.com> <55E62CD4.9060309@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55E62CD4.9060309@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 1/2] util - add automated ID generation utility List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: kwolf@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, armbru@redhat.com, programmingkidx@gmail.com, jsnow@redhat.com On Tue, Sep 01, 2015 at 04:55:16PM -0600, Eric Blake wrote: > On 09/01/2015 04:30 PM, Jeff Cody wrote: > > Multiple sub-systems in QEMU may find it useful to generate IDs > > for objects that a user may reference via QMP or HMP. This patch > > presents a standardized way to do it, so that automatic ID generation > > follows the same rules. > > > > This patch enforces the following rules when generating an ID: > > > > 1.) Guarantee no collisions with a user-specified ID > > 2.) Identify the sub-system the ID belongs to > > 3.) Guarantee of uniqueness > > 4.) Spoiling predictability, to avoid creating an assumption > > of object ordering and parsing (i.e., we don't want users to think > > they can guess the next ID based on prior behavior). > > > > The scheme for this is as follows (no spaces): > > > > # subsys D RR > > Reserved char --| | | | > > Subsystem String ----| | | > > Unique number (64-bit) --| | > > Two-digit random number ---| > > > > For example, a generated node-name for the block sub-system may look > > like this: > > > > #block076 > > > > The caller of id_generate() is responsible for freeing the generated > > node name string with g_free(). > > > > Signed-off-by: Jeff Cody > > --- > > include/qemu-common.h | 8 ++++++++ > > util/id.c | 36 ++++++++++++++++++++++++++++++++++++ > > 2 files changed, 44 insertions(+) > > Reviewed-by: Eric Blake > > > + > > +static const char * const id_subsys_str[] = { > > + [ID_QDEV] = "qdev", > > + [ID_BLOCK] = "block", > > +}; > > We're inconsistent on whether there should be a space in '*const' > (compare commit a91e211 with b86f461, for example). But since qemu.git > has both spellings in various contexts, it's probably not worth changing > here. > If this ends up needing another rev, I'll change it for you :) > > + > > + rnd = g_random_int_range(0, 99); > > Thankfully, g_random_* is a PRNG that is not consuming system entropy > (auto-generated names should not be starving /dev/random). > Yup. Thanks, Jeff