From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57522) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZWuSe-0004Wp-5N for qemu-devel@nongnu.org; Tue, 01 Sep 2015 18:55:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZWuSc-0006ny-Uw for qemu-devel@nongnu.org; Tue, 01 Sep 2015 18:55:28 -0400 References: <45295c490f1d7c2c2209a19fba8c656967d03d5b.1441140367.git.jcody@redhat.com> From: Eric Blake Message-ID: <55E62CD4.9060309@redhat.com> Date: Tue, 1 Sep 2015 16:55:16 -0600 MIME-Version: 1.0 In-Reply-To: <45295c490f1d7c2c2209a19fba8c656967d03d5b.1441140367.git.jcody@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="10HoVKPGStCi0xAiLQ9Cqekruo1278nfl" 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: Jeff Cody , qemu-devel@nongnu.org Cc: kwolf@redhat.com, qemu-block@nongnu.org, armbru@redhat.com, programmingkidx@gmail.com, jsnow@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --10HoVKPGStCi0xAiLQ9Cqekruo1278nfl Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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. >=20 > This patch enforces the following rules when generating an ID: >=20 > 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). >=20 > The scheme for this is as follows (no spaces): >=20 > # subsys D RR > Reserved char --| | | | > Subsystem String ----| | | > Unique number (64-bit) --| | > Two-digit random number ---| >=20 > For example, a generated node-name for the block sub-system may look > like this: >=20 > #block076 >=20 > The caller of id_generate() is responsible for freeing the generated > node name string with g_free(). >=20 > 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[] =3D { > + [ID_QDEV] =3D "qdev", > + [ID_BLOCK] =3D "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. > + > + rnd =3D 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). --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --10HoVKPGStCi0xAiLQ9Cqekruo1278nfl Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJV5izUAAoJEKeha0olJ0NqBJUIAJTFXflBethHpGVh2WbrU7LM gWMk0FMOfhhA4f5V4hvVSB8ArC39UfnhyNLAFd7z/ul6UxtRzXgDrXZPWiyXQjms 9RE3FTubFvVNuPHnRWatCCJlU1B3vtDSQ14jyboVfhlqujAL5EBAlHs5d/jesI5y VSgDyn3geGHrIF4qB3Mx90k2+nO6KAHmujn4dnPYGZgdD+U+9pdpnlDlIrN4dWVo 8hf6YVK14iRhD1i6I6mgpHv3TV1PmY+YXJcPP8OTptArSGElWIXXAgbuhPW/30HA qNemQCSBbn1tFAreW5cKOKOVqFcMAeuJ23CXuQLA679UAgor5QD2cJfCCjeYCYg= =4QDV -----END PGP SIGNATURE----- --10HoVKPGStCi0xAiLQ9Cqekruo1278nfl--