[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v2 1/2] util - add automated ID generation utili
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v2 1/2] util - add automated ID generation utility |
Date: |
Tue, 1 Sep 2015 16:55:16 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
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 <address@hidden>
> ---
> include/qemu-common.h | 8 ++++++++
> util/id.c | 36 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 44 insertions(+)
Reviewed-by: Eric Blake <address@hidden>
> +
> +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.
> +
> + 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).
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature