On 3/20/19 1:40 AM, Eric Blake wrote:
> Upcoming patches want to add virDomainCheckpoint that behaves very
> similarly to virDomainSnapshot; the easiest way to share common code
> is to give both classes a common base class. Thanks to the accessor
> functions in the previous patch, we have very few changes required
> outside of datatypes.[ch]. The subclass does have to use a dummy
> field, though, to satisfy virobject's insistence on size
> differentiation for type safety.
>
> Note that virClassNew() supports a NULL dispose method for a class
> that has nothing to clean up, but VIR_CLASS_NEW has no easy way to
> register such a class without a #define hack.
>
> I promised my teenage daughter Evelyn that I'd give her credit for her
> contribution to this commit. I asked her "What would be a good name
> for a base class for DomainSnapshot and DomainCheckpoint". After
> explaining what a base class was (using the classic OOB Square and
> Circle inherit from Shape), she came up with "DomainMoment", which is
> way better than my initial thought of "DomainPointInTime" or
> "DomainPIT".
Maybe it was her way to ensure some sort of "mom" 'ent'ry got included
into libvirt ;-}
>
> Signed-off-by: Eric Blake <eblake@xxxxxxxxxx>
> ---
> src/datatypes.h | 26 ++++++--
> src/datatypes.c | 110 ++++++++++++++++++++--------------
> src/libvirt-domain-snapshot.c | 2 +-
> 3 files changed, 88 insertions(+), 50 deletions(-)
>
[...]
>
>
> +/**
> + * virGetDomainMoment:
> + * @domain: the domain involved in a point-in-time moment
> + * @name: pointer to the domain moment name
* @subclass: Either virDomainSnapshotClass or virDomainCheckpointClass
[ok that second one is eventually.... and it's only internal so
validation is left to the developer ;-}]
> + *
> + * Allocates a new concrete subclass of a domain moment object. When
> + * the object is no longer needed, virObjectUnref() must be called in
> + * order to not leak data.
> + *
> + * Returns a pointer to the domain moment object, or NULL on error.
> + */
> +static virDomainMomentPtr
> +virGetDomainMoment(virDomainPtr domain, const char *name, virClassPtr subclass)
> +{
> + virDomainMomentPtr ret = NULL;
> +
> + if (virDataTypesInitialize() < 0)
> + return NULL;
> +
> + virCheckDomainGoto(domain, error);
> + virCheckNonNullArgGoto(name, error);
> +
> + if (!(ret = virObjectNew(subclass)))
> + goto error;
> + if (VIR_STRDUP(ret->name, name) < 0)
> + goto error;
> +
> + ret->domain = virObjectRef(domain);
> +
> + return ret;
> +
> + error:
> + virObjectUnref(ret);
> + return NULL;
> +}
> +
> +
Reviewed-by: John Ferlan <jferlan@xxxxxxxxxx>
John
I have to say I did pause to stop and think about the Dispose thing...
Especially with the "parent" class having a NULL ->dispose, but also
having a klass->parent which would have the MomentDispose.
[...]
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list
