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@redhat.com> --- 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@redhat.com> 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. [...]