Re: [libvirt] [PATCH 09/10] python: events: Fix C->Python handle callback prototype

On Wed, Jun 15, 2011 at 09:23:18PM -0400, Cole Robinson wrote: > If registering our own event loop implementation written in python, > any handles or timeouts callbacks registered by libvirt C code must > are wrapped in a python function. There is some argument trickery that "must be" :-) > makes this all work, by wrapping the user passed opaque value in > a tuple, along with the callback function. > > Problem is, the current setup requires the user's event loop to know > about this trickery, rather than just treating the opaque value > as truly opaque. > > Fix this in a backwards compatible manner, and adjust the example > python event loop to do things the proper way. > > Signed-off-by: Cole Robinson <crobinso(a)redhat.com&gt; > --- > examples/domain-events/events-python/event-test.py | 6 +--- > python/libvirt-override.py | 26 ++++++++++++++++++- > 2 files changed, 26 insertions(+), 6 deletions(-) > > diff --git a/examples/domain-events/events-python/event-test.py b/examples/domain-events/events-python/event-test.py > index df75dce..76fda2b 100644 > --- a/examples/domain-events/events-python/event-test.py > +++ b/examples/domain-events/events-python/event-test.py > @@ -66,8 +66,7 @@ class virEventLoopPure: > self.cb(self.handle, > self.fd, > events, > - self.opaque[0], > - self.opaque[1]) > + self.opaque) > > # This class contains the data we need to track for a > # single periodic timer > @@ -96,8 +95,7 @@ class virEventLoopPure: > > def dispatch(self): > self.cb(self.timer, > - self.opaque[0], > - self.opaque[1]) > + self.opaque) > > > def __init__(self): > diff --git a/python/libvirt-override.py b/python/libvirt-override.py > index b611ca4..8df9dc1 100644 > --- a/python/libvirt-override.py > +++ b/python/libvirt-override.py > @@ -117,19 +117,41 @@ def getVersion (name = None): > # > # Invoke an EventHandle callback > # > -def eventInvokeHandleCallback (watch, fd, event, callback, opaque): > +def eventInvokeHandleCallback(watch, fd, event, opaque, opaquecompat=None): > """ > Invoke the Event Impl Handle Callback in C > """ > + # libvirt 0.9.2 and earlier required custom event loops to know > + # that opaque=(cb, original_opaque) and pass the values individually > + # to this wrapper. This should handle the back compat case, and make > + # future invocations match the virEventHandleCallback prototype > + if opaquecompat: > + callback = opaque > + opaque = opaquecompat > + else: > + callback = opaque[0] > + opaque = opaque[1] > + > libvirtmod.virEventInvokeHandleCallback(watch, fd, event, callback, opaque); I would rather use dynamic type test like if type(callback) == type(()) and type(callback[0]) == type(lambda x:x): than rely on an extra argument detection Note: I didn't tried, I don't know if python type will allow the test for functions and lambda to work, otherwise use a predefined function or another one from the module.