On Tuesday 02 November 2010, 13:26:44 Phil Thompson wrote: > On Tue, 02 Nov 2010 13:19:06 +0100, Giovanni Bajo <ra...@develer.com> > > wrote: > > On mar, 2010-11-02 at 13:57 +0200, Hans-Peter Jansen wrote: > >> On Tuesday 02 November 2010, 11:26:46 Giovanni Bajo wrote: > >> > On mar, 2010-11-02 at 10:16 +0000, Phil Thompson wrote: > >> > > On Tue, 2 Nov 2010 00:00:06 +0200, "Hans-Peter Jansen" > >> > > <h...@urpla.net> > >> > > > >> > > wrote: > >> > > > Hi Phil, > >> > > > > >> > > > end of July last year, Alexandre Raczynski asked about > >> > > > accessing QSharedMemory, and you replied, that: > >> > > > > >> > > > mutable_data = buffer(sharedMemory.data()) > >> > > > > >> > > > ...should give _write_ access to the memory. > >> > > > >> > > ...bad advice. I didn't realise that you can't create mutable > >> > > buffers from Python. (Although there is no reason why you > >> > > shouldn't be able to.) > >> > > >> > Actually, Python 2.7 has memoryview(); if > >> > memoryview(sharedMemory.data()) worked, it would be possible to > >> > use memoryview's method to mutate the buffer, without having to > >> > come up with a different API for sip.voidptr. > >> > >> Giovanni, isn't memoryview just a different _interface_ to the > >> buffer protocol? > > > > To the best of my understanding, it is a more complete interface > > that also allows writable buffers. I think it is the best match to > > allow access to the "contents" of a sip.voidptr and its const > > version. > > Agreed - it's implemented in the hg repo. > > >> Anyway, being able to use QSharedMemory with 2.7 and higher > >> only looks like an arbitrary restriction to me. At least many of > >> my production systems would be locked out, then. For proper > >> support, Phil might have to do both variants of the buffer > >> protocol anyway.. > > > > I understand your concerns. Support for memoryview (as a silent > > conversion to/from void* at SIP level) would still be required for > > interoperability with libraries which don't know sip.voidptr but > > can use/produce a memoryview. > > > > I was just wondering if there was a better solution than coming up > > with a custom API for sip.voidptr for pre-2.7, but I can't see it. > > It's not really a custom API - just standard slice and index > assignment.
If I'm not mistaken, it should work like:
self.sharedMemory.data()[:] = buf.data().data()
where buf is a QtCore.QBuffer() instance, but:
File "dialog.py", line 87, in loadFromFile
self.sharedMemory.data()[:] = buf.data().data()
TypeError: 'sip.voidptr' object does not support item assignment
with:
python: 2.6
sip: 4.12-snapshot-f9dfbda5844f
qt4: 4.7.0
pyqt4: 4.8.1
Shared memory example for the collection (when fixed) attached ;-).
Pete
sharedmemory.tar.gz
Description: application/tgz
_______________________________________________ PyQt mailing list PyQt@riverbankcomputing.com http://www.riverbankcomputing.com/mailman/listinfo/pyqt
