On 2008-11-21 17:30, Josiah Carlson wrote: > On Thu, Nov 20, 2008 at 2:12 AM, M.-A. Lemburg <[EMAIL PROTECTED]> wrote: >> I've had a look at the new memoryview and associated buffer API >> and have a question: how is a C extension supposed to use the buffer >> API without going directly into the C struct Py_buffer ? >> >> I have not found any macros for accessing Py_buffer internals and >> the docs mention the struct members directly (which is a bit unusual >> for the Python C API). >> >> Shouldn't there be a set of macros providing some form of abstraction >> for the struct members ? >> >> BTW: I was looking for a suitable replacement for the buffer object >> which isn't available in Python 3 anymore. >> >> Thanks, >> -- >> Marc-Andre Lemburg >> eGenix.com > >>From what I understand of the memoryview when I tried to do the same > thing a few months ago (use memoryview to replace buffer in > asyncore/asynchat), memoryview is incomplete. It didn't support > character buffer slicing (you know, the 'offset' and 'size' arguments > that were in buffer), and at least a handful of other things (that I > can't remember at the moment).
True, memoryview objects aren't as useful in Python as the underlying Py_buffer "C" objects are in the C API. But then I only need it to signal "this is binary data" for the purpose of using the memoryview in DB-API extensions. However, this would only be of effective use if there's a documented way of accessing the actual C char* buffer behind the object, instead of having to allocate a new buffer and copy the data over - only to reference it like that. In the past, we've always tried to provide abstract access methods to C struct internals of Python objects and I wonder whether this was deliberately not done for Py_buffer structs or simply not considered. I don't think it's a good idea to use my_Py_buffer->buf in a C extension and would rather like to write: Py_Buffer_AS_BUFFER(my_Py_buffer) Py_Buffer_GET_SIZE(my_Py_buffer) Py_Buffer_GET_ITEM_SIZE(my_Py_buffer) etc. -- Marc-Andre Lemburg eGenix.com Professional Python Services directly from the Source (#1, Nov 21 2008) >>> Python/Zope Consulting and Support ... http://www.egenix.com/ >>> mxODBC.Zope.Database.Adapter ... http://zope.egenix.com/ >>> mxODBC, mxDateTime, mxTextTools ... http://python.egenix.com/ ________________________________________________________________________ 2008-11-12: Released mxODBC.Connect 0.9.3 http://python.egenix.com/ :::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,MacOSX for free ! :::: eGenix.com Software, Skills and Services GmbH Pastor-Loeh-Str.48 D-40764 Langenfeld, Germany. CEO Dipl.-Math. Marc-Andre Lemburg Registered at Amtsgericht Duesseldorf: HRB 46611 _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
