Question

I am in the process of extending the classes in our library (which supports Python 2.7) to support PEP 3118, which has been back-ported to 2.7.

From the documentation, I need to initialize the tp_as_buffer field to point to a PyBufferProcs. From the documentation for 2.7, however, the description of this structure only contains entries for the old buffer protocol. From the sources, I gather that PyBufferProcs has some additional entries for the new protocol (bf_getbuffer and bf_releasebuffer).

The questions remain:

  • Do I have to do something special to tell Python that these new entries are valid?

  • Do I have to fill in the entries for the old protocol? (The documentation for 2.7 says, for example, that bf_getsegcount may not be null. But this entry shouldn't be used if I'm supporting PEP 3118.)

No correct solution

OTHER TIPS

You can just fill the last two fields of PyBufferProcs but you have to add the Py_TPFLAGS_HAVE_NEWBUFFER flag to the tp_flags of your types. This is the special thing that was introduced in python2 to make the new protocol available together with the old one.

I have no idea why this isn't documented anywhere, but you can see it used in the definition of the bytearray type for python 2.7 (see here):

    &bytearray_as_buffer,               /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
    Py_TPFLAGS_HAVE_NEWBUFFER,          /* tp_flags */

This content was already posted in comments, but it deserves an answer.

Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow
scroll top