Issue 3163: module struct support for ssize_t and size_t

Attached is a (simplistic) patch for the struct module to support C types 
ssize_t and size_t with format characters 'z' resp. 'Z'.

The patch updates Python 2.6b1 files Modules/_struct.c and 
Doc/library/struct.rst.

Note, format character 'Z' is also proposed in PEP 3118 for C type complex  
and that has to be something else, perhaps 'C'.

Now that Python 2.6 is in beta, new features should be deferred to 2.7.

Please ignore the first patch.  Use the rev2 patch which includes an 
update for test file  Lib/test/test_struct.py as well.

The proposed addition seems reasonable to me, for native packing and unpacking.

For standard mode packing and unpacking, I don't see the point;  we'd have to pick a standard size, which would almost certainly be either 4 or 8, and so would already be covered by either the 'iI' or the 'qQ' codes.  So I'd suggest adding the size_t/ssize_t codes only for native mode, and leaving them unsupported for the standard modes.

To avoid clashing with PEP 3118, we could use 'n' and 'N' instead of 'z' and 'Z'.

Jean, if you're still around:

Do you still have interest in pursuing this?

Yes I am and I will get back to you on this after check my (old) notes.

/Jean

On Wed, Jul 14, 2010 at 12:08 PM, Mark Dickinson <report@bugs.python.org>wrote:

>
> Mark Dickinson <dickinsm@gmail.com> added the comment:
>
> Jean, if you're still around:
>
> Do you still have interest in pursuing this?
>
> ----------
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue3163>
> _______________________________________
>

It would be sufficient to support size_t/ssize_t in native mode for my usage.  The workaround I have been using is in this recipe

  <http://code.activestate.com/recipes/546530/>

in the function calcsize.  That maps the 'z' and 'Z' format to either 'l', 'L' or 'P' for lack of anything better.

Okay;  would you be interested in updating your patch?

#3163 is a duplicate.

Ooops, I meant #13098.

Here is a patch.

Mostly LGTM.  I have a few comments in rietveld.

Thanks. I have answered one of your comments, and here is a new patch.

New patch with cosmetic doc fix.

Found a few test case nits.  Comments in rietveld.

Thanks for the comments. Here is an updated patch.

No problem.  This last version LGTM.

New changeset db3e15017172 by Antoine Pitrou in branch 'default':
Issue #3163: The struct module gets new format characters 'n' and 'N'
http://hg.python.org/cpython/rev/db3e15017172

Thanks for the reviews!

stage: patch review -> resolved

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stage: needs patch -> patch review

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nosy: + pitrou
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stage: patch review -> needs patch

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nosy: + mark.dickinson