Re: feature request for setting _pack_ to a higher value

Axel Seibert schrieb:
> Hi, Thomas!
> 
> Thanx for asking -- no, I have not found any other solution yet.

Ok, so the remaining question was:  How can I change a (generated) ctypes Union
definition so that the packing is a multiple of an arbitrary value, 8 in this case.

Background:  A Union contains all the _fields_ in the same memory block (they overlay
each other; only one is normally valid), so the Union size is the size of the largest
field.  We have now the goal to bring the union size up to a multiple of 8 by adding
a dummy field.  Here is the ode that I wrote:

<snip>
from ctypes import *

def fill_union(value, fields):
    size = 0
    for name, typ in fields:
        size = max(size, sizeof(typ))
    delta = 8 - size % 8
    return fields + [("", c_char * (size + delta))]

class X(Union):
    _fields_ = fill_union(8, [("a", c_char),
                              ("b", c_short),
                              ("c", c_char * 31)])

print sizeof(X)
<snip/>

> So long,
> Axel
> 
> Am 09.04.2010 um 10:02 schrieb Thomas Heller:
> 
>> Axel Seibert schrieb:
>>> Hi, Thomas!
>>> 
>>> I tried to apply your solution to my problem. I found two issues with that:
>>> a) a couple of my structs that require padding are Unions. Do you have a solution for that?
>>> b) I believe that line "missing = a - size % a" needs to be replaced by missing = a - sizeof(t) % a
>> 
>> Axel - sorry for this delayed reply; I'm very short on time.  Is the question
>> still open or did you find a solution yourself in the meantime?
>> 
>> -- 
>> Thanks,
>> Thomas
>> 
>> 
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> 
> 
> ------------------------------------------------------------------------------
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-- 
Thanks,
Thomas


------------------------------------------------------------------------------
Download Intel&#174; Parallel Studio Eval
Try the new software tools for yourself. Speed compiling, find bugs
proactively, and fine-tune applications for parallel performance.
See why Intel Parallel Studio got high marks during beta.
http://p.sf.net/sfu/intel-sw-dev