On Mar 13, 5:42 pm, Matteo <tadweles...@gmail.com> wrote:
> On 13 Mar, 22:35, Aaron Brady <castiro...@gmail.com> wrote:
>
>
>
> > On Mar 13, 1:34 pm, Matteo <tadweles...@gmail.com> wrote:
>
> > > hmmm... looks like SWIG has a problem with double pointers. I googled
> > > around a bit and found:
>
> > >http://osdir.com/ml/programming.swig/2003-02/msg00029.html
>
> > > anyone knows how to write a small wrapper to do the appropriate
> > > dereferencing?
>
> > 'ctypes' may be able to do it. I've done something like this in the
> > past:
>
> > double_ptr= ctypes._cast( PyObject, sing_ptr )
>
> > Up your alley?
>
> Thanks for your suggestions, but still no luck here.
>
> ctypes appears to work only with its own types, I tried its cast,
> byref and pointer functions, but only received TypeError exceptions
> such as:
> TypeError: byref() argument must be a ctypes instance, not 'list'
> TypeError: _type_ must have storage info
>
> This is getting really annoying :(
>
> The following link may contain useful info, but I find it somewhat
> obscurehttp://embedded.eecs.berkeley.edu/Alumni/pinhong/scriptEDA/pyTypemapF...
I'm on my last one (suggestion). To get a pointer to the actual
address of an mmap instance, (and access it's 'data' attribute), I
used the following:
from _ctypes import _cast_addr
from ctypes import *
_mmap_cast= _data_cast= PYFUNCTYPE(py_object, py_object, py_object,
py_object)(_cast_addr)
_offset_cast= _record_cast = PYFUNCTYPE(py_object, c_void_p,
py_object, py_object)(_cast_addr)
class MMAP(Structure):
_fields_= [
#("next",c_int),
#("prev",c_int),
("refcnt",c_int),
("type",c_int),
("data",c_long)
]
def pdata( map ):
a= _data_cast( map, None, POINTER( MMAP ) )
return a.contents.data
It worked on my machine in 2.5, no promises. It was a workaround for
the '_type_ must have storage info' error. Lo and behold,
'a.contents' was an MMAP, so '.data' was a 'c_long' interpretation of
the 'char* data' member of the C structure, PyMmapObject or
something. I found it by studying the 'ctypes.cast' code. Well good
luck and sorry for the suggestions.
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