[Pyrex] Sharing a C pointer between Pyrex objects

[John Arbash Meinel]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Anand Patil wrote:
> Hi all,
> 
> I'd like to make an int* pointer stored in one Pyrex object available to
> another:
> 
> cdef class NumberHolder:
>     cdef int number
>     def __init__(self):
>         self.number = 0
> 
> cdef class PointerHolder:
>     cdef int* my_pointer
>     def __init__(self, number_holder):
>         my_pointer = number_holder.number
> 
> If I try it this way, of course, I get errors like 'NumberHolder' object
> has no attribute 'number'. I'm currently creating a NumPy array in
> NumberHolder and using PyArray_DATA from PointerHolder, but it seems
> excessive and possibly dangerous, since PointerHolder may change
> *my_pointer later. What's the best way to do this?
> 
> Thanks,
> Anand
> 

I believe you can do:


cdef class PointerHolder:
    cdef int* my_pointer
    def __init__(self, number_holder):
	cdef NumberHolder real_holder
        real_holder = number_holder
        self.my_pointer = &real_holder.number

You need to indicate to pyrex that number_holder is really a
NumberHolder object, and not just a generic python object. Further, I'm
pretty sure the & is necessary, since you want to point to the int, and
not point at whatever the int points at.

John
=:->
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iEYEARECAAYFAklmMXUACgkQJdeBCYSNAAO2ygCfSsARbUIzUJODVy3moKdFCCJ2
638AoKAyWfJ8vMo2l1oRUUgV1x8hbQEM
=owSx
-----END PGP SIGNATURE-----