[Numpy-discussion] mtrand.c update 1.11 breaks my crappy code

[Neal Becker]

Neal Becker wrote:

> Robert Kern wrote:
> 
>> On Wed, Apr 6, 2016 at 2:18 PM, Neal Becker <ndbecker2 at gmail.com> wrote:
>>>
>>> I have C++ code that tries to share the mtrand state.  It unfortunately
>>> depends on the layout of RandomState which used to be:
>>>
>>> struct __pyx_obj_6mtrand_RandomState {
>>>   PyObject_HEAD
>>>   rk_state *internal_state;
>>>   PyObject *lock;
>>> };
>>>
>>> But with 1.11 it's:
>>> struct __pyx_obj_6mtrand_RandomState {
>>>   PyObject_HEAD
>>>   struct __pyx_vtabstruct_6mtrand_RandomState *__pyx_vtab;
>>>   rk_state *internal_state;
>>>   PyObject *lock;
>>>   PyObject *state_address;
>>> };
>>>
>>> So
>>> 1. Why the change?
>>> 2. How can I write portable code?
>> 
>> There is no C API to RandomState at this time, stable, portable or
>> otherwise. It's all private implementation detail. If you would like a
>> stable and portable C API for RandomState, you will need to contribute
>> one using PyCapsules to expose the underlying rk_state* pointer.
>> 
>> https://docs.python.org/2.7/c-api/capsule.html
>> 
>> --
>> Robert Kern
> 
> I don't see how pycapsule helps here.  What I need is, my C++ code
> receives
> a RandomState object.  I need to call e.g., rk_random, passing the pointer
> to rk_state - code looks like this;
> 
>     RandomState* r = (RandomState*)(rs.ptr());
>     //    result_type buffer;
>     //    rk_fill ((void*)&buffer, sizeof(buffer), r->internal_state);
>     if (sizeof(result_type) == sizeof (uint64_t))
>       return rk_ulong (r->internal_state);
>     else if (sizeof(result_type) == sizeof (uint32_t))
>       return rk_random (r->internal_state);

Nevermind, I see it's described here:
https://docs.python.org/2.7/extending/extending.html#using-capsules