[Numpy-discussion] C extension in new numpy: help to port from numarray

[Travis Oliphant]

Sebastian Haase wrote:
> Hi,
> I'm a long time numarray user.
> I have some SWIG typemaps that I'm using for quite some time.
> They are C++ oriented and support creating template'd function.
> I only cover the case of contiguous "input" arrays of 1D,2D and 3D.
> (I would like to ensure that NO implicit type conversions are made so 
> that I can use the same scheme to have arrays changed on the C/C++ 
> side and can later see/access those in python.)
>
> (as I just added some text to the scipy wiki: 
> www.scipy.org/Converting_from_numarray)
> I use something like:
>
> PyArrayObject *NAarr  = NA_InputArray(inputPyObject, PYARR_TC, 
> NUM_C_ARRAY);
>  arr = (double *) NA_OFFSETDATA(NAarr);
>
>
> What is new numpy's equivalent of    NA_InputArray

In the scipy/Lib/ndimage package is a numcompat.c and numcompat.h file 
that implements several of the equivalents.

I'd like to see a module like this get formalized and placed into numpy 
itself so that most numarray extensions simply have to be re-compiled to 
work with NumPy.


Here is the relevant information (although I don't know what PYARR_TC is...)


typedef enum
{
  tAny,
  tBool=PyArray_BOOL,
  tInt8=PyArray_INT8,
  tUInt8=PyArray_UINT8,
  tInt16=PyArray_INT16,
  tUInt16=PyArray_UINT16,
  tInt32=PyArray_INT32,
  tUInt32=PyArray_UINT32,
  tInt64=PyArray_INT64,
  tUInt64=PyArray_UINT64,
  tFloat32=PyArray_FLOAT32,
  tFloat64=PyArray_FLOAT64,
  tComplex32=PyArray_COMPLEX64,
  tComplex64=PyArray_COMPLEX128,
  tObject=PyArray_OBJECT,        /* placeholder... does nothing */
  tDefault = tFloat64,
#if BITSOF_LONG == 64
  tLong = tInt64,
#else
  tLong = tInt32,
#endif
  tMaxType
} NumarrayType;


typedef enum
{
        NUM_CONTIGUOUS=CONTIGUOUS,
        NUM_NOTSWAPPED=NOTSWAPPED,
        NUM_ALIGNED=ALIGNED,
        NUM_WRITABLE=WRITEABLE,
        NUM_COPY=ENSURECOPY,

        NUM_C_ARRAY  = (NUM_CONTIGUOUS | NUM_ALIGNED | NUM_NOTSWAPPED),
        NUM_UNCONVERTED = 0
} NumRequirements;


#define _NAtype_toDescr(type) (((type)==tAny) ? NULL :  \
                               PyArray_DescrFromType(type))

#define NA_InputArray(obj, type, flags) \
        (PyArrayObject *)\
                PyArray_FromAny(obj, _NAtype_toDescr(type), 0, 0, flags, 
NULL)

#define NA_OFFSETDATA(a) ((void *) PyArray_DATA(a))