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How to create a barycentre python module		 Parent
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The C++ module file

9.5.1 : The wrapper function

The header file barycentreWrapper.h is very simple : 
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/***************************************
	Auteur : Pierre Aubert
	Mail : aubertp7@gmail.com
	Licence : CeCILL-C
****************************************/

#ifndef __BARYCENTRE_WRAPPER_H__
#define __BARYCENTRE_WRAPPER_H__

#include <Python.h>
#include "structmember.h"

PyObject * barycentreWrapper(PyObject *self, PyObject *args);

#endif
You can download it here.

Now, let's write the barycentreWrapper.cpp file :

Again in this example, since we are using numpy in the module, we have to define the NO_IMPORT_ARRAY to avoid multiple definitions of the same numpy function. And we also have to specify the version of the numpy API to avoid warnings : 
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#define NO_IMPORT_ARRAY
#ifndef DISABLE_COOL_ARRAY
#define PY_ARRAY_UNIQUE_SYMBOL core_ARRAY_API
#endif

#define NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION
Then we include appropriate files. Do not forget to include the asterics_alloc.h file to use our allocation function : 
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#include <iostream>
#include <numpy/arrayobject.h>
#include <bytearrayobject.h>

#include "barycentre_intrinsics.h"
#include "barycentreWrapper.h"
To parse static parameters, we have to use the function PyArg_ParseTuple, this function works the same as the scanf function from the C standard library.

Here, we parse the output table and the two input tables with 'O' which corresponds to a PyObject type. 

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///Do the barycentre computation
/**	@param self : parent of the function if it exist
 * 	@param args : arguments passed to the function
 * 	@return result of the barycentre
*/
PyObject * barycentreWrapper(PyObject *self, PyObject *args){
	PyArrayObject *objTabX = NULL, *objTabY = NULL, *objTabA = NULL;
	
	if(!PyArg_ParseTuple(args, "OOO", &objTabX, &objTabY, &objTabA)){
		PyErr_SetString(PyExc_RuntimeError, "barycentreWrapper : wrong set of arguments. Expect tabX, tabY, tabA\n");
		return NULL;
	}
	if(PyArray_NDIM(objTabX) != 1 || PyArray_NDIM(objTabY) != 1 || PyArray_NDIM(objTabA) != 1){
		PyErr_SetString(PyExc_TypeError, "barycentreWrapper : input table must be a one dimension array");
		return NULL;
	}
	if(PyArray_DIMS(objTabX)[0] != PyArray_DIMS(objTabY)[0] || PyArray_DIMS(objTabX)[0] != PyArray_DIMS(objTabA)[0]){
		PyErr_SetString(PyExc_TypeError, "barycentreWrapper : input table must be of the same size");
		return NULL;
	}
	long unsigned int sizeElement(PyArray_DIMS(objTabX)[0]);
	
	const float * tabX = (const float*)PyArray_DATA(objTabX);
	const float * tabY = (const float*)PyArray_DATA(objTabY);
	const float * tabA = (float*)PyArray_DATA(objTabA);
	float gx(0.0f), gy(0.0f);
	barycentre(gx, gy, tabX, tabY, tabA, sizeElement);
	
	return Py_BuildValue("ff", gx, gy);
}
The full barycentreWrapper.cpp file : 
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/***************************************
	Auteur : Pierre Aubert
	Mail : aubertp7@gmail.com
	Licence : CeCILL-C
****************************************/

#define NO_IMPORT_ARRAY
#ifndef DISABLE_COOL_ARRAY
#define PY_ARRAY_UNIQUE_SYMBOL core_ARRAY_API
#endif

#define NPY_NO_DEPRECATED_API NPY_1_7_API_VERSION

#include <iostream>
#include <numpy/arrayobject.h>
#include <bytearrayobject.h>

#include "barycentre_intrinsics.h"
#include "barycentreWrapper.h"

///Do the barycentre computation
/**	@param self : parent of the function if it exist
 * 	@param args : arguments passed to the function
 * 	@return result of the barycentre
*/
PyObject * barycentreWrapper(PyObject *self, PyObject *args){
	PyArrayObject *objTabX = NULL, *objTabY = NULL, *objTabA = NULL;
	
	if(!PyArg_ParseTuple(args, "OOO", &objTabX, &objTabY, &objTabA)){
		PyErr_SetString(PyExc_RuntimeError, "barycentreWrapper : wrong set of arguments. Expect tabX, tabY, tabA\n");
		return NULL;
	}
	if(PyArray_NDIM(objTabX) != 1 || PyArray_NDIM(objTabY) != 1 || PyArray_NDIM(objTabA) != 1){
		PyErr_SetString(PyExc_TypeError, "barycentreWrapper : input table must be a one dimension array");
		return NULL;
	}
	if(PyArray_DIMS(objTabX)[0] != PyArray_DIMS(objTabY)[0] || PyArray_DIMS(objTabX)[0] != PyArray_DIMS(objTabA)[0]){
		PyErr_SetString(PyExc_TypeError, "barycentreWrapper : input table must be of the same size");
		return NULL;
	}
	long unsigned int sizeElement(PyArray_DIMS(objTabX)[0]);
	
	const float * tabX = (const float*)PyArray_DATA(objTabX);
	const float * tabY = (const float*)PyArray_DATA(objTabY);
	const float * tabA = (float*)PyArray_DATA(objTabA);
	float gx(0.0f), gy(0.0f);
	barycentre(gx, gy, tabX, tabY, tabA, sizeElement);
	
	return Py_BuildValue("ff", gx, gy);
}
You can download it here.
Previous
How to create a barycentre python module		 Parent
How to create a barycentre python module		 Outline Next
The C++ module file