MATLAB: How to access raw data via the mex c++ api

c++ apiderefencing typedarrayMATLAB

I want to use the mex c++ api to interface existing external code. The API of the external application is fairly low level, but I cannot work out how I can access the double pointers I'd like to pass. As this is not specific to the code I have, assume I have a function
void foo(int n, const double *a, const double *b, double *c)
to which I pass the arrays a and b and their lengths n and it calculates something and puts it onto the array c.
In order to use the mex function with the c++ api I don't know how I can avoid copying the data into some dummy pod arrays along the lines of:
#include "mex.hpp"
#include "mexAdapter.hpp"
using namespace matlab::data;
using matlab::mex::ArgumentList;
class MexFunction : public matlab::mex::Function
{
private:
    ArrayFactory factory;
    std::shared_ptr<matlab::engine::MATLABEngine> matlabPtr;
    void validateArguments(ArgumentList outputs, ArgumentList inputs)
    {
        if (inputs.size() != 2)
            matlabPtr->feval(u"error", 0, std::vector<Array>({ factory.createScalar("Require 2 inputs")}));
        
        if (inputs[0].getType() != ArrayType::DOUBLE || inputs[0].getType() == ArrayType::COMPLEX_DOUBLE )
            matlabPtr->feval(u"error", 0, std::vector<Array>({ factory.createScalar("First input has to be a double array") } ));
        if (inputs[1].getType() != ArrayType::DOUBLE || inputs[1].getType() == ArrayType::COMPLEX_DOUBLE )
            matlabPtr->feval(u"error", 0, std::vector<Array>( {factory.createScalar("second input has to be a double array")}));
        if (outputs.size() > 1)
            matlabPtr->feval(u"error", 0, std::vector<Array>( {factory.createScalar("One output only")}));
    }
    void foo(int n, const double *a, const double *b, double *c){
        int i;
        for (i=0;i<n;i++)
            c[i] = a[i] + b[i];
    }
public:
    MexFunction() : matlabPtr(getEngine()) {}
    ~MexFunction() {}
    void operator() (ArgumentList outputs, ArgumentList inputs)
    {
        validateArguments(outputs,inputs);
        double *retVal, *a, *b;
        int i, n = inputs[0].getNumberOfElements();
        retVal = new double[n];
        a = new double[n];
        b = new double[n];
        for (i =0; i<n;i++){
            a[i] = inputs[0][i];
            b[i] = inputs[1][i];
        }
        foo(n, a, b, retVal);
        ArrayDimensions dims = inputs[0].getDimensions();
        outputs[0] = factory.createArray(dims, retVal, retVal+n);
        delete a;
        delete b;
        delete retVal;
    }
};
This copying and creating of placeholders seems unelegant and wasteful. What am I missing? Please help!
Thank you!
Manuel

Best Answer

There is a "release" member function that returns a unique pointer of the raw data: TypedArray Documentation.
Instead of copying data from the typed array, the following should just work:
double* a=inputs[0].release().get();
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