Converting from a jagged array to double pointer in C#

Question

Simple question here: is there any way to convert from a jagged array to a double pointer?

e.g. Convert a double[][] to double**

This can't be done just by casting unfortunately (as it can in plain old C), unfortunately. Using a fixed statement doesn't seem to resolve the problem either. Is there any (preferably as efficient as possible) way to accomplish this in C#? I suspect the solution may not be very obvious at all, though I'm hoping for a straightforward one nonetheless.

Answer 1

A double[][] is an array of double[], not of double* , so to get a double** , we first need a double*[]

double[][] array = //whatever
//initialize as necessary

fixed (double* junk = &array[0][0]){

    double*[] arrayofptr = new double*[array.Length];
    for (int i = 0; i < array.Length; i++)
        fixed (double* ptr = &array[i][0])
        {
            arrayofptr[i] = ptr;
        }

    fixed (double** ptrptr = &arrayofptr[0])
    {
        //whatever
    }
}

I can't help but wonder what this is for and if there is a better solution than requiring a double-pointer.

Answer 2

I've gone with zachrrs solution for the time being (which was what I was suspecting might need to be done in the first place). Here it is an extension method:

public static double** ToPointer(this double[][] array)
{
    fixed (double* arrayPtr = array[0])
    {
        double*[] ptrArray = new double*[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            fixed (double* ptr = array[i])
                ptrArray[i] = ptr;
        }

        fixed (double** ptr = ptrArray)
            return ptr;
    }
}