Assign 1D array values to multidimensional array, of unknown dimensions / type

Question

I have an N-dimensional array which I want to be able to assign any primitive value to. (one type for single array, but alg must be generic for all primitive types).

I've written a method which can do this:

var element = Array.CreateInstance(dataType, dataDims);

foreach (var index in GetIndexes(dataDims))
{
     element.SetValue(SomeKindOfValue, index);
}

The function GetIndexes generates all possible indexes for the given dimensions:

     public static IEnumerable<int[]> GetIndexes(int[] dims)
     {
        int lastIndex = dims.Length - 1;
        int lastDim = dims[lastIndex];
        int[] Index = new int[dims.Length];
        int currentDim = lastIndex;

        while (currentDim >= 0) 
        {
            if (currentDim == lastIndex)
            {
                for (int i = 0; i < lastDim; i++)
                {
                    yield return Index;
                    Index[currentDim]++;
                }

                Index[currentDim] = 0;
                currentDim--;
                continue;
            }
            else
            {
                if (Index[currentDim] == dims[currentDim] - 1)
                {
                    Index[currentDim] = 0;
                    currentDim--;
                    continue;
                }
                else
                {
                    Index[currentDim]++;
                    currentDim = lastIndex;
                    continue;
                }
            }
        }
    }

EXAMPLE: for GetIndexes(new int[] {4,2,3}) the output will be:

0, 0, 0 |
0, 0, 1 |
0, 0, 2 | 
0, 1, 0 | 
0, 1, 1 |
0, 1, 2 | 
1, 0, 0 | 
1, 0, 1 | 
1, 0, 2 | 
1, 1, 0 | 
1, 1, 1 | 
1, 1, 2 | 
2, 0, 0 | 
2, 0, 1 | 
2, 0, 2 | 
2, 1, 0 | 
2, 1, 1 | 
2, 1, 2 | 
3, 0, 0 | 
3, 0, 1 | 
3, 0, 2 | 
3, 1, 0 | 
3, 1, 1 | 
3, 1, 2 |

The problem is, that assigning values this way is time-costly, and this alg need to be as efficient as possible.

I was thinking that multidimensional array is actually 1d array in the memory, so if I could access the pointer of each element, then I could assign the values w/o any calculations, and directly. The problem is that I was unable to find a way to create a pointer to a generic class Array(or to it's first element).

Basically, I'm trying to write a generic func of this (which will accept any primitive type as datatype of array, and will accept any multidimensional array):

public static unsafe void SetElementsByPointer(int[,] array, int[] values)
{
            if (values.Length != array.LongLength)
                 throw new Exception("array and values length mismatch.");

            fixed (int* pStart = array)
            {
                for (int i = 0; i < array.LongLength; i++)
                {
                    int* pElement = pStart + i;
                    *pElement = values[i];
                }
            }
        }

I will appreciate any other ideas for setting values into n-dimensional array, but the pointer way seems the most efficient, just that I can't figure it out

Thanks in advance.

Answer 1

To copy stuff, you may use this: https://dotnetfiddle.net/vTzJv4

// 1D array
int[] values = new int[] {
    1, 2, 3,
    4, 5, 6
};
// 2D array
int[,] marr = new int[2,3];

// Copy here
System.Buffer.BlockCopy((Array)values, 0, (Array)marr, 0, (int)marr.LongLength * sizeof(int));