Fastest way to separate the digits of an int into an array in .NET?

Question

I want to separate the digits of an integer, say 12345, into an array of bytes {1,2,3,4,5}, but I want the most performance effective way to do that, because my program does tha

Answer 1

The allocation of a new int[] every time takes up a significant amount of the time according to my testing. If you know these values will be used once and thrown away before the next call, you could instead reuse a static array for a significant speed improvement:

    private static readonly int[] _buffer = new int[10];
    public static int[] ConvertToArrayOfDigits(int value)
    {
        for (int index = 9; index >= 0; index--)
        {
            _buffer[index] = value % 10;
            value = value / 10;
        }
        return _buffer;
    }

to keep the code small, I am returning trailing zero's for smaller numbers, but this could easily be changed by using 9 different static arrays instead (or an array of arrays).

Alternatively, 2 seperate ConvertToArrayOfDigits methods could be provided, one taking a precreated int array as an extra parameter, and one without that which creates the resulting buffer prior to calling the first method.

    public static void ConvertToArrayOfDigits(int value, int[] digits) { ... }
    public static int[] ConvertToArrayOfDigits(int value)
    {
        int size = DetermineDigitCount(value);
        int[] digits = new int[size];
        ConvertToArrayOfDigits(value, digits);
        return digits;
    }

This way, it would be up to the caller to potentially create a static reusable buffer if their usecase allows for it.