Fast unit ipaddress to string

FastIntegerToIPAddress.cs

public unsafe static string FastIntegerToIPAddress(uint input)
{
    var input0 = (input & 0xff000000) >> 24;
    var input1 = (input & 0xff0000) >> 16;
    var input2 = (input & 0xff00) >> 8;
    var input3 = (input & 0xff);

    var length0 = input0 > 99 ? 3 : input0 > 9 ? 2 : 1;
    var length1 = input1 > 99 ? 3 : input1 > 9 ? 2 : 1;
    var length2 = input2 > 99 ? 3 : input2 > 9 ? 2 : 1;
    var length3 = input3 > 99 ? 3 : input3 > 9 ? 2 : 1;

    var value = new string('\0', length0 + length1 + length2 + length3 + 3);

    fixed (char* ptr = value)
    {
        var start0 = ptr + length0;
        var start1 = 1 + ptr + length1 + length0;
        var start2 = 2 + ptr + length2 + length1 + length0;
        var start3 = 2 + ptr + length3 + length2 + length1 + length0;

        *start0 = '.';
        *start1 = '.';
        *start2 = '.';

        if (length0 == 3)
        {
            var digit = input0 * 41 >> 12;
            input0 -= digit * 100;
            *(start0 - 3) = (char)('0' + digit);
        }

        if (length1 == 3)
        {
            var digit = input1 * 41 >> 12;
            input1 -= digit * 100;
            *(start1 - 3) = (char)('0' + digit);
        }

        if (length2 == 3)
        {
            var digit = input2 * 41 >> 12;
            input2 -= digit * 100;
            *(start2 - 3) = (char)('0' + digit);
        }

        if (length3 == 3)
        {
            var digit = input3 * 41 >> 12;
            input3 -= digit * 100;
            *(start3 - 2) = (char)('0' + digit);
        }

        if (length0 >= 2)
        {
            var digit = input0 * 205 >> 11;
            input0 -= digit * 10;
            *(start0 - 2) = (char)('0' + digit);
        }

        if (length1 >= 2)
        {
            var digit = input1 * 205 >> 11;
            input1 -= digit * 10;
            *(start1 - 2) = (char)('0' + digit);
        }

        if (length2 >= 2)
        {
            var digit = input2 * 205 >> 11;
            input2 -= digit * 10;
            *(start2 - 2) = (char)('0' + digit);
        }

        if (length3 >= 2)
        {
            var digit = input3 * 205 >> 11;
            input3 -= digit * 10;
            *(start3 - 1) = (char)('0' + digit);
        }

        *(start0 - 1) = (char)('0' + input0);
        *(start1 - 1) = (char)('0' + input1);
        *(start2 - 1) = (char)('0' + input2);
        *start3 = (char)('0' + input3);
    }

    return value;
}