FastIntAsTextToStringBuilder

.cs

        static unsafe void FastIntAsTextToStringBuilder(int input, StringBuilder sb)
        {
            const string sign = "-";
            const int signSize = 1;
            const int size = 15 + signSize;

            var charbuf = stackalloc char[size];
            var p = charbuf + size - 1;

            var minDigits = 1;
            var value = (uint)(input > 0 ? input : -input);
            while (--minDigits >= 0 || value != 0)
            {
                *--p = (char)(value % 10 + '0');
                value /= 10;
            }

            if (input < 0)
            {
                for (var i = signSize - 1; i >= 0; i--)
                {
                    *--p = sign[i];
                }
            }

            sb.Append(p, (int)(charbuf + (size - 1) - p));
        }