Implementing Int64.ToString without using string [duplicate]

Thanks to @SLaks for the idea and @gypsoCoder for pointing me to a related answer. This does the trick:

  private static byte[] chars = new byte[] { (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6', (byte)'7', (byte)'8', (byte)'9' };

  /// <summary>
  /// Converts a long to a byte, in string format
  /// 
  /// This method essentially performs the same operation as ToString, with the output being a byte array,
  /// rather than a string
  /// </summary>
  /// <param name="val">long integer input, with as many or fewer digits as the output buffer length</param>
  /// <param name="longBuffer">output buffer</param>
  private void ConvertLong(long val, byte[] longBuffer)
  {
     // The buffer must be large enough to hold the output

     long limit = (long)Math.Pow(10, longBuffer.Length - 1);
     if (val >= limit * 10)
     {
        throw new ArgumentException("Value will not fit in output buffer");
     }

     // Note: Depending on your output expectation, you may do something different to initialize the data here.
     // My expectation was that the string would be at the "front" in string format, e.g. the end of the array, with '0' in any extra space

     int bufferIndex = 1;
     for (long longIndex = limit; longIndex > val; longIndex /= 10)
     {
        longBuffer[longBuffer.Length - bufferIndex] = 0;
        ++bufferIndex;
     }

     // Finally, loop through the digits of the input, converting them from a static buffer of byte values

     while (val > 0)
     {
        longBuffer[longBuffer.Length - bufferIndex] = chars[val % 10];
        val /= 10;
        ++bufferIndex;
     }
  }

I should note that this only accepts positive numbers and doesn't do any validation of that or anything else. Just a basic algorithm to accomplish the goal of converting a long to a string to a byte array without allocating any strings.