static void writeHexByte(char[] data, int pos, byte b) {
    data[pos + 0] = HEX_DIGITS[(b >> 4) & 0xf];
    data[pos + 1] = HEX_DIGITS[b & 0xf];
  }
Inspired by {@code okio.Buffer.writeLong}
zipkin/src/main/java/zipkin2/Span.java