copyTo(prefix, 0, byteCount)
    for (i in 0 until 16) {
      if (prefix.exhausted()) {
        break
      }
      val codePoint = prefix.readUtf8CodePoint()
      if (Character.isISOControl(codePoint) && !Character.isWhitespace(codePoint)) {
        return false
      }
    }
    return true
  } catch (_: EOFException) {
    return false // Truncated UTF-8 sequence.
  }

                }
                c[ci++] = ' ';
                i = src[srcIndex + si] & 0xFF;
                toHexChars(i, c, ci, 2);
                ci += 2;
                if (i < 0 || Character.isISOControl((char) i)) {
                    d[si % 16] = '.';
                } else {
                    d[si % 16] = (char) i;
                }
            } while (++si % 16 != 0);
            c[ci++] = ' ';