) {
  var codePoint: Int
  var i = pos
  while (i < limit) {
    codePoint = encoded.codePointAt(i)
    if (codePoint == '%'.code && i + 2 < limit) {
      val d1 = encoded[i + 1].parseHexDigit()
      val d2 = encoded[i + 2].parseHexDigit()
      if (d1 != -1 && d2 != -1) {
        writeByte((d1 shl 4) + d2)
        i += 2
        i += Character.charCount(codePoint)
        continue
      }

        return null // Wrong delimiter.
      }
    }

    // Read a group, one to four hex digits.
    var value = 0
    groupOffset = i
    while (i < limit) {
      val hexDigit = input[i].parseHexDigit()
      if (hexDigit == -1) break
      value = (value shl 4) + hexDigit
      i++
    }
    val groupLength = i - groupOffset
    if (groupLength == 0 || groupLength > 4) return null // Group is the wrong size.

    name.equals("Cookie", ignoreCase = true) ||
    name.equals("Proxy-Authorization", ignoreCase = true) ||
    name.equals("Set-Cookie", ignoreCase = true)
}

internal fun Char.parseHexDigit(): Int =
  when (this) {
    in '0'..'9' -> this - '0'
    in 'a'..'f' -> this - 'a' + 10
    in 'A'..'F' -> this - 'A' + 10
    else -> -1
  }