private def rowIx()

in http-core/src/main/scala/org/apache/pekko/http/impl/engine/parsing/HttpHeaderParser.scala [334:386]
49 lines of code
15 McCabe index (conditional complexity)

  private def rowIx(msb: Int) = (msb - 1) * 3
  private def nodeBits(rowIx: Int, char: Int) = (((rowIx / 3 + 1) << 8) | char).toChar

  /**
   * Renders the trie structure into an ASCII representation.
   */
  def formatTrie: String = {
    def recurse(nodeIx: Int = 0): (Seq[List[String]], Int) = {
      def recurseAndPrefixLines(subNodeIx: Int, p1: String, p2: String, p3: String) = {
        val (lines, mainIx) = recurse(subNodeIx)
        val prefixedLines = lines.zipWithIndex.map {
          case (line, ix) => (if (ix < mainIx) p1 else if (ix > mainIx) p3 else p2) :: line
        }
        prefixedLines -> mainIx
      }
      def branchLines(dataIx: Int, p1: String, p2: String, p3: String) = branchData(dataIx) match {
        case 0         => Seq.empty
        case subNodeIx => recurseAndPrefixLines(subNodeIx, p1, p2, p3)._1
      }
      val node = nodes(nodeIx)
      val char = escape((node & 0xFF).toChar)
      node >>> 8 match {
        case 0 => recurseAndPrefixLines(nodeIx + 1, "  ", char + "-", "  ")
        case msb => node & 0xFF match {
            case 0 => values(msb - 1) match {
                case ValueBranch(_, valueParser, branchRootNodeIx, _) =>
                  val pad = " " * (valueParser.headerName.length + 3)
                  recurseAndPrefixLines(branchRootNodeIx, pad, "(" + valueParser.headerName + ")-", pad)
                case vp: HeaderValueParser => Seq(" (" :: vp.headerName :: ")" :: Nil) -> 0
                case value: RawHeader      => Seq(" *" :: value.toString :: Nil) -> 0
                case value                 => Seq(" " :: value.toString :: Nil) -> 0
              }
            case nodeChar =>
              val rix = rowIx(msb)
              val preLines = branchLines(rix, "  ", "┌─", "| ")
              val postLines = branchLines(rix + 2, "| ", "└─", "  ")
              val p1 = if (preLines.nonEmpty) "| " else "  "
              val p3 = if (postLines.nonEmpty) "| " else "  "
              val (matchLines, mainLineIx) = recurseAndPrefixLines(branchData(rix + 1), p1, char + '-', p3)
              (preLines ++ matchLines ++ postLines, mainLineIx + preLines.size)
          }
      }
    }
    val sb = new JStringBuilder()
    val (lines, mainLineIx) = recurse()
    lines.zipWithIndex.foreach {
      case (line, ix) =>
        sb.append(if (ix == mainLineIx) '-' else ' ')
        line.foreach(s => sb.append(s))
        sb.append('\n')
    }
    sb.toString
  }