in atlas-core/src/main/scala/com/netflix/atlas/core/model/ItemId.scala [120:127]
private def hexToInt(c: Char): Int = {
c match {
case _ if c >= '0' && c <= '9' => c - '0'
case _ if c >= 'a' && c <= 'f' => c - 'a' + 10
case _ if c >= 'A' && c <= 'F' => c - 'A' + 10
case _ => throw new IllegalArgumentException(s"invalid hex digit: $c")
}
}