UnsafeUnbounded.scala

  // ported with love from http://psy-lob-saw.blogspot.com/2014/04/notes-on-concurrent-ring-buffer-queue.html
  private[effect] final class UnsafeBounded[A](bound: Int) {
    private[this] val buffer = new Array[AnyRef](bound)

    private[this] val sequenceBuffer = new AtomicLongArray(bound)
    private[this] val head = new AtomicLong(0)
    private[this] val tail = new AtomicLong(0)

    0.until(bound).foreach(i => sequenceBuffer.set(i, i.toLong))

    private[this] val length = new AtomicInteger(0)

    def debug(): String = buffer.mkString("[", ", ", "]")

    def size(): Int = length.get()

    def put(data: A): Unit = {
      @tailrec
      def loop(): Long = {
        val currentTail = tail.get()
        val seq = sequenceBuffer.get(project(currentTail))
        val delta = seq - currentTail

        if (delta == 0) {
          if (tail.compareAndSet(currentTail, currentTail + 1))
            currentTail
          else
            loop()
        } else if (delta < 0) {
          throw FailureSignal
        } else {
          loop()
        }
      }

      val currentTail = loop()
      buffer(project(currentTail)) = data.asInstanceOf[AnyRef]
      sequenceBuffer.incrementAndGet(project(currentTail))
      length.incrementAndGet()

      ()
    }

    def take(): A = {
      @tailrec
      def loop(): Long = {
        val currentHead = head.get()
        val seq = sequenceBuffer.get(project(currentHead))
        val delta = seq - (currentHead + 1)

        if (delta == 0) {
          if (head.compareAndSet(currentHead, currentHead + 1))
            currentHead
          else
            loop()
        } else if (delta < 0) {
          throw FailureSignal
        } else {
          loop()
        }
      }

      val currentHead = loop()

      val back = buffer(project(currentHead)).asInstanceOf[A]
      buffer(project(currentHead)) = null
      sequenceBuffer.set(project(currentHead), currentHead + bound)
      length.decrementAndGet()

      back
    }

    // TODO handle wraparound negative
    private[this] def project(idx: Long): Int =
      (idx % bound).toInt
  }