FixedCapacityQueue

fixedCapQueue.scala

import scala.reflect.ClassTag

class FixedCapQueue[A: ClassTag](size: Int) {
  val queue: Array[A] = new Array(size)
  var start: Int = 0
  var end: Int = 0
  var empty = size > 0

  def take(): A = {
    if (end == start && empty) throw new Exception("Queue empty")

    val res = queue(start)
    queue.update(start, _: A) // let's not hold references
    start = (start + 1) % size
    empty = start == end
    res
  }

  def add(elem: A) : Unit = {
    if (end == start && !empty) throw new Error("Queue full")

    queue.update(end, elem)
    end = (end + 1) % size
    empty = false
  }
}