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package scala.reactive
package util






class WeakBuffer[M <: AnyRef](initialSize: Int = 4) {
  protected[reactive] var array = new Array[WeakRef[M]](initialSize)
  protected[reactive] var size = 0

  def apply(idx: Int) = array(idx).get

  def addEntry(elem: M) {
    if (size == array.length) growArray()
    array(size) = new WeakRef(elem)
    size += 1
  }

  def removeEntry(elem: M) {
    var i = 0
    while (i < size) {
      if (array(i).get eq elem) {
        removeEntryAt(i)
        i = size
      }
      i += 1
    }
  }

  def invalidateEntry(elem: M) {
    var i = 0
    while (i < size) {
      if (array(i).get eq elem) {
        array(i).clear()
        i = size
      }
      i += 1
    }
  }

  protected[reactive] def addRef(ref: WeakRef[M]) {
    if (size == array.length) growArray()
    array(size) = ref
    size += 1
  }

  def removeEntryAt(idx: Int) {
    if (idx < size) {
      array(idx) = array(size - 1)
      array(size - 1) = null
      size -= 1
    } else throw new IndexOutOfBoundsException
  }

  private def growArray() {
    val oldarray = array
    val oldsize = size
    array = new Array[WeakRef[M]](array.length * 2)
    size = 0
    var i = 0
    while (i < oldsize) {
      val entry = oldarray(i)
      if (entry != null && entry.get != null) {
        array(size) = entry
        size += 1
      }
      i += 1
    }
  }

  override def toString = getClass.getSimpleName + array.filter(_ != null).map(_.get).mkString(s"($size, ${array.length}:", ", ", ")")
}