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package scala.reflect.internal.util
import scala.collection.mutable
import scala.collection.mutable.ArrayBuffer
import scala.collection.mutable.Builder
import scala.collection.mutable.SetBuilder
import scala.collection.generic.Clearable
import scala.runtime.AbstractFunction1
/** A bare-bones implementation of a mutable `Set` that uses weak references
* to hold the elements.
*
* This implementation offers only add/remove/test operations,
* therefore it does not fulfill the contract of Scala collection sets.
*/
class WeakHashSet[T <: AnyRef] extends AbstractFunction1[T, Boolean] with Clearable {
private val underlying = mutable.HashSet[WeakReferenceWithEquals[T]]()
/** Add the given element to this set. */
def +=(elem: T): this.type = {
underlying += new WeakReferenceWithEquals(elem)
this
}
/** Remove the given element from this set. */
def -=(elem: T): this.type = {
underlying -= new WeakReferenceWithEquals(elem)
this
}
/** Does the given element belong to this set? */
def contains(elem: T): Boolean =
underlying.contains(new WeakReferenceWithEquals(elem))
/** Does the given element belong to this set? */
def apply(elem: T): Boolean = contains(elem)
/** Return the number of elements in this set, including reclaimed elements. */
def size = underlying.size
/** Remove all elements in this set. */
def clear() = underlying.clear()
}
/** A WeakReference implementation that implements equals and hashCode by
* delegating to the referent.
*/
class WeakReferenceWithEquals[T <: AnyRef](ref: T) {
def get(): T = underlying.get()
override val hashCode = ref.hashCode
override def equals(other: Any): Boolean = other match {
case wf: WeakReferenceWithEquals[_] =>
underlying.get() == wf.get()
case _ =>
false
}
private val underlying = new java.lang.ref.WeakReference(ref)
}
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