breeze.util.Interner.scala Maven / Gradle / Ivy
package breeze.util;
/*
Copyright 2009 David Hall, Daniel Ramage
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
import scala.collection.mutable.WeakHashMap;
import scala.collection.generic._;
import scala.collection._;
import scala.collection.Traversable;
import scala.collection.TraversableLike;
import java.lang.ref.WeakReference
import java.io.{ObjectInputStream, ObjectOutputStream}
;
/**
* Class that mimics Java's string interner, but for anything.
* Threadsafe.
*
* @author dlwh
*/
@SerialVersionUID(1L)
class Interner[T] extends (T=>T) with Serializable {
override def apply(t :T) = intern(t);
def intern(t : T):T = synchronized {
inner.getOrElseUpdate(t,new WeakReference[T](t)).get;
}
def clear() = inner.clear();
def size = inner.size;
def internAll[C<:TraversableLike[T,C] with Traversable[T],That](c : C)(implicit bf:CanBuildFrom[T,That,C]) = c map apply
def internAll(c : List[T]) = c map apply
def internAll(c : Array[T]) = c map apply
def internAll(c : Set[T]) = c map apply
def internKeys[V](c: scala.collection.Map[T,V]) = {
Map[T,V]() ++ c.map{ case (k,v) => (intern(k),v)}
}
def internValues[K](c: scala.collection.Map[K,T]) = {
Map[K,T]() ++ c.map{ case (k,v) => (k,intern(v))}
}
@transient private var inner = new WeakHashMap[T,WeakReference[T]];
@throws(classOf[java.io.IOException])
private def writeObject(oos: ObjectOutputStream ) {
oos.defaultWriteObject();
}
@throws(classOf[java.io.IOException])
@throws(classOf[ClassNotFoundException])
private def readObject(ois: ObjectInputStream) {
ois.defaultReadObject();
inner = new WeakHashMap[T,WeakReference[T]]
}
}
object Interner {
private val typedInterners = new scala.collection.mutable.HashMap[Class[_],Interner[_]] {
override def default(c: Class[_]) = getOrElseUpdate(c,new Interner[Any]);
}
def apply[T](implicit m: scala.reflect.Manifest[T]) = forClass[T](m.runtimeClass.asInstanceOf[Class[T]]);
def forClass[T](c: Class[T]) = typedInterners(c).asInstanceOf[Interner[T]];
}