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Standard library for the Scala Programming Language
/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc.
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala
package collection
package mutable
import generic._
/** $factoryInfo
* @define Coll `LinkedHashMap`
* @define coll linked hash map
*/
object LinkedHashMap extends MutableMapFactory[LinkedHashMap] {
implicit def canBuildFrom[A, B]: CanBuildFrom[Coll, (A, B), LinkedHashMap[A, B]] =
ReusableCBF.asInstanceOf[CanBuildFrom[Coll, (A, B), LinkedHashMap[A, B]]]
private [this] val ReusableCBF = new MapCanBuildFrom[Any, Any]
def empty[A, B] = new LinkedHashMap[A, B]
}
/** This class implements mutable maps using a hashtable.
* The iterator and all traversal methods of this class visit elements in the order they were inserted.
*
* @tparam A the type of the keys contained in this hash map.
* @tparam B the type of the values assigned to keys in this hash map.
*
* @define Coll `LinkedHashMap`
* @define coll linked hash map
* @define thatinfo the class of the returned collection. In the standard library configuration,
* `That` is always `LinkedHashMap[A, B]` if the elements contained in the resulting collection are
* pairs of type `(A, B)`. This is because an implicit of type `CanBuildFrom[LinkedHashMap, (A, B), LinkedHashMap[A, B]]`
* is defined in object `LinkedHashMap`. Otherwise, `That` resolves to the most specific type that doesn't have
* to contain pairs of type `(A, B)`, which is `Iterable`.
* @define bfinfo an implicit value of class `CanBuildFrom` which determines the
* result class `That` from the current representation type `Repr`
* and the new element type `B`. This is usually the `canBuildFrom` value
* defined in object `LinkedHashMap`.
* @define mayNotTerminateInf
* @define willNotTerminateInf
* @define orderDependent
* @define orderDependentFold
*/
@SerialVersionUID(1L)
class LinkedHashMap[A, B] extends AbstractMap[A, B]
with Map[A, B]
with MapLike[A, B, LinkedHashMap[A, B]]
with HashTable[A, LinkedEntry[A, B]]
with Serializable
{
override def empty = LinkedHashMap.empty[A, B]
override def size = tableSize
type Entry = LinkedEntry[A, B]
@transient protected var firstEntry: Entry = null
@transient protected var lastEntry: Entry = null
def get(key: A): Option[B] = {
val e = findEntry(key)
if (e == null) None
else Some(e.value)
}
override def contains(key: A): Boolean = {
if (getClass eq classOf[LinkedHashMap[_, _]])
findEntry(key) != null
else
super.contains(key) // A subclass might override `get`, use the default implementation `contains`.
}
override def put(key: A, value: B): Option[B] = {
val e = findOrAddEntry(key, value)
if (e eq null) None
else { val v = e.value; e.value = value; Some(v) }
}
override def remove(key: A): Option[B] = {
val e = removeEntry(key)
if (e eq null) None
else {
if (e.earlier eq null) firstEntry = e.later
else e.earlier.later = e.later
if (e.later eq null) lastEntry = e.earlier
else e.later.earlier = e.earlier
e.earlier = null // Null references to prevent nepotism
e.later = null
Some(e.value)
}
}
@deprecatedOverriding("+= should not be overridden so it stays consistent with put.", "2.11.0")
def += (kv: (A, B)): this.type = { put(kv._1, kv._2); this }
@deprecatedOverriding("-= should not be overridden so it stays consistent with remove.", "2.11.0")
def -=(key: A): this.type = { remove(key); this }
def iterator: Iterator[(A, B)] = new AbstractIterator[(A, B)] {
private var cur = firstEntry
def hasNext = cur ne null
def next =
if (hasNext) { val res = (cur.key, cur.value); cur = cur.later; res }
else Iterator.empty.next()
}
protected class FilteredKeys(p: A => Boolean) extends super.FilteredKeys(p) {
override def empty = LinkedHashMap.empty
}
override def filterKeys(p: A => Boolean): scala.collection.Map[A, B] = new FilteredKeys(p)
protected class MappedValues[C](f: B => C) extends super.MappedValues[C](f) {
override def empty = LinkedHashMap.empty
}
override def mapValues[C](f: B => C): scala.collection.Map[A, C] = new MappedValues(f)
protected class DefaultKeySet extends super.DefaultKeySet {
override def empty = LinkedHashSet.empty
}
override def keySet: scala.collection.Set[A] = new DefaultKeySet
override def keysIterator: Iterator[A] = new AbstractIterator[A] {
private var cur = firstEntry
def hasNext = cur ne null
def next =
if (hasNext) { val res = cur.key; cur = cur.later; res }
else Iterator.empty.next()
}
override def valuesIterator: Iterator[B] = new AbstractIterator[B] {
private var cur = firstEntry
def hasNext = cur ne null
def next =
if (hasNext) { val res = cur.value; cur = cur.later; res }
else Iterator.empty.next()
}
override def foreach[U](f: ((A, B)) => U) {
var cur = firstEntry
while (cur ne null) {
f((cur.key, cur.value))
cur = cur.later
}
}
protected override def foreachEntry[U](f: Entry => U) {
var cur = firstEntry
while (cur ne null) {
f(cur)
cur = cur.later
}
}
protected def createNewEntry[B1](key: A, value: B1): Entry = {
val e = new Entry(key, value.asInstanceOf[B])
if (firstEntry eq null) firstEntry = e
else { lastEntry.later = e; e.earlier = lastEntry }
lastEntry = e
e
}
override def clear() {
clearTable()
firstEntry = null
lastEntry = null
}
private def writeObject(out: java.io.ObjectOutputStream) {
serializeTo(out, { entry =>
out.writeObject(entry.key)
out.writeObject(entry.value)
})
}
private def readObject(in: java.io.ObjectInputStream) {
firstEntry = null
lastEntry = null
init(in, createNewEntry(in.readObject().asInstanceOf[A], in.readObject()))
}
}