scala.collection.mutable.LinkedHashMap.scala Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of scala-library Show documentation
Show all versions of scala-library Show documentation
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 scala.annotation.nowarn
import scala.collection.generic.DefaultSerializable
/** $factoryInfo
* @define Coll `LinkedHashMap`
* @define coll linked hash map
*/
@SerialVersionUID(3L)
object LinkedHashMap extends MapFactory[LinkedHashMap] {
def empty[K, V] = new LinkedHashMap[K, V]
def from[K, V](it: collection.IterableOnce[(K, V)]) =
it match {
case lhm: LinkedHashMap[K, V] => lhm
case _ => Growable.from(empty[K, V], it)
}
def newBuilder[K, V] = new GrowableBuilder(empty[K, V])
/** Class for the linked hash map entry, used internally.
*/
private[mutable] final class LinkedEntry[K, V](val key: K, var value: V)
extends HashEntry[K, LinkedEntry[K, V]] {
var earlier: LinkedEntry[K, V] = null
var later: LinkedEntry[K, V] = null
}
}
/** 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 K the type of the keys contained in this hash map.
* @tparam V the type of the values assigned to keys in this hash map.
*
* @define Coll `LinkedHashMap`
* @define coll linked hash map
* @define mayNotTerminateInf
* @define willNotTerminateInf
* @define orderDependent
* @define orderDependentFold
*/
class LinkedHashMap[K, V]
extends AbstractMap[K, V]
with SeqMap[K, V]
with MapOps[K, V, LinkedHashMap, LinkedHashMap[K, V]]
with StrictOptimizedIterableOps[(K, V), Iterable, LinkedHashMap[K, V]]
with StrictOptimizedMapOps[K, V, LinkedHashMap, LinkedHashMap[K, V]]
with MapFactoryDefaults[K, V, LinkedHashMap, Iterable]
with DefaultSerializable {
override def mapFactory: MapFactory[LinkedHashMap] = LinkedHashMap
// stepper / keyStepper / valueStepper are not overridden to use XTableStepper because that stepper
// would not return the elements in insertion order
private[collection] type Entry = LinkedHashMap.LinkedEntry[K, V]
private[collection] def _firstEntry: Entry = firstEntry
@transient protected var firstEntry: Entry = null
@transient protected var lastEntry: Entry = null
@transient private[this] var table: HashTable[K, V, Entry] = newHashTable
// Used by scala-java8-compat (private[mutable] erases to public, so Java code can access it)
private[mutable] def getTable: HashTable[K, V, Entry] = table
private def newHashTable =
new HashTable[K, V, Entry] {
def createNewEntry(key: K, value: V): Entry = {
val e = new Entry(key, value)
if (firstEntry eq null) firstEntry = e
else { lastEntry.later = e; e.earlier = lastEntry }
lastEntry = e
e
}
override def foreachEntry[U](f: Entry => U): Unit = {
var cur = firstEntry
while (cur ne null) {
f(cur)
cur = cur.later
}
}
}
override def last: (K, V) =
if (size > 0) (lastEntry.key, lastEntry.value)
else throw new NoSuchElementException("Cannot call .last on empty LinkedHashMap")
override def lastOption: Option[(K, V)] =
if (size > 0) Some((lastEntry.key, lastEntry.value))
else None
override def head: (K, V) =
if (size > 0) (firstEntry.key, firstEntry.value)
else throw new NoSuchElementException("Cannot call .head on empty LinkedHashMap")
override def headOption: Option[(K, V)] =
if (size > 0) Some((firstEntry.key, firstEntry.value))
else None
override def size = table.tableSize
override def knownSize: Int = size
override def isEmpty: Boolean = table.tableSize == 0
def get(key: K): Option[V] = {
val e = table.findEntry(key)
if (e == null) None
else Some(e.value)
}
override def contains(key: K): Boolean = {
if (getClass eq classOf[LinkedHashMap[_, _]])
table.findEntry(key) != null
else
super.contains(key) // A subclass might override `get`, use the default implementation `contains`.
}
override def put(key: K, value: V): Option[V] = {
val e = table.findOrAddEntry(key, value)
if (e eq null) None
else { val v = e.value; e.value = value; Some(v) }
}
override def update(key: K, value: V): Unit = {
val e = table.findOrAddEntry(key, value)
if (e ne null) e.value = value
}
override def remove(key: K): Option[V] = {
val e = table.removeEntry(key)
if (e eq null) None
else Some(remove0(e))
}
private[this] def remove0(e: Entry): V = {
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
e.value
}
def addOne(kv: (K, V)): this.type = { put(kv._1, kv._2); this }
def subtractOne(key: K): this.type = { remove(key); this }
def iterator: Iterator[(K, V)] = new AbstractIterator[(K, V)] {
private[this] 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 LinkedKeySet extends KeySet {
override def iterableFactory: IterableFactory[collection.Set] = LinkedHashSet
}
override def keySet: collection.Set[K] = new LinkedKeySet
override def keysIterator: Iterator[K] = new AbstractIterator[K] {
private[this] 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 updateWith for performance, so we can do the update while hashing
// the input key only once and performing one lookup into the hash table
override def updateWith(key: K)(remappingFunction: Option[V] => Option[V]): Option[V] = {
val keyIndex = table.index(table.elemHashCode(key))
val entry = table.findEntry0(key, keyIndex)
val previousValue =
if (entry == null) None
else Some(entry.value)
val nextValue = remappingFunction(previousValue)
(previousValue, nextValue) match {
case (None, None) => // do nothing
case (Some(_), None) =>
remove0(entry)
table.removeEntry0(key, keyIndex)
case (None, Some(value)) =>
table.addEntry0(table.createNewEntry(key, value), keyIndex)
case (Some(_), Some(value)) =>
entry.value = value
}
nextValue
}
override def valuesIterator: Iterator[V] = new AbstractIterator[V] {
private[this] 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: ((K, V)) => U): Unit = {
var cur = firstEntry
while (cur ne null) {
f((cur.key, cur.value))
cur = cur.later
}
}
override def foreachEntry[U](f: (K, V) => U): Unit = {
var cur = firstEntry
while (cur ne null) {
f(cur.key, cur.value)
cur = cur.later
}
}
override def clear(): Unit = {
table.clearTable()
firstEntry = null
lastEntry = null
}
private def writeObject(out: java.io.ObjectOutputStream): Unit = {
out.defaultWriteObject()
table.serializeTo(out, { entry =>
out.writeObject(entry.key)
out.writeObject(entry.value)
})
}
private def readObject(in: java.io.ObjectInputStream): Unit = {
in.defaultReadObject()
table = newHashTable
table.init(in, table.createNewEntry(in.readObject().asInstanceOf[K], in.readObject().asInstanceOf[V]))
}
@nowarn("""cat=deprecation&origin=scala\.collection\.Iterable\.stringPrefix""")
override protected[this] def stringPrefix = "LinkedHashMap"
}