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/*
* 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.collection
package mutable
import scala.annotation.{nowarn, tailrec}
import scala.collection.Stepper.EfficientSplit
import scala.collection.generic.DefaultSerializationProxy
import scala.util.hashing.MurmurHash3
/** This class implements mutable maps using a hashtable.
*
* @see [[https://docs.scala-lang.org/overviews/collections/concrete-mutable-collection-classes.html#hash-tables "Scala's Collection Library overview"]]
* section on `Hash Tables` for more information.
*
* @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 `mutable.HashMap`
* @define coll mutable hash map
* @define mayNotTerminateInf
* @define willNotTerminateInf
*/
@deprecatedInheritance("HashMap will be made final; use .withDefault for the common use case of computing a default value", "2.13.0")
class HashMap[K, V](initialCapacity: Int, loadFactor: Double)
extends AbstractMap[K, V]
with MapOps[K, V, HashMap, HashMap[K, V]]
with StrictOptimizedIterableOps[(K, V), Iterable, HashMap[K, V]]
with StrictOptimizedMapOps[K, V, HashMap, HashMap[K, V]]
with MapFactoryDefaults[K, V, HashMap, Iterable]
with Serializable {
/* The HashMap class holds the following invariant:
* - For each i between 0 and table.length, the bucket at table(i) only contains keys whose hash-index is i.
* - Every bucket is sorted in ascendent hash order
* - The sum of the lengths of all buckets is equal to contentSize.
*/
def this() = this(HashMap.defaultInitialCapacity, HashMap.defaultLoadFactor)
import HashMap.Node
/** The actual hash table. */
private[this] var table = new Array[Node[K, V]](tableSizeFor(initialCapacity))
/** The next size value at which to resize (capacity * load factor). */
private[this] var threshold: Int = newThreshold(table.length)
private[this] var contentSize = 0
override def size: Int = contentSize
/** Performs the inverse operation of improveHash. In this case, it happens to be identical to improveHash*/
@`inline` private[collection] def unimproveHash(improvedHash: Int): Int = improveHash(improvedHash)
/** Computes the improved hash of an original (`any.##`) hash. */
@`inline` private[this] def improveHash(originalHash: Int): Int = {
// Improve the hash by xoring the high 16 bits into the low 16 bits just in case entropy is skewed towards the
// high-value bits. We only use the lowest bits to determine the hash bucket. This is the same improvement
// algorithm as in java.util.HashMap.
//
// This function is also its own inverse. That is, for all ints i, improveHash(improveHash(i)) = i
// this allows us to retrieve the original hash when we need it, for instance when appending to an immutable.HashMap
// and that is why unimproveHash simply forwards to this method
originalHash ^ (originalHash >>> 16)
}
/** Computes the improved hash of this key */
@`inline` private[this] def computeHash(o: K): Int = improveHash(o.##)
@`inline` private[this] def index(hash: Int) = hash & (table.length - 1)
override def contains(key: K): Boolean = findNode(key) ne null
@`inline` private[this] def findNode(key: K): Node[K, V] = {
val hash = computeHash(key)
table(index(hash)) match {
case null => null
case nd => nd.findNode(key, hash)
}
}
override def sizeHint(size: Int): Unit = {
val target = tableSizeFor(((size + 1).toDouble / loadFactor).toInt)
if(target > table.length) growTable(target)
}
override def addAll(xs: IterableOnce[(K, V)]): this.type = {
sizeHint(xs.knownSize)
xs match {
case hm: immutable.HashMap[K, V] =>
hm.foreachWithHash((k, v, h) => put0(k, v, improveHash(h), getOld = false))
this
case hm: mutable.HashMap[K, V] =>
val iter = hm.nodeIterator
while (iter.hasNext) {
val next = iter.next()
put0(next.key, next.value, next.hash, getOld = false)
}
this
case thatMap: Map[K, V] =>
thatMap.foreachEntry { (key: K, value: V) =>
put0(key, value, improveHash(key.##), getOld = false)
}
this
case _ =>
super.addAll(xs)
}
}
// 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] = {
if (getClass != classOf[HashMap[_, _]]) {
// subclasses of HashMap might customise `get` ...
super.updateWith(key)(remappingFunction)
} else {
val hash = computeHash(key)
val indexedHash = index(hash)
var foundNode: Node[K, V] = null
var previousNode: Node[K, V] = null
table(indexedHash) match {
case null =>
case nd =>
@tailrec
def findNode(prev: Node[K, V], nd: Node[K, V], k: K, h: Int): Unit = {
if (h == nd.hash && k == nd.key) {
previousNode = prev
foundNode = nd
}
else if ((nd.next eq null) || (nd.hash > h)) ()
else findNode(nd, nd.next, k, h)
}
findNode(null, nd, key, hash)
}
val previousValue = foundNode match {
case null => None
case nd => Some(nd.value)
}
val nextValue = remappingFunction(previousValue)
(previousValue, nextValue) match {
case (None, None) => // do nothing
case (Some(_), None) =>
if (previousNode != null) previousNode.next = foundNode.next
else table(indexedHash) = foundNode.next
contentSize -= 1
case (None, Some(value)) =>
val newIndexedHash =
if (contentSize + 1 >= threshold) {
growTable(table.length * 2)
index(hash)
} else indexedHash
put0(key, value, false, hash, newIndexedHash)
case (Some(_), Some(newValue)) => foundNode.value = newValue
}
nextValue
}
}
override def subtractAll(xs: IterableOnce[K]): this.type = {
if (size == 0) {
return this
}
xs match {
case hs: immutable.HashSet[K] =>
hs.foreachWithHashWhile { (k, h) =>
remove0(k, improveHash(h))
size > 0
}
this
case hs: mutable.HashSet[K] =>
val iter = hs.nodeIterator
while (iter.hasNext) {
val next = iter.next()
remove0(next.key, next.hash)
if (size == 0) return this
}
this
case _ => super.subtractAll(xs)
}
}
/** Adds a key-value pair to this map
*
* @param key the key to add
* @param value the value to add
* @param hash the **improved** hashcode of `key` (see computeHash)
* @param getOld if true, then the previous value for `key` will be returned, otherwise, false
*/
private[this] def put0(key: K, value: V, hash: Int, getOld: Boolean): Some[V] = {
if(contentSize + 1 >= threshold) growTable(table.length * 2)
val idx = index(hash)
put0(key, value, getOld, hash, idx)
}
private[this] def put0(key: K, value: V, getOld: Boolean): Some[V] = {
if(contentSize + 1 >= threshold) growTable(table.length * 2)
val hash = computeHash(key)
val idx = index(hash)
put0(key, value, getOld, hash, idx)
}
private[this] def put0(key: K, value: V, getOld: Boolean, hash: Int, idx: Int): Some[V] = {
table(idx) match {
case null =>
table(idx) = new Node[K, V](key, hash, value, null)
case old =>
var prev: Node[K, V] = null
var n = old
while((n ne null) && n.hash <= hash) {
if(n.hash == hash && key == n.key) {
val old = n.value
n.value = value
return if(getOld) Some(old) else null
}
prev = n
n = n.next
}
if(prev eq null) table(idx) = new Node(key, hash, value, old)
else prev.next = new Node(key, hash, value, prev.next)
}
contentSize += 1
null
}
private def remove0(elem: K) : Node[K, V] = remove0(elem, computeHash(elem))
/** Removes a key from this map if it exists
*
* @param elem the element to remove
* @param hash the **improved** hashcode of `element` (see computeHash)
* @return the node that contained element if it was present, otherwise null
*/
private[this] def remove0(elem: K, hash: Int) : Node[K, V] = {
val idx = index(hash)
table(idx) match {
case null => null
case nd if nd.hash == hash && nd.key == elem =>
// first element matches
table(idx) = nd.next
contentSize -= 1
nd
case nd =>
// find an element that matches
var prev = nd
var next = nd.next
while((next ne null) && next.hash <= hash) {
if(next.hash == hash && next.key == elem) {
prev.next = next.next
contentSize -= 1
return next
}
prev = next
next = next.next
}
null
}
}
private[this] abstract class HashMapIterator[A] extends AbstractIterator[A] {
private[this] var i = 0
private[this] var node: Node[K, V] = null
private[this] val len = table.length
protected[this] def extract(nd: Node[K, V]): A
def hasNext: Boolean = {
if(node ne null) true
else {
while(i < len) {
val n = table(i)
i += 1
if(n ne null) { node = n; return true }
}
false
}
}
def next(): A =
if(!hasNext) Iterator.empty.next()
else {
val r = extract(node)
node = node.next
r
}
}
override def iterator: Iterator[(K, V)] =
if(size == 0) Iterator.empty
else new HashMapIterator[(K, V)] {
protected[this] def extract(nd: Node[K, V]) = (nd.key, nd.value)
}
override def keysIterator: Iterator[K] =
if(size == 0) Iterator.empty
else new HashMapIterator[K] {
protected[this] def extract(nd: Node[K, V]) = nd.key
}
override def valuesIterator: Iterator[V] =
if(size == 0) Iterator.empty
else new HashMapIterator[V] {
protected[this] def extract(nd: Node[K, V]) = nd.value
}
/** Returns an iterator over the nodes stored in this HashMap */
private[collection] def nodeIterator: Iterator[Node[K, V]] =
if(size == 0) Iterator.empty
else new HashMapIterator[Node[K, V]] {
protected[this] def extract(nd: Node[K, V]) = nd
}
override def stepper[S <: Stepper[_]](implicit shape: StepperShape[(K, V), S]): S with EfficientSplit =
shape.
parUnbox(new convert.impl.AnyTableStepper[(K, V), Node[K, V]](size, table, _.next, node => (node.key, node.value), 0, table.length)).
asInstanceOf[S with EfficientSplit]
override def keyStepper[S <: Stepper[_]](implicit shape: StepperShape[K, S]): S with EfficientSplit = {
import convert.impl._
val s = shape.shape match {
case StepperShape.IntShape => new IntTableStepper[Node[K, V]] (size, table, _.next, _.key.asInstanceOf[Int], 0, table.length)
case StepperShape.LongShape => new LongTableStepper[Node[K, V]] (size, table, _.next, _.key.asInstanceOf[Long], 0, table.length)
case StepperShape.DoubleShape => new DoubleTableStepper[Node[K, V]](size, table, _.next, _.key.asInstanceOf[Double], 0, table.length)
case _ => shape.parUnbox(new AnyTableStepper[K, Node[K, V]](size, table, _.next, _.key, 0, table.length))
}
s.asInstanceOf[S with EfficientSplit]
}
override def valueStepper[S <: Stepper[_]](implicit shape: StepperShape[V, S]): S with EfficientSplit = {
import convert.impl._
val s = shape.shape match {
case StepperShape.IntShape => new IntTableStepper[Node[K, V]] (size, table, _.next, _.value.asInstanceOf[Int], 0, table.length)
case StepperShape.LongShape => new LongTableStepper[Node[K, V]] (size, table, _.next, _.value.asInstanceOf[Long], 0, table.length)
case StepperShape.DoubleShape => new DoubleTableStepper[Node[K, V]](size, table, _.next, _.value.asInstanceOf[Double], 0, table.length)
case _ => shape.parUnbox(new AnyTableStepper[V, Node[K, V]](size, table, _.next, _.value, 0, table.length))
}
s.asInstanceOf[S with EfficientSplit]
}
private[this] def growTable(newlen: Int) = {
if (newlen < 0)
throw new RuntimeException(s"new HashMap table size $newlen exceeds maximum")
var oldlen = table.length
threshold = newThreshold(newlen)
if(size == 0) table = new Array(newlen)
else {
table = java.util.Arrays.copyOf(table, newlen)
val preLow: Node[K, V] = new Node(null.asInstanceOf[K], 0, null.asInstanceOf[V], null)
val preHigh: Node[K, V] = new Node(null.asInstanceOf[K], 0, null.asInstanceOf[V], null)
// Split buckets until the new length has been reached. This could be done more
// efficiently when growing an already filled table to more than double the size.
while(oldlen < newlen) {
var i = 0
while (i < oldlen) {
val old = table(i)
if(old ne null) {
preLow.next = null
preHigh.next = null
var lastLow: Node[K, V] = preLow
var lastHigh: Node[K, V] = preHigh
var n = old
while(n ne null) {
val next = n.next
if((n.hash & oldlen) == 0) { // keep low
lastLow.next = n
lastLow = n
} else { // move to high
lastHigh.next = n
lastHigh = n
}
n = next
}
lastLow.next = null
if(old ne preLow.next) table(i) = preLow.next
if(preHigh.next ne null) {
table(i + oldlen) = preHigh.next
lastHigh.next = null
}
}
i += 1
}
oldlen *= 2
}
}
}
private[this] def tableSizeFor(capacity: Int) =
(Integer.highestOneBit((capacity-1).max(4))*2).min(1 << 30)
private[this] def newThreshold(size: Int) = (size.toDouble * loadFactor).toInt
override def clear(): Unit = {
java.util.Arrays.fill(table.asInstanceOf[Array[AnyRef]], null)
contentSize = 0
}
def get(key: K): Option[V] = findNode(key) match {
case null => None
case nd => Some(nd.value)
}
@throws[NoSuchElementException]
override def apply(key: K): V = findNode(key) match {
case null => default(key)
case nd => nd.value
}
override def getOrElse[V1 >: V](key: K, default: => V1): V1 = {
if (getClass != classOf[HashMap[_, _]]) {
// subclasses of HashMap might customise `get` ...
super.getOrElse(key, default)
} else {
// .. but in the common case, we can avoid the Option boxing.
val nd = findNode(key)
if (nd eq null) default else nd.value
}
}
override def getOrElseUpdate(key: K, defaultValue: => V): V = {
if (getClass != classOf[HashMap[_, _]]) {
// subclasses of HashMap might customise `get` ...
super.getOrElseUpdate(key, defaultValue)
} else {
val hash = computeHash(key)
val idx = index(hash)
val nd = table(idx) match {
case null => null
case nd => nd.findNode(key, hash)
}
if(nd != null) nd.value
else {
val table0 = table
val default = defaultValue
if(contentSize + 1 >= threshold) growTable(table.length * 2)
// Avoid recomputing index if the `defaultValue()` or new element hasn't triggered a table resize.
val newIdx = if (table0 eq table) idx else index(hash)
put0(key, default, false, hash, newIdx)
default
}
}
}
override def put(key: K, value: V): Option[V] = put0(key, value, true) match {
case null => None
case sm => sm
}
override def remove(key: K): Option[V] = remove0(key) match {
case null => None
case nd => Some(nd.value)
}
override def update(key: K, value: V): Unit = put0(key, value, false)
def addOne(elem: (K, V)): this.type = { put0(elem._1, elem._2, false); this }
def subtractOne(elem: K): this.type = { remove0(elem); this }
override def knownSize: Int = size
override def isEmpty: Boolean = size == 0
override def foreach[U](f: ((K, V)) => U): Unit = {
val len = table.length
var i = 0
while(i < len) {
val n = table(i)
if(n ne null) n.foreach(f)
i += 1
}
}
override def foreachEntry[U](f: (K, V) => U): Unit = {
val len = table.length
var i = 0
while(i < len) {
val n = table(i)
if(n ne null) n.foreachEntry(f)
i += 1
}
}
protected[this] def writeReplace(): AnyRef = new DefaultSerializationProxy(new mutable.HashMap.DeserializationFactory[K, V](table.length, loadFactor), this)
override def filterInPlace(p: (K, V) => Boolean): this.type = {
if (nonEmpty) {
var bucket = 0
while (bucket < table.length) {
var head = table(bucket)
while ((head ne null) && !p(head.key, head.value)) {
head = head.next
contentSize -= 1
}
if (head ne null) {
var prev = head
var next = head.next
while (next ne null) {
if (p(next.key, next.value)) {
prev = next
} else {
prev.next = next.next
contentSize -= 1
}
next = next.next
}
}
table(bucket) = head
bucket += 1
}
}
this
}
// TODO: rename to `mapValuesInPlace` and override the base version (not binary compatible)
private[mutable] def mapValuesInPlaceImpl(f: (K, V) => V): this.type = {
val len = table.length
var i = 0
while (i < len) {
var n = table(i)
while (n ne null) {
n.value = f(n.key, n.value)
n = n.next
}
i += 1
}
this
}
override def mapFactory: MapFactory[HashMap] = HashMap
@nowarn("""cat=deprecation&origin=scala\.collection\.Iterable\.stringPrefix""")
override protected[this] def stringPrefix = "HashMap"
override def hashCode: Int = {
if (isEmpty) MurmurHash3.emptyMapHash
else {
val tupleHashIterator = new HashMapIterator[Any] {
var hash: Int = 0
override def hashCode: Int = hash
override protected[this] def extract(nd: Node[K, V]): Any = {
hash = MurmurHash3.tuple2Hash(unimproveHash(nd.hash), nd.value.##)
this
}
}
MurmurHash3.unorderedHash(tupleHashIterator, MurmurHash3.mapSeed)
}
}
}
/**
* $factoryInfo
* @define Coll `mutable.HashMap`
* @define coll mutable hash map
*/
@SerialVersionUID(3L)
object HashMap extends MapFactory[HashMap] {
def empty[K, V]: HashMap[K, V] = new HashMap[K, V]
def from[K, V](it: collection.IterableOnce[(K, V)]): HashMap[K, V] = {
val k = it.knownSize
val cap = if(k > 0) ((k + 1).toDouble / defaultLoadFactor).toInt else defaultInitialCapacity
new HashMap[K, V](cap, defaultLoadFactor).addAll(it)
}
def newBuilder[K, V]: Builder[(K, V), HashMap[K, V]] = newBuilder(defaultInitialCapacity, defaultLoadFactor)
def newBuilder[K, V](initialCapacity: Int, loadFactor: Double): Builder[(K, V), HashMap[K, V]] =
new GrowableBuilder[(K, V), HashMap[K, V]](new HashMap[K, V](initialCapacity, loadFactor)) {
override def sizeHint(size: Int) = elems.sizeHint(size)
}
/** The default load factor for the hash table */
final def defaultLoadFactor: Double = 0.75
/** The default initial capacity for the hash table */
final def defaultInitialCapacity: Int = 16
@SerialVersionUID(3L)
private final class DeserializationFactory[K, V](val tableLength: Int, val loadFactor: Double) extends Factory[(K, V), HashMap[K, V]] with Serializable {
def fromSpecific(it: IterableOnce[(K, V)]): HashMap[K, V] = new HashMap[K, V](tableLength, loadFactor).addAll(it)
def newBuilder: Builder[(K, V), HashMap[K, V]] = HashMap.newBuilder(tableLength, loadFactor)
}
private[collection] final class Node[K, V](_key: K, _hash: Int, private[this] var _value: V, private[this] var _next: Node[K, V]) {
def key: K = _key
def hash: Int = _hash
def value: V = _value
def value_= (v: V): Unit = _value = v
def next: Node[K, V] = _next
def next_= (n: Node[K, V]): Unit = _next = n
@tailrec
def findNode(k: K, h: Int): Node[K, V] =
if(h == _hash && k == _key) this
else if((_next eq null) || (_hash > h)) null
else _next.findNode(k, h)
@tailrec
def foreach[U](f: ((K, V)) => U): Unit = {
f((_key, _value))
if(_next ne null) _next.foreach(f)
}
@tailrec
def foreachEntry[U](f: (K, V) => U): Unit = {
f(_key, _value)
if(_next ne null) _next.foreachEntry(f)
}
override def toString = s"Node($key, $value, $hash) -> $next"
}
}
