Add OpenHashMap to stdlib

Author: odersky

tests/pos-special/stdlib/collection/mutable/OpenHashMap.scala

@@ -0,0 +1,307 @@
+/*
+ * 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 java.lang.Integer.numberOfLeadingZeros
+import java.util.ConcurrentModificationException
+import scala.collection.generic.DefaultSerializable
+import language.experimental.captureChecking
+
+/**
+  *  @define Coll `OpenHashMap`
+  *  @define coll open hash map
+  */
+@deprecated("Use HashMap or one of the specialized versions (LongMap, AnyRefMap) instead of OpenHashMap", "2.13.0")
+@SerialVersionUID(3L)
+object OpenHashMap extends MapFactory[OpenHashMap] {
+
+  def empty[sealed K, sealed V] = new OpenHashMap[K, V]
+  def from[sealed K, sealed V](it: IterableOnce[(K, V)]^): OpenHashMap[K,V] = empty ++= it
+
+  def newBuilder[sealed K, sealed V]: Builder[(K, V), OpenHashMap[K,V]] =
+    new GrowableBuilder[(K, V), OpenHashMap[K, V]](empty)
+
+  /** A hash table entry.
+    *
+    * The entry is occupied if and only if its `value` is a `Some`;
+    * deleted if and only if its `value` is `None`.
+    * If its `key` is not the default value of type `Key`, the entry is occupied.
+    * If the entry is occupied, `hash` contains the hash value of `key`.
+    */
+  final private class OpenEntry[sealed Key, sealed Value](var key: Key,
+                                            var hash: Int,
+                                            var value: Option[Value])
+
+  private[mutable] def nextPositivePowerOfTwo(target: Int): Int = 1 << -numberOfLeadingZeros(target - 1)
+}
+
+/** A mutable hash map based on an open addressing method. The precise scheme is
+  *  undefined, but it should make a reasonable effort to ensure that an insert
+  *  with consecutive hash codes is not unnecessarily penalised. In particular,
+  *  mappings of consecutive integer keys should work without significant
+  *  performance loss.
+  *
+  *  @tparam Key          type of the keys in this map.
+  *  @tparam Value        type of the values in this map.
+  *  @param initialSize   the initial size of the internal hash table.
+  *
+  *  @define Coll `OpenHashMap`
+  *  @define coll open hash map
+  *  @define mayNotTerminateInf
+  *  @define willNotTerminateInf
+  */
+@deprecated("Use HashMap or one of the specialized versions (LongMap, AnyRefMap) instead of OpenHashMap", "2.13.0")
+class OpenHashMap[sealed Key, sealed Value](initialSize : Int)
+  extends AbstractMap[Key, Value]
+    with MapOps[Key, Value, OpenHashMap, OpenHashMap[Key, Value]]
+    with StrictOptimizedIterableOps[(Key, Value), Iterable, OpenHashMap[Key, Value]]
+    with MapFactoryDefaults[Key, Value, OpenHashMap, Iterable]
+    with DefaultSerializable {
+
+  import OpenHashMap.OpenEntry
+  private type Entry = OpenEntry[Key, Value]
+
+  /** A default constructor creates a hashmap with initial size `8`.
+    */
+  def this() = this(8)
+
+  override def mapFactory: MapFactory[OpenHashMap] = OpenHashMap
+
+  private[this] val actualInitialSize = OpenHashMap.nextPositivePowerOfTwo(initialSize)
+
+  private[this] var mask = actualInitialSize - 1
+
+  /** The hash table.
+    *
+    * The table's entries are initialized to `null`, indication of an empty slot.
+    * A slot is either deleted or occupied if and only if the entry is non-`null`.
+    */
+  private[this] var table = new Array[Entry](actualInitialSize)
+
+  private[this] var _size = 0
+  private[this] var deleted = 0
+
+  // Used for tracking inserts so that iterators can determine if concurrent modification has occurred.
+  private[this] var modCount = 0
+
+  override def size = _size
+  override def knownSize: Int = size
+  private[this] def size_=(s : Int): Unit = _size = s
+  override def isEmpty: Boolean = _size == 0
+  /** Returns a mangled hash code of the provided key. */
+  protected def hashOf(key: Key) = {
+    var h = key.##
+    h ^= ((h >>> 20) ^ (h >>> 12))
+    h ^ (h >>> 7) ^ (h >>> 4)
+  }
+
+  /** Increase the size of the table.
+    * Copy only the occupied slots, effectively eliminating the deleted slots.
+    */
+  private[this] def growTable() = {
+    val oldSize = mask + 1
+    val newSize = 4 * oldSize
+    val oldTable = table
+    table = new Array[Entry](newSize)
+    mask = newSize - 1
+    oldTable.foreach( entry =>
+      if (entry != null && entry.value != None)
+        table(findIndex(entry.key, entry.hash)) = entry )
+    deleted = 0
+  }
+
+  /** Return the index of the first slot in the hash table (in probe order)
+    * that is, in order of preference, either occupied by the given key, deleted, or empty.
+    *
+    * @param hash hash value for `key`
+    */
+  private[this] def findIndex(key: Key, hash: Int): Int = {
+    var index = hash & mask
+    var j = 0
+
+    // Index of the first slot containing a deleted entry, or -1 if none found yet
+    var firstDeletedIndex = -1
+
+    var entry = table(index)
+    while (entry != null) {
+      if (entry.hash == hash && entry.key == key && entry.value != None)
+        return index
+
+      if (firstDeletedIndex == -1 && entry.value == None)
+        firstDeletedIndex = index
+
+      j += 1
+      index = (index + j) & mask
+      entry = table(index)
+    }
+
+    if (firstDeletedIndex == -1) index else firstDeletedIndex
+  }
+
+  // TODO refactor `put` to extract `findOrAddEntry` and implement this in terms of that to avoid Some boxing.
+  override def update(key: Key, value: Value): Unit = put(key, value)
+
+  @deprecatedOverriding("addOne should not be overridden in order to maintain consistency with put.", "2.11.0")
+  def addOne (kv: (Key, Value)): this.type = { put(kv._1, kv._2); this }
+
+  @deprecatedOverriding("subtractOne should not be overridden in order to maintain consistency with remove.", "2.11.0")
+  def subtractOne (key: Key): this.type = { remove(key); this }
+
+  override def put(key: Key, value: Value): Option[Value] =
+    put(key, hashOf(key), value)
+
+  private def put(key: Key, hash: Int, value: Value): Option[Value] = {
+    if (2 * (size + deleted) > mask) growTable()
+    val index = findIndex(key, hash)
+    val entry = table(index)
+    if (entry == null) {
+      table(index) = new OpenEntry(key, hash, Some(value))
+      modCount += 1
+      size += 1
+      None
+    } else {
+      val res = entry.value
+      if (entry.value == None) {
+        entry.key = key
+        entry.hash = hash
+        size += 1
+        deleted -= 1
+        modCount += 1
+      }
+      entry.value = Some(value)
+      res
+    }
+  }
+
+  /** Delete the hash table slot contained in the given entry. */
+  @`inline`
+  private[this] def deleteSlot(entry: Entry) = {
+    entry.key = null.asInstanceOf[Key]
+    entry.hash = 0
+    entry.value = None
+
+    size -= 1
+    deleted += 1
+  }
+
+  override def remove(key : Key): Option[Value] = {
+    val entry = table(findIndex(key, hashOf(key)))
+    if (entry != null && entry.value != None) {
+      val res = entry.value
+      deleteSlot(entry)
+      res
+    } else None
+  }
+
+  def get(key : Key) : Option[Value] = {
+    val hash = hashOf(key)
+    var index = hash & mask
+    var entry = table(index)
+    var j = 0
+    while(entry != null){
+      if (entry.hash == hash &&
+        entry.key == key){
+        return entry.value
+      }
+
+      j += 1
+      index = (index + j) & mask
+      entry = table(index)
+    }
+    None
+  }
+
+  /** An iterator over the elements of this map. Use of this iterator follows
+    *  the same contract for concurrent modification as the foreach method.
+    *
+    *  @return   the iterator
+    */
+  def iterator: Iterator[(Key, Value)] = new OpenHashMapIterator[(Key, Value)] {
+    override protected def nextResult(node: Entry): (Key, Value) = (node.key, node.value.get)
+  }
+
+  override def keysIterator: Iterator[Key] = new OpenHashMapIterator[Key] {
+    override protected def nextResult(node: Entry): Key = node.key
+  }
+  override def valuesIterator: Iterator[Value] = new OpenHashMapIterator[Value] {
+    override protected def nextResult(node: Entry): Value = node.value.get
+  }
+
+  private abstract class OpenHashMapIterator[A] extends AbstractIterator[A] {
+    private[this] var index = 0
+    private[this] val initialModCount = modCount
+
+    private[this] def advance(): Unit = {
+      if (initialModCount != modCount) throw new ConcurrentModificationException
+      while((index <= mask) && (table(index) == null || table(index).value == None)) index+=1
+    }
+
+    def hasNext = {advance(); index <= mask }
+
+    def next() = {
+      advance()
+      val result = table(index)
+      index += 1
+      nextResult(result)
+    }
+    protected def nextResult(node: Entry): A
+  }
+
+  override def clone() = {
+    val it = new OpenHashMap[Key, Value]
+    foreachUndeletedEntry(entry => it.put(entry.key, entry.hash, entry.value.get))
+    it
+  }
+
+  /** Loop over the key, value mappings of this map.
+    *
+    *  The behaviour of modifying the map during an iteration is as follows:
+    *  - Deleting a mapping is always permitted.
+    *  - Changing the value of mapping which is already present is permitted.
+    *  - Anything else is not permitted. It will usually, but not always, throw an exception.
+    *
+    *  @tparam U  The return type of the specified function `f`, return result of which is ignored.
+    *  @param f   The function to apply to each key, value mapping.
+    */
+  override def foreach[U](f : ((Key, Value)) => U): Unit = {
+    val startModCount = modCount
+    foreachUndeletedEntry(entry => {
+      if (modCount != startModCount) throw new ConcurrentModificationException
+      f((entry.key, entry.value.get))}
+    )
+  }
+  override def foreachEntry[U](f : (Key, Value) => U): Unit = {
+    val startModCount = modCount
+    foreachUndeletedEntry(entry => {
+      if (modCount != startModCount) throw new ConcurrentModificationException
+      f(entry.key, entry.value.get)}
+    )
+  }
+
+  private[this] def foreachUndeletedEntry(f : Entry => Unit): Unit = {
+    table.foreach(entry => if (entry != null && entry.value != None) f(entry))
+  }
+
+  override def mapValuesInPlace(f : (Key, Value) => Value): this.type = {
+    foreachUndeletedEntry(entry => entry.value = Some(f(entry.key, entry.value.get)))
+    this
+  }
+
+  override def filterInPlace(f : (Key, Value) => Boolean): this.type = {
+    foreachUndeletedEntry(entry => if (!f(entry.key, entry.value.get)) deleteSlot(entry))
+    this
+  }
+
+  override protected[this] def stringPrefix = "OpenHashMap"
+}