--- old/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/objects/LinkedMap.java 2020-04-15 18:48:33.000000000 +0530
+++ /dev/null 2020-04-15 18:48:33.000000000 +0530
@@ -1,249 +0,0 @@
-/*
- * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
- * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
- *
- * This code is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 only, as
- * published by the Free Software Foundation. Oracle designates this
- * particular file as subject to the "Classpath" exception as provided
- * by Oracle in the LICENSE file that accompanied this code.
- *
- * This code is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
- * version 2 for more details (a copy is included in the LICENSE file that
- * accompanied this code).
- *
- * You should have received a copy of the GNU General Public License version
- * 2 along with this work; if not, write to the Free Software Foundation,
- * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
- * or visit www.oracle.com if you need additional information or have any
- * questions.
- */
-
-package jdk.nashorn.internal.objects;
-
-import jdk.nashorn.internal.runtime.Undefined;
-
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.Map;
-
-/**
- * A linked hash map used by the ES6 Map and Set objects. As required by the ECMA specification for these objects,
- * this class allows arbitrary modifications to the base collection while being iterated over. However, note that
- * such modifications are only safe from the same thread performing the iteration; the class is not thread-safe.
- *
- * Deletions and additions that occur during iteration are reflected in the elements visited by the iterator
- * (except for deletion of elements that have already been visited). In non-concurrent Java collections such as
- * {@code java.util.LinkedHashMap} this would result in a {@link java.util.ConcurrentModificationException}
- * being thrown.
- *
- * This class is implemented using a {@link java.util.HashMap} as backing storage with doubly-linked
- * list nodes as values.
- *
- * @see Map.prototype.forEach
- * @see Set.prototype.forEach
- */
-public class LinkedMap {
-
- // We use a plain hash map as our hash storage.
- private final Map data = new HashMap<>();
-
- // The head and tail of our doubly-linked list. We use the same node to represent both the head and the
- // tail of the list, so the list is circular. This node is never unlinked and thus always remain alive.
- private final Node head = new Node();
-
- /**
- * A node of a linked list that is used as value in our map. The linked list uses insertion order
- * and allows fast iteration over its element even while the map is modified.
- */
- static class Node {
- private final Object key;
- private volatile Object value;
-
- private volatile boolean alive = true;
- private volatile Node prev;
- private volatile Node next;
-
- /**
- * Constructor for the list head. This creates an empty circular list.
- */
- private Node() {
- this(null, null);
- this.next = this;
- this.prev = this;
- }
-
- /**
- * Constructor for value nodes.
- *
- * @param key the key
- * @param value the value
- */
- private Node(final Object key, final Object value) {
- this.key = key;
- this.value = value;
- }
-
- /**
- * Get the node's key.
- * @return the hash key
- */
- public Object getKey() {
- return key;
- }
-
- /**
- * Get the node's value.
- * @return the value
- */
- public Object getValue() {
- return value;
- }
-
- /**
- * Set the node's value
- * @param value the new value
- */
- void setValue(final Object value) {
- this.value = value;
- }
- }
-
- /**
- * An iterator over the elements in the map.
- */
- class LinkedMapIterator {
-
- private Node cursor;
-
- private LinkedMapIterator() {
- this.cursor = head;
- }
-
- /**
- * Get the next node in this iteration. Changes in the underlying map are reflected in the iteration
- * as required by the ES6 specification. Note that this method could return a deleted node if deletion
- * occurred concurrently on another thread.
- *
- * @return the next node
- */
- public Node next() {
-
- if (cursor != null) {
- // If last node is not alive anymore (i.e. has been deleted) go back to the last live node
- // and continue from there. This may be the list head, which always remains alive.
- while (!cursor.alive) {
- assert cursor != head;
- cursor = cursor.prev;
- }
-
- cursor = cursor.next;
-
- if (cursor == head) {
- cursor = null; // We've come full circle to the end
- }
- }
-
- return cursor;
- }
- }
-
- /**
- * Add a key-value pair to the map.
- * @param key the key
- * @param value the value
- */
- public void set(final Object key, final Object value) {
- Node node = data.get(key);
- if (node != null) {
- node.setValue(value);
- } else {
- node = new Node(key, value);
- data.put(key, node);
- link(node);
- }
- }
-
- /**
- * Get the value associated with {@code key}.
- * @param key the key
- * @return the associated value, or {@code null} if {@code key} is not contained in the map
- */
- public Object get(final Object key) {
- final Node node = data.get(key);
- return node == null ? Undefined.getUndefined() : node.getValue();
- }
-
- /**
- * Returns {@code true} if {@code key} is contained in the map.
- * @param key the key
- * @return {@code true} if {@code key} is contained
- */
- public boolean has(final Object key) {
- return data.containsKey(key);
- }
-
- /**
- * Delete the node associated with {@code key} from the map.
- * @param key the key
- * @return {@code true} if {@code key} was contained in the map
- */
- public boolean delete (final Object key) {
- final Node node = data.remove(key);
- if (node != null) {
- unlink(node);
- return true;
- }
- return false;
- }
-
- /**
- * Remove all key-value pairs from the map.
- */
- public void clear() {
- data.clear();
- for (Node node = head.next; node != head; node = node.next) {
- node.alive = false;
- }
- head.next = head;
- head.prev = head;
- }
-
- /**
- * Return the current number of key-value pairs in the map.
- * @return the map size
- */
- public int size() {
- return data.size();
- }
-
- /**
- * Get an iterator over the key-value pairs in the map.
- * @return an iterator
- */
- public LinkedMapIterator getIterator() {
- return new LinkedMapIterator();
- }
-
- private void link(final Node newNode) {
- // We always insert at the end (head == tail)
- newNode.next = head;
- newNode.prev = head.prev;
- newNode.prev.next = newNode;
- head.prev = newNode;
- }
-
- private void unlink(final Node oldNode) {
- // Note that we unlink references to the node being deleted, but keep the references from the deleted node.
- // This is necessary to allow iterators to go back to the last live node in case the current node has been
- // deleted. Also, the forward link of a deleted node may still be followed by an iterator and must not be null.
- oldNode.prev.next = oldNode.next;
- oldNode.next.prev = oldNode.prev;
- oldNode.alive = false;
- }
-
-}