/*
* Copyright (C) 2010 The Android Open Source Project
* Copyright (C) 2012 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.gson.internal;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Comparator;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* A map of comparable keys to values. Unlike {@code TreeMap}, this class uses insertion order for
* iteration order. Comparison order is only used as an optimization for efficient insertion and
* removal.
*
* <p>
* This implementation was derived from Android 4.1's TreeMap class.
*/
public final class LinkedTreeMap<K, V> extends AbstractMap<K, V> implements Serializable {
@SuppressWarnings({"unchecked", "rawtypes"}) // to avoid Comparable<Comparable<Comparable<...>>>
private static final Comparator<Comparable> NATURAL_ORDER = new Comparator<Comparable>() {
public int compare(Comparable a, Comparable b) {
return a.compareTo(b);
}
};
Comparator<? super K> comparator;
Node<K, V> root;
int size = 0;
int modCount = 0;
// Used to preserve iteration order
final Node<K, V> header = new Node<K, V>();
/**
* Create a natural order, empty tree map whose keys must be mutually comparable and non-null.
*/
@SuppressWarnings("unchecked") // unsafe! this assumes K is comparable
public LinkedTreeMap() {
this((Comparator<? super K>) NATURAL_ORDER);
}
/**
* Create a tree map ordered by {@code comparator}. This map's keys may only be null if
* {@code comparator} permits.
*
* @param comparator the comparator to order elements with, or {@code null} to use the natural
* ordering.
*/
@SuppressWarnings({"unchecked", "rawtypes"}) // unsafe! if comparator is null, this assumes K is comparable
public LinkedTreeMap(Comparator<? super K> comparator) {
this.comparator = comparator != null
? comparator
: (Comparator) NATURAL_ORDER;
}
@Override
public int size() {
return size;
}
@Override
public V get(Object key) {
Node<K, V> node = findByObject(key);
return node != null ? node.value : null;
}
@Override
public boolean containsKey(Object key) {
return findByObject(key) != null;
}
@Override
public V put(K key, V value) {
if (key == null) {
throw new NullPointerException("key == null");
}
Node<K, V> created = find(key, true);
V result = created.value;
created.value = value;
return result;
}
@Override
public void clear() {
root = null;
size = 0;
modCount++;
// Clear iteration order
Node<K, V> header = this.header;
header.next = header.prev = header;
}
@Override
public V remove(Object key) {
Node<K, V> node = removeInternalByKey(key);
return node != null ? node.value : null;
}
/**
* Returns the node at or adjacent to the given key, creating it if requested.
*
* @throws ClassCastException if {@code key} and the tree's keys aren't mutually comparable.
*/
Node<K, V> find(K key, boolean create) {
Comparator<? super K> comparator = this.comparator;
Node<K, V> nearest = root;
int comparison = 0;
if (nearest != null) {
// Micro-optimization: avoid polymorphic calls to Comparator.compare().
@SuppressWarnings("unchecked") // Throws a ClassCastException below if there's trouble.
Comparable<Object> comparableKey = (comparator == NATURAL_ORDER)
? (Comparable<Object>) key
: null;
while (true) {
comparison = (comparableKey != null)
? comparableKey.compareTo(nearest.key)
: comparator.compare(key, nearest.key);
// We found the requested key.
if (comparison == 0) {
return nearest;
}
// If it exists, the key is in a subtree. Go deeper.
Node<K, V> child = (comparison < 0) ? nearest.left : nearest.right;
if (child == null) {
break;
}
nearest = child;
}
}
// The key doesn't exist in this tree.
if (!create) {
return null;
}
// Create the node and add it to the tree or the table.
Node<K, V> header = this.header;
Node<K, V> created;
if (nearest == null) {
// Check that the value is comparable if we didn't do any comparisons.
if (comparator == NATURAL_ORDER && !(key instanceof Comparable)) {
throw new ClassCastException(key.getClass().getName() + " is not Comparable");
}
created = new Node<K, V>(nearest, key, header, header.prev);
root = created;
} else {
created = new Node<K, V>(nearest, key, header, header.prev);
if (comparison < 0) { // nearest.key is higher
nearest.left = created;
} else { // comparison > 0, nearest.key is lower
nearest.right = created;
}
rebalance(nearest, true);
}
size++;
modCount++;
return created;
}
@SuppressWarnings("unchecked")
Node<K, V> findByObject(Object key) {
try {
return key != null ? find((K) key, false) : null;
} catch (ClassCastException e) {
return null;
}
}
/**
* Returns this map's entry that has the same key and value as {@code
* entry}, or null if this map has no such entry.
*
* <p>
* This method uses the comparator for key equality rather than {@code
* equals}. If this map's comparator isn't consistent with equals (such as
* {@code String.CASE_INSENSITIVE_ORDER}), then {@code remove()} and {@code
* contains()} will violate the collections API.
*/
Node<K, V> findByEntry(Entry<?, ?> entry) {
Node<K, V> mine = findByObject(entry.getKey());
boolean valuesEqual = mine != null && equal(mine.value, entry.getValue());
return valuesEqual ? mine : null;
}
private boolean equal(Object a, Object b) {
return a == b || (a != null && a.equals(b));
}
/**
* Removes {@code node} from this tree, rearranging the tree's structure as necessary.
*
* @param unlink true to also unlink this node from the iteration linked list.
*/
void removeInternal(Node<K, V> node, boolean unlink) {
if (unlink) {
node.prev.next = node.next;
node.next.prev = node.prev;
}
Node<K, V> left = node.left;
Node<K, V> right = node.right;
Node<K, V> originalParent = node.parent;
if (left != null && right != null) {
/*
* To remove a node with both left and right subtrees, move an
* adjacent node from one of those subtrees into this node's place.
*
* Removing the adjacent node may change this node's subtrees. This
* node may no longer have two subtrees once the adjacent node is
* gone!
*/
Node<K, V> adjacent = (left.height > right.height) ? left.last() : right.first();
removeInternal(adjacent, false); // takes care of rebalance and size--
int leftHeight = 0;
left = node.left;
if (left != null) {
leftHeight = left.height;
adjacent.left = left;
left.parent = adjacent;
node.left = null;
}
int rightHeight = 0;
right = node.right;
if (right != null) {
rightHeight = right.height;
adjacent.right = right;
right.parent = adjacent;
node.right = null;
}
adjacent.height = Math.max(leftHeight, rightHeight) + 1;
replaceInParent(node, adjacent);
return;
} else if (left != null) {
replaceInParent(node, left);
node.left = null;
} else if (right != null) {
replaceInParent(node, right);
node.right = null;
} else {
replaceInParent(node, null);
}
rebalance(originalParent, false);
size--;
modCount++;
}
Node<K, V> removeInternalByKey(Object key) {
Node<K, V> node = findByObject(key);
if (node != null) {
removeInternal(node, true);
}
return node;
}
private void replaceInParent(Node<K, V> node, Node<K, V> replacement) {
Node<K, V> parent = node.parent;
node.parent = null;
if (replacement != null) {
replacement.parent = parent;
}
if (parent != null) {
if (parent.left == node) {
parent.left = replacement;
} else {
assert (parent.right == node);
parent.right = replacement;
}
} else {
root = replacement;
}
}
/**
* Rebalances the tree by making any AVL rotations necessary between the newly-unbalanced node
* and the tree's root.
*
* @param insert true if the node was unbalanced by an insert; false if it was by a removal.
*/
private void rebalance(Node<K, V> unbalanced, boolean insert) {
for (Node<K, V> node = unbalanced; node != null; node = node.parent) {
Node<K, V> left = node.left;
Node<K, V> right = node.right;
int leftHeight = left != null ? left.height : 0;
int rightHeight = right != null ? right.height : 0;
int delta = leftHeight - rightHeight;
if (delta == -2) {
Node<K, V> rightLeft = right.left;
Node<K, V> rightRight = right.right;
int rightRightHeight = rightRight != null ? rightRight.height : 0;
int rightLeftHeight = rightLeft != null ? rightLeft.height : 0;
int rightDelta = rightLeftHeight - rightRightHeight;
if (rightDelta == -1 || (rightDelta == 0 && !insert)) {
rotateLeft(node); // AVL right right
} else {
assert (rightDelta == 1);
rotateRight(right); // AVL right left
rotateLeft(node);
}
if (insert) {
break; // no further rotations will be necessary
}
} else if (delta == 2) {
Node<K, V> leftLeft = left.left;
Node<K, V> leftRight = left.right;
int leftRightHeight = leftRight != null ? leftRight.height : 0;
int leftLeftHeight = leftLeft != null ? leftLeft.height : 0;
int leftDelta = leftLeftHeight - leftRightHeight;
if (leftDelta == 1 || (leftDelta == 0 && !insert)) {
rotateRight(node); // AVL left left
} else {
assert (leftDelta == -1);
rotateLeft(left); // AVL left right
rotateRight(node);
}
if (insert) {
break; // no further rotations will be necessary
}
} else if (delta == 0) {
node.height = leftHeight + 1; // leftHeight == rightHeight
if (insert) {
break; // the insert caused balance, so rebalancing is done!
}
} else {
assert (delta == -1 || delta == 1);
node.height = Math.max(leftHeight, rightHeight) + 1;
if (!insert) {
break; // the height hasn't changed, so rebalancing is done!
}
}
}
}
/**
* Rotates the subtree so that its root's right child is the new root.
*/
private void rotateLeft(Node<K, V> root) {
Node<K, V> left = root.left;
Node<K, V> pivot = root.right;
Node<K, V> pivotLeft = pivot.left;
Node<K, V> pivotRight = pivot.right;
// move the pivot's left child to the root's right
root.right = pivotLeft;
if (pivotLeft != null) {
pivotLeft.parent = root;
}
replaceInParent(root, pivot);
// move the root to the pivot's left
pivot.left = root;
root.parent = pivot;
// fix heights
root.height = Math.max(left != null ? left.height : 0,
pivotLeft != null ? pivotLeft.height : 0) + 1;
pivot.height = Math.max(root.height,
pivotRight != null ? pivotRight.height : 0) + 1;
}
/**
* Rotates the subtree so that its root's left child is the new root.
*/
private void rotateRight(Node<K, V> root) {
Node<K, V> pivot = root.left;
Node<K, V> right = root.right;
Node<K, V> pivotLeft = pivot.left;
Node<K, V> pivotRight = pivot.right;
// move the pivot's right child to the root's left
root.left = pivotRight;
if (pivotRight != null) {
pivotRight.parent = root;
}
replaceInParent(root, pivot);
// move the root to the pivot's right
pivot.right = root;
root.parent = pivot;
// fixup heights
root.height = Math.max(right != null ? right.height : 0,
pivotRight != null ? pivotRight.height : 0) + 1;
pivot.height = Math.max(root.height,
pivotLeft != null ? pivotLeft.height : 0) + 1;
}
private EntrySet entrySet;
private KeySet keySet;
@Override
public Set<Entry<K, V>> entrySet() {
EntrySet result = entrySet;
return result != null ? result : (entrySet = new EntrySet());
}
@Override
public Set<K> keySet() {
KeySet result = keySet;
return result != null ? result : (keySet = new KeySet());
}
static final class Node<K, V> implements Entry<K, V> {
Node<K, V> parent;
Node<K, V> left;
Node<K, V> right;
Node<K, V> next;
Node<K, V> prev;
final K key;
V value;
int height;
/**
* Create the header entry
*/
Node() {
key = null;
next = prev = this;
}
/**
* Create a regular entry
*/
Node(Node<K, V> parent, K key, Node<K, V> next, Node<K, V> prev) {
this.parent = parent;
this.key = key;
this.height = 1;
this.next = next;
this.prev = prev;
prev.next = this;
next.prev = this;
}
public K getKey() {
return key;
}
public V getValue() {
return value;
}
public V setValue(V value) {
V oldValue = this.value;
this.value = value;
return oldValue;
}
@SuppressWarnings("rawtypes")
@Override
public boolean equals(Object o) {
if (o instanceof Entry) {
Entry other = (Entry) o;
return (key == null ? other.getKey() == null : key.equals(other.getKey()))
&& (value == null ? other.getValue() == null : value.equals(other.getValue()));
}
return false;
}
@Override
public int hashCode() {
return (key == null ? 0 : key.hashCode())
^ (value == null ? 0 : value.hashCode());
}
@Override
public String toString() {
return key + "=" + value;
}
/**
* Returns the first node in this subtree.
*/
public Node<K, V> first() {
Node<K, V> node = this;
Node<K, V> child = node.left;
while (child != null) {
node = child;
child = node.left;
}
return node;
}
/**
* Returns the last node in this subtree.
*/
public Node<K, V> last() {
Node<K, V> node = this;
Node<K, V> child = node.right;
while (child != null) {
node = child;
child = node.right;
}
return node;
}
}
private abstract class LinkedTreeMapIterator<T> implements Iterator<T> {
Node<K, V> next = header.next;
Node<K, V> lastReturned = null;
int expectedModCount = modCount;
public final boolean hasNext() {
return next != header;
}
final Node<K, V> nextNode() {
Node<K, V> e = next;
if (e == header) {
throw new NoSuchElementException();
}
if (modCount != expectedModCount) {
throw new ConcurrentModificationException();
}
next = e.next;
return lastReturned = e;
}
public final void remove() {
if (lastReturned == null) {
throw new IllegalStateException();
}
removeInternal(lastReturned, true);
lastReturned = null;
expectedModCount = modCount;
}
}
class EntrySet extends AbstractSet<Entry<K, V>> {
@Override
public int size() {
return size;
}
@Override
public Iterator<Entry<K, V>> iterator() {
return new LinkedTreeMapIterator<Entry<K, V>>() {
public Entry<K, V> next() {
return nextNode();
}
};
}
@Override
public boolean contains(Object o) {
return o instanceof Entry && findByEntry((Entry<?, ?>) o) != null;
}
@Override
public boolean remove(Object o) {
if (!(o instanceof Entry)) {
return false;
}
Node<K, V> node = findByEntry((Entry<?, ?>) o);
if (node == null) {
return false;
}
removeInternal(node, true);
return true;
}
@Override
public void clear() {
LinkedTreeMap.this.clear();
}
}
class KeySet extends AbstractSet<K> {
@Override
public int size() {
return size;
}
@Override
public Iterator<K> iterator() {
return new LinkedTreeMapIterator<K>() {
public K next() {
return nextNode().key;
}
};
}
@Override
public boolean contains(Object o) {
return containsKey(o);
}
@Override
public boolean remove(Object key) {
return removeInternalByKey(key) != null;
}
@Override
public void clear() {
LinkedTreeMap.this.clear();
}
}
/**
* If somebody is unlucky enough to have to serialize one of these, serialize it as a
* LinkedHashMap so that they won't need Gson on the other side to deserialize it. Using
* serialization defeats our DoS defence, so most apps shouldn't use it.
*/
private Object writeReplace() throws ObjectStreamException {
return new LinkedHashMap<K, V>(this);
}
}