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Diffstat (limited to 'gson/src/main/java/com/google/gson/internal/LinkedHashTreeMap.java')
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1 files changed, 861 insertions, 0 deletions
diff --git a/gson/src/main/java/com/google/gson/internal/LinkedHashTreeMap.java b/gson/src/main/java/com/google/gson/internal/LinkedHashTreeMap.java new file mode 100644 index 00000000..e251ec2f --- /dev/null +++ b/gson/src/main/java/com/google/gson/internal/LinkedHashTreeMap.java @@ -0,0 +1,861 @@ +/* + * 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.Arrays; +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 and + * LinkedHashMap classes. + */ +public final class LinkedHashTreeMap<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>[] table; + final Node<K, V> header; + int size = 0; + int modCount = 0; + int threshold; + + /** + * 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 LinkedHashTreeMap() { + 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 LinkedHashTreeMap(Comparator<? super K> comparator) { + this.comparator = comparator != null + ? comparator + : (Comparator) NATURAL_ORDER; + this.header = new Node<K, V>(); + this.table = new Node[16]; // TODO: sizing/resizing policies + this.threshold = (table.length / 2) + (table.length / 4); // 3/4 capacity + } + + @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() { + Arrays.fill(table, null); + size = 0; + modCount++; + + // Clear all links to help GC + Node<K, V> header = this.header; + for (Node<K, V> e = header.next; e != header; ) { + Node<K, V> next = e.next; + e.next = e.prev = null; + e = next; + } + + 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>[] table = this.table; + int hash = secondaryHash(key.hashCode()); + int index = hash & (table.length - 1); + Node<K, V> nearest = table[index]; + 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, hash, header, header.prev); + table[index] = created; + } else { + created = new Node<K, V>(nearest, key, hash, 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); + } + + if (size++ > threshold) { + doubleCapacity(); + } + 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)); + } + + /** + * Applies a supplemental hash function to a given hashCode, which defends + * against poor quality hash functions. This is critical because HashMap + * uses power-of-two length hash tables, that otherwise encounter collisions + * for hashCodes that do not differ in lower or upper bits. + */ + private static int secondaryHash(int h) { + // Doug Lea's supplemental hash function + h ^= (h >>> 20) ^ (h >>> 12); + return h ^ (h >>> 7) ^ (h >>> 4); + } + + /** + * 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.next = node.prev = null; // Help the GC (for performance) + } + + 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 { + int index = node.hash & (table.length - 1); + table[index] = 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; + final int hash; + V value; + int height; + + /** Create the header entry */ + Node() { + key = null; + hash = -1; + next = prev = this; + } + + /** Create a regular entry */ + Node(Node<K, V> parent, K key, int hash, Node<K, V> next, Node<K, V> prev) { + this.parent = parent; + this.key = key; + this.hash = hash; + 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 void doubleCapacity() { + table = doubleCapacity(table); + threshold = (table.length / 2) + (table.length / 4); // 3/4 capacity + } + + /** + * Returns a new array containing the same nodes as {@code oldTable}, but with + * twice as many trees, each of (approximately) half the previous size. + */ + static <K, V> Node<K, V>[] doubleCapacity(Node<K, V>[] oldTable) { + // TODO: don't do anything if we're already at MAX_CAPACITY + int oldCapacity = oldTable.length; + @SuppressWarnings("unchecked") // Arrays and generics don't get along. + Node<K, V>[] newTable = new Node[oldCapacity * 2]; + AvlIterator<K, V> iterator = new AvlIterator<K, V>(); + AvlBuilder<K, V> leftBuilder = new AvlBuilder<K, V>(); + AvlBuilder<K, V> rightBuilder = new AvlBuilder<K, V>(); + + // Split each tree into two trees. + for (int i = 0; i < oldCapacity; i++) { + Node<K, V> root = oldTable[i]; + if (root == null) { + continue; + } + + // Compute the sizes of the left and right trees. + iterator.reset(root); + int leftSize = 0; + int rightSize = 0; + for (Node<K, V> node; (node = iterator.next()) != null; ) { + if ((node.hash & oldCapacity) == 0) { + leftSize++; + } else { + rightSize++; + } + } + + // Split the tree into two. + leftBuilder.reset(leftSize); + rightBuilder.reset(rightSize); + iterator.reset(root); + for (Node<K, V> node; (node = iterator.next()) != null; ) { + if ((node.hash & oldCapacity) == 0) { + leftBuilder.add(node); + } else { + rightBuilder.add(node); + } + } + + // Populate the enlarged array with these new roots. + newTable[i] = leftSize > 0 ? leftBuilder.root() : null; + newTable[i + oldCapacity] = rightSize > 0 ? rightBuilder.root() : null; + } + return newTable; + } + + /** + * Walks an AVL tree in iteration order. Once a node has been returned, its + * left, right and parent links are <strong>no longer used</strong>. For this + * reason it is safe to transform these links as you walk a tree. + * + * <p><strong>Warning:</strong> this iterator is destructive. It clears the + * parent node of all nodes in the tree. It is an error to make a partial + * iteration of a tree. + */ + static class AvlIterator<K, V> { + /** This stack is a singly linked list, linked by the 'parent' field. */ + private Node<K, V> stackTop; + + void reset(Node<K, V> root) { + Node<K, V> stackTop = null; + for (Node<K, V> n = root; n != null; n = n.left) { + n.parent = stackTop; + stackTop = n; // Stack push. + } + this.stackTop = stackTop; + } + + public Node<K, V> next() { + Node<K, V> stackTop = this.stackTop; + if (stackTop == null) { + return null; + } + Node<K, V> result = stackTop; + stackTop = result.parent; + result.parent = null; + for (Node<K, V> n = result.right; n != null; n = n.left) { + n.parent = stackTop; + stackTop = n; // Stack push. + } + this.stackTop = stackTop; + return result; + } + } + + /** + * Builds AVL trees of a predetermined size by accepting nodes of increasing + * value. To use: + * <ol> + * <li>Call {@link #reset} to initialize the target size <i>size</i>. + * <li>Call {@link #add} <i>size</i> times with increasing values. + * <li>Call {@link #root} to get the root of the balanced tree. + * </ol> + * + * <p>The returned tree will satisfy the AVL constraint: for every node + * <i>N</i>, the height of <i>N.left</i> and <i>N.right</i> is different by at + * most 1. It accomplishes this by omitting deepest-level leaf nodes when + * building trees whose size isn't a power of 2 minus 1. + * + * <p>Unlike rebuilding a tree from scratch, this approach requires no value + * comparisons. Using this class to create a tree of size <i>S</i> is + * {@code O(S)}. + */ + final static class AvlBuilder<K, V> { + /** This stack is a singly linked list, linked by the 'parent' field. */ + private Node<K, V> stack; + private int leavesToSkip; + private int leavesSkipped; + private int size; + + void reset(int targetSize) { + // compute the target tree size. This is a power of 2 minus one, like 15 or 31. + int treeCapacity = Integer.highestOneBit(targetSize) * 2 - 1; + leavesToSkip = treeCapacity - targetSize; + size = 0; + leavesSkipped = 0; + stack = null; + } + + void add(Node<K, V> node) { + node.left = node.parent = node.right = null; + node.height = 1; + + // Skip a leaf if necessary. + if (leavesToSkip > 0 && (size & 1) == 0) { + size++; + leavesToSkip--; + leavesSkipped++; + } + + node.parent = stack; + stack = node; // Stack push. + size++; + + // Skip a leaf if necessary. + if (leavesToSkip > 0 && (size & 1) == 0) { + size++; + leavesToSkip--; + leavesSkipped++; + } + + /* + * Combine 3 nodes into subtrees whenever the size is one less than a + * multiple of 4. For example we combine the nodes A, B, C into a + * 3-element tree with B as the root. + * + * Combine two subtrees and a spare single value whenever the size is one + * less than a multiple of 8. For example at 8 we may combine subtrees + * (A B C) and (E F G) with D as the root to form ((A B C) D (E F G)). + * + * Just as we combine single nodes when size nears a multiple of 4, and + * 3-element trees when size nears a multiple of 8, we combine subtrees of + * size (N-1) whenever the total size is 2N-1 whenever N is a power of 2. + */ + for (int scale = 4; (size & scale - 1) == scale - 1; scale *= 2) { + if (leavesSkipped == 0) { + // Pop right, center and left, then make center the top of the stack. + Node<K, V> right = stack; + Node<K, V> center = right.parent; + Node<K, V> left = center.parent; + center.parent = left.parent; + stack = center; + // Construct a tree. + center.left = left; + center.right = right; + center.height = right.height + 1; + left.parent = center; + right.parent = center; + } else if (leavesSkipped == 1) { + // Pop right and center, then make center the top of the stack. + Node<K, V> right = stack; + Node<K, V> center = right.parent; + stack = center; + // Construct a tree with no left child. + center.right = right; + center.height = right.height + 1; + right.parent = center; + leavesSkipped = 0; + } else if (leavesSkipped == 2) { + leavesSkipped = 0; + } + } + } + + Node<K, V> root() { + Node<K, V> stackTop = this.stack; + if (stackTop.parent != null) { + throw new IllegalStateException(); + } + return stackTop; + } + } + + 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; + } + } + + final 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() { + LinkedHashTreeMap.this.clear(); + } + } + + final 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() { + LinkedHashTreeMap.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); + } +} |