Java tutorial
/******************************************************************************* * Copyright 2011 See AUTHORS file. * * 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.badlogic.gdx.utils; import java.util.Iterator; import java.util.NoSuchElementException; import com.badlogic.gdx.math.MathUtils; /** An unordered map. This implementation is a cuckoo hash map using 3 hashes, random walking, and a small stash for problematic * keys. Null keys are not allowed. Null values are allowed. No allocation is done except when growing the table size. <br> * <br> * This map performs very fast get, containsKey, and remove (typically O(1), worst case O(log(n))). Put may be a bit slower, * depending on hash collisions. Load factors greater than 0.91 greatly increase the chances the map will have to rehash to the * next higher POT size. * @author Nathan Sweet */ public class ObjectMap<K, V> implements Iterable<ObjectMap.Entry<K, V>> { private static final int PRIME1 = 0xbe1f14b1; private static final int PRIME2 = 0xb4b82e39; private static final int PRIME3 = 0xced1c241; public int size; K[] keyTable; V[] valueTable; int capacity, stashSize; private float loadFactor; private int hashShift, mask, threshold; private int stashCapacity; private int pushIterations; private Entries entries1, entries2; private Values values1, values2; private Keys keys1, keys2; /** Creates a new map with an initial capacity of 32 and a load factor of 0.8. This map will hold 25 items before growing the * backing table. */ public ObjectMap() { this(32, 0.8f); } /** Creates a new map with a load factor of 0.8. This map will hold initialCapacity * 0.8 items before growing the backing * table. */ public ObjectMap(int initialCapacity) { this(initialCapacity, 0.8f); } /** Creates a new map with the specified initial capacity and load factor. This map will hold initialCapacity * loadFactor items * before growing the backing table. */ public ObjectMap(int initialCapacity, float loadFactor) { if (initialCapacity < 0) throw new IllegalArgumentException("initialCapacity must be >= 0: " + initialCapacity); if (initialCapacity > 1 << 30) throw new IllegalArgumentException("initialCapacity is too large: " + initialCapacity); capacity = MathUtils.nextPowerOfTwo(initialCapacity); if (loadFactor <= 0) throw new IllegalArgumentException("loadFactor must be > 0: " + loadFactor); this.loadFactor = loadFactor; threshold = (int) (capacity * loadFactor); mask = capacity - 1; hashShift = 31 - Integer.numberOfTrailingZeros(capacity); stashCapacity = Math.max(3, (int) Math.ceil(Math.log(capacity)) * 2); pushIterations = Math.max(Math.min(capacity, 8), (int) Math.sqrt(capacity) / 8); keyTable = (K[]) new Object[capacity + stashCapacity]; valueTable = (V[]) new Object[keyTable.length]; } /** Creates a new map identical to the specified map. */ public ObjectMap(ObjectMap<? extends K, ? extends V> map) { this(map.capacity, map.loadFactor); stashSize = map.stashSize; System.arraycopy(map.keyTable, 0, keyTable, 0, map.keyTable.length); System.arraycopy(map.valueTable, 0, valueTable, 0, map.valueTable.length); size = map.size; } /** Returns the old value associated with the specified key, or null. */ public V put(K key, V value) { if (key == null) throw new IllegalArgumentException("key cannot be null."); return put_internal(key, value); } private V put_internal(K key, V value) { K[] keyTable = this.keyTable; // Check for existing keys. int hashCode = key.hashCode(); int index1 = hashCode & mask; K key1 = keyTable[index1]; if (key.equals(key1)) { V oldValue = valueTable[index1]; valueTable[index1] = value; return oldValue; } int index2 = hash2(hashCode); K key2 = keyTable[index2]; if (key.equals(key2)) { V oldValue = valueTable[index2]; valueTable[index2] = value; return oldValue; } int index3 = hash3(hashCode); K key3 = keyTable[index3]; if (key.equals(key3)) { V oldValue = valueTable[index3]; valueTable[index3] = value; return oldValue; } // Update key in the stash. for (int i = capacity, n = i + stashSize; i < n; i++) { if (key.equals(keyTable[i])) { V oldValue = valueTable[i]; valueTable[i] = value; return oldValue; } } // Check for empty buckets. if (key1 == null) { keyTable[index1] = key; valueTable[index1] = value; if (size++ >= threshold) resize(capacity << 1); return null; } if (key2 == null) { keyTable[index2] = key; valueTable[index2] = value; if (size++ >= threshold) resize(capacity << 1); return null; } if (key3 == null) { keyTable[index3] = key; valueTable[index3] = value; if (size++ >= threshold) resize(capacity << 1); return null; } push(key, value, index1, key1, index2, key2, index3, key3); return null; } public void putAll(ObjectMap<K, V> map) { ensureCapacity(map.size); for (Entry<K, V> entry : map) put(entry.key, entry.value); } /** Skips checks for existing keys. */ private void putResize(K key, V value) { // Check for empty buckets. int hashCode = key.hashCode(); int index1 = hashCode & mask; K key1 = keyTable[index1]; if (key1 == null) { keyTable[index1] = key; valueTable[index1] = value; if (size++ >= threshold) resize(capacity << 1); return; } int index2 = hash2(hashCode); K key2 = keyTable[index2]; if (key2 == null) { keyTable[index2] = key; valueTable[index2] = value; if (size++ >= threshold) resize(capacity << 1); return; } int index3 = hash3(hashCode); K key3 = keyTable[index3]; if (key3 == null) { keyTable[index3] = key; valueTable[index3] = value; if (size++ >= threshold) resize(capacity << 1); return; } push(key, value, index1, key1, index2, key2, index3, key3); } private void push(K insertKey, V insertValue, int index1, K key1, int index2, K key2, int index3, K key3) { K[] keyTable = this.keyTable; V[] valueTable = this.valueTable; int mask = this.mask; // Push keys until an empty bucket is found. K evictedKey; V evictedValue; int i = 0, pushIterations = this.pushIterations; do { // Replace the key and value for one of the hashes. switch (MathUtils.random(2)) { case 0: evictedKey = key1; evictedValue = valueTable[index1]; keyTable[index1] = insertKey; valueTable[index1] = insertValue; break; case 1: evictedKey = key2; evictedValue = valueTable[index2]; keyTable[index2] = insertKey; valueTable[index2] = insertValue; break; default: evictedKey = key3; evictedValue = valueTable[index3]; keyTable[index3] = insertKey; valueTable[index3] = insertValue; break; } // If the evicted key hashes to an empty bucket, put it there and stop. int hashCode = evictedKey.hashCode(); index1 = hashCode & mask; key1 = keyTable[index1]; if (key1 == null) { keyTable[index1] = evictedKey; valueTable[index1] = evictedValue; if (size++ >= threshold) resize(capacity << 1); return; } index2 = hash2(hashCode); key2 = keyTable[index2]; if (key2 == null) { keyTable[index2] = evictedKey; valueTable[index2] = evictedValue; if (size++ >= threshold) resize(capacity << 1); return; } index3 = hash3(hashCode); key3 = keyTable[index3]; if (key3 == null) { keyTable[index3] = evictedKey; valueTable[index3] = evictedValue; if (size++ >= threshold) resize(capacity << 1); return; } if (++i == pushIterations) break; insertKey = evictedKey; insertValue = evictedValue; } while (true); putStash(evictedKey, evictedValue); } private void putStash(K key, V value) { if (stashSize == stashCapacity) { // Too many pushes occurred and the stash is full, increase the table size. resize(capacity << 1); put_internal(key, value); return; } // Store key in the stash. int index = capacity + stashSize; keyTable[index] = key; valueTable[index] = value; stashSize++; size++; } public V get(K key) { int hashCode = key.hashCode(); int index = hashCode & mask; if (!key.equals(keyTable[index])) { index = hash2(hashCode); if (!key.equals(keyTable[index])) { index = hash3(hashCode); if (!key.equals(keyTable[index])) return getStash(key); } } return valueTable[index]; } private V getStash(K key) { K[] keyTable = this.keyTable; for (int i = capacity, n = i + stashSize; i < n; i++) if (key.equals(keyTable[i])) return valueTable[i]; return null; } /** Returns the value for the specified key, or the default value if the key is not in the map. */ public V get(K key, V defaultValue) { int hashCode = key.hashCode(); int index = hashCode & mask; if (!key.equals(keyTable[index])) { index = hash2(hashCode); if (!key.equals(keyTable[index])) { index = hash3(hashCode); if (!key.equals(keyTable[index])) return getStash(key, defaultValue); } } return valueTable[index]; } private V getStash(K key, V defaultValue) { K[] keyTable = this.keyTable; for (int i = capacity, n = i + stashSize; i < n; i++) if (key.equals(keyTable[i])) return valueTable[i]; return defaultValue; } public V remove(K key) { int hashCode = key.hashCode(); int index = hashCode & mask; if (key.equals(keyTable[index])) { keyTable[index] = null; V oldValue = valueTable[index]; valueTable[index] = null; size--; return oldValue; } index = hash2(hashCode); if (key.equals(keyTable[index])) { keyTable[index] = null; V oldValue = valueTable[index]; valueTable[index] = null; size--; return oldValue; } index = hash3(hashCode); if (key.equals(keyTable[index])) { keyTable[index] = null; V oldValue = valueTable[index]; valueTable[index] = null; size--; return oldValue; } return removeStash(key); } V removeStash(K key) { K[] keyTable = this.keyTable; for (int i = capacity, n = i + stashSize; i < n; i++) { if (key.equals(keyTable[i])) { V oldValue = valueTable[i]; removeStashIndex(i); size--; return oldValue; } } return null; } void removeStashIndex(int index) { // If the removed location was not last, move the last tuple to the removed location. stashSize--; int lastIndex = capacity + stashSize; if (index < lastIndex) { keyTable[index] = keyTable[lastIndex]; valueTable[index] = valueTable[lastIndex]; valueTable[lastIndex] = null; } else valueTable[index] = null; } /** Reduces the size of the backing arrays to be the specified capacity or less. If the capacity is already less, nothing is * done. If the map contains more items than the specified capacity, the next highest power of two capacity is used instead. */ public void shrink(int maximumCapacity) { if (maximumCapacity < 0) throw new IllegalArgumentException("maximumCapacity must be >= 0: " + maximumCapacity); if (size > maximumCapacity) maximumCapacity = size; if (capacity <= maximumCapacity) return; maximumCapacity = MathUtils.nextPowerOfTwo(maximumCapacity); resize(maximumCapacity); } /** Clears the map and reduces the size of the backing arrays to be the specified capacity if they are larger. */ public void clear(int maximumCapacity) { if (capacity <= maximumCapacity) { clear(); return; } size = 0; resize(maximumCapacity); } public void clear() { if (size == 0) return; K[] keyTable = this.keyTable; V[] valueTable = this.valueTable; for (int i = capacity + stashSize; i-- > 0;) { keyTable[i] = null; valueTable[i] = null; } size = 0; stashSize = 0; } /** Returns true if the specified value is in the map. Note this traverses the entire map and compares every value, which may be * an expensive operation. * @param identity If true, uses == to compare the specified value with values in the map. If false, uses * {@link #equals(Object)}. */ public boolean containsValue(Object value, boolean identity) { V[] valueTable = this.valueTable; if (value == null) { K[] keyTable = this.keyTable; for (int i = capacity + stashSize; i-- > 0;) if (keyTable[i] != null && valueTable[i] == null) return true; } else if (identity) { for (int i = capacity + stashSize; i-- > 0;) if (valueTable[i] == value) return true; } else { for (int i = capacity + stashSize; i-- > 0;) if (value.equals(valueTable[i])) return true; } return false; } public boolean containsKey(K key) { int hashCode = key.hashCode(); int index = hashCode & mask; if (!key.equals(keyTable[index])) { index = hash2(hashCode); if (!key.equals(keyTable[index])) { index = hash3(hashCode); if (!key.equals(keyTable[index])) return containsKeyStash(key); } } return true; } private boolean containsKeyStash(K key) { K[] keyTable = this.keyTable; for (int i = capacity, n = i + stashSize; i < n; i++) if (key.equals(keyTable[i])) return true; return false; } /** Returns the key for the specified value, or null if it is not in the map. Note this traverses the entire map and compares * every value, which may be an expensive operation. * @param identity If true, uses == to compare the specified value with values in the map. If false, uses * {@link #equals(Object)}. */ public K findKey(Object value, boolean identity) { V[] valueTable = this.valueTable; if (value == null) { K[] keyTable = this.keyTable; for (int i = capacity + stashSize; i-- > 0;) if (keyTable[i] != null && valueTable[i] == null) return keyTable[i]; } else if (identity) { for (int i = capacity + stashSize; i-- > 0;) if (valueTable[i] == value) return keyTable[i]; } else { for (int i = capacity + stashSize; i-- > 0;) if (value.equals(valueTable[i])) return keyTable[i]; } return null; } /** Increases the size of the backing array to accommodate the specified number of additional items. Useful before adding many * items to avoid multiple backing array resizes. */ public void ensureCapacity(int additionalCapacity) { int sizeNeeded = size + additionalCapacity; if (sizeNeeded >= threshold) resize(MathUtils.nextPowerOfTwo((int) (sizeNeeded / loadFactor))); } private void resize(int newSize) { int oldEndIndex = capacity + stashSize; capacity = newSize; threshold = (int) (newSize * loadFactor); mask = newSize - 1; hashShift = 31 - Integer.numberOfTrailingZeros(newSize); stashCapacity = Math.max(3, (int) Math.ceil(Math.log(newSize)) * 2); pushIterations = Math.max(Math.min(newSize, 8), (int) Math.sqrt(newSize) / 8); K[] oldKeyTable = keyTable; V[] oldValueTable = valueTable; keyTable = (K[]) new Object[newSize + stashCapacity]; valueTable = (V[]) new Object[newSize + stashCapacity]; int oldSize = size; size = 0; stashSize = 0; if (oldSize > 0) { for (int i = 0; i < oldEndIndex; i++) { K key = oldKeyTable[i]; if (key != null) putResize(key, oldValueTable[i]); } } } private int hash2(int h) { h *= PRIME2; return (h ^ h >>> hashShift) & mask; } private int hash3(int h) { h *= PRIME3; return (h ^ h >>> hashShift) & mask; } public String toString(String separator) { return toString(separator, false); } public String toString() { return toString(", ", true); } private String toString(String separator, boolean braces) { if (size == 0) return braces ? "{}" : ""; StringBuilder buffer = new StringBuilder(32); if (braces) buffer.append('{'); K[] keyTable = this.keyTable; V[] valueTable = this.valueTable; int i = keyTable.length; while (i-- > 0) { K key = keyTable[i]; if (key == null) continue; buffer.append(key); buffer.append('='); buffer.append(valueTable[i]); break; } while (i-- > 0) { K key = keyTable[i]; if (key == null) continue; buffer.append(separator); buffer.append(key); buffer.append('='); buffer.append(valueTable[i]); } if (braces) buffer.append('}'); return buffer.toString(); } public Iterator<Entry<K, V>> iterator() { return entries(); } /** Returns an iterator for the entries in the map. Remove is supported. Note that the same iterator instance is returned each * time this method is called. Use the {@link Entries} constructor for nested or multithreaded iteration. */ public Entries<K, V> entries() { if (entries1 == null) { entries1 = new Entries(this); entries2 = new Entries(this); } if (!entries1.valid) { entries1.reset(); entries1.valid = true; entries2.valid = false; return entries1; } entries2.reset(); entries2.valid = true; entries1.valid = false; return entries2; } /** Returns an iterator for the values in the map. Remove is supported. Note that the same iterator instance is returned each * time this method is called. Use the {@link Values} constructor for nested or multithreaded iteration. */ public Values<V> values() { if (values1 == null) { values1 = new Values(this); values2 = new Values(this); } if (!values1.valid) { values1.reset(); values1.valid = true; values2.valid = false; return values1; } values2.reset(); values2.valid = true; values1.valid = false; return values2; } /** Returns an iterator for the keys in the map. Remove is supported. Note that the same iterator instance is returned each time * this method is called. Use the {@link Keys} constructor for nested or multithreaded iteration. */ public Keys<K> keys() { if (keys1 == null) { keys1 = new Keys(this); keys2 = new Keys(this); } if (!keys1.valid) { keys1.reset(); keys1.valid = true; keys2.valid = false; return keys1; } keys2.reset(); keys2.valid = true; keys1.valid = false; return keys2; } static public class Entry<K, V> { public K key; public V value; public String toString() { return key + "=" + value; } } static private abstract class MapIterator<K, V, I> implements Iterable<I>, Iterator<I> { public boolean hasNext; final ObjectMap<K, V> map; int nextIndex, currentIndex; boolean valid = true; public MapIterator(ObjectMap<K, V> map) { this.map = map; reset(); } public void reset() { currentIndex = -1; nextIndex = -1; findNextIndex(); } void findNextIndex() { hasNext = false; K[] keyTable = map.keyTable; for (int n = map.capacity + map.stashSize; ++nextIndex < n;) { if (keyTable[nextIndex] != null) { hasNext = true; break; } } } public void remove() { if (currentIndex < 0) throw new IllegalStateException("next must be called before remove."); if (currentIndex >= map.capacity) { map.removeStashIndex(currentIndex); nextIndex = currentIndex - 1; findNextIndex(); } else { map.keyTable[currentIndex] = null; map.valueTable[currentIndex] = null; } currentIndex = -1; map.size--; } } static public class Entries<K, V> extends MapIterator<K, V, Entry<K, V>> { Entry<K, V> entry = new Entry(); public Entries(ObjectMap<K, V> map) { super(map); } /** Note the same entry instance is returned each time this method is called. */ public Entry<K, V> next() { if (!hasNext) throw new NoSuchElementException(); if (!valid) throw new GdxRuntimeException("#iterator() cannot be used nested."); K[] keyTable = map.keyTable; entry.key = keyTable[nextIndex]; entry.value = map.valueTable[nextIndex]; currentIndex = nextIndex; findNextIndex(); return entry; } public boolean hasNext() { if (!valid) throw new GdxRuntimeException("#iterator() cannot be used nested."); return hasNext; } public Iterator<Entry<K, V>> iterator() { return this; } } static public class Values<V> extends MapIterator<Object, V, V> { public Values(ObjectMap<?, V> map) { super((ObjectMap<Object, V>) map); } public boolean hasNext() { if (!valid) throw new GdxRuntimeException("#iterator() cannot be used nested."); return hasNext; } public V next() { if (!hasNext) throw new NoSuchElementException(); if (!valid) throw new GdxRuntimeException("#iterator() cannot be used nested."); V value = map.valueTable[nextIndex]; currentIndex = nextIndex; findNextIndex(); return value; } public Iterator<V> iterator() { return this; } /** Returns a new array containing the remaining values. */ public Array<V> toArray() { return toArray(new Array(true, map.size)); } /** Adds the remaining values to the specified array. */ public Array<V> toArray(Array<V> array) { while (hasNext) array.add(next()); return array; } } static public class Keys<K> extends MapIterator<K, Object, K> { public Keys(ObjectMap<K, ?> map) { super((ObjectMap<K, Object>) map); } public boolean hasNext() { if (!valid) throw new GdxRuntimeException("#iterator() cannot be used nested."); return hasNext; } public K next() { if (!hasNext) throw new NoSuchElementException(); if (!valid) throw new GdxRuntimeException("#iterator() cannot be used nested."); K key = map.keyTable[nextIndex]; currentIndex = nextIndex; findNextIndex(); return key; } public Iterator<K> iterator() { return this; } /** Returns a new array containing the remaining keys. */ public Array<K> toArray() { return toArray(new Array(true, map.size)); } /** Adds the remaining keys to the array. */ public Array<K> toArray(Array<K> array) { while (hasNext) array.add(next()); return array; } } }