| // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| // Hash map implementation with open addressing and quadratic probing. |
| class HashMapImplementation<K, V> implements HashMap<K, V> { |
| |
| // The [_keys] list contains the keys inserted in the map. |
| // The [_keys] list must be a raw list because it |
| // will contain both elements of type K, and the [_DELETED_KEY] of type |
| // [_DeletedKeySentinel]. |
| // The alternative of declaring the [_keys] list as of type Object |
| // does not work, because the HashSetIterator constructor would fail: |
| // HashSetIterator(HashSet<E> set) |
| // : _nextValidIndex = -1, |
| // _entries = set_._backingMap._keys { |
| // _advance(); |
| // } |
| // With K being type int, for example, it would fail because |
| // List<Object> is not assignable to type List<int> of entries. |
| List _keys; |
| |
| // The values inserted in the map. For a filled entry index in this |
| // list, there is always the corresponding key in the [keys_] list |
| // at the same entry index. |
| List<V> _values; |
| |
| // The load limit is the number of entries we allow until we double |
| // the size of the lists. |
| int _loadLimit; |
| |
| // The current number of entries in the map. Will never be greater |
| // than [_loadLimit]. |
| int _numberOfEntries; |
| |
| // The current number of deleted entries in the map. |
| int _numberOfDeleted; |
| |
| // The sentinel when a key is deleted from the map. |
| static const _DeletedKeySentinel _DELETED_KEY = const _DeletedKeySentinel(); |
| |
| // The initial capacity of a hash map. |
| static const int _INITIAL_CAPACITY = 8; // must be power of 2 |
| |
| HashMapImplementation() { |
| _numberOfEntries = 0; |
| _numberOfDeleted = 0; |
| _loadLimit = _computeLoadLimit(_INITIAL_CAPACITY); |
| _keys = new List(_INITIAL_CAPACITY); |
| _values = new List<V>(_INITIAL_CAPACITY); |
| } |
| |
| factory HashMapImplementation.from(Map<K, V> other) { |
| Map<K, V> result = new HashMapImplementation<K, V>(); |
| other.forEach((K key, V value) { result[key] = value; }); |
| return result; |
| } |
| |
| static int _computeLoadLimit(int capacity) { |
| return (capacity * 3) ~/ 4; |
| } |
| |
| static int _firstProbe(int hashCode, int length) { |
| return hashCode & (length - 1); |
| } |
| |
| static int _nextProbe(int currentProbe, int numberOfProbes, int length) { |
| return (currentProbe + numberOfProbes) & (length - 1); |
| } |
| |
| int _probeForAdding(K key) { |
| if (key == null) throw const NullPointerException(); |
| int hash = _firstProbe(key.hashCode, _keys.length); |
| int numberOfProbes = 1; |
| int initialHash = hash; |
| // insertionIndex points to a slot where a key was deleted. |
| int insertionIndex = -1; |
| while (true) { |
| // [existingKey] can be either of type [K] or [_DeletedKeySentinel]. |
| Object existingKey = _keys[hash]; |
| if (existingKey === null) { |
| // We are sure the key is not already in the set. |
| // If the current slot is empty and we didn't find any |
| // insertion slot before, return this slot. |
| if (insertionIndex < 0) return hash; |
| // If we did find an insertion slot before, return it. |
| return insertionIndex; |
| } else if (existingKey == key) { |
| // The key is already in the map. Return its slot. |
| return hash; |
| } else if ((insertionIndex < 0) && (_DELETED_KEY === existingKey)) { |
| // The slot contains a deleted element. Because previous calls to this |
| // method may not have had this slot deleted, we must continue iterate |
| // to find if there is a slot with the given key. |
| insertionIndex = hash; |
| } |
| |
| // We did not find an insertion slot. Look at the next one. |
| hash = _nextProbe(hash, numberOfProbes++, _keys.length); |
| // _ensureCapacity has guaranteed the following cannot happen. |
| // assert(hash != initialHash); |
| } |
| } |
| |
| int _probeForLookup(K key) { |
| if (key == null) throw const NullPointerException(); |
| int hash = _firstProbe(key.hashCode, _keys.length); |
| int numberOfProbes = 1; |
| int initialHash = hash; |
| while (true) { |
| // [existingKey] can be either of type [K] or [_DeletedKeySentinel]. |
| Object existingKey = _keys[hash]; |
| // If the slot does not contain anything (in particular, it does not |
| // contain a deleted key), we know the key is not in the map. |
| if (existingKey === null) return -1; |
| // The key is in the map, return its index. |
| if (existingKey == key) return hash; |
| // Go to the next probe. |
| hash = _nextProbe(hash, numberOfProbes++, _keys.length); |
| // _ensureCapacity has guaranteed the following cannot happen. |
| // assert(hash != initialHash); |
| } |
| } |
| |
| void _ensureCapacity() { |
| int newNumberOfEntries = _numberOfEntries + 1; |
| // Test if adding an element will reach the load limit. |
| if (newNumberOfEntries >= _loadLimit) { |
| _grow(_keys.length * 2); |
| return; |
| } |
| |
| // Make sure that we don't have poor performance when a map |
| // contains lots of deleted entries: we _grow if |
| // there are more deleted entried than free entries. |
| int capacity = _keys.length; |
| int numberOfFreeOrDeleted = capacity - newNumberOfEntries; |
| int numberOfFree = numberOfFreeOrDeleted - _numberOfDeleted; |
| // assert(numberOfFree > 0); |
| if (_numberOfDeleted > numberOfFree) { |
| _grow(_keys.length); |
| } |
| } |
| |
| static bool _isPowerOfTwo(int x) { |
| return ((x & (x - 1)) == 0); |
| } |
| |
| void _grow(int newCapacity) { |
| assert(_isPowerOfTwo(newCapacity)); |
| int capacity = _keys.length; |
| _loadLimit = _computeLoadLimit(newCapacity); |
| List oldKeys = _keys; |
| List<V> oldValues = _values; |
| _keys = new List(newCapacity); |
| _values = new List<V>(newCapacity); |
| for (int i = 0; i < capacity; i++) { |
| // [key] can be either of type [K] or [_DeletedKeySentinel]. |
| Object key = oldKeys[i]; |
| // If there is no key, we don't need to deal with the current slot. |
| if (key === null || key === _DELETED_KEY) { |
| continue; |
| } |
| V value = oldValues[i]; |
| // Insert the {key, value} pair in their new slot. |
| int newIndex = _probeForAdding(key); |
| _keys[newIndex] = key; |
| _values[newIndex] = value; |
| } |
| _numberOfDeleted = 0; |
| } |
| |
| void clear() { |
| _numberOfEntries = 0; |
| _numberOfDeleted = 0; |
| int length = _keys.length; |
| for (int i = 0; i < length; i++) { |
| _keys[i] = null; |
| _values[i] = null; |
| } |
| } |
| |
| void operator []=(K key, V value) { |
| _ensureCapacity(); |
| int index = _probeForAdding(key); |
| if ((_keys[index] === null) || (_keys[index] === _DELETED_KEY)) { |
| _numberOfEntries++; |
| } |
| _keys[index] = key; |
| _values[index] = value; |
| } |
| |
| V operator [](K key) { |
| int index = _probeForLookup(key); |
| if (index < 0) return null; |
| return _values[index]; |
| } |
| |
| V putIfAbsent(K key, V ifAbsent()) { |
| int index = _probeForLookup(key); |
| if (index >= 0) return _values[index]; |
| |
| V value = ifAbsent(); |
| this[key] = value; |
| return value; |
| } |
| |
| V remove(K key) { |
| int index = _probeForLookup(key); |
| if (index >= 0) { |
| _numberOfEntries--; |
| V value = _values[index]; |
| _values[index] = null; |
| // Set the key to the sentinel to not break the probing chain. |
| _keys[index] = _DELETED_KEY; |
| _numberOfDeleted++; |
| return value; |
| } |
| return null; |
| } |
| |
| bool get isEmpty { |
| return _numberOfEntries == 0; |
| } |
| |
| int get length { |
| return _numberOfEntries; |
| } |
| |
| void forEach(void f(K key, V value)) { |
| int length = _keys.length; |
| for (int i = 0; i < length; i++) { |
| var key = _keys[i]; |
| if ((key !== null) && (key !== _DELETED_KEY)) { |
| f(key, _values[i]); |
| } |
| } |
| } |
| |
| |
| Collection<K> get keys { |
| List<K> list = new List<K>(length); |
| int i = 0; |
| forEach(void _(K key, V value) { |
| list[i++] = key; |
| }); |
| return list; |
| } |
| |
| Collection<V> get values { |
| List<V> list = new List<V>(length); |
| int i = 0; |
| forEach(void _(K key, V value) { |
| list[i++] = value; |
| }); |
| return list; |
| } |
| |
| bool containsKey(K key) { |
| return (_probeForLookup(key) != -1); |
| } |
| |
| bool containsValue(V value) { |
| int length = _values.length; |
| for (int i = 0; i < length; i++) { |
| var key = _keys[i]; |
| if ((key !== null) && (key !== _DELETED_KEY)) { |
| if (_values[i] == value) return true; |
| } |
| } |
| return false; |
| } |
| |
| String toString() { |
| return Maps.mapToString(this); |
| } |
| } |
| |
| class HashSetImplementation<E > implements HashSet<E> { |
| |
| HashSetImplementation() { |
| _backingMap = new HashMapImplementation<E, E>(); |
| } |
| |
| factory HashSetImplementation.from(Iterable<E> other) { |
| Set<E> set = new HashSetImplementation<E>(); |
| for (final e in other) { |
| set.add(e); |
| } |
| return set; |
| } |
| |
| void clear() { |
| _backingMap.clear(); |
| } |
| |
| void add(E value) { |
| _backingMap[value] = value; |
| } |
| |
| bool contains(E value) { |
| return _backingMap.containsKey(value); |
| } |
| |
| bool remove(E value) { |
| if (!_backingMap.containsKey(value)) return false; |
| _backingMap.remove(value); |
| return true; |
| } |
| |
| void addAll(Collection<E> collection) { |
| collection.forEach(void _(E value) { |
| add(value); |
| }); |
| } |
| |
| Set<E> intersection(Collection<E> collection) { |
| Set<E> result = new Set<E>(); |
| collection.forEach(void _(E value) { |
| if (contains(value)) result.add(value); |
| }); |
| return result; |
| } |
| |
| bool isSubsetOf(Collection<E> other) { |
| return new Set<E>.from(other).containsAll(this); |
| } |
| |
| void removeAll(Collection<E> collection) { |
| collection.forEach(void _(E value) { |
| remove(value); |
| }); |
| } |
| |
| bool containsAll(Collection<E> collection) { |
| return collection.every(bool _(E value) { |
| return contains(value); |
| }); |
| } |
| |
| void forEach(void f(E element)) { |
| _backingMap.forEach(void _(E key, E value) { |
| f(key); |
| }); |
| } |
| |
| Set map(f(E element)) { |
| Set result = new Set(); |
| _backingMap.forEach(void _(E key, E value) { |
| result.add(f(key)); |
| }); |
| return result; |
| } |
| |
| Dynamic reduce(Dynamic initialValue, |
| Dynamic combine(Dynamic previousValue, E element)) { |
| return Collections.reduce(this, initialValue, combine); |
| } |
| |
| Set<E> filter(bool f(E element)) { |
| Set<E> result = new Set<E>(); |
| _backingMap.forEach(void _(E key, E value) { |
| if (f(key)) result.add(key); |
| }); |
| return result; |
| } |
| |
| bool every(bool f(E element)) { |
| Collection<E> keys = _backingMap.keys; |
| return keys.every(f); |
| } |
| |
| bool some(bool f(E element)) { |
| Collection<E> keys = _backingMap.keys; |
| return keys.some(f); |
| } |
| |
| bool get isEmpty { |
| return _backingMap.isEmpty; |
| } |
| |
| int get length { |
| return _backingMap.length; |
| } |
| |
| Iterator<E> iterator() { |
| return new HashSetIterator<E>(this); |
| } |
| |
| String toString() { |
| return Collections.collectionToString(this); |
| } |
| |
| // The map backing this set. The associations in this map are all |
| // of the form element -> element. If a value is not in the map, |
| // then it is not in the set. |
| HashMapImplementation<E, E> _backingMap; |
| } |
| |
| class HashSetIterator<E> implements Iterator<E> { |
| |
| // TODO(4504458): Replace set_ with set. |
| HashSetIterator(HashSetImplementation<E> set_) |
| : _nextValidIndex = -1, |
| _entries = set_._backingMap._keys { |
| _advance(); |
| } |
| |
| bool get hasNext { |
| if (_nextValidIndex >= _entries.length) return false; |
| if (_entries[_nextValidIndex] === HashMapImplementation._DELETED_KEY) { |
| // This happens in case the set was modified in the meantime. |
| // A modification on the set may make this iterator misbehave, |
| // but we should never return the sentinel. |
| _advance(); |
| } |
| return _nextValidIndex < _entries.length; |
| } |
| |
| E next() { |
| if (!hasNext) { |
| throw new StateError("No more elements"); |
| } |
| E res = _entries[_nextValidIndex]; |
| _advance(); |
| return res; |
| } |
| |
| void _advance() { |
| int length = _entries.length; |
| var entry; |
| final deletedKey = HashMapImplementation._DELETED_KEY; |
| do { |
| if (++_nextValidIndex >= length) break; |
| entry = _entries[_nextValidIndex]; |
| } while ((entry === null) || (entry === deletedKey)); |
| } |
| |
| // The entries in the set. May contain null or the sentinel value. |
| List<E> _entries; |
| |
| // The next valid index in [_entries] or the length of [entries_]. |
| // If it is the length of [_entries], calling [hasNext] on the |
| // iterator will return false. |
| int _nextValidIndex; |
| } |
| |
| /** |
| * A singleton sentinel used to represent when a key is deleted from the map. |
| * We can't use [: const Object() :] as a sentinel because it would end up |
| * canonicalized and then we cannot distinguish the deleted key from the |
| * canonicalized [: Object() :]. |
| */ |
| class _DeletedKeySentinel { |
| const _DeletedKeySentinel(); |
| } |