| /* |
| * Copyright 2000-2013 JetBrains s.r.o. |
| * |
| * 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.intellij.util.containers; |
| |
| import gnu.trove.TObjectHashingStrategy; |
| import org.jetbrains.annotations.NotNull; |
| import org.jetbrains.annotations.Nullable; |
| |
| import java.util.*; |
| import java.util.concurrent.ConcurrentMap; |
| |
| /** |
| * similar to java.util.ConcurrentHashMap except: |
| * conserved as much memory as possible by |
| * -- using only one Segment |
| * -- eliminating unnecessary fields |
| * -- using one of 256 ReentrantLock for Segment statically preallocated in {@link StripedReentrantLocks} |
| * added hashing strategy argument |
| * made not Serializable |
| */ |
| public class StripedLockConcurrentHashMap<K, V> extends _CHMSegment<K, V> implements ConcurrentMap<K, V> { |
| /* ---------------- Constants -------------- */ |
| |
| /** |
| * The default initial number of table slots for this table. |
| * Used when not otherwise specified in constructor. |
| */ |
| static int DEFAULT_INITIAL_CAPACITY = 16; |
| |
| /** |
| * The maximum capacity, used if a higher value is implicitly |
| * specified by either of the constructors with arguments. MUST |
| * be a power of two <= 1<<30 to ensure that entries are indexible |
| * using ints. |
| */ |
| static final int MAXIMUM_CAPACITY = 1 << 30; |
| |
| /** |
| * The default load factor for this table. Used when not |
| * otherwise specified in constructor. |
| */ |
| public static final float DEFAULT_LOAD_FACTOR = 0.75f; |
| |
| |
| /* ---------------- Public operations -------------- */ |
| |
| public static <K,V> StripedLockConcurrentHashMap<K,V> createWithStrategy(@NotNull final TObjectHashingStrategy<K> hashingStrategy, int initialCapacity) { |
| return new StripedLockConcurrentHashMap<K, V>(initialCapacity){ |
| @Override |
| protected TObjectHashingStrategy<K> getHashingStrategy() { |
| return hashingStrategy; |
| } |
| }; |
| } |
| |
| public StripedLockConcurrentHashMap(int initialCapacity) { |
| super(getInitCap(initialCapacity, DEFAULT_LOAD_FACTOR)); |
| } |
| |
| private static int getInitCap(int initialCapacity, float loadFactor) { |
| if (loadFactor <= 0 || initialCapacity < 0) { |
| throw new IllegalArgumentException(); |
| } |
| |
| if (initialCapacity > MAXIMUM_CAPACITY) { |
| initialCapacity = MAXIMUM_CAPACITY; |
| } |
| int cap = 1; |
| while (cap < initialCapacity) { |
| cap <<= 1; |
| } |
| return cap; |
| } |
| |
| /** |
| * Creates a new, empty map with a default initial capacity, |
| * load factor, and concurrencyLevel. |
| */ |
| public StripedLockConcurrentHashMap() { |
| this(DEFAULT_INITIAL_CAPACITY); |
| } |
| |
| /** |
| * Creates a new map with the same mappings as the given map. The |
| * map is created with a capacity of twice the number of mappings in |
| * the given map or 11 (whichever is greater), and a default load factor |
| * and concurrencyLevel. |
| * |
| * @param t the map |
| */ |
| public StripedLockConcurrentHashMap(@NotNull Map<? extends K, ? extends V> t) { |
| this(Math.max((int)(t.size() / DEFAULT_LOAD_FACTOR) + 1, 11)); |
| putAll(t); |
| } |
| |
| // inherit Map javadoc |
| |
| @Override |
| public boolean isEmpty() { |
| return count == 0; |
| } |
| |
| // inherit Map javadoc |
| |
| @Override |
| public int size() { |
| return count; |
| } |
| |
| |
| /** |
| * Returns the value to which the specified key is mapped in this table. |
| * |
| * @param key a key in the table. |
| * @return the value to which the key is mapped in this table; |
| * <tt>null</tt> if the key is not mapped to any value in |
| * this table. |
| * @throws NullPointerException if the key is |
| * <tt>null</tt>. |
| */ |
| @Override |
| public V get(@NotNull Object key) { |
| K kKey = (K)key; |
| int hash = getHashingStrategy().computeHashCode(kKey); // throws NullPointerException if key null |
| return get(kKey, hash); |
| } |
| |
| /** |
| * Tests if the specified object is a key in this table. |
| * |
| * @param key possible key. |
| * @return <tt>true</tt> if and only if the specified object |
| * is a key in this table, as determined by the |
| * <tt>equals</tt> method; <tt>false</tt> otherwise. |
| * @throws NullPointerException if the key is |
| * <tt>null</tt>. |
| */ |
| @Override |
| public boolean containsKey(@NotNull Object key) { |
| K kKey = (K)key; |
| int hash = getHashingStrategy().computeHashCode(kKey); // throws NullPointerException if key null |
| return containsKey(kKey, hash); |
| } |
| |
| /** |
| * Legacy method testing if some key maps into the specified value |
| * in this table. This method is identical in functionality to |
| * {@link #containsValue}, and exists solely to ensure |
| * full compatibility with class {@link java.util.Hashtable}, |
| * which supported this method prior to introduction of the |
| * Java Collections framework. |
| * |
| * @param value a value to search for. |
| * @return <tt>true</tt> if and only if some key maps to the |
| * <tt>value</tt> argument in this table as |
| * determined by the <tt>equals</tt> method; |
| * <tt>false</tt> otherwise. |
| * @throws NullPointerException if the value is <tt>null</tt>. |
| */ |
| public boolean contains(@NotNull Object value) { |
| return containsValue(value); |
| } |
| |
| /** |
| * Maps the specified <tt>key</tt> to the specified |
| * <tt>value</tt> in this table. Neither the key nor the |
| * value can be <tt>null</tt>. |
| * <p/> |
| * <p> The value can be retrieved by calling the <tt>get</tt> method |
| * with a key that is equal to the original key. |
| * |
| * @param key the table key. |
| * @param value the value. |
| * @return the previous value of the specified key in this table, |
| * or <tt>null</tt> if it did not have one. |
| * @throws NullPointerException if the key or value is |
| * <tt>null</tt>. |
| */ |
| @Override |
| public V put(@NotNull K key, @NotNull V value) { |
| int hash = getHashingStrategy().computeHashCode(key); |
| return put(key, hash, value, false); |
| } |
| |
| /** |
| * If the specified key is not already associated |
| * with a value, associate it with the given value. |
| * This is equivalent to |
| * <pre> |
| * if (!map.containsKey(key)) |
| * return map.put(key, value); |
| * else |
| * return map.get(key); |
| * </pre> |
| * Except that the action is performed atomically. |
| * |
| * @param key key with which the specified value is to be associated. |
| * @param value value to be associated with the specified key. |
| * @return previous value associated with specified key, or <tt>null</tt> |
| * if there was no mapping for key. |
| * @throws NullPointerException if the specified key or value is |
| * <tt>null</tt>. |
| */ |
| @Override |
| public V putIfAbsent(@NotNull K key, @NotNull V value) { |
| int hash = getHashingStrategy().computeHashCode(key); |
| return put(key, hash, value, true); |
| } |
| |
| |
| /** |
| * Copies all of the mappings from the specified map to this one. |
| * <p/> |
| * These mappings replace any mappings that this map had for any of the |
| * keys currently in the specified Map. |
| * |
| * @param t Mappings to be stored in this map. |
| */ |
| @Override |
| public void putAll(@NotNull Map<? extends K, ? extends V> t) { |
| for (Entry<? extends K, ? extends V> e : t.entrySet()) { |
| V value = e.getValue(); |
| if (value != null) { // null is possible if the entry has just been removed |
| put(e.getKey(), value); |
| } |
| } |
| } |
| |
| /** |
| * Removes the key (and its corresponding value) from this |
| * table. This method does nothing if the key is not in the table. |
| * |
| * @param key the key that needs to be removed. |
| * @return the value to which the key had been mapped in this table, |
| * or <tt>null</tt> if the key did not have a mapping. |
| * @throws NullPointerException if the key is |
| * <tt>null</tt>. |
| */ |
| @Override |
| public V remove(@NotNull Object key) { |
| K kKey = (K)key; |
| int hash = getHashingStrategy().computeHashCode(kKey); |
| return remove(kKey, hash, null); |
| } |
| |
| /** |
| * Remove entry for key only if currently mapped to given value. |
| * Acts as |
| * <pre> |
| * if (map.get(key).equals(value)) { |
| * map.remove(key); |
| * return true; |
| * } else return false; |
| * </pre> |
| * except that the action is performed atomically. |
| * |
| * @param key key with which the specified value is associated. |
| * @param value value associated with the specified key. |
| * @return true if the value was removed |
| * @throws NullPointerException if the specified key is |
| * <tt>null</tt>. |
| */ |
| @Override |
| public boolean remove(@NotNull Object key, @NotNull Object value) { |
| K kKey = (K)key; |
| int hash = getHashingStrategy().computeHashCode(kKey); |
| return remove(kKey, hash, value) != null; |
| } |
| |
| |
| /** |
| * Replace entry for key only if currently mapped to given value. |
| * Acts as |
| * <pre> |
| * if (map.get(key).equals(oldValue)) { |
| * map.put(key, newValue); |
| * return true; |
| * } else return false; |
| * </pre> |
| * except that the action is performed atomically. |
| * |
| * @param key key with which the specified value is associated. |
| * @param oldValue value expected to be associated with the specified key. |
| * @param newValue value to be associated with the specified key. |
| * @return true if the value was replaced |
| * @throws NullPointerException if the specified key or values are |
| * <tt>null</tt>. |
| */ |
| @Override |
| public boolean replace(@NotNull K key, @NotNull V oldValue, @NotNull V newValue) { |
| int hash = getHashingStrategy().computeHashCode(key); |
| return replace(key, hash, oldValue, newValue); |
| } |
| |
| /** |
| * Replace entry for key only if currently mapped to some value. |
| * Acts as |
| * <pre> |
| * if ((map.containsKey(key)) { |
| * return map.put(key, value); |
| * } else return null; |
| * </pre> |
| * except that the action is performed atomically. |
| * |
| * @param key key with which the specified value is associated. |
| * @param value value to be associated with the specified key. |
| * @return previous value associated with specified key, or <tt>null</tt> |
| * if there was no mapping for key. |
| * @throws NullPointerException if the specified key or value is |
| * <tt>null</tt>. |
| */ |
| @Override |
| public V replace(@NotNull K key, @NotNull V value) { |
| int hash = getHashingStrategy().computeHashCode(key); |
| return replace(key, hash, value); |
| } |
| |
| |
| /** |
| * Returns a set view of the keys contained in this map. The set is |
| * backed by the map, so changes to the map are reflected in the set, and |
| * vice-versa. The set supports element removal, which removes the |
| * corresponding mapping from this map, via the <tt>Iterator.remove</tt>, |
| * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and |
| * <tt>clear</tt> operations. It does not support the <tt>add</tt> or |
| * <tt>addAll</tt> operations. |
| * The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that |
| * will never throw {@link java.util.ConcurrentModificationException}, |
| * and guarantees to traverse elements as they existed upon |
| * construction of the iterator, and may (but is not guaranteed to) |
| * reflect any modifications subsequent to construction. |
| * |
| * @return a set view of the keys contained in this map. |
| */ |
| @NotNull |
| @Override |
| public Set<K> keySet() { |
| return new KeySet(); //conserve memory by not caching keyset |
| } |
| |
| |
| /** |
| * Returns a collection view of the values contained in this map. The |
| * collection is backed by the map, so changes to the map are reflected in |
| * the collection, and vice-versa. The collection supports element |
| * removal, which removes the corresponding mapping from this map, via the |
| * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>, |
| * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations. |
| * It does not support the <tt>add</tt> or <tt>addAll</tt> operations. |
| * The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that |
| * will never throw {@link java.util.ConcurrentModificationException}, |
| * and guarantees to traverse elements as they existed upon |
| * construction of the iterator, and may (but is not guaranteed to) |
| * reflect any modifications subsequent to construction. |
| * |
| * @return a collection view of the values contained in this map. |
| */ |
| @NotNull |
| @Override |
| public Collection<V> values() { |
| return new Values(); //conserve memory by not caching |
| } |
| |
| |
| /** |
| * Returns a collection view of the mappings contained in this map. Each |
| * element in the returned collection is a <tt>Map.Entry</tt>. The |
| * collection is backed by the map, so changes to the map are reflected in |
| * the collection, and vice-versa. The collection supports element |
| * removal, which removes the corresponding mapping from the map, via the |
| * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>, |
| * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations. |
| * It does not support the <tt>add</tt> or <tt>addAll</tt> operations. |
| * The view's returned <tt>iterator</tt> is a "weakly consistent" iterator that |
| * will never throw {@link java.util.ConcurrentModificationException}, |
| * and guarantees to traverse elements as they existed upon |
| * construction of the iterator, and may (but is not guaranteed to) |
| * reflect any modifications subsequent to construction. |
| * |
| * @return a collection view of the mappings contained in this map. |
| */ |
| @NotNull |
| @Override |
| public Set<Entry<K, V>> entrySet() { |
| return new EntrySet(); //conserve memory by not caching |
| } |
| |
| |
| /** |
| * Returns an enumeration of the keys in this table. |
| * |
| * @return an enumeration of the keys in this table. |
| * @see #keySet |
| */ |
| public Enumeration<K> keys() { |
| return new KeyIterator(); |
| } |
| |
| /** |
| * Returns an enumeration of the values in this table. |
| * |
| * @return an enumeration of the values in this table. |
| * @see #values |
| */ |
| public Enumeration<V> elements() { |
| return new ValueIterator(); |
| } |
| |
| /* ---------------- Iterator Support -------------- */ |
| |
| abstract class HashIterator { |
| int nextSegmentIndex; |
| int nextTableIndex; |
| HashEntry[] currentTable; |
| HashEntry<K, V> nextEntry; |
| HashEntry<K, V> lastReturned; |
| |
| HashIterator() { |
| nextSegmentIndex = 0; |
| nextTableIndex = -1; |
| advance(); |
| } |
| |
| public boolean hasMoreElements() { |
| return hasNext(); |
| } |
| |
| final void advance() { |
| if (nextEntry != null && (nextEntry = nextEntry.next) != null) { |
| return; |
| } |
| |
| while (nextTableIndex >= 0) { |
| if ((nextEntry = (HashEntry<K, V>)currentTable[nextTableIndex--]) != null) { |
| return; |
| } |
| } |
| |
| while (nextSegmentIndex >= 0) { |
| _CHMSegment seg = StripedLockConcurrentHashMap.this; |
| nextSegmentIndex--; |
| if (seg.count != 0) { |
| currentTable = seg.table; |
| for (int j = currentTable.length - 1; j >= 0; --j) { |
| if ((nextEntry = (HashEntry<K, V>)currentTable[j]) != null) { |
| nextTableIndex = j - 1; |
| return; |
| } |
| } |
| } |
| } |
| } |
| |
| public boolean hasNext() { |
| return nextEntry != null; |
| } |
| |
| HashEntry<K, V> nextEntry() { |
| if (nextEntry == null) { |
| throw new NoSuchElementException(); |
| } |
| lastReturned = nextEntry; |
| advance(); |
| return lastReturned; |
| } |
| |
| public void remove() { |
| if (lastReturned == null) { |
| throw new IllegalStateException(); |
| } |
| StripedLockConcurrentHashMap.this.remove(lastReturned.key); |
| lastReturned = null; |
| } |
| } |
| |
| final class KeyIterator extends HashIterator implements Iterator<K>, Enumeration<K> { |
| @Override |
| @NotNull |
| public K next() { |
| return nextEntry().key; |
| } |
| |
| @Override |
| @NotNull |
| public K nextElement() { |
| return nextEntry().key; |
| } |
| } |
| |
| final class ValueIterator extends HashIterator implements Iterator<V>, Enumeration<V> { |
| @Override |
| @NotNull |
| public V next() { |
| return nextEntry().value; |
| } |
| |
| @Override |
| @NotNull |
| public V nextElement() { |
| return nextEntry().value; |
| } |
| } |
| |
| |
| /** |
| * Entry iterator. Exported Entry objects must write-through |
| * changes in setValue, even if the nodes have been cloned. So we |
| * cannot return internal HashEntry objects. Instead, the iterator |
| * itself acts as a forwarding pseudo-entry. |
| */ |
| final class EntryIterator extends HashIterator implements Entry<K, V>, Iterator<Entry<K, V>> { |
| @Override |
| @NotNull |
| public Entry<K, V> next() { |
| nextEntry(); |
| return this; |
| } |
| |
| @Override |
| @NotNull |
| public K getKey() { |
| if (lastReturned == null) { |
| throw new IllegalStateException("Entry was removed"); |
| } |
| return lastReturned.key; |
| } |
| |
| @Override |
| @Nullable("null means the entry has just been removed") |
| public V getValue() { |
| if (lastReturned == null) { |
| throw new IllegalStateException("Entry was removed"); |
| } |
| return get(lastReturned.key); |
| } |
| |
| @Override |
| public V setValue(@NotNull V value) { |
| if (lastReturned == null) { |
| throw new IllegalStateException("Entry was removed"); |
| } |
| return put(lastReturned.key, value); |
| } |
| |
| public boolean equals(Object o) { |
| // If not acting as entry, just use default. |
| if (lastReturned == null) { |
| return super.equals(o); |
| } |
| if (!(o instanceof Entry)) { |
| return false; |
| } |
| Entry e = (Entry)o; |
| K o1 = getKey(); |
| K o2 = (K)e.getKey(); |
| return getHashingStrategy().equals(o1, o2) && getValue().equals(e.getValue()); |
| } |
| |
| public int hashCode() { |
| // If not acting as entry, just use default. |
| if (lastReturned == null) { |
| return super.hashCode(); |
| } |
| |
| Object k = getKey(); |
| Object v = getValue(); |
| return k.hashCode() ^ v.hashCode(); |
| } |
| |
| public String toString() { |
| // If not acting as entry, just use default. |
| if (lastReturned == null) { |
| return super.toString(); |
| } |
| return getKey() + "=" + getValue(); |
| } |
| } |
| |
| final class KeySet extends AbstractSet<K> { |
| @NotNull |
| @Override |
| public Iterator<K> iterator() { |
| return new KeyIterator(); |
| } |
| |
| @Override |
| public int size() { |
| return StripedLockConcurrentHashMap.this.size(); |
| } |
| |
| @Override |
| public boolean contains(Object o) { |
| return containsKey(o); |
| } |
| |
| @Override |
| public boolean remove(Object o) { |
| return StripedLockConcurrentHashMap.this.remove(o) != null; |
| } |
| |
| @Override |
| public void clear() { |
| StripedLockConcurrentHashMap.this.clear(); |
| } |
| |
| @NotNull |
| @Override |
| public Object[] toArray() { |
| Collection<K> c = new ArrayList<K>(); |
| for (K k : this) { |
| c.add(k); |
| } |
| return c.toArray(); |
| } |
| |
| @NotNull |
| @Override |
| public <T> T[] toArray(@NotNull T[] a) { |
| Collection<K> c = new ArrayList<K>(); |
| for (K k : this) { |
| c.add(k); |
| } |
| return c.toArray(a); |
| } |
| } |
| |
| final class Values extends AbstractCollection<V> { |
| @NotNull |
| @Override |
| public Iterator<V> iterator() { |
| return new ValueIterator(); |
| } |
| |
| @Override |
| public int size() { |
| return StripedLockConcurrentHashMap.this.size(); |
| } |
| |
| @Override |
| public boolean contains(Object o) { |
| return containsValue(o); |
| } |
| |
| @Override |
| public void clear() { |
| StripedLockConcurrentHashMap.this.clear(); |
| } |
| |
| @NotNull |
| @Override |
| public Object[] toArray() { |
| Collection<V> c = new ArrayList<V>(); |
| for (V k : this) { |
| c.add(k); |
| } |
| return c.toArray(); |
| } |
| |
| @NotNull |
| @Override |
| public <T> T[] toArray(@NotNull T[] a) { |
| Collection<V> c = new ArrayList<V>(); |
| for (V k : this) { |
| c.add(k); |
| } |
| return c.toArray(a); |
| } |
| } |
| |
| final class EntrySet extends AbstractSet<Entry<K, V>> { |
| @NotNull |
| @Override |
| public Iterator<Entry<K, V>> iterator() { |
| return new EntryIterator(); |
| } |
| |
| @Override |
| public boolean contains(Object o) { |
| if (!(o instanceof Entry)) { |
| return false; |
| } |
| Entry<K, V> e = (Entry<K, V>)o; |
| V v = get(e.getKey()); |
| return v != null && v.equals(e.getValue()); |
| } |
| |
| @Override |
| public boolean remove(Object o) { |
| if (!(o instanceof Entry)) { |
| return false; |
| } |
| Entry<K, V> e = (Entry<K, V>)o; |
| return StripedLockConcurrentHashMap.this.remove(e.getKey(), e.getValue()); |
| } |
| |
| @Override |
| public int size() { |
| return StripedLockConcurrentHashMap.this.size(); |
| } |
| |
| @Override |
| public void clear() { |
| StripedLockConcurrentHashMap.this.clear(); |
| } |
| |
| @NotNull |
| @Override |
| public Object[] toArray() { |
| // Since we don't ordinarily have distinct Entry objects, we |
| // must pack elements using exportable SimpleEntry |
| Collection<Entry<K, V>> c = new ArrayList<Entry<K, V>>(size()); |
| for (Entry<K, V> i : this) { |
| c.add(new SimpleEntry(i)); |
| } |
| return c.toArray(); |
| } |
| |
| @NotNull |
| @Override |
| public <T> T[] toArray(@NotNull T[] a) { |
| Collection<Entry<K, V>> c = new ArrayList<Entry<K, V>>(size()); |
| for (Entry<K, V> i : this) { |
| c.add(new SimpleEntry(i)); |
| } |
| return c.toArray(a); |
| } |
| } |
| |
| /** |
| * This duplicates java.util.AbstractMap.SimpleEntry until this class |
| * is made accessible. |
| */ |
| final class SimpleEntry implements Entry<K, V> { |
| final K key; |
| V value; |
| |
| public SimpleEntry(@NotNull Entry<K, V> e) { |
| key = e.getKey(); |
| value = e.getValue(); |
| } |
| |
| @Override |
| @NotNull |
| public K getKey() { |
| return key; |
| } |
| |
| @Override |
| @NotNull |
| public V getValue() { |
| return value; |
| } |
| |
| @Override |
| public V setValue(@NotNull V value) { |
| V oldValue = this.value; |
| this.value = value; |
| return oldValue; |
| } |
| |
| public boolean equals(Object o) { |
| if (!(o instanceof Entry)) { |
| return false; |
| } |
| Entry e = (Entry)o; |
| K o2 = (K)e.getKey(); |
| return getHashingStrategy().equals(key, o2) && value.equals(e.getValue()); |
| } |
| |
| public int hashCode() { |
| return key.hashCode() ^ value.hashCode(); |
| } |
| |
| public String toString() { |
| return key + "=" + value; |
| } |
| } |
| |
| static class CanonicalHashingStrategy<K> implements TObjectHashingStrategy<K> { |
| private static final CanonicalHashingStrategy INSTANCE = new CanonicalHashingStrategy(); |
| |
| @SuppressWarnings("unchecked") |
| static <K> CanonicalHashingStrategy<K> getInstance() { |
| return INSTANCE; |
| } |
| |
| @Override |
| public int computeHashCode(final K object) { |
| int h = object.hashCode(); |
| // performance matters here |
| //h += ~(h << 9); |
| //h ^= h >>> 14; |
| //h += h << 4; |
| //h ^= h >>> 10; |
| return h; |
| } |
| |
| @Override |
| public boolean equals(@NotNull K o1, @NotNull K o2) { |
| return o1.equals(o2); |
| } |
| } |
| } |
| |
| /** |
| * Segments are specialized versions of hash tables. This |
| * subclasses from ReentrantLock opportunistically, just to |
| * simplify some locking and avoid separate construction. |
| */ |
| class _CHMSegment<K, V> { |
| private static final StripedReentrantLocks STRIPED_REENTRANT_LOCKS = StripedReentrantLocks.getInstance(); |
| private final byte lockIndex = (byte)STRIPED_REENTRANT_LOCKS.allocateLockIndex(); |
| |
| private void lock() { |
| STRIPED_REENTRANT_LOCKS.lock((int)lockIndex & 0xff); |
| if (modificationBlocked) throw new ConcurrentModificationException(); |
| } |
| |
| private void unlock() { |
| STRIPED_REENTRANT_LOCKS.unlock((int)lockIndex & 0xff); |
| } |
| /* |
| * Segments maintain a table of entry lists that are ALWAYS |
| * kept in a consistent state, so can be read without locking. |
| * Next fields of nodes are immutable (final). All list |
| * additions are performed at the front of each bin. This |
| * makes it easy to check changes, and also fast to traverse. |
| * When nodes would otherwise be changed, new nodes are |
| * created to replace them. This works well for hash tables |
| * since the bin lists tend to be short. (The average length |
| * is less than two for the default load factor threshold.) |
| * |
| * Read operations can thus proceed without locking, but rely |
| * on selected uses of volatiles to ensure that completed |
| * write operations performed by other threads are |
| * noticed. For most purposes, the "count" field, tracking the |
| * number of elements, serves as that volatile variable |
| * ensuring visibility. This is convenient because this field |
| * needs to be read in many read operations anyway: |
| * |
| * - All (unsynchronized) read operations must first read the |
| * "count" field, and should not look at table entries if |
| * it is 0. |
| * |
| * - All (synchronized) write operations should write to |
| * the "count" field after structurally changing any bin. |
| * The operations must not take any action that could even |
| * momentarily cause a concurrent read operation to see |
| * inconsistent data. This is made easier by the nature of |
| * the read operations in Map. For example, no operation |
| * can reveal that the table has grown but the threshold |
| * has not yet been updated, so there are no atomicity |
| * requirements for this with respect to reads. |
| * |
| * As a guide, all critical volatile reads and writes to the |
| * count field are marked in code comments. |
| */ |
| |
| /** |
| * The number of elements in this segment's region. |
| */ |
| volatile int count; |
| |
| /* |
| * The table is rehashed when its size exceeds this threshold. |
| */ |
| private int threshold() { |
| return (int)(table.length * loadFactor); |
| } |
| |
| /** |
| * The per-segment table. Declared as a raw type, casted |
| * to HashEntry<K,V> on each use. |
| */ |
| volatile HashEntry[] table; |
| |
| private static final float loadFactor = 0.75f; |
| private volatile boolean modificationBlocked; // the only state transition is 0 -> 1 |
| |
| _CHMSegment(int initialCapacity) { |
| setTable(new HashEntry[initialCapacity]); |
| } |
| |
| public void blockModification() { |
| try { |
| lock(); |
| modificationBlocked = true; |
| } |
| finally { |
| unlock(); |
| } |
| } |
| |
| /* |
| * Set table to new HashEntry array. |
| * Call only while holding lock or in constructor. |
| */ |
| void setTable(HashEntry[] newTable) { |
| table = newTable; |
| } |
| |
| /* |
| * Return properly casted first entry of bin for given hash |
| */ |
| HashEntry<K, V> getFirst(int hash) { |
| HashEntry[] tab = table; |
| return tab[hash & tab.length - 1]; |
| } |
| |
| /* |
| * Read value field of an entry under lock. Called if value |
| * field ever appears to be null. This is possible only if a |
| * compiler happens to reorder a HashEntry initialization with |
| * its table assignment, which is legal under memory model |
| * but is not known to ever occur. |
| */ |
| V readValueUnderLock(HashEntry<K, V> e) { |
| try { |
| lock(); |
| return e.value; |
| } |
| finally { |
| unlock(); |
| } |
| } |
| |
| /* Specialized implementations of map methods */ |
| |
| V get(K key, int hash) { |
| if (count != 0) { // read-volatile |
| HashEntry<K, V> e = getFirst(hash); |
| while (e != null) { |
| if (e.hash == hash && getHashingStrategy().equals(key, e.key)) { |
| V v = e.value; |
| if (v != null) { |
| return v; |
| } |
| return readValueUnderLock(e); // recheck |
| } |
| e = e.next; |
| } |
| } |
| return null; |
| } |
| |
| boolean containsKey(K key, int hash) { |
| if (count != 0) { // read-volatile |
| HashEntry<K, V> e = getFirst(hash); |
| while (e != null) { |
| if (e.hash == hash && getHashingStrategy().equals(key, e.key)) { |
| return true; |
| } |
| e = e.next; |
| } |
| } |
| return false; |
| } |
| |
| public boolean containsValue(Object value) { |
| if (count != 0) { // read-volatile |
| HashEntry[] tab = table; |
| int len = tab.length; |
| for (int i = 0; i < len; i++) { |
| for (HashEntry<K, V> e = tab[i]; e != null; e = e.next) { |
| V v = e.value; |
| if (v == null) // recheck |
| { |
| v = readValueUnderLock(e); |
| } |
| if (value.equals(v)) { |
| return true; |
| } |
| } |
| } |
| } |
| return false; |
| } |
| |
| boolean replace(@NotNull K key, int hash, @NotNull V oldValue, @NotNull V newValue) { |
| try { |
| lock(); |
| HashEntry<K, V> e = getFirst(hash); |
| while (e != null && (e.hash != hash || !getHashingStrategy().equals(key, e.key))) { |
| e = e.next; |
| } |
| |
| boolean replaced = false; |
| if (e != null && oldValue.equals(e.value)) { |
| replaced = true; |
| e.value = newValue; |
| } |
| return replaced; |
| } |
| finally { |
| unlock(); |
| } |
| } |
| |
| V replace(@NotNull K key, int hash, @NotNull V newValue) { |
| try { |
| lock(); |
| HashEntry<K, V> e = getFirst(hash); |
| while (e != null && (e.hash != hash || !getHashingStrategy().equals(key, e.key))) { |
| e = e.next; |
| } |
| |
| V oldValue = null; |
| if (e != null) { |
| oldValue = e.value; |
| e.value = newValue; |
| } |
| return oldValue; |
| } |
| finally { |
| unlock(); |
| } |
| } |
| |
| |
| V put(@NotNull K key, int hash, @NotNull V value, boolean onlyIfAbsent) { |
| try { |
| lock(); |
| int c = count; |
| if (c++ > threshold()) // ensure capacity |
| { |
| rehash(); |
| } |
| HashEntry[] tab = table; |
| int index = hash & tab.length - 1; |
| HashEntry<K, V> first = tab[index]; |
| HashEntry<K, V> e = first; |
| while (e != null && (e.hash != hash || !getHashingStrategy().equals(key, e.key))) { |
| e = e.next; |
| } |
| |
| V oldValue; |
| if (e != null) { |
| oldValue = e.value; |
| if (!onlyIfAbsent) { |
| e.value = value; |
| } |
| } |
| else { |
| oldValue = null; |
| tab[index] = new HashEntry<K, V>(key, hash, first, value); |
| count = c; // write-volatile |
| } |
| return oldValue; |
| } |
| finally { |
| unlock(); |
| } |
| } |
| |
| void rehash() { |
| HashEntry[] oldTable = table; |
| int oldCapacity = oldTable.length; |
| if (oldCapacity >= StripedLockConcurrentHashMap.MAXIMUM_CAPACITY) { |
| return; |
| } |
| |
| /* |
| * Reclassify nodes in each list to new Map. Because we are |
| * using power-of-two expansion, the elements from each bin |
| * must either stay at same index, or move with a power of two |
| * offset. We eliminate unnecessary node creation by catching |
| * cases where old nodes can be reused because their next |
| * fields won't change. Statistically, at the default |
| * threshold, only about one-sixth of them need cloning when |
| * a table doubles. The nodes they replace will be garbage |
| * collectable as soon as they are no longer referenced by any |
| * reader thread that may be in the midst of traversing table |
| * right now. |
| */ |
| |
| HashEntry[] newTable = new HashEntry[oldCapacity << 1]; |
| int sizeMask = newTable.length - 1; |
| for (int i = 0; i < oldCapacity; i++) { |
| // We need to guarantee that any existing reads of old Map can |
| // proceed. So we cannot yet null out each bin. |
| HashEntry<K, V> e = oldTable[i]; |
| |
| if (e != null) { |
| HashEntry<K, V> next = e.next; |
| int idx = e.hash & sizeMask; |
| |
| // Single node on list |
| if (next == null) { |
| newTable[idx] = e; |
| } |
| |
| else { |
| // Reuse trailing consecutive sequence at same slot |
| HashEntry<K, V> lastRun = e; |
| int lastIdx = idx; |
| for (HashEntry<K, V> last = next; |
| last != null; |
| last = last.next) { |
| int k = last.hash & sizeMask; |
| if (k != lastIdx) { |
| lastIdx = k; |
| lastRun = last; |
| } |
| } |
| newTable[lastIdx] = lastRun; |
| |
| // Clone all remaining nodes |
| for (HashEntry<K, V> p = e; p != lastRun; p = p.next) { |
| int k = p.hash & sizeMask; |
| HashEntry<K, V> n = newTable[k]; |
| newTable[k] = new HashEntry<K, V>(p.key, p.hash, n, p.value); |
| } |
| } |
| } |
| } |
| setTable(newTable); |
| } |
| |
| /* |
| * Remove; match on key only if value null, else match both. |
| */ |
| V remove(@NotNull K key, int hash, @Nullable("null means don't care") Object value) { |
| try { |
| lock(); |
| int c = count - 1; |
| HashEntry[] tab = table; |
| int index = hash & tab.length - 1; |
| HashEntry<K, V> first = tab[index]; |
| HashEntry<K, V> e = first; |
| while (e != null && (e.hash != hash || !getHashingStrategy().equals(key, e.key))) { |
| e = e.next; |
| } |
| |
| V oldValue = null; |
| if (e != null) { |
| V v = e.value; |
| if (value == null || value.equals(v)) { |
| oldValue = v; |
| // All entries following removed node can stay |
| // in list, but all preceding ones need to be |
| // cloned. |
| HashEntry<K, V> newFirst = e.next; |
| for (HashEntry<K, V> p = first; p != e; p = p.next) { |
| newFirst = new HashEntry<K, V>(p.key, p.hash, newFirst, p.value); |
| } |
| tab[index] = newFirst; |
| count = c; // write-volatile |
| } |
| } |
| return oldValue; |
| } |
| finally { |
| unlock(); |
| } |
| } |
| |
| public void clear() { |
| if (count != 0) { |
| try { |
| lock(); |
| HashEntry[] tab = table; |
| for (int i = 0; i < tab.length; i++) { |
| tab[i] = null; |
| } |
| count = 0; // write-volatile |
| } |
| finally { |
| unlock(); |
| } |
| } |
| } |
| |
| protected TObjectHashingStrategy<K> getHashingStrategy() { |
| return StripedLockConcurrentHashMap.CanonicalHashingStrategy.getInstance(); |
| } |
| |
| /** |
| * ConcurrentHashMap list entry. Note that this is never exported |
| * out as a user-visible Map.Entry. |
| * <p/> |
| * Because the value field is volatile, not final, it is legal wrt |
| * the Java Memory Model for an unsynchronized reader to see null |
| * instead of initial value when read via a data race. Although a |
| * reordering leading to this is not likely to ever actually |
| * occur, the Segment.readValueUnderLock method is used as a |
| * backup in case a null (pre-initialized) value is ever seen in |
| * an unsynchronized access method. |
| */ |
| static final class HashEntry<K, V> { |
| @NotNull final K key; |
| final int hash; |
| @NotNull volatile V value; |
| final HashEntry<K, V> next; |
| |
| HashEntry(@NotNull K key, int hash, HashEntry<K, V> next, @NotNull V value) { |
| this.key = key; |
| this.hash = hash; |
| this.next = next; |
| this.value = value; |
| } |
| } |
| } |
| |
| |
