com.alibaba.fastjson.util.AntiCollisionHashMap Maven / Gradle / Ivy
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/*
* Copyright 2019 the original author or authors.
*
* Licensed under the Apache, 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.gnu.org/licenses/lgpl-3.0.html
*
* 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.alibaba.fastjson.util;
import java.io.IOException;
import java.io.Serializable;
import java.util.*;
/**
* @deprecated
*/
public class AntiCollisionHashMap extends AbstractMap implements
Map, Cloneable, Serializable {
transient volatile Set keySet = null;
transient volatile Collection values = null;
/**
* The default initial capacity - MUST be a power of two.
*/
static final 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.
*/
static final int MAXIMUM_CAPACITY = 1 << 30;
/**
* The load factor used when none specified in constructor.
*/
static final float DEFAULT_LOAD_FACTOR = 0.75f;
/**
* The table, resized as necessary. Length MUST Always be a power of two.
*/
transient Entry[] table;
/**
* The number of key-value mappings contained in this map.
*/
transient int size;
/**
* The next size value at which to resize (capacity * load factor).
*
* @serial
*/
int threshold;
/**
* The load factor for the hash table.
*
* @serial
*/
final float loadFactor;
/**
* The number of times this SafelyHashMap has been structurally modified
* Structural modifications are those that change the number of mappings in
* the SafelyHashMap or otherwise modify its internal structure (e.g.,
* rehash). This field is used to make iterators on Collection-views of the
* SafelyHashMap fail-fast. (See ConcurrentModificationException).
*/
transient volatile int modCount;
/**
* Constructs an empty SafelyHashMap with the specified initial
* capacity and load factor.
*
* @param initialCapacity
* the initial capacity
* @param loadFactor
* the load factor
* @throws IllegalArgumentException
* if the initial capacity is negative or the load factor is
* nonpositive
*/
final static int M_MASK = 0x8765fed3;
final static int SEED = -2128831035;
final static int KEY = 16777619;
final int random = new Random().nextInt(99999); // a fixed value in an instance
private int hashString(String key) {
int hash = SEED * random;
for (int i = 0; i < key.length(); i++)
hash = (hash * KEY) ^ key.charAt(i);
return (hash ^ (hash >> 1)) & M_MASK;
}
public AntiCollisionHashMap(int initialCapacity, float loadFactor) {
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal initial capacity: "
+ initialCapacity);
if (initialCapacity > MAXIMUM_CAPACITY)
initialCapacity = MAXIMUM_CAPACITY;
if (loadFactor <= 0 || Float.isNaN(loadFactor))
throw new IllegalArgumentException("Illegal load factor: "
+ loadFactor);
// Find a power of 2 >= initialCapacity
int capacity = 1;
while (capacity < initialCapacity)
capacity <<= 1;
this.loadFactor = loadFactor;
threshold = (int) (capacity * loadFactor);
table = new Entry[capacity];
init();
}
/**
* Constructs an empty SafelyHashMap with the specified initial
* capacity and the default load factor (0.75).
*
* @param initialCapacity the initial capacity.
* @throws IllegalArgumentException if the initial capacity is negative.
*/
public AntiCollisionHashMap(int initialCapacity) {
this(initialCapacity, DEFAULT_LOAD_FACTOR);
}
/**
* Constructs an empty SafelyHashMap with the default initial
* capacity (16) and the default load factor (0.75).
*/
public AntiCollisionHashMap() {
this.loadFactor = DEFAULT_LOAD_FACTOR;
threshold = (int) (DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
table = new Entry[DEFAULT_INITIAL_CAPACITY];
init();
}
/**
* Constructs a new SafelyHashMap with the same mappings as the
* specified Map. The SafelyHashMap is created with
* default load factor (0.75) and an initial capacity sufficient to hold the
* mappings in the specified Map.
*
* @param m the map whose mappings are to be placed in this map
* @throws NullPointerException if the specified map is null
*/
public AntiCollisionHashMap(Map m) {
this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
putAllForCreate(m);
}
// internal utilities
/**
* Initialization hook for subclasses. This method is called in all
* constructors and pseudo-constructors (clone, readObject) after
* SafelyHashMap has been initialized but before any entries have been
* inserted. (In the absence of this method, readObject would require
* explicit knowledge of subclasses.)
*/
void init() {
}
/**
* Applies a supplemental hash function to a given hashCode, which defends
* against poor quality hash functions. This is critical because
* SafelyHashMap uses power-of-two length hash tables, that otherwise
* encounter collisions for hashCodes that do not differ in lower bits.
* Note: Null keys always map to hash 0, thus index 0.
*/
static int hash(int h) {
// This function ensures that hashCodes that differ only by
// constant multiples at each bit position have a bounded
// number of collisions (approximately 8 at default load factor).
h = h * h;
h ^= (h >>> 20) ^ (h >>> 12);
return h ^ (h >>> 7) ^ (h >>> 4);
}
/**
* Returns index for hash code h.
*/
static int indexFor(int h, int length) {
return h & (length - 1);
}
/**
* Returns the number of key-value mappings in this map.
*
* @return the number of key-value mappings in this map
*/
public int size() {
return size;
}
/**
* Returns true if this map contains no key-value mappings.
*
* @return true if this map contains no key-value mappings
*/
public boolean isEmpty() {
return size == 0;
}
/**
* Returns the value to which the specified key is mapped, or {@code null}
* if this map contains no mapping for the key.
*
*
* More formally, if this map contains a mapping from a key {@code k} to a
* value {@code v} such that {@code (key==null ? k==null :
* key.equals(k))}, then this method returns {@code v}; otherwise it returns
* {@code null}. (There can be at most one such mapping.)
*
*
* A return value of {@code null} does not necessarily indicate that
* the map contains no mapping for the key; it's also possible that the map
* explicitly maps the key to {@code null}. The {@link #containsKey
* containsKey} operation may be used to distinguish these two cases.
*
* @see #put(Object, Object)
*/
public V get(Object key) {
if (key == null)
return getForNullKey();
int hash = 0;
if (key instanceof String)
hash = hash(hashString((String) key));
else
hash = hash(key.hashCode());
for (Entry e = table[indexFor(hash, table.length)]; e != null; e = e.next) {
Object k;
if (e.hash == hash && ((k = e.key) == key || key.equals(k)))
return e.value;
}
return null;
}
/**
* Offloaded version of get() to look up null keys. Null keys map to index
* 0. This null case is split out into separate methods for the sake of
* performance in the two most commonly used operations (get and put), but
* incorporated with conditionals in others.
*/
private V getForNullKey() {
for (Entry e = table[0]; e != null; e = e.next) {
if (e.key == null)
return e.value;
}
return null;
}
/**
* Returns true if this map contains a mapping for the specified
* key.
*
* @param key The key whose presence in this map is to be tested
* @return true if this map contains a mapping for the specified
* key.
*/
public boolean containsKey(Object key) {
return getEntry(key) != null;
}
/**
* Returns the entry associated with the specified key in the SafelyHashMap.
* Returns null if the SafelyHashMap contains no mapping for the key.
*/
final Entry getEntry(Object key) {
int hash = (key == null) ? 0
: (key instanceof String) ? hash(hashString((String) key))
: hash(key.hashCode());
for (Entry e = table[indexFor(hash, table.length)]; e != null; e = e.next) {
Object k;
if (e.hash == hash
&& ((k = e.key) == key || (key != null && key.equals(k))))
return e;
}
return null;
}
/**
* Associates the specified value with the specified key in this map. If the
* map previously contained a mapping for the key, the old value is
* replaced.
*
* @param key key with which the specified value is to be associated
* @param value value to be associated with the specified key
* @return the previous value associated with key, or null
* if there was no mapping for key. (A null return
* can also indicate that the map previously associated
* null with key.)
*/
public V put(K key, V value) {
if (key == null)
return putForNullKey(value);
int hash = 0;
if (key instanceof String)
hash = hash(hashString((String) key));
else
hash = hash(key.hashCode());
int i = indexFor(hash, table.length);
for (Entry e = table[i]; e != null; e = e.next) {
Object k;
if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
V oldValue = e.value;
e.value = value;
return oldValue;
}
}
modCount++;
addEntry(hash, key, value, i);
return null;
}
/**
* Offloaded version of put for null keys
*/
private V putForNullKey(V value) {
for (Entry e = table[0]; e != null; e = e.next) {
if (e.key == null) {
V oldValue = e.value;
e.value = value;
return oldValue;
}
}
modCount++;
addEntry(0, null, value, 0);
return null;
}
/**
* This method is used instead of put by constructors and pseudoconstructors
* (clone, readObject). It does not resize the table, check for
* comodification, etc. It calls createEntry rather than addEntry.
*/
private void putForCreate(K key, V value) {
int hash = (key == null) ? 0
: (key instanceof String) ? hash(hashString((String) key))
: hash(key.hashCode());
int i = indexFor(hash, table.length);
/**
* Look for preexisting entry for key. This will never happen for clone
* or deserialize. It will only happen for construction if the input Map
* is a sorted map whose ordering is inconsistent w/ equals.
*/
for (Entry e = table[i]; e != null; e = e.next) {
Object k;
if (e.hash == hash
&& ((k = e.key) == key || (key != null && key.equals(k)))) {
e.value = value;
return;
}
}
createEntry(hash, key, value, i);
}
private void putAllForCreate(Map m) {
for (Iterator> i = m
.entrySet().iterator(); i.hasNext(); ) {
Map.Entry e = i.next();
putForCreate(e.getKey(), e.getValue());
}
}
/**
* Rehashes the contents of this map into a new array with a larger
* capacity. This method is called automatically when the number of keys in
* this map reaches its threshold.
*
* If current capacity is MAXIMUM_CAPACITY, this method does not resize the
* map, but sets threshold to Integer.MAX_VALUE. This has the effect of
* preventing future calls.
*
* @param newCapacity the new capacity, MUST be a power of two; must be greater than
* current capacity unless current capacity is MAXIMUM_CAPACITY
* (in which case value is irrelevant).
*/
void resize(int newCapacity) {
Entry[] oldTable = table;
int oldCapacity = oldTable.length;
if (oldCapacity == MAXIMUM_CAPACITY) {
threshold = Integer.MAX_VALUE;
return;
}
Entry[] newTable = new Entry[newCapacity];
transfer(newTable);
table = newTable;
threshold = (int) (newCapacity * loadFactor);
}
/**
* Transfers all entries from current table to newTable.
*/
void transfer(Entry[] newTable) {
Entry[] src = table;
int newCapacity = newTable.length;
for (int j = 0; j < src.length; j++) {
Entry e = src[j];
if (e != null) {
src[j] = null;
do {
Entry next = e.next;
int i = indexFor(e.hash, newCapacity);
e.next = newTable[i];
newTable[i] = e;
e = next;
} while (e != null);
}
}
}
/**
* Copies all of the mappings from the specified map to this map. These
* mappings will replace any mappings that this map had for any of the keys
* currently in the specified map.
*
* @param m mappings to be stored in this map
* @throws NullPointerException if the specified map is null
*/
public void putAll(Map m) {
int numKeysToBeAdded = m.size();
if (numKeysToBeAdded == 0)
return;
/*
* Expand the map if the map if the number of mappings to be added is
* greater than or equal to threshold. This is conservative; the obvious
* condition is (m.size() + size) >= threshold, but this condition could
* result in a map with twice the appropriate capacity, if the keys to
* be added overlap with the keys already in this map. By using the
* conservative calculation, we subject ourself to at most one extra
* resize.
*/
if (numKeysToBeAdded > threshold) {
int targetCapacity = (int) (numKeysToBeAdded / loadFactor + 1);
if (targetCapacity > MAXIMUM_CAPACITY)
targetCapacity = MAXIMUM_CAPACITY;
int newCapacity = table.length;
while (newCapacity < targetCapacity)
newCapacity <<= 1;
if (newCapacity > table.length)
resize(newCapacity);
}
for (Iterator> i = m
.entrySet().iterator(); i.hasNext(); ) {
Map.Entry e = i.next();
put(e.getKey(), e.getValue());
}
}
/**
* Removes the mapping for the specified key from this map if present.
*
* @param key key whose mapping is to be removed from the map
* @return the previous value associated with key, or null
* if there was no mapping for key. (A null return
* can also indicate that the map previously associated
* null with key.)
*/
public V remove(Object key) {
Entry e = removeEntryForKey(key);
return (e == null ? null : e.value);
}
/**
* Removes and returns the entry associated with the specified key in the
* SafelyHashMap. Returns null if the SafelyHashMap contains no mapping for
* this key.
*/
final Entry removeEntryForKey(Object key) {
int hash = (key == null) ? 0
: (key instanceof String) ? hash(hashString((String) key))
: hash(key.hashCode());
int i = indexFor(hash, table.length);
Entry prev = table[i];
Entry e = prev;
while (e != null) {
Entry next = e.next;
Object k;
if (e.hash == hash
&& ((k = e.key) == key || (key != null && key.equals(k)))) {
modCount++;
size--;
if (prev == e)
table[i] = next;
else
prev.next = next;
return e;
}
prev = e;
e = next;
}
return e;
}
/**
* Special version of remove for EntrySet.
*/
final Entry removeMapping(Object o) {
if (!(o instanceof Map.Entry))
return null;
Map.Entry entry = (Map.Entry) o;
Object key = entry.getKey();
int hash = (key == null) ? 0
: (key instanceof String) ? hash(hashString((String) key))
: hash(key.hashCode());
int i = indexFor(hash, table.length);
Entry prev = table[i];
Entry e = prev;
while (e != null) {
Entry next = e.next;
if (e.hash == hash && e.equals(entry)) {
modCount++;
size--;
if (prev == e)
table[i] = next;
else
prev.next = next;
return e;
}
prev = e;
e = next;
}
return e;
}
/**
* Removes all of the mappings from this map. The map will be empty after
* this call returns.
*/
public void clear() {
modCount++;
Entry[] tab = table;
for (int i = 0; i < tab.length; i++)
tab[i] = null;
size = 0;
}
/**
* Returns true if this map maps one or more keys to the specified
* value.
*
* @param value value whose presence in this map is to be tested
* @return true if this map maps one or more keys to the specified
* value
*/
public boolean containsValue(Object value) {
if (value == null)
return containsNullValue();
Entry[] tab = table;
for (int i = 0; i < tab.length; i++)
for (Entry e = tab[i]; e != null; e = e.next)
if (value.equals(e.value))
return true;
return false;
}
/**
* Special-case code for containsValue with null argument
*/
private boolean containsNullValue() {
Entry[] tab = table;
for (int i = 0; i < tab.length; i++)
for (Entry e = tab[i]; e != null; e = e.next)
if (e.value == null)
return true;
return false;
}
/**
* Returns a shallow copy of this SafelyHashMap instance: the keys
* and values themselves are not cloned.
*
* @return a shallow copy of this map
*/
public Object clone() {
AntiCollisionHashMap result = null;
try {
result = (AntiCollisionHashMap) super.clone();
} catch (CloneNotSupportedException e) {
// assert false;
}
result.table = new Entry[table.length];
result.entrySet = null;
result.modCount = 0;
result.size = 0;
result.init();
result.putAllForCreate(this);
return result;
}
static class Entry implements Map.Entry {
final K key;
V value;
Entry next;
final int hash;
/**
* Creates new entry.
*/
Entry(int h, K k, V v, Entry n) {
value = v;
next = n;
key = k;
hash = h;
}
public final K getKey() {
return key;
}
public final V getValue() {
return value;
}
public final V setValue(V newValue) {
V oldValue = value;
value = newValue;
return oldValue;
}
public final boolean equals(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry) o;
Object k1 = getKey();
Object k2 = e.getKey();
if (k1 == k2 || (k1 != null && k1.equals(k2))) {
Object v1 = getValue();
Object v2 = e.getValue();
if (v1 == v2 || (v1 != null && v1.equals(v2)))
return true;
}
return false;
}
public final int hashCode() {
return (key == null ? 0 : key.hashCode())
^ (value == null ? 0 : value.hashCode());
}
public final String toString() {
return getKey() + "=" + getValue();
}
}
/**
* Adds a new entry with the specified key, value and hash code to the
* specified bucket. It is the responsibility of this method to resize the
* table if appropriate.
*
* Subclass overrides this to alter the behavior of put method.
*/
void addEntry(int hash, K key, V value, int bucketIndex) {
Entry e = table[bucketIndex];
table[bucketIndex] = new Entry(hash, key, value, e);
if (size++ >= threshold)
resize(2 * table.length);
}
/**
* Like addEntry except that this version is used when creating entries as
* part of Map construction or "pseudo-construction" (cloning,
* deserialization). This version needn't worry about resizing the table.
*
* Subclass overrides this to alter the behavior of SafelyHashMap(Map),
* clone, and readObject.
*/
void createEntry(int hash, K key, V value, int bucketIndex) {
Entry e = table[bucketIndex];
table[bucketIndex] = new Entry(hash, key, value, e);
size++;
}
private abstract class HashIterator implements Iterator {
Entry next; // next entry to return
int expectedModCount; // For fast-fail
int index; // current slot
Entry current; // current entry
HashIterator() {
expectedModCount = modCount;
if (size > 0) { // advance to first entry
Entry[] t = table;
while (index < t.length && (next = t[index++]) == null)
;
}
}
public final boolean hasNext() {
return next != null;
}
final Entry nextEntry() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Entry e = next;
if (e == null)
throw new NoSuchElementException();
if ((next = e.next) == null) {
Entry[] t = table;
while (index < t.length && (next = t[index++]) == null)
;
}
current = e;
return e;
}
public void remove() {
if (current == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
Object k = current.key;
current = null;
AntiCollisionHashMap.this.removeEntryForKey(k);
expectedModCount = modCount;
}
}
private final class ValueIterator extends HashIterator {
public V next() {
return nextEntry().value;
}
}
private final class KeyIterator extends HashIterator {
public K next() {
return nextEntry().getKey();
}
}
private final class EntryIterator extends HashIterator> {
public Map.Entry next() {
return nextEntry();
}
}
// Subclass overrides these to alter behavior of views' iterator() method
Iterator newKeyIterator() {
return new KeyIterator();
}
Iterator newValueIterator() {
return new ValueIterator();
}
Iterator> newEntryIterator() {
return new EntryIterator();
}
// Views
private transient Set> entrySet = null;
/**
* Returns a {@link 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. If the map is modified while an iteration over the set is in
* progress (except through the iterator's own remove operation),
* the results of the iteration are undefined. The set supports element
* removal, which removes the corresponding mapping from the map, via the
* Iterator.remove, Set.remove, removeAll,
* retainAll, and clear operations. It does not support
* the add or addAll operations.
*/
public Set keySet() {
Set ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
}
private final class KeySet extends AbstractSet {
public Iterator iterator() {
return newKeyIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
return AntiCollisionHashMap.this.removeEntryForKey(o) != null;
}
public void clear() {
AntiCollisionHashMap.this.clear();
}
}
/**
* Returns a {@link 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. If the map is modified while an
* iteration over the collection is in progress (except through the
* iterator's own remove operation), the results of the iteration
* are undefined. The collection supports element removal, which removes the
* corresponding mapping from the map, via the Iterator.remove,
* Collection.remove, removeAll, retainAll and
* clear operations. It does not support the add or
* addAll operations.
*/
public Collection values() {
Collection vs = values;
return (vs != null ? vs : (values = new Values()));
}
private final class Values extends AbstractCollection {
public Iterator iterator() {
return newValueIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
AntiCollisionHashMap.this.clear();
}
}
/**
* Returns a {@link Set} view of the mappings contained in this map. The set
* is backed by the map, so changes to the map are reflected in the set, and
* vice-versa. If the map is modified while an iteration over the set is in
* progress (except through the iterator's own remove operation, or
* through the setValue operation on a map entry returned by the
* iterator) the results of the iteration are undefined. The set supports
* element removal, which removes the corresponding mapping from the map,
* via the Iterator.remove, Set.remove, removeAll
* , retainAll and clear operations. It does not support
* the add or addAll operations.
*
* @return a set view of the mappings contained in this map
*/
public Set> entrySet() {
return entrySet0();
}
private Set> entrySet0() {
Set> es = entrySet;
return es != null ? es : (entrySet = new EntrySet());
}
private final class EntrySet extends AbstractSet> {
public Iterator> iterator() {
return newEntryIterator();
}
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry) o;
Entry candidate = getEntry(e.getKey());
return candidate != null && candidate.equals(e);
}
public boolean remove(Object o) {
return removeMapping(o) != null;
}
public int size() {
return size;
}
public void clear() {
AntiCollisionHashMap.this.clear();
}
}
/**
* Save the state of the SafelyHashMap instance to a stream (i.e.,
* serialize it).
*
* @serialData The capacity of the SafelyHashMap (the length of the
* bucket array) is emitted (int), followed by the size
* (an int, the number of key-value mappings), followed by the
* key (Object) and value (Object) for each key-value mapping.
* The key-value mappings are emitted in no particular order.
*/
private void writeObject(java.io.ObjectOutputStream s) throws IOException {
Iterator> i = (size > 0) ? entrySet0().iterator()
: null;
// Write out the threshold, loadfactor, and any hidden stuff
s.defaultWriteObject();
// Write out number of buckets
s.writeInt(table.length);
// Write out size (number of Mappings)
s.writeInt(size);
// Write out keys and values (alternating)
if (i != null) {
while (i.hasNext()) {
Map.Entry e = i.next();
s.writeObject(e.getKey());
s.writeObject(e.getValue());
}
}
}
private static final long serialVersionUID = 362498820763181265L;
/**
* Reconstitute the SafelyHashMap instance from a stream (i.e.,
* deserialize it).
*/
private void readObject(java.io.ObjectInputStream s) throws IOException,
ClassNotFoundException {
// Read in the threshold, loadfactor, and any hidden stuff
s.defaultReadObject();
// Read in number of buckets and allocate the bucket array;
int numBuckets = s.readInt();
table = new Entry[numBuckets];
init(); // Give subclass a chance to do its thing.
// Read in size (number of Mappings)
int size = s.readInt();
// Read the keys and values, and put the mappings in the SafelyHashMap
for (int i = 0; i < size; i++) {
K key = (K) s.readObject();
V value = (V) s.readObject();
putForCreate(key, value);
}
}
}