/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 hivemall.utils.collections;
import hivemall.utils.lang.Copyable;
import hivemall.utils.math.Primes;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.util.Arrays;
import java.util.HashMap;
import javax.annotation.Nonnull;
/**
* An open-addressing hash table with double-hashing that requires less memory to {@link HashMap}.
*/
public final class OpenHashTable<K, V> implements Externalizable {
public static final float DEFAULT_LOAD_FACTOR = 0.7f;
public static final float DEFAULT_GROW_FACTOR = 2.0f;
protected static final byte FREE = 0;
protected static final byte FULL = 1;
protected static final byte REMOVED = 2;
protected/* final */float _loadFactor;
protected/* final */float _growFactor;
protected int _used = 0;
protected int _threshold;
protected K[] _keys;
protected V[] _values;
protected byte[] _states;
public OpenHashTable() {} // for Externalizable
public OpenHashTable(int size) {
this(size, DEFAULT_LOAD_FACTOR, DEFAULT_GROW_FACTOR);
}
@SuppressWarnings("unchecked")
public OpenHashTable(int size, float loadFactor, float growFactor) {
if (size < 1) {
throw new IllegalArgumentException();
}
this._loadFactor = loadFactor;
this._growFactor = growFactor;
int actualSize = Primes.findLeastPrimeNumber(size);
this._keys = (K[]) new Object[actualSize];
this._values = (V[]) new Object[actualSize];
this._states = new byte[actualSize];
this._threshold = Math.round(actualSize * _loadFactor);
}
public OpenHashTable(@Nonnull K[] keys, @Nonnull V[] values, @Nonnull byte[] states, int used) {
this._used = used;
this._threshold = keys.length;
this._keys = keys;
this._values = values;
this._states = states;
}
public Object[] getKeys() {
return _keys;
}
public Object[] getValues() {
return _values;
}
public byte[] getStates() {
return _states;
}
public boolean containsKey(final K key) {
return findKey(key) >= 0;
}
public V get(final K key) {
final int i = findKey(key);
if (i < 0) {
return null;
}
return _values[i];
}
public V put(final K key, final V value) {
int hash = keyHash(key);
int keyLength = _keys.length;
int keyIdx = hash % keyLength;
boolean expanded = preAddEntry(keyIdx);
if (expanded) {
keyLength = _keys.length;
keyIdx = hash % keyLength;
}
K[] keys = _keys;
V[] values = _values;
byte[] states = _states;
if (states[keyIdx] == FULL) {
if (equals(keys[keyIdx], key)) {
V old = values[keyIdx];
values[keyIdx] = value;
return old;
}
// try second hash
int decr = 1 + (hash % (keyLength - 2));
for (;;) {
keyIdx -= decr;
if (keyIdx < 0) {
keyIdx += keyLength;
}
if (isFree(keyIdx, key)) {
break;
}
if (states[keyIdx] == FULL && equals(keys[keyIdx], key)) {
V old = values[keyIdx];
values[keyIdx] = value;
return old;
}
}
}
keys[keyIdx] = key;
values[keyIdx] = value;
states[keyIdx] = FULL;
++_used;
return null;
}
private static boolean equals(final Object k1, final Object k2) {
return k1 == k2 || k1.equals(k2);
}
/** Return weather the required slot is free for new entry */
protected boolean isFree(int index, K key) {
byte stat = _states[index];
if (stat == FREE) {
return true;
}
if (stat == REMOVED && equals(_keys[index], key)) {
return true;
}
return false;
}
/** @return expanded or not */
protected boolean preAddEntry(int index) {
if ((_used + 1) >= _threshold) {// filled enough
int newCapacity = Math.round(_keys.length * _growFactor);
ensureCapacity(newCapacity);
return true;
}
return false;
}
protected int findKey(final K key) {
K[] keys = _keys;
byte[] states = _states;
int keyLength = keys.length;
int hash = keyHash(key);
int keyIdx = hash % keyLength;
if (states[keyIdx] != FREE) {
if (states[keyIdx] == FULL && equals(keys[keyIdx], key)) {
return keyIdx;
}
// try second hash
int decr = 1 + (hash % (keyLength - 2));
for (;;) {
keyIdx -= decr;
if (keyIdx < 0) {
keyIdx += keyLength;
}
if (isFree(keyIdx, key)) {
return -1;
}
if (states[keyIdx] == FULL && equals(keys[keyIdx], key)) {
return keyIdx;
}
}
}
return -1;
}
public V remove(final K key) {
K[] keys = _keys;
V[] values = _values;
byte[] states = _states;
int keyLength = keys.length;
int hash = keyHash(key);
int keyIdx = hash % keyLength;
if (states[keyIdx] != FREE) {
if (states[keyIdx] == FULL && equals(keys[keyIdx], key)) {
V old = values[keyIdx];
states[keyIdx] = REMOVED;
--_used;
return old;
}
// second hash
int decr = 1 + (hash % (keyLength - 2));
for (;;) {
keyIdx -= decr;
if (keyIdx < 0) {
keyIdx += keyLength;
}
if (states[keyIdx] == FREE) {
return null;
}
if (states[keyIdx] == FULL && equals(keys[keyIdx], key)) {
V old = values[keyIdx];
states[keyIdx] = REMOVED;
--_used;
return old;
}
}
}
return null;
}
public int size() {
return _used;
}
public void clear() {
Arrays.fill(_states, FREE);
this._used = 0;
}
public IMapIterator<K, V> entries() {
return new MapIterator();
}
@Override
public String toString() {
int len = size() * 10 + 2;
final StringBuilder buf = new StringBuilder(len);
buf.append('{');
final IMapIterator<K, V> i = entries();
while (i.next() != -1) {
String key = i.getKey().toString();
buf.append(key);
buf.append('=');
buf.append(i.getValue());
if (i.hasNext()) {
buf.append(',');
}
}
buf.append('}');
return buf.toString();
}
protected void ensureCapacity(int newCapacity) {
int prime = Primes.findLeastPrimeNumber(newCapacity);
rehash(prime);
this._threshold = Math.round(prime * _loadFactor);
}
@SuppressWarnings("unchecked")
private void rehash(int newCapacity) {
int oldCapacity = _keys.length;
if (newCapacity <= oldCapacity) {
throw new IllegalArgumentException("new: " + newCapacity + ", old: " + oldCapacity);
}
final K[] newkeys = (K[]) new Object[newCapacity];
final V[] newValues = (V[]) new Object[newCapacity];
final byte[] newStates = new byte[newCapacity];
int used = 0;
for (int i = 0; i < oldCapacity; i++) {
if (_states[i] == FULL) {
used++;
K k = _keys[i];
V v = _values[i];
int hash = keyHash(k);
int keyIdx = hash % newCapacity;
if (newStates[keyIdx] == FULL) {// second hashing
int decr = 1 + (hash % (newCapacity - 2));
while (newStates[keyIdx] != FREE) {
keyIdx -= decr;
if (keyIdx < 0) {
keyIdx += newCapacity;
}
}
}
newStates[keyIdx] = FULL;
newkeys[keyIdx] = k;
newValues[keyIdx] = v;
}
}
this._keys = newkeys;
this._values = newValues;
this._states = newStates;
this._used = used;
}
private static int keyHash(final Object key) {
int hash = key.hashCode();
return hash & 0x7fffffff;
}
private final class MapIterator implements IMapIterator<K, V> {
int nextEntry;
int lastEntry = -1;
MapIterator() {
this.nextEntry = nextEntry(0);
}
/** find the index of next full entry */
int nextEntry(int index) {
while (index < _keys.length && _states[index] != FULL) {
index++;
}
return index;
}
public boolean hasNext() {
return nextEntry < _keys.length;
}
public int next() {
if (!hasNext()) {
return -1;
}
int curEntry = nextEntry;
this.lastEntry = nextEntry;
this.nextEntry = nextEntry(nextEntry + 1);
return curEntry;
}
public K getKey() {
if (lastEntry == -1) {
throw new IllegalStateException();
}
return _keys[lastEntry];
}
public V getValue() {
if (lastEntry == -1) {
throw new IllegalStateException();
}
return _values[lastEntry];
}
@Override
public <T extends Copyable<V>> void getValue(T probe) {
probe.copyFrom(getValue());
}
}
@Override
public void writeExternal(ObjectOutput out) throws IOException {
out.writeFloat(_loadFactor);
out.writeFloat(_growFactor);
out.writeInt(_used);
final int size = _keys.length;
out.writeInt(size);
for (int i = 0; i < size; i++) {
out.writeObject(_keys[i]);
out.writeObject(_values[i]);
out.writeByte(_states[i]);
}
}
@SuppressWarnings("unchecked")
@Override
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
this._loadFactor = in.readFloat();
this._growFactor = in.readFloat();
this._used = in.readInt();
final int size = in.readInt();
final Object[] keys = new Object[size];
final Object[] values = new Object[size];
final byte[] states = new byte[size];
for (int i = 0; i < size; i++) {
keys[i] = in.readObject();
values[i] = in.readObject();
states[i] = in.readByte();
}
this._threshold = size;
this._keys = (K[]) keys;
this._values = (V[]) values;
this._states = states;
}
}