org.htmlunit.cyberneko.util.FastHashMap Maven / Gradle / Ivy
/*
* Copyright (c) 2005-2024 René Schwietzke
*
* 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 org.htmlunit.cyberneko.util;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Simple hash map implementation taken from here
* https://github.com/mikvor/hashmapTest/blob/master/src/main/java/map/objobj/ObjObjMap.java
* No concrete license specified at the source. The project is public domain.
*
* Not thread-safe! Null support was removed.
*
* @param the type of the key
* @param the type of the value
*
* @author René Schwietzke
* @since 3.10.0
*/
public class FastHashMap {
private static final Object FREE_KEY = new Object();
private static final Object REMOVED_KEY = new Object();
/** Keys and values */
private Object[] m_data_;
/** Fill factor, must be between (0 and 1) */
private final float m_fillFactor_;
/** We will resize a map once it reaches this size */
private int m_threshold_;
/** Current map size */
private int m_size_;
/** Mask to calculate the original position */
private int m_mask_;
/** Mask to wrap the actual array pointer */
private int m_mask2_;
public FastHashMap() {
this(13, 0.5f);
}
public FastHashMap(final int size, final float fillFactor) {
if (fillFactor <= 0 || fillFactor >= 1) {
throw new IllegalArgumentException("FillFactor must be in (0, 1)");
}
if (size <= 0) {
throw new IllegalArgumentException("Size must be positive!");
}
final int capacity = arraySize(size, fillFactor);
m_mask_ = capacity - 1;
m_mask2_ = capacity * 2 - 1;
m_fillFactor_ = fillFactor;
m_data_ = new Object[capacity * 2];
Arrays.fill(m_data_, FREE_KEY);
m_threshold_ = (int) (capacity * fillFactor);
}
public V get(final K key) {
final int srcHashCode = key.hashCode();
int ptr = (srcHashCode & m_mask_) << 1;
Object k = m_data_[ptr];
if (k == FREE_KEY) {
//end of chain already
return null;
}
//we check FREE and REMOVED prior to this call
if (k.hashCode() == srcHashCode && k.equals(key)) {
return (V) m_data_[ptr + 1];
}
while (true) {
ptr = (ptr + 2) & m_mask2_; //that's next index
k = m_data_[ ptr ];
if (k == FREE_KEY) {
return null;
}
if (k.hashCode() == srcHashCode && k.equals(key)) {
return (V) m_data_[ptr + 1];
}
}
}
public V put(final K key, final V value) {
int ptr = getStartIndex(key) << 1;
Object k = m_data_[ptr];
if (k == FREE_KEY) {
//end of chain already
m_data_[ ptr ] = key;
m_data_[ ptr + 1 ] = value;
if (m_size_ >= m_threshold_) {
rehash(m_data_.length * 2); //size is set inside
}
else {
++m_size_;
}
return null;
}
else if (k.equals(key)) {
//we check FREE and REMOVED prior to this call
final Object ret = m_data_[ ptr + 1 ];
m_data_[ ptr + 1 ] = value;
return (V) ret;
}
int firstRemoved = -1;
if (k == REMOVED_KEY) {
//we may find a key later
firstRemoved = ptr;
}
while (true) {
// that's next index calculation
ptr = (ptr + 2) & m_mask2_;
k = m_data_[ ptr ];
if (k == FREE_KEY) {
if (firstRemoved != -1) {
ptr = firstRemoved;
}
m_data_[ ptr ] = key;
m_data_[ ptr + 1 ] = value;
if (m_size_ >= m_threshold_) {
//size is set inside
rehash(m_data_.length * 2);
}
else {
++m_size_;
}
return null;
}
else if (k.equals(key)) {
final Object ret = m_data_[ ptr + 1 ];
m_data_[ ptr + 1 ] = value;
return (V) ret;
}
else if (k == REMOVED_KEY) {
if (firstRemoved == -1) {
firstRemoved = ptr;
}
}
}
}
public V remove(final K key) {
int ptr = getStartIndex(key) << 1;
Object k = m_data_[ ptr ];
if (k == FREE_KEY) {
// end of chain already
return null;
}
else if (k.equals(key)) {
// we check FREE and REMOVED prior to this call
--m_size_;
if (m_data_[ (ptr + 2) & m_mask2_ ] == FREE_KEY) {
m_data_[ ptr ] = FREE_KEY;
}
else {
m_data_[ ptr ] = REMOVED_KEY;
}
final V ret = (V) m_data_[ ptr + 1 ];
m_data_[ ptr + 1 ] = null;
return ret;
}
while (true) {
//that's next index calculation
ptr = (ptr + 2) & m_mask2_;
k = m_data_[ ptr ];
if (k == FREE_KEY) {
return null;
}
else if (k.equals(key)) {
--m_size_;
if (m_data_[ (ptr + 2) & m_mask2_ ] == FREE_KEY) {
m_data_[ ptr ] = FREE_KEY;
}
else {
m_data_[ ptr ] = REMOVED_KEY;
}
final V ret = (V) m_data_[ ptr + 1 ];
m_data_[ ptr + 1 ] = null;
return ret;
}
}
}
public int size() {
return m_size_;
}
private void rehash(final int newCapacity) {
m_threshold_ = (int) (newCapacity / 2 * m_fillFactor_);
m_mask_ = newCapacity / 2 - 1;
m_mask2_ = newCapacity - 1;
final int oldCapacity = m_data_.length;
final Object[] oldData = m_data_;
m_data_ = new Object[ newCapacity ];
Arrays.fill(m_data_, FREE_KEY);
m_size_ = 0;
for (int i = 0; i < oldCapacity; i += 2) {
final Object oldKey = oldData[ i ];
if (oldKey != FREE_KEY && oldKey != REMOVED_KEY) {
put((K) oldKey, (V) oldData[ i + 1 ]);
}
}
}
/**
* @return a list of all keys
*/
public List keys() {
final List result = new ArrayList<>(this.size());
final int length = m_data_.length;
for (int i = 0; i < length; i += 2) {
final Object o = m_data_[i];
if (o != FREE_KEY && o != REMOVED_KEY) {
result.add((K) o);
}
}
return result;
}
/**
* @return a list of all values
*/
public List values() {
final List result = new ArrayList<>(this.size());
final int length = m_data_.length;
for (int i = 0; i < length; i += 2) {
final Object o = m_data_[i];
if (o != FREE_KEY && o != REMOVED_KEY) {
result.add((V) m_data_[i + 1]);
}
}
return result;
}
/**
* Clears the map, reuses the data structure by clearing it out.
* It won't shrink the underlying array!
*/
public void clear() {
this.m_size_ = 0;
Arrays.fill(m_data_, FREE_KEY);
}
private int getStartIndex(final Object key) {
//key is not null here
return key.hashCode() & m_mask_;
}
/** Return the least power of two greater than or equal to the specified value.
*
* Note that this function will return 1 when the argument is 0.
*
* @param x a long integer smaller than or equal to 262.
* @return the least power of two greater than or equal to the specified value.
*/
public static long nextPowerOfTwo(long x) {
if (x == 0) {
return 1;
}
x--;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
return (x | x >> 32) + 1;
}
/** Returns the least power of two smaller than or equal to 230 and larger than or equal to Math.ceil( expected / f ).
*
* @param expected the expected number of elements in a hash table.
* @param f the load factor.
* @return the minimum possible size for a backing array.
* @throws IllegalArgumentException if the necessary size is larger than 230.
*/
public static int arraySize(final int expected, final float f) {
final long s = Math.max(2, nextPowerOfTwo((long) Math.ceil(expected / f)));
if (s > (1 << 30)) {
throw new IllegalArgumentException("Too large (" + expected + " expected elements with load factor " + f + ")");
}
return (int) s;
}
}