/*
* 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.
*/
/*
* Note: originally released under the GNU LGPL v2.1,
* but rereleased by the original author under the ASF license (above).
*/
package com.navercorp.pinpoint.common.util.apache;
/**
* <p>A hash map that uses primitive ints for the key rather than objects.</p>
*
* <p>Note that this class is for internal optimization purposes only, and may
* not be supported in future releases of Apache Commons Lang. Utilities of
* this sort may be included in future releases of Apache Commons Collections.</p>
*
* @author Apache Software Foundation
* @author Justin Couch
* @author Alex Chaffee (alex@apache.org)
* @since 2.0
* @version $Revision$
* @see java.util.HashMap
*/
public class IntHashMap<T> {
/**
* The hash table data.
*/
private transient Entry table[];
/**
* The total number of entries in the hash table.
*/
private transient int count;
/**
* The table is rehashed when its size exceeds this threshold. (The
* value of this field is (int)(capacity * loadFactor).)
*
* @serial
*/
private int threshold;
/**
* The load factor for the hashtable.
*
* @serial
*/
private final float loadFactor;
/**
* <p>Innerclass that acts as a datastructure to create a new entry in the
* table.</p>
*/
private static class Entry<T> {
final int hash;
final int key; // TODO not read; seems to be always same as hash
T value;
Entry<T> next;
/**
* <p>Create a new entry with the given values.</p>
*
* @param hash The code used to hash the object with
* @param key The key used to enter this in the table
* @param value The value for this key
* @param next A reference to the next entry in the table
*/
protected Entry(int hash, int key, T value, Entry<T> next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
}
/**
* <p>Constructs a new, empty hashtable with a default capacity and load
* factor, which is <code>20</code> and <code>0.75</code> respectively.</p>
*/
public IntHashMap() {
this(20, 0.75f);
}
/**
* <p>Constructs a new, empty hashtable with the specified initial capacity
* and default load factor, which is <code>0.75</code>.</p>
*
* @param initialCapacity the initial capacity of the hashtable.
* @throws IllegalArgumentException if the initial capacity is less
* than zero.
*/
public IntHashMap(int initialCapacity) {
this(initialCapacity, 0.75f);
}
/**
* <p>Constructs a new, empty hashtable with the specified initial
* capacity and the specified load factor.</p>
*
* @param initialCapacity the initial capacity of the hashtable.
* @param loadFactor the load factor of the hashtable.
* @throws IllegalArgumentException if the initial capacity is less
* than zero, or if the load factor is nonpositive.
*/
public IntHashMap(int initialCapacity, float loadFactor) {
super();
if (initialCapacity < 0) {
throw new IllegalArgumentException("Illegal Capacity: " + initialCapacity);
}
if (loadFactor <= 0) {
throw new IllegalArgumentException("Illegal Load: " + loadFactor);
}
if (initialCapacity == 0) {
initialCapacity = 1;
}
this.loadFactor = loadFactor;
table = new Entry[initialCapacity];
threshold = (int) (initialCapacity * loadFactor);
}
/**
* <p>Returns the number of keys in this hashtable.</p>
*
* @return the number of keys in this hashtable.
*/
public int size() {
return count;
}
/**
* <p>Tests if this hashtable maps no keys to values.</p>
*
* @return <code>true</code> if this hashtable maps no keys to values;
* <code>false</code> otherwise.
*/
public boolean isEmpty() {
return count == 0;
}
/**
* <p>Returns the value to which the specified key is mapped in this map.</p>
*
* @param key a key in the hashtable.
* @return the value to which the key is mapped in this hashtable;
* <code>null</code> if the key is not mapped to any value in
* this hashtable.
* @see #put(int, T)
*/
public T get(int key) {
Entry<T> tab[] = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry<T> e = tab[index]; e != null; e = e.next) {
if (e.hash == hash) {
return e.value;
}
}
return null;
}
/**
* <p>Increases the capacity of and internally reorganizes this
* hashtable, in order to accommodate and access its entries more
* efficiently.</p>
*
* <p>This method is called automatically when the number of keys
* in the hashtable exceeds this hashtable's capacity and load
* factor.</p>
*/
protected void rehash() {
int oldCapacity = table.length;
Entry<T> oldMap[] = table;
int newCapacity = oldCapacity * 2 + 1;
Entry<T> newMap[] = new Entry[newCapacity];
threshold = (int) (newCapacity * loadFactor);
table = newMap;
for (int i = oldCapacity; i-- > 0;) {
for (Entry<T> old = oldMap[i]; old != null;) {
Entry<T> e = old;
old = old.next;
int index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newMap[index];
newMap[index] = e;
}
}
}
/**
* <p>Maps the specified <code>key</code> to the specified
* <code>value</code> in this hashtable. The key cannot be
* <code>null</code>. </p>
*
* <p>The value can be retrieved by calling the <code>get</code> method
* with a key that is equal to the original key.</p>
*
* @param key the hashtable key.
* @param value the value.
* @return the previous value of the specified key in this hashtable,
* or <code>null</code> if it did not have one.
* @throws NullPointerException if the key is <code>null</code>.
* @see #get(int)
*/
public T put(int key, T value) {
// Makes sure the key is not already in the hashtable.
Entry<T> tab[] = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry<T> e = tab[index]; e != null; e = e.next) {
if (e.hash == hash) {
T old = e.value;
e.value = value;
return old;
}
}
if (count >= threshold) {
// Rehash the table if the threshold is exceeded
rehash();
tab = table;
index = (hash & 0x7FFFFFFF) % tab.length;
}
// Creates the new entry.
Entry<T> e = new Entry<T>(hash, key, value, tab[index]);
tab[index] = e;
count++;
return null;
}
}