IntHashtable.java
/*
* This class is based on org.apache.IntHashMap.commons.lang
* http://jakarta.apache.org/commons/lang/xref/org/apache/commons/lang/IntHashMap.html
* It was adapted by Bruno Lowagie for use in iText,
* reusing methods that were written by Paulo Soares.
* Instead of being a hashtable that stores objects with an int as key,
* it stores int values with an int as key.
*
* This is the original license of the original class IntHashMap:
*
* 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 org.openpdf.text.pdf;
import org.openpdf.text.error_messages.MessageLocalization;
import java.util.Iterator;
import java.util.NoSuchElementException;
/***
* <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 Jakarta Commons Lang. Utilities of
* this sort may be included in future releases of Jakarta Commons Collections.</p>
*
* @author Justin Couch
* @author Alex Chaffee (alex@apache.org)
* @author Stephen Colebourne
* @author Bruno Lowagie (change Objects as keys into int values)
* @author Paulo Soares (added extra methods)
*/
public class IntHashtable implements Cloneable {
/***
* 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>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 IntHashtable() {
this(150, 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 IntHashtable(int initialCapacity, float loadFactor) {
super();
if (initialCapacity < 0) {
throw new IllegalArgumentException(
MessageLocalization.getComposedMessage("illegal.capacity.1", initialCapacity));
}
if (loadFactor <= 0) {
throw new IllegalArgumentException(
MessageLocalization.getComposedMessage("illegal.load.1", String.valueOf(loadFactor)));
}
if (initialCapacity == 0) {
initialCapacity = 1;
}
this.loadFactor = loadFactor;
table = new Entry[initialCapacity];
threshold = (int) (initialCapacity * loadFactor);
}
/***
* <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>Tests if the specified int is a key in this hashtable.</p>
*
* @param key possible key.
* @return <code>true</code> if and only if the specified int is a
* key in this hashtable, as determined by the <code>equals</code>
* method; <code>false</code> otherwise.
*/
public boolean containsKey(int key) {
Entry[] tab = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.hash == hash && e.key == key) {
return true;
}
}
return false;
}
/***
* <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, int)
*/
public int get(int key) {
Entry[] tab = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.hash == hash && e.key == key) {
return e.value;
}
}
return 0;
}
/***
* <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[] oldMap = table;
int newCapacity = oldCapacity * 2 + 1;
Entry[] newMap = new Entry[newCapacity];
threshold = (int) (newCapacity * loadFactor);
table = newMap;
for (int i = oldCapacity; i-- > 0; ) {
for (Entry old = oldMap[i]; old != null; ) {
Entry 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 int put(int key, int value) {
// Makes sure the key is not already in the hashtable.
Entry[] tab = table;
int hash = key;
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if (e.hash == hash && e.key == key) {
int 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 e = new Entry(hash, key, value, tab[index]);
tab[index] = e;
count++;
return 0;
}
// extra methods by Paulo Soares:
public Object clone() {
try {
IntHashtable t = (IntHashtable) super.clone();
t.table = new Entry[table.length];
for (int i = table.length; i-- > 0; ) {
t.table[i] = (table[i] != null)
? (Entry) table[i].clone() : null;
}
return t;
} catch (CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
/***
* <p>Innerclass that acts as a datastructure to create a new entry in the
* table.</p>
*/
static class Entry {
int hash;
int key;
int value;
Entry next;
/***
* <p>Create a new entry with the given values.</p>
*
* @param hash The code used to hash the int 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, int value, Entry next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
protected Object clone() {
Entry entry = new Entry(hash, key, value, (next != null) ? (Entry) next.clone() : null);
return entry;
}
}
// extra inner class by Paulo
static class IntHashtableIterator implements Iterator {
int index;
Entry[] table;
Entry entry;
public boolean hasNext() {
if (entry != null) {
return true;
}
while (index-- > 0) {
if ((entry = table[index]) != null) {
return true;
}
}
return false;
}
public Object next() {
if (entry == null) {
while ((index-- > 0) && ((entry = table[index]) == null)) {
// searching
}
}
if (entry != null) {
Entry e = entry;
entry = e.next;
return e;
}
throw new NoSuchElementException(MessageLocalization.getComposedMessage("inthashtableiterator"));
}
public void remove() {
throw new UnsupportedOperationException(MessageLocalization.getComposedMessage("remove.not.supported"));
}
}
}