com.aowagie.text.pdf.IntHashtable Maven / Gradle / Ivy
/*
* 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 com.aowagie.text.pdf;
import java.util.Arrays;
import java.util.Iterator;
import java.util.NoSuchElementException;
/***
* A hash map that uses primitive ints for the key rather than objects.
*
* 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.
*
* @author Justin Couch
* @author Alex Chaffee ([email protected])
* @author Stephen Colebourne
* @author Bruno Lowagie (change Objects as keys into int values)
* @author Paulo Soares (added extra methods)
*/
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;
/***
* Constructs a new, empty hashtable with a default capacity and load
* factor, which is 20 and 0.75 respectively.
*/
public IntHashtable() {
this(150, 0.75f);
}
/***
* Constructs a new, empty hashtable with the specified initial capacity
* and default load factor, which is 0.75.
*
* @param initialCapacity the initial capacity of the hashtable.
* @throws IllegalArgumentException if the initial capacity is less
* than zero.
*/
public IntHashtable(final int initialCapacity) {
this(initialCapacity, 0.75f);
}
/***
* Constructs a new, empty hashtable with the specified initial
* capacity and the specified load factor.
*
* @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.
*/
private IntHashtable(int initialCapacity, final 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;
this.table = new Entry[initialCapacity];
this.threshold = (int) (initialCapacity * loadFactor);
}
/***
* Returns the number of keys in this hashtable.
*
* @return the number of keys in this hashtable.
*/
int size() {
return this.count;
}
/***
* Tests if this hashtable maps no keys to values.
*
* @return true if this hashtable maps no keys to values;
* false otherwise.
*/
public boolean isEmpty() {
return this.count == 0;
}
/***
* Tests if the specified int is a key in this hashtable.
*
* @param key possible key.
* @return true if and only if the specified int is a
* key in this hashtable, as determined by the equals
* method; false otherwise.
* @see #contains(int)
*/
boolean containsKey(final int key) {
final Entry tab[] = this.table;
final int hash = key;
final 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;
}
/***
* Returns the value to which the specified key is mapped in this map.
*
* @param key a key in the hashtable.
* @return the value to which the key is mapped in this hashtable;
* null if the key is not mapped to any value in
* this hashtable.
* @see #put(int, int)
*/
int get(final int key) {
final Entry tab[] = this.table;
final int hash = key;
final 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;
}
/***
* Increases the capacity of and internally reorganizes this
* hashtable, in order to accommodate and access its entries more
* efficiently.
*
* This method is called automatically when the number of keys
* in the hashtable exceeds this hashtable's capacity and load
* factor.
*/
private void rehash() {
final int oldCapacity = this.table.length;
final Entry oldMap[] = this.table;
final int newCapacity = oldCapacity * 2 + 1;
final Entry newMap[] = new Entry[newCapacity];
this.threshold = (int) (newCapacity * this.loadFactor);
this.table = newMap;
for (int i = oldCapacity; i-- > 0;) {
for (Entry old = oldMap[i]; old != null;) {
final Entry e = old;
old = old.next;
final int index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newMap[index];
newMap[index] = e;
}
}
}
/***
* Maps the specified key to the specified
* value in this hashtable. The key cannot be
* null.
*
* The value can be retrieved by calling the get method
* with a key that is equal to the original key.
*
* @param key the hashtable key.
* @param value the value.
* @return the previous value of the specified key in this hashtable,
* or null if it did not have one.
* @throws NullPointerException if the key is null.
* @see #get(int)
*/
int put(final int key, final int value) {
// Makes sure the key is not already in the hashtable.
Entry tab[] = this.table;
final 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) {
final int old = e.value;
e.value = value;
return old;
}
}
if (this.count >= this.threshold) {
// Rehash the table if the threshold is exceeded
rehash();
tab = this.table;
index = (hash & 0x7FFFFFFF) % tab.length;
}
// Creates the new entry.
final Entry e = new Entry(hash, key, value, tab[index]);
tab[index] = e;
this.count++;
return 0;
}
/***
* Removes the key (and its corresponding value) from this
* hashtable.
*
* This method does nothing if the key is not present in the
* hashtable.
*
* @param key the key that needs to be removed.
* @return the value to which the key had been mapped in this hashtable,
* or null if the key did not have a mapping.
*/
int remove(final int key) {
final Entry tab[] = this.table;
final int hash = key;
final int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
if (e.hash == hash && e.key == key) {
if (prev != null) {
prev.next = e.next;
} else {
tab[index] = e.next;
}
this.count--;
final int oldValue = e.value;
e.value = 0;
return oldValue;
}
}
return 0;
}
/***
* Clears this hashtable so that it contains no keys.
*/
void clear() {
final Entry tab[] = this.table;
for (int index = tab.length; --index >= 0;) {
tab[index] = null;
}
this.count = 0;
}
/***
* Innerclass that acts as a datastructure to create a new entry in the
* table.
*/
static class Entry {
private final int hash;
private final int key;
private int value;
private Entry next;
/***
* Create a new entry with the given values.
*
* @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
*/
private Entry(final int hash, final int key, final int value, final Entry next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
// extra methods for inner class Entry by Paulo
public int getKey() {
return this.key;
}
public int getValue() {
return this.value;
}
@Override
protected Object clone() {
final Entry entry = new Entry(this.hash, this.key, this.value, this.next != null ? (Entry)this.next.clone() : null);
return entry;
}
}
// extra inner class by Paulo
private static class IntHashtableIterator implements Iterator {
private int index;
private final Entry table[];
private Entry entry;
private IntHashtableIterator(final Entry table[]) {
this.table = table;
this.index = table.length;
}
@Override
public boolean hasNext() {
if (this.entry != null) {
return true;
}
while (this.index-- > 0) {
if ((this.entry = this.table[this.index]) != null) {
return true;
}
}
return false;
}
@Override
public Object next() {
if (this.entry == null) {
while (this.index-- > 0 && (this.entry = this.table[this.index]) == null) {
;
}
}
if (this.entry != null) {
final Entry e = this.entry;
this.entry = e.next;
return e;
}
throw new NoSuchElementException("IntHashtableIterator");
}
@Override
public void remove() {
throw new UnsupportedOperationException("remove() not supported.");
}
}
// extra methods by Paulo Soares:
public Iterator getEntryIterator() {
return new IntHashtableIterator(this.table);
}
int[] toOrderedKeys() {
final int res[] = getKeys();
Arrays.sort(res);
return res;
}
public int[] getKeys() {
final int res[] = new int[this.count];
int ptr = 0;
int index = this.table.length;
Entry entry = null;
while (true) {
if (entry == null) {
while (index-- > 0 && (entry = this.table[index]) == null) {
;
}
}
if (entry == null) {
break;
}
final Entry e = entry;
entry = e.next;
res[ptr++] = e.key;
}
return res;
}
public int getOneKey() {
if (this.count == 0) {
return 0;
}
int index = this.table.length;
Entry entry = null;
while (index-- > 0 && (entry = this.table[index]) == null) {
;
}
if (entry == null) {
return 0;
}
return entry.key;
}
@Override
public Object clone() {
try {
final IntHashtable t = (IntHashtable)super.clone();
t.table = new Entry[this.table.length];
for (int i = this.table.length ; i-- > 0 ; ) {
t.table[i] = this.table[i] != null
? (Entry)this.table[i].clone() : null;
}
return t;
} catch (final CloneNotSupportedException e) {
// this shouldn't happen, since we are Cloneable
throw new InternalError();
}
}
}