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/**
Copyright (c) 2009, Sun Microsystems
All rights reserved.
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
* Neither the name of the Sun Microsystems nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package com.sun.xml.dtdparser;
import java.util.Enumeration;
// This could be replaced by Collections class unless we want
// to be able to run on JDK 1.1
/**
* This class implements a special purpose hashtable. It works like a
* normal java.util.Hashtable except that:
*
* - Keys to "get" are strings which are known to be interned,
* so that "==" is used instead of "String.equals". (Interning
* could be document-relative instead of global.)
*
*
- It's not synchronized, since it's to be used only by
* one thread at a time.
*
*
- The keys () enumerator allocates no memory, with live
* updates to the data disallowed.
*
*
- It's got fewer bells and whistles: fixed threshold and
* load factor, no JDK 1.2 collection support, only keys can be
* enumerated, things can't be removed, simpler inheritance; more.
*
*
*
* The overall result is that it's less expensive to use these in
* performance-critical locations, in terms both of CPU and memory,
* than java.util.Hashtable instances. In this package
* it makes a significant difference when normalizing attributes,
* which is done for each start-element construct.
*
* @version $Revision: 1.2 $
*/
final class SimpleHashtable implements Enumeration {
// entries ...
private Entry table[];
// currently enumerated key
private Entry current = null;
private int currentBucket = 0;
private int count;
private int threshold;
private static final float loadFactor = 0.75f;
/**
* Constructs a new, empty hashtable with the specified initial
* capacity.
*
* @param initialCapacity the initial capacity of the hashtable.
*/
public SimpleHashtable(int initialCapacity) {
if (initialCapacity < 0)
throw new IllegalArgumentException("Illegal Capacity: " +
initialCapacity);
if (initialCapacity == 0)
initialCapacity = 1;
table = new Entry[initialCapacity];
threshold = (int) (initialCapacity * loadFactor);
}
/**
* Constructs a new, empty hashtable with a default capacity.
*/
public SimpleHashtable() {
this(11);
}
/**
*/
public void clear() {
count = 0;
currentBucket = 0;
current = null;
for (int i = 0; i < table.length; i++)
table[i] = null;
}
/**
* Returns the number of keys in this hashtable.
*
* @return the number of keys in this hashtable.
*/
public int size() {
return count;
}
/**
* Returns an enumeration of the keys in this hashtable.
*
* @return an enumeration of the keys in this hashtable.
* @see Enumeration
*/
public Enumeration keys() {
currentBucket = 0;
current = null;
return this;
}
/**
* Used to view this as an enumeration; returns true if there
* are more keys to be enumerated.
*/
public boolean hasMoreElements() {
if (current != null)
return true;
while (currentBucket < table.length) {
current = table[currentBucket++];
if (current != null)
return true;
}
return false;
}
/**
* Used to view this as an enumeration; returns the next key
* in the enumeration.
*/
public Object nextElement() {
Object retval;
if (current == null)
throw new IllegalStateException();
retval = current.key;
current = current.next;
return retval;
}
/**
* Returns the value to which the specified key is mapped in this hashtable.
*/
public Object get(String key) {
Entry tab[] = table;
int hash = key.hashCode();
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 null;
}
/**
* Returns the value to which the specified key is mapped in this
* hashtable ... the key isn't necessarily interned, though.
*/
public Object getNonInterned(String key) {
Entry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
if ((e.hash == hash) && e.key.equals(key))
return e.value;
}
return null;
}
/**
* 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() {
int oldCapacity = table.length;
Entry oldMap[] = table;
int newCapacity = oldCapacity * 2 + 1;
Entry newMap[] = new Entry[newCapacity];
threshold = (int) (newCapacity * loadFactor);
table = newMap;
/*
System.out.println("rehash old=" + oldCapacity
+ ", new=" + newCapacity
+ ", thresh=" + threshold
+ ", count=" + count);
*/
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;
}
}
}
/**
* Maps the specified key to the specified
* value in this hashtable. Neither the key nor the
* value can be null.
*
* The value can be retrieved by calling the get method
* with a key that is equal to the original key.
*/
public Object put(Object key, Object value) {
// Make sure the value is not null
if (value == null) {
throw new NullPointerException();
}
// Makes sure the key is not already in the hashtable.
Entry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (Entry e = tab[index]; e != null; e = e.next) {
// if ((e.hash == hash) && e.key.equals(key)) {
if ((e.hash == hash) && (e.key == key)) {
Object 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 null;
}
/**
* Hashtable collision list.
*/
private static class Entry {
int hash;
Object key;
Object value;
Entry next;
protected Entry(int hash, Object key, Object value, Entry next) {
this.hash = hash;
this.key = key;
this.value = value;
this.next = next;
}
}
}