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/*
* $Id: Hashtable.java,v 1.10 2010-11-01 04:34:28 joehw Exp $
*/
package com.sun.org.apache.xalan.internal.xsltc.runtime;
import java.util.Enumeration;
/**
* IMPORTANT NOTE:
* This code was taken from Sun's Java1.1 JDK java.util.HashTable.java
* All "synchronized" keywords and some methods we do not need have been
* all been removed.
*/
/**
* Object that wraps entries in the hash-table
* @author Morten Jorgensen
*/
class HashtableEntry {
int hash;
Object key;
Object value;
HashtableEntry next;
protected Object clone() {
HashtableEntry entry = new HashtableEntry();
entry.hash = hash;
entry.key = key;
entry.value = value;
entry.next = (next != null) ? (HashtableEntry)next.clone() : null;
return entry;
}
}
/**
* The main hash-table implementation
*/
public class Hashtable {
private transient HashtableEntry table[]; // hash-table entries
private transient int count; // number of entries
private int threshold; // current size of hash-tabke
private float loadFactor; // load factor
/**
* Constructs a new, empty hashtable with the specified initial
* capacity and the specified load factor.
*/
public Hashtable(int initialCapacity, float loadFactor) {
if (initialCapacity <= 0) initialCapacity = 11;
if (loadFactor <= 0.0) loadFactor = 0.75f;
this.loadFactor = loadFactor;
table = new HashtableEntry[initialCapacity];
threshold = (int)(initialCapacity * loadFactor);
}
/**
* Constructs a new, empty hashtable with the specified initial capacity
* and default load factor.
*/
public Hashtable(int initialCapacity) {
this(initialCapacity, 0.75f);
}
/**
* Constructs a new, empty hashtable with a default capacity and load
* factor.
*/
public Hashtable() {
this(101, 0.75f);
}
/**
* Returns the number of keys in this hashtable.
*/
public int size() {
return count;
}
/**
* Tests if this hashtable maps no keys to values.
*/
public boolean isEmpty() {
return count == 0;
}
/**
* Returns an enumeration of the keys in this hashtable.
*/
public Enumeration keys() {
return new HashtableEnumerator(table, true);
}
/**
* Returns an enumeration of the values in this hashtable.
* Use the Enumeration methods on the returned object to fetch the elements
* sequentially.
*/
public Enumeration elements() {
return new HashtableEnumerator(table, false);
}
/**
* Tests if some key maps into the specified value in this hashtable.
* This operation is more expensive than the containsKey
* method.
*/
public boolean contains(Object value) {
if (value == null) throw new NullPointerException();
int i;
HashtableEntry e;
HashtableEntry tab[] = table;
for (i = tab.length ; i-- > 0 ;) {
for (e = tab[i] ; e != null ; e = e.next) {
if (e.value.equals(value)) {
return true;
}
}
}
return false;
}
/**
* Tests if the specified object is a key in this hashtable.
*/
public boolean containsKey(Object key) {
HashtableEntry e;
HashtableEntry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (e = tab[index] ; e != null ; e = e.next)
if ((e.hash == hash) && e.key.equals(key))
return true;
return false;
}
/**
* Returns the value to which the specified key is mapped in this hashtable.
*/
public Object get(Object key) {
HashtableEntry e;
HashtableEntry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (e = tab[index] ; e != null ; e = e.next)
if ((e.hash == hash) && e.key.equals(key))
return e.value;
return null;
}
/**
* Rehashes the contents of the hashtable into a hashtable with a
* larger capacity. This method is called automatically when the
* number of keys in the hashtable exceeds this hashtable's capacity
* and load factor.
*/
protected void rehash() {
HashtableEntry e, old;
int i, index;
int oldCapacity = table.length;
HashtableEntry oldTable[] = table;
int newCapacity = oldCapacity * 2 + 1;
HashtableEntry newTable[] = new HashtableEntry[newCapacity];
threshold = (int)(newCapacity * loadFactor);
table = newTable;
for (i = oldCapacity ; i-- > 0 ;) {
for (old = oldTable[i] ; old != null ; ) {
e = old;
old = old.next;
index = (e.hash & 0x7FFFFFFF) % newCapacity;
e.next = newTable[index];
newTable[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.
HashtableEntry e;
HashtableEntry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (e = tab[index] ; e != null ; e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
Object old = e.value;
e.value = value;
return old;
}
}
// Rehash the table if the threshold is exceeded
if (count >= threshold) {
rehash();
return put(key, value);
}
// Creates the new entry.
e = new HashtableEntry();
e.hash = hash;
e.key = key;
e.value = value;
e.next = tab[index];
tab[index] = e;
count++;
return null;
}
/**
* Removes the key (and its corresponding value) from this
* hashtable. This method does nothing if the key is not in the hashtable.
*/
public Object remove(Object key) {
HashtableEntry e, prev;
HashtableEntry tab[] = table;
int hash = key.hashCode();
int index = (hash & 0x7FFFFFFF) % tab.length;
for (e = tab[index], prev = null ; e != null ; prev = e, e = e.next) {
if ((e.hash == hash) && e.key.equals(key)) {
if (prev != null)
prev.next = e.next;
else
tab[index] = e.next;
count--;
return e.value;
}
}
return null;
}
/**
* Clears this hashtable so that it contains no keys.
*/
public void clear() {
HashtableEntry tab[] = table;
for (int index = tab.length; --index >= 0; )
tab[index] = null;
count = 0;
}
/**
* Returns a rather long string representation of this hashtable.
* Handy for debugging - leave it here!!!
*/
public String toString() {
int i;
int max = size() - 1;
StringBuffer buf = new StringBuffer();
Enumeration k = keys();
Enumeration e = elements();
buf.append("{");
for (i = 0; i <= max; i++) {
String s1 = k.nextElement().toString();
String s2 = e.nextElement().toString();
buf.append(s1 + "=" + s2);
if (i < max) buf.append(", ");
}
buf.append("}");
return buf.toString();
}
/**
* A hashtable enumerator class. This class should remain opaque
* to the client. It will use the Enumeration interface.
*/
class HashtableEnumerator implements Enumeration {
boolean keys;
int index;
HashtableEntry table[];
HashtableEntry entry;
HashtableEnumerator(HashtableEntry table[], boolean keys) {
this.table = table;
this.keys = keys;
this.index = table.length;
}
public boolean hasMoreElements() {
if (entry != null) {
return true;
}
while (index-- > 0) {
if ((entry = table[index]) != null) {
return true;
}
}
return false;
}
public Object nextElement() {
if (entry == null) {
while ((index-- > 0) && ((entry = table[index]) == null));
}
if (entry != null) {
HashtableEntry e = entry;
entry = e.next;
return keys ? e.key : e.value;
}
return null;
}
}
}