org.eclipse.jdt.internal.compiler.codegen.CharArrayCache Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2000, 2008 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.jdt.internal.compiler.codegen;
import org.eclipse.jdt.core.compiler.CharOperation;
public class CharArrayCache {
// to avoid using Enumerations, walk the individual tables skipping nulls
public char[] keyTable[];
public int valueTable[];
int elementSize; // number of elements in the table
int threshold;
/**
* Constructs a new, empty hashtable. A default capacity is used.
* Note that the hashtable will automatically grow when it gets full.
*/
public CharArrayCache() {
this(9);
}
/**
* Constructs a new, empty hashtable with the specified initial
* capacity.
* @param initialCapacity int
* the initial number of buckets; must be less than Integer.MAX_VALUE / 2
*/
public CharArrayCache(int initialCapacity) {
this.elementSize = 0;
this.threshold = (initialCapacity * 2) / 3; // faster than float operation
this.keyTable = new char[initialCapacity][];
this.valueTable = new int[initialCapacity];
}
/**
* Clears the hash table so that it has no more elements in it.
*/
public void clear() {
for (int i = this.keyTable.length; --i >= 0;) {
this.keyTable[i] = null;
this.valueTable[i] = 0;
}
this.elementSize = 0;
}
/** Returns true if the collection contains an element for the key.
*
* @param key char[] the key that we are looking for
* @return boolean
*/
public boolean containsKey(char[] key) {
int length = this.keyTable.length, index = CharOperation.hashCode(key) % length;
while (this.keyTable[index] != null) {
if (CharOperation.equals(this.keyTable[index], key))
return true;
if (++index == length) { // faster than modulo
index = 0;
}
}
return false;
}
/** Gets the object associated with the specified key in the
* hashtable.
* @param key char[] the specified key
* @return int the element for the key or -1 if the key is not
* defined in the hash table.
*/
public int get(char[] key) {
int length = this.keyTable.length, index = CharOperation.hashCode(key) % length;
while (this.keyTable[index] != null) {
if (CharOperation.equals(this.keyTable[index], key))
return this.valueTable[index];
if (++index == length) { // faster than modulo
index = 0;
}
}
return -1;
}
/**
* Puts the specified element into the hashtable if it wasn't there already,
* using the specified key. The element may be retrieved by doing a get() with the same key.
* The key and the element cannot be null.
*
* @param key the given key in the hashtable
* @param value the given value
* @return int the old value of the key, or -value if it did not have one.
*/
public int putIfAbsent(char[] key, int value) {
int length = this.keyTable.length, index = CharOperation.hashCode(key) % length;
while (this.keyTable[index] != null) {
if (CharOperation.equals(this.keyTable[index], key))
return this.valueTable[index];
if (++index == length) { // faster than modulo
index = 0;
}
}
this.keyTable[index] = key;
this.valueTable[index] = value;
// assumes the threshold is never equal to the size of the table
if (++this.elementSize > this.threshold)
rehash();
return -value; // negative when added (value is assumed to be > 0)
}
/**
* Puts the specified element into the hashtable, using the specified
* key. The element may be retrieved by doing a get() with the same key.
* The key and the element cannot be null.
*
* @param key Object the specified key in the hashtable
* @param value int the specified element
* @return int the old value of the key, or -1 if it did not have one.
*/
private int put(char[] key, int value) {
int length = this.keyTable.length, index = CharOperation.hashCode(key) % length;
while (this.keyTable[index] != null) {
if (CharOperation.equals(this.keyTable[index], key))
return this.valueTable[index] = value;
if (++index == length) { // faster than modulo
index = 0;
}
}
this.keyTable[index] = key;
this.valueTable[index] = value;
// assumes the threshold is never equal to the size of the table
if (++this.elementSize > this.threshold)
rehash();
return value;
}
/**
* Rehashes the content of the table into a bigger table.
* This method is called automatically when the hashtable's
* size exceeds the threshold.
*/
private void rehash() {
CharArrayCache newHashtable = new CharArrayCache(this.keyTable.length * 2);
for (int i = this.keyTable.length; --i >= 0;)
if (this.keyTable[i] != null)
newHashtable.put(this.keyTable[i], this.valueTable[i]);
this.keyTable = newHashtable.keyTable;
this.valueTable = newHashtable.valueTable;
this.threshold = newHashtable.threshold;
}
/** Remove the object associated with the specified key in the
* hashtable.
* @param key char[] the specified key
*/
public void remove(char[] key) {
int length = this.keyTable.length, index = CharOperation.hashCode(key) % length;
while (this.keyTable[index] != null) {
if (CharOperation.equals(this.keyTable[index], key)) {
this.valueTable[index] = 0;
this.keyTable[index] = null;
return;
}
if (++index == length) { // faster than modulo
index = 0;
}
}
}
/**
* Returns the key corresponding to the value. Returns null if the
* receiver doesn't contain the value.
* @param value int the value that we are looking for
* @return Object
*/
public char[] returnKeyFor(int value) {
for (int i = this.keyTable.length; i-- > 0;) {
if (this.valueTable[i] == value) {
return this.keyTable[i];
}
}
return null;
}
/**
* Returns the number of elements contained in the hashtable.
*
* @return int The size of the table
*/
public int size() {
return this.elementSize;
}
/**
* Converts to a rather lengthy String.
*
* return String the ascii representation of the receiver
*/
public String toString() {
int max = size();
StringBuffer buf = new StringBuffer();
buf.append("{"); //$NON-NLS-1$
for (int i = 0; i < max; ++i) {
if (this.keyTable[i] != null) {
buf.append(this.keyTable[i]).append("->").append(this.valueTable[i]); //$NON-NLS-1$
}
if (i < max) {
buf.append(", "); //$NON-NLS-1$
}
}
buf.append("}"); //$NON-NLS-1$
return buf.toString();
}
}