org.eclipse.jdt.internal.compiler.codegen.IntegerCache Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2000, 2009 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;
public class IntegerCache {
public int keyTable[];
public int valueTable[];
int elementSize;
int threshold;
/**
* Constructs a new, empty hashtable. A default capacity and
* load factor is used. Note that the hashtable will automatically
* grow when it gets full.
*/
public IntegerCache() {
this(13);
}
/**
* Constructs a new, empty hashtable with the specified initial
* capacity.
* @param initialCapacity int
* the initial number of buckets
*/
public IntegerCache(int initialCapacity) {
this.elementSize = 0;
this.threshold = (int) (initialCapacity * 0.66);
this.keyTable = new int[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] = 0;
this.valueTable[i] = 0;
}
this.elementSize = 0;
}
/** Returns true if the collection contains an element for the key.
*
* @param key double the key that we are looking for
* @return boolean
*/
public boolean containsKey(int key) {
int index = hash(key), length = this.keyTable.length;
while ((this.keyTable[index] != 0) || ((this.keyTable[index] == 0) &&(this.valueTable[index] != 0))) {
if (this.keyTable[index] == key)
return true;
if (++index == length) {
index = 0;
}
}
return false;
}
/**
* Return a hashcode for the value of the key parameter.
* @param key int
* @return int the hash code corresponding to the key value
*/
public int hash(int key) {
return (key & 0x7FFFFFFF) % this.keyTable.length;
}
/**
* Puts the specified element into the hashtable, using the specified
* key. The element may be retrieved by doing a get() with the same key.
*
* @param key int the specified key in the hashtable
* @param value int the specified element
* @return int value
*/
public int put(int key, int value) {
int index = hash(key), length = this.keyTable.length;
while ((this.keyTable[index] != 0) || ((this.keyTable[index] == 0) && (this.valueTable[index] != 0))) {
if (this.keyTable[index] == key)
return this.valueTable[index] = value;
if (++index == length) {
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;
}
/**
* Puts the specified element into the hashtable if absent, using the specified
* key. The element may be retrieved by doing a get() with the same key.
*
* @param key int the specified key in the hashtable
* @param value int the specified element
* @return int value
*/
public int putIfAbsent(int key, int value) {
int index = hash(key), length = this.keyTable.length;
while ((this.keyTable[index] != 0) || ((this.keyTable[index] == 0) && (this.valueTable[index] != 0))) {
if (this.keyTable[index] == key)
return this.valueTable[index];
if (++index == length) {
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, assumes value is > 0
}
/**
* 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() {
IntegerCache newHashtable = new IntegerCache(this.keyTable.length * 2);
for (int i = this.keyTable.length; --i >= 0;) {
int key = this.keyTable[i];
int value = this.valueTable[i];
if ((key != 0) || ((key == 0) && (value != 0))) {
newHashtable.put(key, value);
}
}
this.keyTable = newHashtable.keyTable;
this.valueTable = newHashtable.valueTable;
this.threshold = newHashtable.threshold;
}
/**
* 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] != 0) || ((this.keyTable[i] == 0) && (this.valueTable[i] != 0))) {
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();
}
}