| /******************************************************************************* |
| * 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 <CODE>char[]</CODE> 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 <CODE>Object</CODE> the specified key in the hashtable |
| * @param value <CODE>int</CODE> 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 <CODE>char[]</CODE> 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 <CODE>int</CODE> 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(); |
| } |
| } |