| /******************************************************************************* |
| * 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.util; |
| |
| /** |
| * A simple lookup table is a non-synchronized Hashtable, whose keys |
| * and values are Objects. It also uses linear probing to resolve collisions |
| * rather than a linked list of hash table entries. |
| */ |
| public final class SimpleLookupTable implements Cloneable { |
| |
| // to avoid using Enumerations, walk the individual tables skipping nulls |
| public Object[] keyTable; |
| public Object[] valueTable; |
| public int elementSize; // number of elements in the table |
| public int threshold; |
| |
| public SimpleLookupTable() { |
| this(13); |
| } |
| |
| public SimpleLookupTable(int size) { |
| this.elementSize = 0; |
| this.threshold = size; // size represents the expected number of elements |
| int extraRoom = (int) (size * 1.5f); |
| if (this.threshold == extraRoom) |
| extraRoom++; |
| this.keyTable = new Object[extraRoom]; |
| this.valueTable = new Object[extraRoom]; |
| } |
| |
| public Object clone() throws CloneNotSupportedException { |
| SimpleLookupTable result = (SimpleLookupTable) super.clone(); |
| result.elementSize = this.elementSize; |
| result.threshold = this.threshold; |
| |
| int length = this.keyTable.length; |
| result.keyTable = new Object[length]; |
| System.arraycopy(this.keyTable, 0, result.keyTable, 0, length); |
| |
| length = this.valueTable.length; |
| result.valueTable = new Object[length]; |
| System.arraycopy(this.valueTable, 0, result.valueTable, 0, length); |
| return result; |
| } |
| |
| public boolean containsKey(Object key) { |
| int length = this.keyTable.length; |
| int index = (key.hashCode() & 0x7FFFFFFF) % length; |
| Object currentKey; |
| while ((currentKey = this.keyTable[index]) != null) { |
| if (currentKey.equals(key)) return true; |
| if (++index == length) index = 0; |
| } |
| return false; |
| } |
| |
| public Object get(Object key) { |
| int length = this.keyTable.length; |
| int index = (key.hashCode() & 0x7FFFFFFF) % length; |
| Object currentKey; |
| while ((currentKey = this.keyTable[index]) != null) { |
| if (currentKey.equals(key)) return this.valueTable[index]; |
| if (++index == length) index = 0; |
| } |
| return null; |
| } |
| |
| public Object getKey(Object key) { |
| int length = this.keyTable.length; |
| int index = (key.hashCode() & 0x7FFFFFFF) % length; |
| Object currentKey; |
| while ((currentKey = this.keyTable[index]) != null) { |
| if (currentKey.equals(key)) return currentKey; |
| if (++index == length) index = 0; |
| } |
| return key; |
| } |
| |
| public Object keyForValue(Object valueToMatch) { |
| if (valueToMatch != null) |
| for (int i = 0, l = this.keyTable.length; i < l; i++) |
| if (this.keyTable[i] != null && valueToMatch.equals(this.valueTable[i])) |
| return this.keyTable[i]; |
| return null; |
| } |
| |
| public Object put(Object key, Object value) { |
| int length = this.keyTable.length; |
| int index = (key.hashCode() & 0x7FFFFFFF) % length; |
| Object currentKey; |
| while ((currentKey = this.keyTable[index]) != null) { |
| if (currentKey.equals(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; |
| } |
| |
| public Object removeKey(Object key) { |
| int length = this.keyTable.length; |
| int index = (key.hashCode() & 0x7FFFFFFF) % length; |
| Object currentKey; |
| while ((currentKey = this.keyTable[index]) != null) { |
| if (currentKey.equals(key)) { |
| this.elementSize--; |
| Object oldValue = this.valueTable[index]; |
| this.keyTable[index] = null; |
| this.valueTable[index] = null; |
| if (this.keyTable[index + 1 == length ? 0 : index + 1] != null) |
| rehash(); // only needed if a possible collision existed |
| return oldValue; |
| } |
| if (++index == length) index = 0; |
| } |
| return null; |
| } |
| |
| public void removeValue(Object valueToRemove) { |
| boolean rehash = false; |
| for (int i = 0, l = this.valueTable.length; i < l; i++) { |
| Object value = this.valueTable[i]; |
| if (value != null && value.equals(valueToRemove)) { |
| this.elementSize--; |
| this.keyTable[i] = null; |
| this.valueTable[i] = null; |
| if (!rehash && this.keyTable[i + 1 == l ? 0 : i + 1] != null) |
| rehash = true; // only needed if a possible collision existed |
| } |
| } |
| if (rehash) rehash(); |
| } |
| |
| private void rehash() { |
| SimpleLookupTable newLookupTable = new SimpleLookupTable(this.elementSize * 2); // double the number of expected elements |
| Object currentKey; |
| for (int i = this.keyTable.length; --i >= 0;) |
| if ((currentKey = this.keyTable[i]) != null) |
| newLookupTable.put(currentKey, this.valueTable[i]); |
| |
| this.keyTable = newLookupTable.keyTable; |
| this.valueTable = newLookupTable.valueTable; |
| this.elementSize = newLookupTable.elementSize; |
| this.threshold = newLookupTable.threshold; |
| } |
| |
| public String toString() { |
| String s = ""; //$NON-NLS-1$ |
| Object object; |
| for (int i = 0, l = this.valueTable.length; i < l; i++) |
| if ((object = this.valueTable[i]) != null) |
| s += this.keyTable[i].toString() + " -> " + object.toString() + "\n"; //$NON-NLS-2$ //$NON-NLS-1$ |
| return s; |
| } |
| } |