| /******************************************************************************* |
| * Copyright (c) 2004, 2016 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 |
| * |
| *******************************************************************************/ |
| package org.eclipse.dltk.internal.core.util; |
| import java.lang.ref.ReferenceQueue; |
| import java.lang.ref.WeakReference; |
| |
| /** |
| * A hashset whose values can be garbage collected. |
| */ |
| public class WeakHashSet { |
| |
| public static class HashableWeakReference extends WeakReference { |
| public int hashCode; |
| public HashableWeakReference(Object referent, ReferenceQueue queue) { |
| super(referent, queue); |
| this.hashCode = referent.hashCode(); |
| } |
| @Override |
| public boolean equals(Object obj) { |
| if (!(obj instanceof HashableWeakReference)) return false; |
| Object referent = get(); |
| Object other = ((HashableWeakReference) obj).get(); |
| if (referent == null) return other == null; |
| return referent.equals(other); |
| } |
| @Override |
| public int hashCode() { |
| return this.hashCode; |
| } |
| @Override |
| public String toString() { |
| Object referent = get(); |
| if (referent == null) return "[hashCode=" + this.hashCode + "] <referent was garbage collected>"; //$NON-NLS-1$ //$NON-NLS-2$ |
| return "[hashCode=" + this.hashCode + "] " + referent.toString(); //$NON-NLS-1$ //$NON-NLS-2$ |
| } |
| } |
| |
| HashableWeakReference[] values; |
| public int elementSize; // number of elements in the table |
| int threshold; |
| ReferenceQueue referenceQueue = new ReferenceQueue(); |
| |
| public WeakHashSet() { |
| this(5); |
| } |
| |
| public WeakHashSet(int size) { |
| this.elementSize = 0; |
| this.threshold = size; // size represents the expected number of elements |
| int extraRoom = (int) (size * 1.75f); |
| if (this.threshold == extraRoom) |
| extraRoom++; |
| this.values = new HashableWeakReference[extraRoom]; |
| } |
| |
| /* |
| * Adds the given object to this set. |
| * If an object that is equals to the given object already exists, do nothing. |
| * Returns the existing object or the new object if not found. |
| */ |
| public Object add(Object obj) { |
| cleanupGarbageCollectedValues(); |
| int valuesLength = this.values.length, |
| index = (obj.hashCode() & 0x7FFFFFFF) % valuesLength; |
| HashableWeakReference currentValue; |
| while ((currentValue = this.values[index]) != null) { |
| Object referent; |
| if (obj.equals(referent = currentValue.get())) { |
| return referent; |
| } |
| if (++index == valuesLength) { |
| index = 0; |
| } |
| } |
| this.values[index] = new HashableWeakReference(obj, this.referenceQueue); |
| |
| // assumes the threshold is never equal to the size of the table |
| if (++this.elementSize > this.threshold) |
| rehash(); |
| |
| return obj; |
| } |
| |
| private void addValue(HashableWeakReference value) { |
| Object obj = value.get(); |
| if (obj == null) return; |
| int valuesLength = this.values.length; |
| int index = (value.hashCode & 0x7FFFFFFF) % valuesLength; |
| HashableWeakReference currentValue; |
| while ((currentValue = this.values[index]) != null) { |
| if (obj.equals(currentValue.get())) { |
| return; |
| } |
| if (++index == valuesLength) { |
| index = 0; |
| } |
| } |
| this.values[index] = value; |
| |
| // assumes the threshold is never equal to the size of the table |
| if (++this.elementSize > this.threshold) |
| rehash(); |
| } |
| |
| private void cleanupGarbageCollectedValues() { |
| HashableWeakReference toBeRemoved; |
| while ((toBeRemoved = (HashableWeakReference) this.referenceQueue.poll()) != null) { |
| int hashCode = toBeRemoved.hashCode; |
| int valuesLength = this.values.length; |
| int index = (hashCode & 0x7FFFFFFF) % valuesLength; |
| HashableWeakReference currentValue; |
| while ((currentValue = this.values[index]) != null) { |
| if (currentValue == toBeRemoved) { |
| // replace the value at index with the last value with the same hash |
| int sameHash = index; |
| int current; |
| while ((currentValue = this.values[current = (sameHash + 1) % valuesLength]) != null && currentValue.hashCode == hashCode) |
| sameHash = current; |
| this.values[index] = this.values[sameHash]; |
| this.values[sameHash] = null; |
| this.elementSize--; |
| break; |
| } |
| if (++index == valuesLength) { |
| index = 0; |
| } |
| } |
| } |
| } |
| |
| public boolean contains(Object obj) { |
| return get(obj) != null; |
| } |
| |
| /* |
| * Return the object that is in this set and that is equals to the given object. |
| * Return null if not found. |
| */ |
| public Object get(Object obj) { |
| cleanupGarbageCollectedValues(); |
| int valuesLength = this.values.length; |
| int index = (obj.hashCode() & 0x7FFFFFFF) % valuesLength; |
| HashableWeakReference currentValue; |
| while ((currentValue = this.values[index]) != null) { |
| Object referent; |
| if (obj.equals(referent = currentValue.get())) { |
| return referent; |
| } |
| if (++index == valuesLength) { |
| index = 0; |
| } |
| } |
| return null; |
| } |
| |
| private void rehash() { |
| WeakHashSet newHashSet = new WeakHashSet(this.elementSize * 2); // double the number of expected elements |
| newHashSet.referenceQueue = this.referenceQueue; |
| HashableWeakReference currentValue; |
| for (int i = 0, length = this.values.length; i < length; i++) |
| if ((currentValue = this.values[i]) != null) |
| newHashSet.addValue(currentValue); |
| |
| this.values = newHashSet.values; |
| this.threshold = newHashSet.threshold; |
| this.elementSize = newHashSet.elementSize; |
| } |
| |
| /* |
| * Removes the object that is in this set and that is equals to the given object. |
| * Return the object that was in the set, or null if not found. |
| */ |
| public Object remove(Object obj) { |
| cleanupGarbageCollectedValues(); |
| int valuesLength = this.values.length; |
| int index = (obj.hashCode() & 0x7FFFFFFF) % valuesLength; |
| HashableWeakReference currentValue; |
| while ((currentValue = this.values[index]) != null) { |
| Object referent; |
| if (obj.equals(referent = currentValue.get())) { |
| this.elementSize--; |
| this.values[index] = null; |
| rehash(); |
| return referent; |
| } |
| if (++index == valuesLength) { |
| index = 0; |
| } |
| } |
| return null; |
| } |
| |
| public int size() { |
| return this.elementSize; |
| } |
| |
| @Override |
| public String toString() { |
| StringBuffer buffer = new StringBuffer("{"); //$NON-NLS-1$ |
| for (int i = 0, length = this.values.length; i < length; i++) { |
| HashableWeakReference value = this.values[i]; |
| if (value != null) { |
| Object ref = value.get(); |
| if (ref != null) { |
| buffer.append(ref.toString()); |
| buffer.append(", "); //$NON-NLS-1$ |
| } |
| } |
| } |
| buffer.append("}"); //$NON-NLS-1$ |
| return buffer.toString(); |
| } |
| } |