| /******************************************************************************* |
| * Copyright (c) 2000, 2004 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: |
| * Peter Shipton - original hashtable implementation |
| * Nick Edgar - added element comparer support |
| *******************************************************************************/ |
| |
| package org.eclipse.jface.viewers; |
| |
| import java.util.Enumeration; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * CustomHashtable associates keys with values. Keys and values cannot be null. |
| * The size of the Hashtable is the number of key/value pairs it contains. |
| * The capacity is the number of key/value pairs the Hashtable can hold. |
| * The load factor is a float value which determines how full the Hashtable |
| * gets before expanding the capacity. If the load factor of the Hashtable |
| * is exceeded, the capacity is doubled. |
| * <p> |
| * CustomHashtable allows a custom comparator and hash code provider. |
| */ |
| /* package */final class CustomHashtable { |
| |
| /** |
| * HashMapEntry is an internal class which is used to hold the entries of a Hashtable. |
| */ |
| private static class HashMapEntry { |
| Object key, value; |
| |
| HashMapEntry next; |
| |
| HashMapEntry(Object theKey, Object theValue) { |
| key = theKey; |
| value = theValue; |
| } |
| } |
| |
| private static final class EmptyEnumerator implements Enumeration { |
| public boolean hasMoreElements() { |
| return false; |
| } |
| |
| public Object nextElement() { |
| throw new NoSuchElementException(); |
| } |
| } |
| |
| private class HashEnumerator implements Enumeration { |
| boolean key; |
| |
| int start; |
| |
| HashMapEntry entry; |
| |
| HashEnumerator(boolean isKey) { |
| key = isKey; |
| start = firstSlot; |
| } |
| |
| public boolean hasMoreElements() { |
| if (entry != null) { |
| return true; |
| } |
| while (start <= lastSlot) { |
| if (elementData[start++] != null) { |
| entry = elementData[start - 1]; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| public Object nextElement() { |
| if (hasMoreElements()) { |
| Object result = key ? entry.key : entry.value; |
| entry = entry.next; |
| return result; |
| } else { |
| throw new NoSuchElementException(); |
| } |
| } |
| } |
| |
| transient int elementCount; |
| |
| transient HashMapEntry[] elementData; |
| |
| private float loadFactor; |
| |
| private int threshold; |
| |
| transient int firstSlot = 0; |
| |
| transient int lastSlot = -1; |
| |
| transient private IElementComparer comparer; |
| |
| private static final EmptyEnumerator emptyEnumerator = new EmptyEnumerator(); |
| |
| /** |
| * The default capacity used when not specified in the constructor. |
| */ |
| public static final int DEFAULT_CAPACITY = 13; |
| |
| /** |
| * Constructs a new Hashtable using the default capacity |
| * and load factor. |
| */ |
| public CustomHashtable() { |
| this(13); |
| } |
| |
| /** |
| * Constructs a new Hashtable using the specified capacity |
| * and the default load factor. |
| * |
| * @param capacity the initial capacity |
| */ |
| public CustomHashtable(int capacity) { |
| this(capacity, null); |
| } |
| |
| /** |
| * Constructs a new hash table with the default capacity and the given |
| * element comparer. |
| * |
| * @param comparer the element comparer to use to compare keys and obtain |
| * hash codes for keys, or <code>null</code> to use the normal |
| * <code>equals</code> and <code>hashCode</code> methods |
| */ |
| public CustomHashtable(IElementComparer comparer) { |
| this(DEFAULT_CAPACITY, comparer); |
| } |
| |
| /** |
| * Constructs a new hash table with the given capacity and the given |
| * element comparer. |
| * |
| * @param capacity the maximum number of elements that can be added without |
| * rehashing |
| * @param comparer the element comparer to use to compare keys and obtain |
| * hash codes for keys, or <code>null</code> to use the normal |
| * <code>equals</code> and <code>hashCode</code> methods |
| */ |
| public CustomHashtable(int capacity, IElementComparer comparer) { |
| if (capacity >= 0) { |
| elementCount = 0; |
| elementData = new HashMapEntry[capacity == 0 ? 1 : capacity]; |
| firstSlot = elementData.length; |
| loadFactor = 0.75f; |
| computeMaxSize(); |
| } else { |
| throw new IllegalArgumentException(); |
| } |
| this.comparer = comparer; |
| } |
| |
| /** |
| * Constructs a new hash table with enough capacity to hold all keys in the |
| * given hash table, then adds all key/value pairs in the given hash table |
| * to the new one, using the given element comparer. |
| * |
| * @param capacity the maximum number of elements that can be added without |
| * rehashing |
| * @param comparer the element comparer to use to compare keys and obtain |
| * hash codes for keys, or <code>null</code> to use the normal |
| * <code>equals</code> and <code>hashCode</code> methods |
| */ |
| public CustomHashtable(CustomHashtable table, IElementComparer comparer) { |
| this(table.size() * 2, comparer); |
| for (int i = table.elementData.length; --i >= 0;) { |
| HashMapEntry entry = table.elementData[i]; |
| while (entry != null) { |
| put(entry.key, entry.value); |
| entry = entry.next; |
| } |
| } |
| } |
| |
| /** |
| * Returns the element comparer used to compare keys and to obtain |
| * hash codes for keys, or <code>null</code> if no comparer has been |
| * provided. |
| * |
| * @return the element comparer or <code>null</code> |
| * |
| * @since 3.2 |
| */ |
| public IElementComparer getComparer() { |
| return comparer; |
| } |
| |
| private void computeMaxSize() { |
| threshold = (int) (elementData.length * loadFactor); |
| } |
| |
| /** |
| * Answers if this Hashtable contains the specified object as a key |
| * of one of the key/value pairs. |
| * |
| * @param key the object to look for as a key in this Hashtable |
| * @return true if object is a key in this Hashtable, false otherwise |
| */ |
| public boolean containsKey(Object key) { |
| return getEntry(key) != null; |
| } |
| |
| /** |
| * Answers an Enumeration on the values of this Hashtable. The |
| * results of the Enumeration may be affected if the contents |
| * of this Hashtable are modified. |
| * |
| * @return an Enumeration of the values of this Hashtable |
| */ |
| public Enumeration elements() { |
| if (elementCount == 0) { |
| return emptyEnumerator; |
| } |
| return new HashEnumerator(false); |
| } |
| |
| /** |
| * Answers the value associated with the specified key in |
| * this Hashtable. |
| * |
| * @param key the key of the value returned |
| * @return the value associated with the specified key, null if the specified key |
| * does not exist |
| */ |
| public Object get(Object key) { |
| int index = (hashCode(key) & 0x7FFFFFFF) % elementData.length; |
| HashMapEntry entry = elementData[index]; |
| while (entry != null) { |
| if (keyEquals(key, entry.key)) { |
| return entry.value; |
| } |
| entry = entry.next; |
| } |
| return null; |
| } |
| |
| private HashMapEntry getEntry(Object key) { |
| int index = (hashCode(key) & 0x7FFFFFFF) % elementData.length; |
| HashMapEntry entry = elementData[index]; |
| while (entry != null) { |
| if (keyEquals(key, entry.key)) { |
| return entry; |
| } |
| entry = entry.next; |
| } |
| return null; |
| } |
| |
| /** |
| * Answers the hash code for the given key. |
| */ |
| private int hashCode(Object key) { |
| if (comparer == null) { |
| return key.hashCode(); |
| } else { |
| return comparer.hashCode(key); |
| } |
| } |
| |
| /** |
| * Compares two keys for equality. |
| */ |
| private boolean keyEquals(Object a, Object b) { |
| if (comparer == null) { |
| return a.equals(b); |
| } else { |
| return comparer.equals(a, b); |
| } |
| } |
| |
| /** |
| * Answers an Enumeration on the keys of this Hashtable. The |
| * results of the Enumeration may be affected if the contents |
| * of this Hashtable are modified. |
| * |
| * @return an Enumeration of the keys of this Hashtable |
| */ |
| public Enumeration keys() { |
| if (elementCount == 0) { |
| return emptyEnumerator; |
| } |
| return new HashEnumerator(true); |
| } |
| |
| /** |
| * Associate the specified value with the specified key in this Hashtable. |
| * If the key already exists, the old value is replaced. The key and value |
| * cannot be null. |
| * |
| * @param key the key to add |
| * @param value the value to add |
| * @return the old value associated with the specified key, null if the key did |
| * not exist |
| */ |
| public Object put(Object key, Object value) { |
| if (key != null && value != null) { |
| int index = (hashCode(key) & 0x7FFFFFFF) % elementData.length; |
| HashMapEntry entry = elementData[index]; |
| while (entry != null && !keyEquals(key, entry.key)) { |
| entry = entry.next; |
| } |
| if (entry == null) { |
| if (++elementCount > threshold) { |
| rehash(); |
| index = (hashCode(key) & 0x7FFFFFFF) % elementData.length; |
| } |
| if (index < firstSlot) { |
| firstSlot = index; |
| } |
| if (index > lastSlot) { |
| lastSlot = index; |
| } |
| entry = new HashMapEntry(key, value); |
| entry.next = elementData[index]; |
| elementData[index] = entry; |
| return null; |
| } |
| Object result = entry.value; |
| entry.key = key; // important to avoid hanging onto keys that are equal but "old" -- see bug 30607 |
| entry.value = value; |
| return result; |
| } else { |
| throw new NullPointerException(); |
| } |
| } |
| |
| /** |
| * Increases the capacity of this Hashtable. This method is sent when |
| * the size of this Hashtable exceeds the load factor. |
| */ |
| private void rehash() { |
| int length = elementData.length << 1; |
| if (length == 0) { |
| length = 1; |
| } |
| firstSlot = length; |
| lastSlot = -1; |
| HashMapEntry[] newData = new HashMapEntry[length]; |
| for (int i = elementData.length; --i >= 0;) { |
| HashMapEntry entry = elementData[i]; |
| while (entry != null) { |
| int index = (hashCode(entry.key) & 0x7FFFFFFF) % length; |
| if (index < firstSlot) { |
| firstSlot = index; |
| } |
| if (index > lastSlot) { |
| lastSlot = index; |
| } |
| HashMapEntry next = entry.next; |
| entry.next = newData[index]; |
| newData[index] = entry; |
| entry = next; |
| } |
| } |
| elementData = newData; |
| computeMaxSize(); |
| } |
| |
| /** |
| * Remove the key/value pair with the specified key from this Hashtable. |
| * |
| * @param key the key to remove |
| * @return the value associated with the specified key, null if the specified key |
| * did not exist |
| */ |
| public Object remove(Object key) { |
| HashMapEntry last = null; |
| int index = (hashCode(key) & 0x7FFFFFFF) % elementData.length; |
| HashMapEntry entry = elementData[index]; |
| while (entry != null && !keyEquals(key, entry.key)) { |
| last = entry; |
| entry = entry.next; |
| } |
| if (entry != null) { |
| if (last == null) { |
| elementData[index] = entry.next; |
| } else { |
| last.next = entry.next; |
| } |
| elementCount--; |
| return entry.value; |
| } |
| return null; |
| } |
| |
| /** |
| * Answers the number of key/value pairs in this Hashtable. |
| * |
| * @return the number of key/value pairs in this Hashtable |
| */ |
| public int size() { |
| return elementCount; |
| } |
| |
| /** |
| * Answers the string representation of this Hashtable. |
| * |
| * @return the string representation of this Hashtable |
| */ |
| public String toString() { |
| if (size() == 0) { |
| return "{}"; //$NON-NLS-1$ |
| } |
| |
| StringBuffer buffer = new StringBuffer(); |
| buffer.append('{'); |
| for (int i = elementData.length; --i >= 0;) { |
| HashMapEntry entry = elementData[i]; |
| while (entry != null) { |
| buffer.append(entry.key); |
| buffer.append('='); |
| buffer.append(entry.value); |
| buffer.append(", "); //$NON-NLS-1$ |
| entry = entry.next; |
| } |
| } |
| // Remove the last ", " |
| if (elementCount > 0) { |
| buffer.setLength(buffer.length() - 2); |
| } |
| buffer.append('}'); |
| return buffer.toString(); |
| } |
| } |