| /* |
| * Copyright (c) 2015, 2015, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| package org.graalvm.compiler.core.common.util; |
| |
| import java.util.ArrayList; |
| import java.util.HashMap; |
| import java.util.IdentityHashMap; |
| import java.util.List; |
| import java.util.Map; |
| |
| /** |
| * Creates an array of T objects order by the occurrence frequency of each object. The most |
| * frequently used object is the first one, the least frequently used the last one. If {@code null} |
| * is added, it is always the first element. |
| * |
| * Either object {@link #createIdentityEncoder() identity} or object {@link #createEqualityEncoder() |
| * equality} can be used to build the array and count the frequency. |
| */ |
| public class FrequencyEncoder<T> { |
| |
| static class Entry<T> { |
| protected final T object; |
| protected int frequency; |
| protected int index; |
| |
| protected Entry(T object) { |
| this.object = object; |
| this.index = -1; |
| } |
| } |
| |
| protected final Map<T, Entry<T>> map; |
| protected boolean containsNull; |
| |
| /** |
| * Creates an encoder that uses object identity. |
| */ |
| public static <T> FrequencyEncoder<T> createIdentityEncoder() { |
| return new FrequencyEncoder<>(new IdentityHashMap<>()); |
| } |
| |
| /** |
| * Creates an encoder that uses {@link Object#equals(Object) object equality}. |
| */ |
| public static <T> FrequencyEncoder<T> createEqualityEncoder() { |
| return new FrequencyEncoder<>(new HashMap<>()); |
| } |
| |
| protected FrequencyEncoder(Map<T, Entry<T>> map) { |
| this.map = map; |
| } |
| |
| /** |
| * Adds an object to the array. |
| */ |
| public void addObject(T object) { |
| if (object == null) { |
| containsNull = true; |
| return; |
| } |
| |
| Entry<T> entry = map.get(object); |
| if (entry == null) { |
| entry = new Entry<>(object); |
| map.put(object, entry); |
| } |
| entry.frequency++; |
| } |
| |
| /** |
| * Returns the index of an object in the array. The object must have been |
| * {@link #addObject(Object) added} before. |
| */ |
| public int getIndex(Object object) { |
| if (object == null) { |
| assert containsNull; |
| return 0; |
| } |
| Entry<T> entry = map.get(object); |
| assert entry != null && entry.index >= 0; |
| return entry.index; |
| } |
| |
| /** |
| * Returns the number of distinct objects that have been added, i.e., the length of the array. |
| */ |
| public int getLength() { |
| return map.size() + (containsNull ? 1 : 0); |
| } |
| |
| /** |
| * Fills the provided array with the added objects. The array must have the {@link #getLength() |
| * correct length}. |
| */ |
| public T[] encodeAll(T[] allObjects) { |
| assert allObjects.length == getLength(); |
| List<Entry<T>> sortedEntries = new ArrayList<>(map.values()); |
| sortedEntries.sort((e1, e2) -> -Integer.compare(e1.frequency, e2.frequency)); |
| |
| int offset = 0; |
| if (containsNull) { |
| allObjects[0] = null; |
| offset = 1; |
| } |
| for (int i = 0; i < sortedEntries.size(); i++) { |
| Entry<T> entry = sortedEntries.get(i); |
| int index = i + offset; |
| entry.index = index; |
| allObjects[index] = entry.object; |
| assert entry.object != null; |
| } |
| return allObjects; |
| } |
| } |