| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.hadoop.hdfs.server.namenode; |
| |
| import java.util.HashSet; |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.Set; |
| import java.util.concurrent.ConcurrentHashMap; |
| import java.util.concurrent.ConcurrentMap; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| |
| /** |
| * Map object to serial number. |
| * |
| * <p>It allows to get the serial number of an object, if the object doesn't |
| * exist in the map, a new serial number increased by 1 is generated to |
| * map to the object. The mapped object can also be got through the serial |
| * number. |
| * |
| * <p>The map is thread-safe. |
| */ |
| @InterfaceAudience.Private |
| public class SerialNumberMap<T> { |
| private String name; |
| private final int max; |
| private final AtomicInteger current = new AtomicInteger(1); |
| private final ConcurrentMap<T, Integer> t2i = |
| new ConcurrentHashMap<T, Integer>(); |
| private final ConcurrentMap<Integer, T> i2t = |
| new ConcurrentHashMap<Integer, T>(); |
| |
| SerialNumberMap(SerialNumberManager snm) { |
| this(snm.name(), snm.getLength()); |
| } |
| |
| SerialNumberMap(String name, int bitLength) { |
| this.name = name; |
| this.max = (1 << bitLength) - 1; |
| } |
| |
| public int get(T t) { |
| if (t == null) { |
| return 0; |
| } |
| Integer sn = t2i.get(t); |
| if (sn == null) { |
| sn = current.getAndIncrement(); |
| if (sn > max) { |
| current.getAndDecrement(); |
| throw new IllegalStateException(name + ": serial number map is full"); |
| } |
| Integer old = t2i.putIfAbsent(t, sn); |
| if (old != null) { |
| return old; |
| } |
| i2t.put(sn, t); |
| } |
| return sn; |
| } |
| |
| public T get(int i) { |
| if (i == 0) { |
| return null; |
| } |
| T t = i2t.get(i); |
| if (t == null) { |
| throw new IllegalStateException( |
| name + ": serial number " + i + " does not exist"); |
| } |
| return t; |
| } |
| |
| int getMax() { |
| return max; |
| } |
| |
| Set<Map.Entry<Integer, T>> entrySet() { |
| return new HashSet<>(i2t.entrySet()); |
| } |
| |
| public int size() { |
| return i2t.size(); |
| } |
| |
| @Override |
| public String toString() { |
| return "current=" + current + ",\n" + |
| "max=" + max + ",\n t2i=" + t2i + ",\n i2t=" + i2t; |
| } |
| } |