1 /** 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 package org.apache.hadoop.hdfs.server.common; 19 20 import org.apache.hadoop.classification.InterfaceAudience; 21 import org.apache.hadoop.util.SequentialNumber; 22 23 /**************************************************************** 24 * A GenerationStamp is a Hadoop FS primitive, identified by a long. 25 ****************************************************************/ 26 @InterfaceAudience.Private 27 public class GenerationStamp extends SequentialNumber { 28 /** 29 * The last reserved generation stamp. 30 */ 31 public static final long LAST_RESERVED_STAMP = 1000L; 32 33 /** 34 * Generation stamp of blocks that pre-date the introduction 35 * of a generation stamp. 36 */ 37 public static final long GRANDFATHER_GENERATION_STAMP = 0; 38 39 /** 40 * Create a new instance, initialized to {@link #LAST_RESERVED_STAMP}. 41 */ GenerationStamp()42 public GenerationStamp() { 43 super(LAST_RESERVED_STAMP); 44 } 45 } 46