content: /**
   * 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
   * <p/>
   * http://www.apache.org/licenses/LICENSE-2.0
   * <p/>
   * 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 com.alibaba.jstorm.hdfs.common;
  
  import org.apache.hadoop.fs.FSDataOutputStream;
  import org.apache.hadoop.fs.FileAlreadyExistsException;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.LocatedFileStatus;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.fs.RemoteIterator;
  import org.apache.hadoop.hdfs.DistributedFileSystem;
  import org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException;
  import org.apache.hadoop.ipc.RemoteException;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  
  public class HdfsUtils {
    /** list files sorted by modification time that have not been modified since 'olderThan'. if
     * 'olderThan' is <= 0 then the filtering is disabled */
    public static ArrayList<Path> listFilesByModificationTime(FileSystem fs, Path directory, long olderThan)
            throws IOException {
      ArrayList<LocatedFileStatus> fstats = new ArrayList<>();
  
      RemoteIterator<LocatedFileStatus> itr = fs.listFiles(directory, false);
      while( itr.hasNext() ) {
        LocatedFileStatus fileStatus = itr.next();
        if(olderThan>0) {
          if( fileStatus.getModificationTime()<=olderThan )
            fstats.add(fileStatus);
        }
        else {
          fstats.add(fileStatus);
        }
      }
      Collections.sort(fstats, new ModifTimeComparator() );
  
      ArrayList<Path> result = new ArrayList<>(fstats.size());
      for (LocatedFileStatus fstat : fstats) {
        result.add(fstat.getPath());
      }
      return result;
    }
  
    /**
     * Returns null if file already exists. throws if there was unexpected problem
     */
    public static FSDataOutputStream tryCreateFile(FileSystem fs, Path file) throws IOException {
      try {
        FSDataOutputStream os = fs.create(file, false);
        return os;
      } catch (FileAlreadyExistsException e) {
        return null;
      } catch (RemoteException e) {
        if( e.unwrapRemoteException() instanceof AlreadyBeingCreatedException ) {
          return null;
        } else { // unexpected error
          throw e;
        }
      }
    }
  
    public static class Pair<K,V> {
      private K key;
      private V value;
      public Pair(K key, V value) {
        this.key = key;
        this.value = value;
      }
  
      public K getKey() {
        return key;
      }
  
      public V getValue() {
        return value;
      }
  
      public static <K,V> Pair of(K key, V value) {
        return new Pair(key,value);
      }
    }  // class Pair
  }
  