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
  //
  //   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 com.cloud.storage;
  
  import java.io.File;
  import java.io.IOException;
  import java.util.List;
  
  import com.cloud.utils.component.Manager;
  
  /**
   * StorageLayer is an independence layer for
   *
   *   1. Proper synchronization between threads.
   *
   *
   */
  public interface StorageLayer extends Manager {
      public final static String InstanceConfigKey = "storage.layer.instance";
      public final static String ClassConfigKey = "storage.layer.implementation";
  
      /**
       * @param path path to the file to get the size.
       * @return size of the file.
       */
      long getSize(String path);
  
      File createUniqDir() throws IOException;
  
      /**
       * Is this path a directory?
       * @param path path to check.
       * @return true if it is a directory; false otherwise.
       */
      boolean isDirectory(String path);
  
      /**
       * Is this path a file?
       * @param path path to check.
       * @return true if it is a file; false otherwise.
       */
      boolean isFile(String path);
  
      /**
       * creates the directory.  All parent directories have to already exists.
       * @param path path to make.
       * @return true if created; false if not.
       */
      boolean mkdir(String path);
  
      /**
       * Creates the entire path.
       * @param path path to create.
       * @return true if created; false if not.
       */
      boolean mkdirs(String path);
  
      /**
       * Does this path exists?
       * @param path directory or file to check if it exists.
       * @return true if exists; false if not.
       */
      boolean exists(String path);
  
      /**
       * list all the files in a certain path.
       * @param path directory that the file exists in.
       * @return list of files that exists under this path.
       */
      String[] listFiles(String path);
  
      /**
       * Get the total disk size in bytes.
       * @param path path
       * @return disk size if path given is a disk; -1 if not.
       */
      long getTotalSpace(String path);
  
      /**
       * Get the total available disk size in bytes.
       * @param path path to the disk.
       * @return disk size if path given is a disk; -1 if not.
       */
      long getUsedSpace(String path);
  
      /**
       * Get the total available disk size in bytes.
       * @param path path to the disk.
       * @return disk size if path given is a disk; -1 if not.
       */
      long getUsableSpace(String path);
  
      /**
       * delete the path
       * @param path to delete.
       * @return true if deleted; false if not.
       */
      boolean delete(String path);
  
      /**
       * creates a file on this path.
       * @param path directory to create the file in.
       * @param filename file to create.
       * @return true if created; false if not.
       * @throws IOException if create has problems.
       */
      boolean create(String path, String filename) throws IOException;
  
      /**
       * clean up the path.  This method will delete the parent paths if the parent
       * paths do not contain children.  If the original path cannot be deleted,
       * this method returns false.  If the parent cannot be deleted but does not
       * have any children, this method throws IOException.
       * @param path path to be cleaned up.
       * @param rootPath delete up to this path.
       * @return true if the path is deleted and false if it is not.
       * @throws IOException if the parent has no children but delete failed.
       */
      boolean cleanup(String path, String rootPath) throws IOException;
  
      /**
       * Retrieves the actual file object.
       * @param path path to the file.
       * @return File object representing the file.
       */
      File getFile(String path);
  
      /**
       * Sets permissions for a file to be world readable and writeable
       * @param file
       * @return true if the file was set to be both world readable and writeable
       */
      boolean setWorldReadableAndWriteable(File file);
  
      boolean deleteDir(String dir);
  
      List<String> listMountPointsByMsHost(String path, long msHostId);
  }
  