com.datatorrent.lib.fileaccess.FileAccess Maven / Gradle / Ivy

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/**
 * 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.datatorrent.lib.fileaccess;

import java.io.Closeable;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.TreeMap;

import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.LocatedFileStatus;
import org.apache.hadoop.fs.RemoteIterator;

import com.datatorrent.netlet.util.Slice;

/**
 * Abstraction for file system and format interaction.
 *
 * @since 2.0.0
 */
@InterfaceStability.Evolving
public interface FileAccess extends Closeable
{
  void init();

  DataOutputStream getOutputStream(long bucketKey, String fileName) throws IOException;

  DataInputStream getInputStream(long bucketKey, String fileName) throws IOException;

  /**
   * Atomic file rename.
   * @param bucketKey
   * @param oldName
   * @param newName
   * @throws IOException
   */
  void rename(long bucketKey, String oldName, String newName) throws IOException;

  void delete(long bucketKey, String fileName) throws IOException;

  void deleteBucket(long bucketKey) throws IOException;

  long getFileSize(long bucketKey, String s) throws IOException;

  /**
   * Checks if a file exists under a bucket.
   *
   * @param bucketKey bucket key
   * @param fileName  file name
   * @return true if file exists; false otherwise.
   * @throws IOException
   */
  boolean exists(long bucketKey, String fileName) throws IOException;

  /**
   * Lists the files in the bucket path.
   *
   * @param bucketKey bucket key
   * @return status of all the files in the bucket path if the bucket exists; null otherwise.
   * @throws IOException
   */
  RemoteIterator listFiles(long bucketKey) throws IOException;

  /**
   * Data File Format Reader
   */
  interface FileReader extends Closeable
  {
    /**
     * Read the entire contents of the underlying file into a TreeMap structure
     * @param data
     * @throws IOException
     */
    void readFully(TreeMap data) throws IOException;

    /**
     * Repositions the pointer to the beginning of the underlying file.
     * @throws IOException
     */
    void reset() throws IOException;

    /**
     * Searches for a matching key, and positions the pointer before the start of the key.
     * @param key Byte array representing the key
     * @throws IOException
     * @return true if a given key is found
     */
    boolean seek(Slice key) throws IOException;

    /**
     * Reads next available key/value pair starting from the current pointer position
     * into Slice objects and advances pointer to next key.  If pointer is at the end
     * of the file, false is returned, and Slice objects remains unmodified.
     *
     * @param key Empty slice object
     * @param value Empty slice object
     * @return True if key/value were successfully read, false otherwise
     * @throws IOException
     */
    boolean next(Slice key, Slice value) throws IOException;

  }

  /**
   * Data File Format Writer
   */
  interface FileWriter extends Closeable
  {
    /**
     * Appends key/value pair to the underlying file.
     * @param key
     * @param value
     * @throws IOException
     */
    void append(byte[] key, byte[] value) throws IOException;

    /**
     * Returns number of bytes written to the underlying stream.
     * @return The bytes written.
     * @throws IOException
     */
    long getBytesWritten() throws IOException;
  }

  /**
   * Obtain a reader for the given data file. Since existing file formats may depend on the file system directly (vs.
   * work just based on InputStream), construction of the reader is part of the file system abstraction itself.
   */
  public FileReader getReader(long bucketKey, String fileName) throws IOException;

  /**
   * Obtain a writer for the given data file. Since existing file formats may depend on the file system directly (vs.
   * work just based on OutputStream), construction of the writer is part of the file system abstraction itself.
   */
  public FileWriter getWriter(long bucketKey, String fileName) throws IOException;

}