Android Open Source - libaums Usb File

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License

The source code is released under:

Apache License

Java Source Code

/*
 * (C) Copyright 2014 mjahnen <jahnen@in.tum.de>
 */* w w w.  jav a  2s  .  c  o  m*/
 * Licensed 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.github.mjdev.libaums.fs;

import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;

/**
 * This class represents either an file or an directory. This can be determined
 * by {@link #isDirectory()}. Not all methods make sense for both cases. For
 * example if representing a file methods like {@link #createDirectory(String)}
 * or {@link #createFile(String)} do not make sense and will throw an exception.
 * On the other hand methods like {@link #read(long, ByteBuffer)} or
 * {@link #write(long, ByteBuffer)} do not make sense for directories and will
 * throw an exception!
 * 
 * @author mjahnen
 * 
 */
public interface UsbFile extends Closeable {
  /**
   * 
   * @return True if representing a directory.
   */
  public boolean isDirectory();

  /**
   * 
   * @return The name of the file or directory.
   */
  public String getName();

  /**
   * Set a new name for this file or directory.
   * 
   * @param newName
   *            The new name.
   * @throws IOException
   *             If new name is already assigned or writing to the file system
   *             fails.
   */
  public void setName(String newName) throws IOException;

  /**
   * Returns the parent directory for the file or directory or null if this is
   * the root directory.
   * 
   * @return The parent directory or null.
   */
  public UsbFile getParent();

  /**
   * Lists all files in the directory. Throws an exception if called on a
   * file.
   * 
   * @return String array containing all names in the directory.
   * @throws IOException
   *             If reading fails
   */
  public String[] list() throws IOException;

  /**
   * Lists all files in the directory. Throws an exception if called on a
   * file.
   * 
   * @return UsbFile array containing all files or directories in the
   *         directory.
   * @throws IOException
   *             If reading fails
   */
  public UsbFile[] listFiles() throws IOException;

  /**
   * Returns the file length or throws an exception if called on a directory.
   * 
   * @return File length in bytes.
   */
  public long getLength();

  /**
   * Sets the new file length. This can sometimes be more efficient if all
   * needed place for a file is allocated on the disk at once and before
   * writing to it.
   * <p>
   * If the space is not allocated before writing the space must be exceeded
   * every time a new write occurs. This can sometimes be less efficient.
   * 
   * @param newLength
   *            The file length in bytes.
   * @throws IOException
   *             If requesting the needed space fails.
   */
  public void setLength(long newLength) throws IOException;

  /**
   * Reads from a file or throws an exception if called on a directory.
   * 
   * @param offset
   *            The offset in bytes where reading in the file should be begin.
   * @param destination
   *            Buffer the data shall be transferred to.
   * @throws IOException
   *             If reading fails.
   */
  public void read(long offset, ByteBuffer destination) throws IOException;

  /**
   * Writes to a file or throws an exception if called on a directory.
   * 
   * @param offset
   *            The offset in bytes where writing in the file should be begin.
   * @param destination
   *            Buffer which contains the data which shall be transferred.
   * @throws IOException
   *             If writing fails.
   */
  public void write(long offset, ByteBuffer source) throws IOException;

  /**
   * Forces a write. Every change to the file is then committed to the disk.
   * Throws an exception if called on directories.
   * 
   * @throws IOException
   *             If flushing fails.
   */
  public void flush() throws IOException;

  /**
   * Closes and flushes the file. It is essential to close a file after making
   * changes to it! Throws an exception if called on directories.
   * 
   * @throws IOException
   *             If closing fails.
   */
  @Override
  public void close() throws IOException;

  /**
   * This methods creates a new directory with the given name and returns it.
   * 
   * @param name
   *            The name of the new directory.
   * @return The newly created directory.
   * @throws IOException
   *             If writing to the disk fails or a item with the same name
   *             already exists.
   */
  public UsbFile createDirectory(String name) throws IOException;

  /**
   * This methods creates a new file with the given name and returns it.
   * 
   * @param name
   *            The name of the new file.
   * @return The newly created file.
   * @throws IOException
   *             If writing to the disk fails or a item with the same name
   *             already exists.
   */
  public UsbFile createFile(String name) throws IOException;

  /**
   * This methods moves THIS item to the destination directory. Make sure that
   * the destination is a directory, otherwise an exception will be thrown.
   * Make also sure that both items are on the same logical device (disk,
   * partition, file system). Moving between different file systems is
   * currently not supported. If you want to do this, you have to manually
   * copy the content and delete the old item.
   * 
   * @param destination
   *            The directory where this item should be moved.
   * @throws IOException
   *             If writing fails, or the operation cannot be done (eg. item
   *             already exists in the destination directory)
   */
  public void moveTo(UsbFile destination) throws IOException;

  /**
   * Deletes this file or directory from the parent directory.
   * 
   * @throws IOException
   *             If operation fails due to write errors.
   */
  public void delete() throws IOException;
}

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