Android Open Source - libaums Fat32 File System

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License

The source code is released under:

Apache License

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Java Source Code

/*
 * (C) Copyright 2014 mjahnen <jahnen@in.tum.de>
 */*from w w  w . j a va2 s .co 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.fat32;

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

import com.github.mjdev.libaums.driver.BlockDeviceDriver;
import com.github.mjdev.libaums.fs.FileSystem;
import com.github.mjdev.libaums.fs.UsbFile;

/**
 * This class represents the FAT32 file system and is responsible for setting
 * the FAT32 file system up and extracting the volume label and the root
 * directory.
 * 
 * @author mjahnen
 * 
 */
public class Fat32FileSystem implements FileSystem {

  private Fat32BootSector bootSector;
  private FAT fat;
  private FsInfoStructure fsInfoStructure;
  private FatDirectory rootDirectory;

  /**
   * This method constructs a FAT32 file system for the given block device.
   * There are no further checks that the block device actually represents a
   * valid FAT32 file system. That means it must be ensured that the device
   * actually holds a FAT32 file system in advance!
   * 
   * @param blockDevice
   *            The block device the FAT32 file system is located.
   * @throws IOException
   *             If reading from the device fails.
   */
  private Fat32FileSystem(BlockDeviceDriver blockDevice) throws IOException {
    ByteBuffer buffer = ByteBuffer.allocate(512);
    blockDevice.read(0, buffer);
    bootSector = Fat32BootSector.read(buffer);
    fsInfoStructure = FsInfoStructure.read(blockDevice, bootSector.getFsInfoStartSector()
        * bootSector.getBytesPerSector());
    fat = new FAT(blockDevice, bootSector, fsInfoStructure);
    rootDirectory = FatDirectory.readRoot(blockDevice, fat, bootSector);
  }

  /**
   * This method constructs a FAT32 file system for the given block device.
   * There are no further checks if the block device actually represents a
   * valid FAT32 file system. That means it must be ensured that the device
   * actually holds a FAT32 file system in advance!
   * 
   * @param blockDevice
   *            The block device the FAT32 file system is located.
   * @throws IOException
   *             If reading from the device fails.
   */
  public static Fat32FileSystem read(BlockDeviceDriver blockDevice) throws IOException {
    return new Fat32FileSystem(blockDevice);
  }

  @Override
  public UsbFile getRootDirectory() {
    return rootDirectory;
  }

  @Override
  public String getVolumeLabel() {
    String volumeLabel = rootDirectory.getVolumeLabel();
    if (volumeLabel == null) {
      volumeLabel = bootSector.getVolumeLabel();
    }
    return volumeLabel;
  }
}

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