code: /*
   * Copyright 2015 Cody Goldberg
   *
   * 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 edu.uri.egr.hermes.helpers;
  
  import android.os.Environment;
  
  import java.io.File;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Scanner;
  
  public class ExternalStorage {
      public static final String SD_CARD = "sdCard";
      public static final String EXTERNAL_SD_CARD = "externalSdCard";
  
      /**
       * @return True if the external storage is available. False otherwise.
       */
      public static boolean isAvailable() {
          String state = Environment.getExternalStorageState();
          if (Environment.MEDIA_MOUNTED.equals(state) || Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
              return true;
          }
          return false;
      }
  
      public static String getSdCardPath() {
          return Environment.getExternalStorageDirectory().getPath() + "/";
      }
  
      public static File getBestKnownExternalDirectory() {
          Map<String, File> map = ExternalStorage.getAllStorageLocations();
  
          File external = map.get(ExternalStorage.EXTERNAL_SD_CARD);
          if (external == null)
              external = map.get(ExternalStorage.SD_CARD);
          if (external == null)
              external = Environment.getExternalStorageDirectory();
  
          return external;
      }
  
      /**
       * @return True if the external storage is writable. False otherwise.
       */
      public static boolean isWritable() {
          String state = Environment.getExternalStorageState();
          if (Environment.MEDIA_MOUNTED.equals(state)) {
              return true;
          }
          return false;
  
      }
  
      /**
       * @return A map of all storage locations available
       */
      public static Map<String, File> getAllStorageLocations() {
          Map<String, File> map = new HashMap<String, File>(10);
  
          List<String> mMounts = new ArrayList<String>(10);
          List<String> mVold = new ArrayList<String>(10);
          mMounts.add("/mnt/sdcard");
          mVold.add("/mnt/sdcard");
  
          try {
              File mountFile = new File("/proc/mounts");
              if(mountFile.exists()){
                  Scanner scanner = new Scanner(mountFile);
                  while (scanner.hasNext()) {
                      String line = scanner.nextLine();
                      if (line.startsWith("/dev/block/vold/")) {
                          String[] lineElements = line.split(" ");
                          String element = lineElements[1];
  
                          // don't add the default mount path
                          // it's already in the list.
                          if (!element.equals("/mnt/sdcard"))
                              mMounts.add(element);
                      }
                  }
              }
          } catch (Exception e) {
              e.printStackTrace();
          }
  
          try {
              File voldFile = new File("/system/etc/vold.fstab");
              if(voldFile.exists()){
                  Scanner scanner = new Scanner(voldFile);
                  while (scanner.hasNext()) {
                      String line = scanner.nextLine();
                      if (line.startsWith("dev_mount")) {
                          String[] lineElements = line.split(" ");
                          String element = lineElements[2];
  
                          if (element.contains(":"))
                              element = element.substring(0, element.indexOf(":"));
                          if (!element.equals("/mnt/sdcard"))
                              mVold.add(element);
                      }
                  }
              }
          } catch (Exception e) {
              e.printStackTrace();
          }
  
  
          for (int i = 0; i < mMounts.size(); i++) {
              String mount = mMounts.get(i);
              if (!mVold.contains(mount))
                  mMounts.remove(i--);
          }
          mVold.clear();
  
          List<String> mountHash = new ArrayList<String>(10);
  
          for(String mount : mMounts){
              File root = new File(mount);
              if (root.exists() && root.isDirectory() && root.canWrite()) {
                  File[] list = root.listFiles();
                  String hash = "[";
                  if(list!=null){
                      for(File f : list){
                          hash += f.getName().hashCode()+":"+f.length()+", ";
                      }
                  }
                  hash += "]";
                  if(!mountHash.contains(hash)){
                      String key = SD_CARD + "_" + map.size();
                      if (map.size() == 0) {
                          key = SD_CARD;
                      } else if (map.size() == 1) {
                          key = EXTERNAL_SD_CARD;
                      }
                      mountHash.add(hash);
                      map.put(key, root);
                  }
              }
          }
  
          mMounts.clear();
  
          if(map.isEmpty()){
              map.put(SD_CARD, Environment.getExternalStorageDirectory());
          }
          return map;
      }
  }
  