core/java/android/os/Environment.java

/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * 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 android.os;

import java.io.File;

import android.content.res.Resources;
import android.os.storage.IMountService;

/**
 * Provides access to environment variables.
 */
public class Environment {

    private static final File ROOT_DIRECTORY
            = getDirectory("ANDROID_ROOT", "/system");

    private static final String SYSTEM_PROPERTY_EFS_ENABLED = "persist.security.efs.enabled";

    private static class MountServiceHolder {
        static IMountService mSingleton = IMountService.Stub.asInterface(ServiceManager
                .getService("mount"));
    }

    private static final Object mLock = new Object();

    private volatile static Boolean mIsExternalStorageEmulated = null;

    /**
     * Gets the Android root directory.
     */
    public static File getRootDirectory() {
        return ROOT_DIRECTORY;
    }

    /**
     * Gets the system directory available for secure storage.
     * If Encrypted File system is enabled, it returns an encrypted directory (/data/secure/system).
     * Otherwise, it returns the unencrypted /data/system directory.
     * @return File object representing the secure storage system directory.
     * @hide
     */
    public static File getSystemSecureDirectory() {
        if (isEncryptedFilesystemEnabled()) {
            return new File(SECURE_DATA_DIRECTORY, "system");
        } else {
            return new File(DATA_DIRECTORY, "system");
        }
    }

    /**
     * Gets the data directory for secure storage.
     * If Encrypted File system is enabled, it returns an encrypted directory (/data/secure).
     * Otherwise, it returns the unencrypted /data directory.
     * @return File object representing the data directory for secure storage.
     * @hide
     */
    public static File getSecureDataDirectory() {
        if (isEncryptedFilesystemEnabled()) {
            return SECURE_DATA_DIRECTORY;
        } else {
            return DATA_DIRECTORY;
        }
    }

    /**
     * Returns whether the Encrypted File System feature is enabled on the device or not.
     * @return <code>true</code> if Encrypted File System feature is enabled, <code>false</code>
     * if disabled.
     * @hide
     */
    public static boolean isEncryptedFilesystemEnabled() {
        return SystemProperties.getBoolean(SYSTEM_PROPERTY_EFS_ENABLED, false);
    }

    private static final File DATA_DIRECTORY
            = getDirectory("ANDROID_DATA", "/data");

    /**
     * @hide
     */
    private static final File SECURE_DATA_DIRECTORY
            = getDirectory("ANDROID_SECURE_DATA", "/data/secure");

    private static final File EXTERNAL_STORAGE_DIRECTORY
            = getDirectory("EXTERNAL_STORAGE", "/sdcard");

    private static final File EXTERNAL_STORAGE_ANDROID_DATA_DIRECTORY
            = new File (new File(getDirectory("EXTERNAL_STORAGE", "/sdcard"),
                    "Android"), "data");

    private static final File EXTERNAL_STORAGE_ANDROID_MEDIA_DIRECTORY
            = new File (new File(getDirectory("EXTERNAL_STORAGE", "/sdcard"),
                    "Android"), "media");

    private static final File EXTERNAL_STORAGE_ANDROID_OBB_DIRECTORY
            = new File (new File(getDirectory("EXTERNAL_STORAGE", "/sdcard"),
                    "Android"), "obb");

    private static final File DOWNLOAD_CACHE_DIRECTORY
            = getDirectory("DOWNLOAD_CACHE", "/cache");

    /**
     * Gets the Android data directory.
     */
    public static File getDataDirectory() {
        return DATA_DIRECTORY;
    }

    /**
     * Gets the Android external storage directory.  This directory may not
     * currently be accessible if it has been mounted by the user on their
     * computer, has been removed from the device, or some other problem has
     * happened.  You can determine its current state with
     * {@link #getExternalStorageState()}.
     * 
     * <p><em>Note: don't be confused by the word "external" here.  This
     * directory can better be thought as media/shared storage.  It is a
     * filesystem that can hold a relatively large amount of data and that
     * is shared across all applications (does not enforce permissions).
     * Traditionally this is an SD card, but it may also be implemented as
     * built-in storage in a device that is distinct from the protected
     * internal storage and can be mounted as a filesystem on a computer.</em></p>
     *
     * <p>In devices with multiple "external" storage directories (such as
     * both secure app storage and mountable shared storage), this directory
     * represents the "primary" external storage that the user will interact
     * with.</p>
     *
     * <p>Applications should not directly use this top-level directory, in
     * order to avoid polluting the user's root namespace.  Any files that are
     * private to the application should be placed in a directory returned
     * by {@link android.content.Context#getExternalFilesDir
     * Context.getExternalFilesDir}, which the system will take care of deleting
     * if the application is uninstalled.  Other shared files should be placed
     * in one of the directories returned by
     * {@link #getExternalStoragePublicDirectory}.
     * 
     * <p>Here is an example of typical code to monitor the state of
     * external storage:</p>
     * 
     * {@sample development/samples/ApiDemos/src/com/example/android/apis/content/ExternalStorage.java
     * monitor_storage}
     *
     * @see #getExternalStorageState()
     * @see #isExternalStorageRemovable()
     */
    public static File getExternalStorageDirectory() {
        return EXTERNAL_STORAGE_DIRECTORY;
    }

    /**
     * Standard directory in which to place any audio files that should be
     * in the regular list of music for the user.
     * This may be combined with
     * {@link #DIRECTORY_PODCASTS}, {@link #DIRECTORY_NOTIFICATIONS},
     * {@link #DIRECTORY_ALARMS}, and {@link #DIRECTORY_RINGTONES} as a series
     * of directories to categories a particular audio file as more than one
     * type.
     */
    public static String DIRECTORY_MUSIC = "Music";
    
    /**
     * Standard directory in which to place any audio files that should be
     * in the list of podcasts that the user can select (not as regular
     * music).
     * This may be combined with {@link #DIRECTORY_MUSIC},
     * {@link #DIRECTORY_NOTIFICATIONS},
     * {@link #DIRECTORY_ALARMS}, and {@link #DIRECTORY_RINGTONES} as a series
     * of directories to categories a particular audio file as more than one
     * type.
     */
    public static String DIRECTORY_PODCASTS = "Podcasts";
    
    /**
     * Standard directory in which to place any audio files that should be
     * in the list of ringtones that the user can select (not as regular
     * music).
     * This may be combined with {@link #DIRECTORY_MUSIC},
     * {@link #DIRECTORY_PODCASTS}, {@link #DIRECTORY_NOTIFICATIONS}, and
     * {@link #DIRECTORY_ALARMS} as a series
     * of directories to categories a particular audio file as more than one
     * type.
     */
    public static String DIRECTORY_RINGTONES = "Ringtones";
    
    /**
     * Standard directory in which to place any audio files that should be
     * in the list of alarms that the user can select (not as regular
     * music).
     * This may be combined with {@link #DIRECTORY_MUSIC},
     * {@link #DIRECTORY_PODCASTS}, {@link #DIRECTORY_NOTIFICATIONS},
     * and {@link #DIRECTORY_RINGTONES} as a series
     * of directories to categories a particular audio file as more than one
     * type.
     */
    public static String DIRECTORY_ALARMS = "Alarms";
    
    /**
     * Standard directory in which to place any audio files that should be
     * in the list of notifications that the user can select (not as regular
     * music).
     * This may be combined with {@link #DIRECTORY_MUSIC},
     * {@link #DIRECTORY_PODCASTS},
     * {@link #DIRECTORY_ALARMS}, and {@link #DIRECTORY_RINGTONES} as a series
     * of directories to categories a particular audio file as more than one
     * type.
     */
    public static String DIRECTORY_NOTIFICATIONS = "Notifications";
    
    /**
     * Standard directory in which to place pictures that are available to
     * the user.  Note that this is primarily a convention for the top-level
     * public directory, as the media scanner will find and collect pictures
     * in any directory.
     */
    public static String DIRECTORY_PICTURES = "Pictures";
    
    /**
     * Standard directory in which to place movies that are available to
     * the user.  Note that this is primarily a convention for the top-level
     * public directory, as the media scanner will find and collect movies
     * in any directory.
     */
    public static String DIRECTORY_MOVIES = "Movies";
    
    /**
     * Standard directory in which to place files that have been downloaded by
     * the user.  Note that this is primarily a convention for the top-level
     * public directory, you are free to download files anywhere in your own
     * private directories.  Also note that though the constant here is
     * named DIRECTORY_DOWNLOADS (plural), the actual file name is non-plural for
     * backwards compatibility reasons.
     */
    public static String DIRECTORY_DOWNLOADS = "Download";
    
    /**
     * The traditional location for pictures and videos when mounting the
     * device as a camera.  Note that this is primarily a convention for the
     * top-level public directory, as this convention makes no sense elsewhere.
     */
    public static String DIRECTORY_DCIM = "DCIM";
    
    /**
     * Get a top-level public external storage directory for placing files of
     * a particular type.  This is where the user will typically place and
     * manage their own files, so you should be careful about what you put here
     * to ensure you don't erase their files or get in the way of their own
     * organization.
     * 
     * <p>Here is an example of typical code to manipulate a picture on
     * the public external storage:</p>
     * 
     * {@sample development/samples/ApiDemos/src/com/example/android/apis/content/ExternalStorage.java
     * public_picture}
     * 
     * @param type The type of storage directory to return.  Should be one of
     * {@link #DIRECTORY_MUSIC}, {@link #DIRECTORY_PODCASTS},
     * {@link #DIRECTORY_RINGTONES}, {@link #DIRECTORY_ALARMS},
     * {@link #DIRECTORY_NOTIFICATIONS}, {@link #DIRECTORY_PICTURES},
     * {@link #DIRECTORY_MOVIES}, {@link #DIRECTORY_DOWNLOADS}, or
     * {@link #DIRECTORY_DCIM}.  May not be null.
     * 
     * @return Returns the File path for the directory.  Note that this
     * directory may not yet exist, so you must make sure it exists before
     * using it such as with {@link File#mkdirs File.mkdirs()}.
     */
    public static File getExternalStoragePublicDirectory(String type) {
        return new File(getExternalStorageDirectory(), type);
    }

    /**
     * Returns the path for android-specific data on the SD card.
     * @hide
     */
    public static File getExternalStorageAndroidDataDir() {
        return EXTERNAL_STORAGE_ANDROID_DATA_DIRECTORY;
    }
    
    /**
     * Generates the raw path to an application's data
     * @hide
     */
    public static File getExternalStorageAppDataDirectory(String packageName) {
        return new File(EXTERNAL_STORAGE_ANDROID_DATA_DIRECTORY, packageName);
    }
    
    /**
     * Generates the raw path to an application's media
     * @hide
     */
    public static File getExternalStorageAppMediaDirectory(String packageName) {
        return new File(EXTERNAL_STORAGE_ANDROID_MEDIA_DIRECTORY, packageName);
    }
    
    /**
     * Generates the raw path to an application's OBB files
     * @hide
     */
    public static File getExternalStorageAppObbDirectory(String packageName) {
        return new File(EXTERNAL_STORAGE_ANDROID_OBB_DIRECTORY, packageName);
    }
    
    /**
     * Generates the path to an application's files.
     * @hide
     */
    public static File getExternalStorageAppFilesDirectory(String packageName) {
        return new File(new File(EXTERNAL_STORAGE_ANDROID_DATA_DIRECTORY,
                packageName), "files");
    }
    
    /**
     * Generates the path to an application's cache.
     * @hide
     */
    public static File getExternalStorageAppCacheDirectory(String packageName) {
        return new File(new File(EXTERNAL_STORAGE_ANDROID_DATA_DIRECTORY,
                packageName), "cache");
    }
    
    /**
     * Gets the Android Download/Cache content directory.
     */
    public static File getDownloadCacheDirectory() {
        return DOWNLOAD_CACHE_DIRECTORY;
    }

    /**
     * getExternalStorageState() returns MEDIA_REMOVED if the media is not present. 
     */
    public static final String MEDIA_REMOVED = "removed";
     
    /**
     * getExternalStorageState() returns MEDIA_UNMOUNTED if the media is present
     * but not mounted. 
     */
    public static final String MEDIA_UNMOUNTED = "unmounted";

    /**
     * getExternalStorageState() returns MEDIA_CHECKING if the media is present
     * and being disk-checked
     */
    public static final String MEDIA_CHECKING = "checking";

    /**
     * getExternalStorageState() returns MEDIA_NOFS if the media is present
     * but is blank or is using an unsupported filesystem
     */
    public static final String MEDIA_NOFS = "nofs";

    /**
     * getExternalStorageState() returns MEDIA_MOUNTED if the media is present
     * and mounted at its mount point with read/write access. 
     */
    public static final String MEDIA_MOUNTED = "mounted";

    /**
     * getExternalStorageState() returns MEDIA_MOUNTED_READ_ONLY if the media is present
     * and mounted at its mount point with read only access. 
     */
    public static final String MEDIA_MOUNTED_READ_ONLY = "mounted_ro";

    /**
     * getExternalStorageState() returns MEDIA_SHARED if the media is present
     * not mounted, and shared via USB mass storage. 
     */
    public static final String MEDIA_SHARED = "shared";

    /**
     * getExternalStorageState() returns MEDIA_BAD_REMOVAL if the media was
     * removed before it was unmounted. 
     */
    public static final String MEDIA_BAD_REMOVAL = "bad_removal";

    /**
     * getExternalStorageState() returns MEDIA_UNMOUNTABLE if the media is present
     * but cannot be mounted.  Typically this happens if the file system on the
     * media is corrupted. 
     */
    public static final String MEDIA_UNMOUNTABLE = "unmountable";

    /**
     * Gets the current state of the primary "external" storage device.
     * 
     * <p>See {@link #getExternalStorageDirectory()} for more information.
     */
    public static String getExternalStorageState() {
        try {
            return MountServiceHolder.mSingleton.getVolumeState(getExternalStorageDirectory()
                    .toString());
        } catch (Exception rex) {
            return Environment.MEDIA_REMOVED;
        }
    }

    /**
     * Returns whether the primary "external" storage device is removable.
     * If true is returned, this device is for example an SD card that the
     * user can remove.  If false is returned, the storage is built into
     * the device and can not be physically removed.
     *
     * <p>See {@link #getExternalStorageDirectory()} for more information.
     */
    public static boolean isExternalStorageRemovable() {
        return Resources.getSystem().getBoolean(
                com.android.internal.R.bool.config_externalStorageRemovable);
    }

    /**
     * Returns whether the device has an external storage device which is
     * emulated. If true, the device does not have real external storage
     * and certain system services such as the package manager use this
     * to determine where to install an application.
     */
    public static boolean isExternalStorageEmulated() {
        if (mIsExternalStorageEmulated == null) {
            synchronized (mLock) {
                if (mIsExternalStorageEmulated == null) {
                    boolean externalStorageEmulated;
                    try {
                        externalStorageEmulated =
                                MountServiceHolder.mSingleton.isExternalStorageEmulated();
                    } catch (Exception e) {
                        externalStorageEmulated = false;
                    }
                    mIsExternalStorageEmulated = Boolean.valueOf(externalStorageEmulated);
                }
            }
        }
        return mIsExternalStorageEmulated;
    }

    static File getDirectory(String variableName, String defaultPath) {
        String path = System.getenv(variableName);
        return path == null ? new File(defaultPath) : new File(path);
    }
}