core/java/android/provider/DeviceConfig.java - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2018 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.provider;

 import static android.Manifest.permission.READ_DEVICE_CONFIG;
 import static android.Manifest.permission.WRITE_DEVICE_CONFIG;

 import android.annotation.CallbackExecutor;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.app.ActivityThread;
 import android.content.ContentResolver;
 import android.database.ContentObserver;
 import android.net.Uri;
 import android.provider.Settings.ResetMode;
 import android.util.Pair;

 import com.android.internal.annotations.GuardedBy;

 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.Executor;

 /**
  * Device level configuration parameters which can be tuned by a separate configuration service.
  *
  * @hide
  */
 @SystemApi
 @TestApi
 public final class DeviceConfig {
     /**
      * The content:// style URL for the config table.
      *
      * @hide
      */
     public static final Uri CONTENT_URI = Uri.parse("content://" + Settings.AUTHORITY + "/config");

     /**
      * Namespace for all Game Driver features.
      *
      * @hide
      */
     @SystemApi
     public static final String NAMESPACE_GAME_DRIVER = "game_driver";

     /**
      * Namespace for autofill feature that provides suggestions across all apps when
      * the user interacts with input fields.
      *
      * @hide
      */
     @SystemApi
     public static final String NAMESPACE_AUTOFILL = "autofill";

     /**
      * ContentCapture-related properties definitions.
      *
      * @hide
      */
     @SystemApi
     public interface ContentCapture {
         String NAMESPACE = "content_capture";

         /**
          * Property used by {@code com.android.server.SystemServer} on start to decide whether
          * the Content Capture service should be created or not.
          *
          * <p>Possible values are:
          *
          * <ul>
          *   <li>If set to {@code default}, it will only be set if the OEM provides and defines the
          *   service name by overlaying {@code config_defaultContentCaptureService} (this is the
          *   "default" mode)
          *   <li>If set to {@code always}, it will always be enabled, even when the resource is not
          *   overlaid (this is useful during development and to run the CTS tests on AOSP builds).
          *   <li>Otherwise, it's explicitly disabled (this could work as a "kill switch" so OEMs
          *   can disable it remotely in case of emergency by setting to something else (like
          *   {@code "false"}); notice that it's also disabled if the OEM doesn't explicitly set one
          *   of the values above).
          * </ul>
          *
          * @hide
          */
         // TODO(b/121153631): revert back to SERVICE_EXPLICITLY_ENABLED approach
         String PROPERTY_CONTENTCAPTURE_ENABLED = "enable_contentcapture";
     }

     /**
      * Namespace for content capture feature used by on-device machine intelligence
      * to provide suggestions in a privacy-safe manner.
      *
      * @hide
      */
     @SystemApi
     public static final String NAMESPACE_CONTENT_CAPTURE = "content_capture";

     /**
      * Namespace for all input-related features that are used at the native level.
      * These features are applied at reboot.
      *
      * @hide
      */
     @SystemApi
     public static final String NAMESPACE_INPUT_NATIVE_BOOT = "input_native_boot";

     /**
      * Namespace for all netd related features.
      *
      * @hide
      */
     @SystemApi
     public static final String NAMESPACE_NETD_NATIVE = "netd_native";

     /**
      * Namespace for features related to the ExtServices Notification Assistant.
      * These features are applied immediately.
      *
      * @hide
      */
     @SystemApi
     public interface NotificationAssistant {
         String NAMESPACE = "notification_assistant";
         /**
          * Whether the Notification Assistant should generate replies for notifications.
          */
         String GENERATE_REPLIES = "generate_replies";
         /**
          * Whether the Notification Assistant should generate contextual actions for notifications.
          */
         String GENERATE_ACTIONS = "generate_actions";
     }

     /**
      * Namespace for all runtime native related features.
      *
      * @hide
      */
     @SystemApi
     public interface RuntimeNative {
         String NAMESPACE = "runtime_native";
     }

     /**
      * Namespace for all activity manager related features that are used at the native level.
      * These features are applied at reboot.
      *
      * @hide
      */
     @SystemApi
     public interface ActivityManagerNativeBoot {
         String NAMESPACE = "activity_manager_native_boot";
         String OFFLOAD_QUEUE_ENABLED = "offload_queue_enabled";
     }

     /**
      * Namespace for attention-based features provided by on-device machine intelligence.
      *
      * @hide
      */
     @SystemApi
     public interface IntelligenceAttention {
         String NAMESPACE = "intelligence_attention";

         /** If {@code true}, enables the attention features. */
         String ATTENTION_ENABLED = "attention_enabled";

         /** Settings for the attention features. */
         String ATTENTION_SETTINGS = "attention_settings";
     }

     /**
      * Privacy related properties definitions.
      *
      * @hide
      */
     @SystemApi
     @TestApi
     public interface Privacy {
         String NAMESPACE = "privacy";

         /**
          * Whether to show the Permissions Hub.
          *
          * @hide
          */
         @SystemApi
         String PROPERTY_PERMISSIONS_HUB_ENABLED = "permissions_hub_enabled";

         /**
          * Whether to show location access check notifications.
          */
         String PROPERTY_LOCATION_ACCESS_CHECK_ENABLED = "location_access_check_enabled";
     }

     /**
      * Telephony related properties definitions.
      *
      * @hide
      */
     @SystemApi
     public interface Telephony {
         String NAMESPACE = "telephony";
         /**
          * Ringer ramping time in milliseconds.
          */
         String RAMPING_RINGER_DURATION = "ramping_ringer_duration";
         /**
          * Whether to apply ramping ringer on incoming phone calls.
          */
         String RAMPING_RINGER_ENABLED = "ramping_ringer_enabled";
         /**
          * Vibration time in milliseconds before ramping ringer starts.
          */
         String RAMPING_RINGER_VIBRATION_DURATION = "ramping_ringer_vibration_duration";
     }

     /**
      * Namespace for how dex runs.  The feature may requires reboot to a clean state.
      *
      * @hide
      */
     @SystemApi
     public interface DexBoot {
         String NAMESPACE = "dex_boot";
         String PRIV_APPS_OOB_ENABLED = "priv_apps_oob_enabled";
         String PRIV_APPS_OOB_WHITELIST = "priv_apps_oob_whitelist";
     }

     /**
      * Namespace for activity manager related features. These features will be applied
      * immediately upon change.
      *
      * @hide
      */
     @SystemApi
     public interface ActivityManager {
         String NAMESPACE = "activity_manager";

         /**
          * App compaction flags. See {@link com.android.server.am.AppCompactor}.
          */
         String KEY_USE_COMPACTION = "use_compaction";
         String KEY_COMPACT_ACTION_1 = "compact_action_1";
         String KEY_COMPACT_ACTION_2 = "compact_action_2";
         String KEY_COMPACT_THROTTLE_1 = "compact_throttle_1";
         String KEY_COMPACT_THROTTLE_2 = "compact_throttle_2";
         String KEY_COMPACT_THROTTLE_3 = "compact_throttle_3";
         String KEY_COMPACT_THROTTLE_4 = "compact_throttle_4";
         String KEY_COMPACT_STATSD_SAMPLE_RATE = "compact_statsd_sample_rate";

         /**
          * Maximum number of cached processes. See
          * {@link com.android.server.am.ActivityManagerConstants}.
          */
         String KEY_MAX_CACHED_PROCESSES = "max_cached_processes";
     }

     /**
      * Namespace for {@link AttentionManagerService} related features.
      *
      * @hide
      */
     @SystemApi
     public interface AttentionManagerService {
         String NAMESPACE = "attention_manager_service";

         /** If {@code true}, enables {@link AttentionManagerService} features. */
         String SERVICE_ENABLED = "service_enabled";

         /** Allows a CTS to inject a fake implementation. */
         String COMPONENT_NAME = "component_name";
     }

     /**
      * Namespace for storage-related features.
      *
      * @hide
      */
     @SystemApi
     public interface Storage {
         String NAMESPACE = "storage";

         /**
          * If {@code 1}, enables the isolated storage feature. If {@code -1},
          * disables the isolated storage feature. If {@code 0}, uses the default
          * value from the build system.
          */
         String ISOLATED_STORAGE_ENABLED = "isolated_storage_enabled";
     }

     private static final Object sLock = new Object();
     @GuardedBy("sLock")
     private static Map<OnPropertyChangedListener, Pair<String, Executor>> sListeners =
             new HashMap<>();
     @GuardedBy("sLock")
     private static Map<String, Pair<ContentObserver, Integer>> sNamespaces = new HashMap<>();

     // Should never be invoked
     private DeviceConfig() {
     }

     /**
      * Look up the value of a property for a particular namespace.
      *
      * @param namespace The namespace containing the property to look up.
      * @param name      The name of the property to look up.
      * @return the corresponding value, or null if not present.
      * @hide
      */
     @SystemApi
     @RequiresPermission(READ_DEVICE_CONFIG)
     public static String getProperty(String namespace, String name) {
         ContentResolver contentResolver = ActivityThread.currentApplication().getContentResolver();
         String compositeName = createCompositeName(namespace, name);
         return Settings.Config.getString(contentResolver, compositeName);
     }

     /**
      * Create a new property with the the provided name and value in the provided namespace, or
      * update the value of such a property if it already exists. The same name can exist in multiple
      * namespaces and might have different values in any or all namespaces.
      * <p>
      * The method takes an argument indicating whether to make the value the default for this
      * property.
      * <p>
      * All properties stored for a particular scope can be reverted to their default values
      * by passing the namespace to {@link #resetToDefaults(int, String)}.
      *
      * @param namespace   The namespace containing the property to create or update.
      * @param name        The name of the property to create or update.
      * @param value       The value to store for the property.
      * @param makeDefault Whether to make the new value the default one.
      * @return True if the value was set, false if the storage implementation throws errors.
      * @hide
      * @see #resetToDefaults(int, String).
      */
     @SystemApi
     @TestApi
     @RequiresPermission(WRITE_DEVICE_CONFIG)
     public static boolean setProperty(
             String namespace, String name, String value, boolean makeDefault) {
         ContentResolver contentResolver = ActivityThread.currentApplication().getContentResolver();
         String compositeName = createCompositeName(namespace, name);
         return Settings.Config.putString(contentResolver, compositeName, value, makeDefault);
     }

     /**
      * Reset properties to their default values.
      * <p>
      * The method accepts an optional namespace parameter. If provided, only properties set within
      * that namespace will be reset. Otherwise, all properties will be reset.
      *
      * @param resetMode The reset mode to use.
      * @param namespace Optionally, the specific namespace which resets will be limited to.
      * @hide
      * @see #setProperty(String, String, String, boolean)
      */
     @SystemApi
     @TestApi
     @RequiresPermission(WRITE_DEVICE_CONFIG)
     public static void resetToDefaults(@ResetMode int resetMode, @Nullable String namespace) {
         ContentResolver contentResolver = ActivityThread.currentApplication().getContentResolver();
         Settings.Config.resetToDefaults(contentResolver, resetMode, namespace);
     }

     /**
      * Add a listener for property changes.
      * <p>
      * This listener will be called whenever properties in the specified namespace change. Callbacks
      * will be made on the specified executor. Future calls to this method with the same listener
      * will replace the old namespace and executor. Remove the listener entirely by calling
      * {@link #removeOnPropertyChangedListener(OnPropertyChangedListener)}.
      *
      * @param namespace                 The namespace containing properties to monitor.
      * @param executor                  The executor which will be used to run callbacks.
      * @param onPropertyChangedListener The listener to add.
      * @hide
      * @see #removeOnPropertyChangedListener(OnPropertyChangedListener)
      */
     @SystemApi
     @RequiresPermission(READ_DEVICE_CONFIG)
     public static void addOnPropertyChangedListener(
             @NonNull String namespace,
             @NonNull @CallbackExecutor Executor executor,
             @NonNull OnPropertyChangedListener onPropertyChangedListener) {
         // TODO enforce READ_DEVICE_CONFIG permission
         synchronized (sLock) {
             Pair<String, Executor> oldNamespace = sListeners.get(onPropertyChangedListener);
             if (oldNamespace == null) {
                 // Brand new listener, add it to the list.
                 sListeners.put(onPropertyChangedListener, new Pair<>(namespace, executor));
                 incrementNamespace(namespace);
             } else if (namespace.equals(oldNamespace.first)) {
                 // Listener is already registered for this namespace, update executor just in case.
                 sListeners.put(onPropertyChangedListener, new Pair<>(namespace, executor));
             } else {
                 // Update this listener from an old namespace to the new one.
                 decrementNamespace(sListeners.get(onPropertyChangedListener).first);
                 sListeners.put(onPropertyChangedListener, new Pair<>(namespace, executor));
                 incrementNamespace(namespace);
             }
         }
     }

     /**
      * Remove a listener for property changes. The listener will receive no further notification of
      * property changes.
      *
      * @param onPropertyChangedListener The listener to remove.
      * @hide
      * @see #addOnPropertyChangedListener(String, Executor, OnPropertyChangedListener)
      */
     @SystemApi
     public static void removeOnPropertyChangedListener(
             OnPropertyChangedListener onPropertyChangedListener) {
         synchronized (sLock) {
             if (sListeners.containsKey(onPropertyChangedListener)) {
                 decrementNamespace(sListeners.get(onPropertyChangedListener).first);
                 sListeners.remove(onPropertyChangedListener);
             }
         }
     }

     private static String createCompositeName(String namespace, String name) {
         return namespace + "/" + name;
     }

     private static Uri createNamespaceUri(String namespace) {
         return CONTENT_URI.buildUpon().appendPath(namespace).build();
     }

     /**
      * Increment the count used to represent the number of listeners subscribed to the given
      * namespace. If this is the first (i.e. incrementing from 0 to 1) for the given namespace, a
      * ContentObserver is registered.
      *
      * @param namespace The namespace to increment the count for.
      */
     @GuardedBy("sLock")
     private static void incrementNamespace(String namespace) {
         Pair<ContentObserver, Integer> namespaceCount = sNamespaces.get(namespace);
         if (namespaceCount != null) {
             sNamespaces.put(namespace, new Pair<>(namespaceCount.first, namespaceCount.second + 1));
         } else {
             // This is a new namespace, register a ContentObserver for it.
             ContentObserver contentObserver = new ContentObserver(null) {
                 @Override
                 public void onChange(boolean selfChange, Uri uri) {
                     handleChange(uri);
                 }
             };
             ActivityThread.currentApplication().getContentResolver()
                     .registerContentObserver(createNamespaceUri(namespace), true, contentObserver);
             sNamespaces.put(namespace, new Pair<>(contentObserver, 1));
         }
     }

     /**
      * Decrement the count used to represent th enumber of listeners subscribed to the given
      * namespace. If this is the final decrement call (i.e. decrementing from 1 to 0) for the given
      * namespace, the ContentObserver that had been tracking it will be removed.
      *
      * @param namespace The namespace to decrement the count for.
      */
     @GuardedBy("sLock")
     private static void decrementNamespace(String namespace) {
         Pair<ContentObserver, Integer> namespaceCount = sNamespaces.get(namespace);
         if (namespaceCount == null) {
             // This namespace is not registered and does not need to be decremented
             return;
         } else if (namespaceCount.second > 1) {
             sNamespaces.put(namespace, new Pair<>(namespaceCount.first, namespaceCount.second - 1));
         } else {
             // Decrementing a namespace to zero means we no longer need its ContentObserver.
             ActivityThread.currentApplication().getContentResolver()
                     .unregisterContentObserver(namespaceCount.first);
             sNamespaces.remove(namespace);
         }
     }

     private static void handleChange(Uri uri) {
         List<String> pathSegments = uri.getPathSegments();
         // pathSegments(0) is "config"
         String namespace = pathSegments.get(1);
         String name = pathSegments.get(2);
         String value = getProperty(namespace, name);
         synchronized (sLock) {
             for (OnPropertyChangedListener listener : sListeners.keySet()) {
                 if (namespace.equals(sListeners.get(listener).first)) {
                     sListeners.get(listener).second.execute(new Runnable() {
                         @Override
                         public void run() {
                             listener.onPropertyChanged(namespace, name, value);
                         }

                     });
                 }
             }
         }
     }

     /**
      * Interface for monitoring to properties.
      * <p>
      * Override {@link #onPropertyChanged(String, String, String)} to handle callbacks for changes.
      *
      * @hide
      */
     @SystemApi
     public interface OnPropertyChangedListener {
         /**
          * Called when a property has changed.
          *
          * @param namespace The namespace containing the property which has changed.
          * @param name      The name of the property which has changed.
          * @param value     The new value of the property which has changed.
          */
         void onPropertyChanged(String namespace, String name, String value);
     }
 }
	/*
	* Copyright (C) 2018 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.provider;

	import static android.Manifest.permission.READ_DEVICE_CONFIG;
	import static android.Manifest.permission.WRITE_DEVICE_CONFIG;

	import android.annotation.CallbackExecutor;
	import android.annotation.NonNull;
	import android.annotation.Nullable;
	import android.annotation.RequiresPermission;
	import android.annotation.SystemApi;
	import android.annotation.TestApi;
	import android.app.ActivityThread;
	import android.content.ContentResolver;
	import android.database.ContentObserver;
	import android.net.Uri;
	import android.provider.Settings.ResetMode;
	import android.util.Pair;

	import com.android.internal.annotations.GuardedBy;

	import java.util.HashMap;
	import java.util.List;
	import java.util.Map;
	import java.util.concurrent.Executor;

	/**
	* Device level configuration parameters which can be tuned by a separate configuration service.
	*
	* @hide
	*/
	@SystemApi
	@TestApi
	public final class DeviceConfig {
	/**
	* The content:// style URL for the config table.
	*
	* @hide
	*/
	public static final Uri CONTENT_URI = Uri.parse("content://" + Settings.AUTHORITY + "/config");

	/**
	* Namespace for all Game Driver features.
	*
	* @hide
	*/
	@SystemApi
	public static final String NAMESPACE_GAME_DRIVER = "game_driver";

	/**
	* Namespace for autofill feature that provides suggestions across all apps when
	* the user interacts with input fields.
	*
	* @hide
	*/
	@SystemApi
	public static final String NAMESPACE_AUTOFILL = "autofill";

	/**
	* ContentCapture-related properties definitions.
	*
	* @hide
	*/
	@SystemApi
	public interface ContentCapture {
	String NAMESPACE = "content_capture";

	/**
	* Property used by {@code com.android.server.SystemServer} on start to decide whether
	* the Content Capture service should be created or not.
	*
	* <p>Possible values are:
	*
	* <ul>
	* <li>If set to {@code default}, it will only be set if the OEM provides and defines the
	* service name by overlaying {@code config_defaultContentCaptureService} (this is the
	* "default" mode)
	* <li>If set to {@code always}, it will always be enabled, even when the resource is not
	* overlaid (this is useful during development and to run the CTS tests on AOSP builds).
	* <li>Otherwise, it's explicitly disabled (this could work as a "kill switch" so OEMs
	* can disable it remotely in case of emergency by setting to something else (like
	* {@code "false"}); notice that it's also disabled if the OEM doesn't explicitly set one
	* of the values above).
	* </ul>
	*
	* @hide
	*/
	// TODO(b/121153631): revert back to SERVICE_EXPLICITLY_ENABLED approach
	String PROPERTY_CONTENTCAPTURE_ENABLED = "enable_contentcapture";
	}

	/**
	* Namespace for content capture feature used by on-device machine intelligence
	* to provide suggestions in a privacy-safe manner.
	*
	* @hide
	*/
	@SystemApi
	public static final String NAMESPACE_CONTENT_CAPTURE = "content_capture";

	/**
	* Namespace for all input-related features that are used at the native level.
	* These features are applied at reboot.
	*
	* @hide
	*/
	@SystemApi
	public static final String NAMESPACE_INPUT_NATIVE_BOOT = "input_native_boot";

	/**
	* Namespace for all netd related features.
	*
	* @hide
	*/
	@SystemApi
	public static final String NAMESPACE_NETD_NATIVE = "netd_native";

	/**
	* Namespace for features related to the ExtServices Notification Assistant.
	* These features are applied immediately.
	*
	* @hide
	*/
	@SystemApi
	public interface NotificationAssistant {
	String NAMESPACE = "notification_assistant";
	/**
	* Whether the Notification Assistant should generate replies for notifications.
	*/
	String GENERATE_REPLIES = "generate_replies";
	/**
	* Whether the Notification Assistant should generate contextual actions for notifications.
	*/
	String GENERATE_ACTIONS = "generate_actions";
	}

	/**
	* Namespace for all runtime native related features.
	*
	* @hide
	*/
	@SystemApi
	public interface RuntimeNative {
	String NAMESPACE = "runtime_native";
	}

	/**
	* Namespace for all activity manager related features that are used at the native level.
	* These features are applied at reboot.
	*
	* @hide
	*/
	@SystemApi
	public interface ActivityManagerNativeBoot {
	String NAMESPACE = "activity_manager_native_boot";
	String OFFLOAD_QUEUE_ENABLED = "offload_queue_enabled";
	}

	/**
	* Namespace for attention-based features provided by on-device machine intelligence.
	*
	* @hide
	*/
	@SystemApi
	public interface IntelligenceAttention {
	String NAMESPACE = "intelligence_attention";

	/** If {@code true}, enables the attention features. */
	String ATTENTION_ENABLED = "attention_enabled";

	/** Settings for the attention features. */
	String ATTENTION_SETTINGS = "attention_settings";
	}

	/**
	* Privacy related properties definitions.
	*
	* @hide
	*/
	@SystemApi
	@TestApi
	public interface Privacy {
	String NAMESPACE = "privacy";

	/**
	* Whether to show the Permissions Hub.
	*
	* @hide
	*/
	@SystemApi
	String PROPERTY_PERMISSIONS_HUB_ENABLED = "permissions_hub_enabled";

	/**
	* Whether to show location access check notifications.
	*/
	String PROPERTY_LOCATION_ACCESS_CHECK_ENABLED = "location_access_check_enabled";
	}

	/**
	* Telephony related properties definitions.
	*
	* @hide
	*/
	@SystemApi
	public interface Telephony {
	String NAMESPACE = "telephony";
	/**
	* Ringer ramping time in milliseconds.
	*/
	String RAMPING_RINGER_DURATION = "ramping_ringer_duration";
	/**
	* Whether to apply ramping ringer on incoming phone calls.
	*/
	String RAMPING_RINGER_ENABLED = "ramping_ringer_enabled";
	/**
	* Vibration time in milliseconds before ramping ringer starts.
	*/
	String RAMPING_RINGER_VIBRATION_DURATION = "ramping_ringer_vibration_duration";
	}

	/**
	* Namespace for how dex runs. The feature may requires reboot to a clean state.
	*
	* @hide
	*/
	@SystemApi
	public interface DexBoot {
	String NAMESPACE = "dex_boot";
	String PRIV_APPS_OOB_ENABLED = "priv_apps_oob_enabled";
	String PRIV_APPS_OOB_WHITELIST = "priv_apps_oob_whitelist";
	}

	/**
	* Namespace for activity manager related features. These features will be applied
	* immediately upon change.
	*
	* @hide
	*/
	@SystemApi
	public interface ActivityManager {
	String NAMESPACE = "activity_manager";

	/**
	* App compaction flags. See {@link com.android.server.am.AppCompactor}.
	*/
	String KEY_USE_COMPACTION = "use_compaction";
	String KEY_COMPACT_ACTION_1 = "compact_action_1";
	String KEY_COMPACT_ACTION_2 = "compact_action_2";
	String KEY_COMPACT_THROTTLE_1 = "compact_throttle_1";
	String KEY_COMPACT_THROTTLE_2 = "compact_throttle_2";
	String KEY_COMPACT_THROTTLE_3 = "compact_throttle_3";
	String KEY_COMPACT_THROTTLE_4 = "compact_throttle_4";
	String KEY_COMPACT_STATSD_SAMPLE_RATE = "compact_statsd_sample_rate";

	/**
	* Maximum number of cached processes. See
	* {@link com.android.server.am.ActivityManagerConstants}.
	*/
	String KEY_MAX_CACHED_PROCESSES = "max_cached_processes";
	}

	/**
	* Namespace for {@link AttentionManagerService} related features.
	*
	* @hide
	*/
	@SystemApi
	public interface AttentionManagerService {
	String NAMESPACE = "attention_manager_service";

	/** If {@code true}, enables {@link AttentionManagerService} features. */
	String SERVICE_ENABLED = "service_enabled";

	/** Allows a CTS to inject a fake implementation. */
	String COMPONENT_NAME = "component_name";
	}

	/**
	* Namespace for storage-related features.
	*
	* @hide
	*/
	@SystemApi
	public interface Storage {
	String NAMESPACE = "storage";

	/**
	* If {@code 1}, enables the isolated storage feature. If {@code -1},
	* disables the isolated storage feature. If {@code 0}, uses the default
	* value from the build system.
	*/
	String ISOLATED_STORAGE_ENABLED = "isolated_storage_enabled";
	}

	private static final Object sLock = new Object();
	@GuardedBy("sLock")
	private static Map<OnPropertyChangedListener, Pair<String, Executor>> sListeners =
	new HashMap<>();
	@GuardedBy("sLock")
	private static Map<String, Pair<ContentObserver, Integer>> sNamespaces = new HashMap<>();

	// Should never be invoked
	private DeviceConfig() {
	}

	/**
	* Look up the value of a property for a particular namespace.
	*
	* @param namespace The namespace containing the property to look up.
	* @param name The name of the property to look up.
	* @return the corresponding value, or null if not present.
	* @hide
	*/
	@SystemApi
	@RequiresPermission(READ_DEVICE_CONFIG)
	public static String getProperty(String namespace, String name) {
	ContentResolver contentResolver = ActivityThread.currentApplication().getContentResolver();
	String compositeName = createCompositeName(namespace, name);
	return Settings.Config.getString(contentResolver, compositeName);
	}

	/**
	* Create a new property with the the provided name and value in the provided namespace, or
	* update the value of such a property if it already exists. The same name can exist in multiple
	* namespaces and might have different values in any or all namespaces.
	* <p>
	* The method takes an argument indicating whether to make the value the default for this
	* property.
	* <p>
	* All properties stored for a particular scope can be reverted to their default values
	* by passing the namespace to {@link #resetToDefaults(int, String)}.
	*
	* @param namespace The namespace containing the property to create or update.
	* @param name The name of the property to create or update.
	* @param value The value to store for the property.
	* @param makeDefault Whether to make the new value the default one.
	* @return True if the value was set, false if the storage implementation throws errors.
	* @hide
	* @see #resetToDefaults(int, String).
	*/
	@SystemApi
	@TestApi
	@RequiresPermission(WRITE_DEVICE_CONFIG)
	public static boolean setProperty(
	String namespace, String name, String value, boolean makeDefault) {
	ContentResolver contentResolver = ActivityThread.currentApplication().getContentResolver();
	String compositeName = createCompositeName(namespace, name);
	return Settings.Config.putString(contentResolver, compositeName, value, makeDefault);
	}

	/**
	* Reset properties to their default values.
	* <p>
	* The method accepts an optional namespace parameter. If provided, only properties set within
	* that namespace will be reset. Otherwise, all properties will be reset.
	*
	* @param resetMode The reset mode to use.
	* @param namespace Optionally, the specific namespace which resets will be limited to.
	* @hide
	* @see #setProperty(String, String, String, boolean)
	*/
	@SystemApi
	@TestApi
	@RequiresPermission(WRITE_DEVICE_CONFIG)
	public static void resetToDefaults(@ResetMode int resetMode, @Nullable String namespace) {
	ContentResolver contentResolver = ActivityThread.currentApplication().getContentResolver();
	Settings.Config.resetToDefaults(contentResolver, resetMode, namespace);
	}

	/**
	* Add a listener for property changes.
	* <p>
	* This listener will be called whenever properties in the specified namespace change. Callbacks
	* will be made on the specified executor. Future calls to this method with the same listener
	* will replace the old namespace and executor. Remove the listener entirely by calling
	* {@link #removeOnPropertyChangedListener(OnPropertyChangedListener)}.
	*
	* @param namespace The namespace containing properties to monitor.
	* @param executor The executor which will be used to run callbacks.
	* @param onPropertyChangedListener The listener to add.
	* @hide
	* @see #removeOnPropertyChangedListener(OnPropertyChangedListener)
	*/
	@SystemApi
	@RequiresPermission(READ_DEVICE_CONFIG)
	public static void addOnPropertyChangedListener(
	@NonNull String namespace,
	@NonNull @CallbackExecutor Executor executor,
	@NonNull OnPropertyChangedListener onPropertyChangedListener) {
	// TODO enforce READ_DEVICE_CONFIG permission
	synchronized (sLock) {
	Pair<String, Executor> oldNamespace = sListeners.get(onPropertyChangedListener);
	if (oldNamespace == null) {
	// Brand new listener, add it to the list.
	sListeners.put(onPropertyChangedListener, new Pair<>(namespace, executor));
	incrementNamespace(namespace);
	} else if (namespace.equals(oldNamespace.first)) {
	// Listener is already registered for this namespace, update executor just in case.
	sListeners.put(onPropertyChangedListener, new Pair<>(namespace, executor));
	} else {
	// Update this listener from an old namespace to the new one.
	decrementNamespace(sListeners.get(onPropertyChangedListener).first);
	sListeners.put(onPropertyChangedListener, new Pair<>(namespace, executor));
	incrementNamespace(namespace);
	}
	}
	}

	/**
	* Remove a listener for property changes. The listener will receive no further notification of
	* property changes.
	*
	* @param onPropertyChangedListener The listener to remove.
	* @hide
	* @see #addOnPropertyChangedListener(String, Executor, OnPropertyChangedListener)
	*/
	@SystemApi
	public static void removeOnPropertyChangedListener(
	OnPropertyChangedListener onPropertyChangedListener) {
	synchronized (sLock) {
	if (sListeners.containsKey(onPropertyChangedListener)) {
	decrementNamespace(sListeners.get(onPropertyChangedListener).first);
	sListeners.remove(onPropertyChangedListener);
	}
	}
	}

	private static String createCompositeName(String namespace, String name) {
	return namespace + "/" + name;
	}

	private static Uri createNamespaceUri(String namespace) {
	return CONTENT_URI.buildUpon().appendPath(namespace).build();
	}

	/**
	* Increment the count used to represent the number of listeners subscribed to the given
	* namespace. If this is the first (i.e. incrementing from 0 to 1) for the given namespace, a
	* ContentObserver is registered.
	*
	* @param namespace The namespace to increment the count for.
	*/
	@GuardedBy("sLock")
	private static void incrementNamespace(String namespace) {
	Pair<ContentObserver, Integer> namespaceCount = sNamespaces.get(namespace);
	if (namespaceCount != null) {
	sNamespaces.put(namespace, new Pair<>(namespaceCount.first, namespaceCount.second + 1));
	} else {
	// This is a new namespace, register a ContentObserver for it.
	ContentObserver contentObserver = new ContentObserver(null) {
	@Override
	public void onChange(boolean selfChange, Uri uri) {
	handleChange(uri);
	}
	};
	ActivityThread.currentApplication().getContentResolver()
	.registerContentObserver(createNamespaceUri(namespace), true, contentObserver);
	sNamespaces.put(namespace, new Pair<>(contentObserver, 1));
	}
	}

	/**
	* Decrement the count used to represent th enumber of listeners subscribed to the given
	* namespace. If this is the final decrement call (i.e. decrementing from 1 to 0) for the given
	* namespace, the ContentObserver that had been tracking it will be removed.
	*
	* @param namespace The namespace to decrement the count for.
	*/
	@GuardedBy("sLock")
	private static void decrementNamespace(String namespace) {
	Pair<ContentObserver, Integer> namespaceCount = sNamespaces.get(namespace);
	if (namespaceCount == null) {
	// This namespace is not registered and does not need to be decremented
	return;
	} else if (namespaceCount.second > 1) {
	sNamespaces.put(namespace, new Pair<>(namespaceCount.first, namespaceCount.second - 1));
	} else {
	// Decrementing a namespace to zero means we no longer need its ContentObserver.
	ActivityThread.currentApplication().getContentResolver()
	.unregisterContentObserver(namespaceCount.first);
	sNamespaces.remove(namespace);
	}
	}

	private static void handleChange(Uri uri) {
	List<String> pathSegments = uri.getPathSegments();
	// pathSegments(0) is "config"
	String namespace = pathSegments.get(1);
	String name = pathSegments.get(2);
	String value = getProperty(namespace, name);
	synchronized (sLock) {
	for (OnPropertyChangedListener listener : sListeners.keySet()) {
	if (namespace.equals(sListeners.get(listener).first)) {
	sListeners.get(listener).second.execute(new Runnable() {
	@Override
	public void run() {
	listener.onPropertyChanged(namespace, name, value);
	}

	});
	}
	}
	}
	}

	/**
	* Interface for monitoring to properties.
	* <p>
	* Override {@link #onPropertyChanged(String, String, String)} to handle callbacks for changes.
	*
	* @hide
	*/
	@SystemApi
	public interface OnPropertyChangedListener {
	/**
	* Called when a property has changed.
	*
	* @param namespace The namespace containing the property which has changed.
	* @param name The name of the property which has changed.
	* @param value The new value of the property which has changed.
	*/
	void onPropertyChanged(String namespace, String name, String value);
	}
	}