/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.server.am;
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import android.annotation.NonNull;
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import android.content.ContentResolver;
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import android.database.ContentObserver;
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import android.net.Uri;
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import android.os.AsyncTask;
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import android.os.Build;
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import android.os.SystemProperties;
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import android.provider.DeviceConfig;
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import android.provider.Settings;
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import android.text.TextUtils;
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import android.util.Slog;
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import com.android.internal.annotations.VisibleForTesting;
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import java.io.BufferedReader;
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import java.io.File;
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import java.io.FileReader;
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import java.io.IOException;
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import java.util.HashSet;
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/**
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* Maps system settings to system properties.
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* <p>The properties are dynamically updated when settings change.
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* @hide
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*/
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public class SettingsToPropertiesMapper {
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private static final String TAG = "SettingsToPropertiesMapper";
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private static final String SYSTEM_PROPERTY_PREFIX = "persist.device_config.";
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private static final String RESET_PERFORMED_PROPERTY = "device_config.reset_performed";
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private static final String RESET_RECORD_FILE_PATH =
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"/data/server_configurable_flags/reset_flags";
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private static final String SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX = "^[\\w\\.\\-@:]*$";
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private static final String SYSTEM_PROPERTY_INVALID_SUBSTRING = "..";
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private static final int SYSTEM_PROPERTY_MAX_LENGTH = 92;
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// experiment flags added to Global.Settings(before new "Config" provider table is available)
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// will be added under this category.
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private static final String GLOBAL_SETTINGS_CATEGORY = "global_settings";
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// Add the global setting you want to push to native level as experiment flag into this list.
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//
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// NOTE: please grant write permission system property prefix
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// with format persist.device_config.global_settings.[flag_name] in system_server.te and grant
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// read permission in the corresponding .te file your feature belongs to.
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@VisibleForTesting
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static final String[] sGlobalSettings = new String[] {
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Settings.Global.NATIVE_FLAGS_HEALTH_CHECK_ENABLED,
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};
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// All the flags under the listed DeviceConfig scopes will be synced to native level.
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//
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// NOTE: please grant write permission system property prefix
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// with format persist.device_config.[device_config_scope]. in system_server.te and grant read
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// permission in the corresponding .te file your feature belongs to.
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@VisibleForTesting
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static final String[] sDeviceConfigScopes = new String[] {
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DeviceConfig.NAMESPACE_ACTIVITY_MANAGER_NATIVE_BOOT,
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DeviceConfig.NAMESPACE_INPUT_NATIVE_BOOT,
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DeviceConfig.NAMESPACE_INTELLIGENCE_CONTENT_SUGGESTIONS,
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DeviceConfig.NAMESPACE_MEDIA_NATIVE,
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DeviceConfig.NAMESPACE_NETD_NATIVE,
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DeviceConfig.NAMESPACE_RUNTIME_NATIVE,
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DeviceConfig.NAMESPACE_RUNTIME_NATIVE_BOOT,
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};
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private final String[] mGlobalSettings;
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private final String[] mDeviceConfigScopes;
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private final ContentResolver mContentResolver;
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@VisibleForTesting
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protected SettingsToPropertiesMapper(ContentResolver contentResolver,
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String[] globalSettings,
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String[] deviceConfigScopes) {
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mContentResolver = contentResolver;
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mGlobalSettings = globalSettings;
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mDeviceConfigScopes = deviceConfigScopes;
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}
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@VisibleForTesting
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void updatePropertiesFromSettings() {
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for (String globalSetting : mGlobalSettings) {
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Uri settingUri = Settings.Global.getUriFor(globalSetting);
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String propName = makePropertyName(GLOBAL_SETTINGS_CATEGORY, globalSetting);
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if (settingUri == null) {
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log("setting uri is null for globalSetting " + globalSetting);
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continue;
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}
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if (propName == null) {
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log("invalid prop name for globalSetting " + globalSetting);
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continue;
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}
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ContentObserver co = new ContentObserver(null) {
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@Override
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public void onChange(boolean selfChange) {
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updatePropertyFromSetting(globalSetting, propName);
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}
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};
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// only updating on starting up when no native flags reset is performed during current
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// booting.
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if (!isNativeFlagsResetPerformed()) {
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updatePropertyFromSetting(globalSetting, propName);
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}
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mContentResolver.registerContentObserver(settingUri, false, co);
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}
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for (String deviceConfigScope : mDeviceConfigScopes) {
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DeviceConfig.addOnPropertiesChangedListener(
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deviceConfigScope,
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AsyncTask.THREAD_POOL_EXECUTOR,
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(DeviceConfig.Properties properties) -> {
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String scope = properties.getNamespace();
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for (String key : properties.getKeyset()) {
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String propertyName = makePropertyName(scope, key);
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if (propertyName == null) {
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log("unable to construct system property for " + scope + "/"
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+ key);
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return;
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}
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setProperty(propertyName, properties.getString(key, null));
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}
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});
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}
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}
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public static SettingsToPropertiesMapper start(ContentResolver contentResolver) {
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SettingsToPropertiesMapper mapper = new SettingsToPropertiesMapper(
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contentResolver, sGlobalSettings, sDeviceConfigScopes);
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mapper.updatePropertiesFromSettings();
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return mapper;
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}
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/**
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* If native level flags reset has been performed as an attempt to recover from a crash loop
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* during current device booting.
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* @return
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*/
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public static boolean isNativeFlagsResetPerformed() {
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String value = SystemProperties.get(RESET_PERFORMED_PROPERTY);
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return "true".equals(value);
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}
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/**
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* return an array of native flag categories under which flags got reset during current device
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* booting.
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* @return
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*/
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public static @NonNull String[] getResetNativeCategories() {
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if (!isNativeFlagsResetPerformed()) {
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return new String[0];
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}
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String content = getResetFlagsFileContent();
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if (TextUtils.isEmpty(content)) {
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return new String[0];
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}
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String[] property_names = content.split(";");
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HashSet<String> categories = new HashSet<>();
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for (String property_name : property_names) {
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String[] segments = property_name.split("\\.");
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if (segments.length < 3) {
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log("failed to extract category name from property " + property_name);
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continue;
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}
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categories.add(segments[2]);
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}
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return categories.toArray(new String[0]);
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}
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/**
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* system property name constructing rule: "persist.device_config.[category_name].[flag_name]".
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* If the name contains invalid characters or substrings for system property name,
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* will return null.
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* @param categoryName
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* @param flagName
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* @return
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*/
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@VisibleForTesting
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static String makePropertyName(String categoryName, String flagName) {
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String propertyName = SYSTEM_PROPERTY_PREFIX + categoryName + "." + flagName;
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if (!propertyName.matches(SYSTEM_PROPERTY_VALID_CHARACTERS_REGEX)
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|| propertyName.contains(SYSTEM_PROPERTY_INVALID_SUBSTRING)) {
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return null;
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}
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return propertyName;
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}
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private void setProperty(String key, String value) {
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// Check if need to clear the property
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if (value == null) {
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// It's impossible to remove system property, therefore we check previous value to
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// avoid setting an empty string if the property wasn't set.
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if (TextUtils.isEmpty(SystemProperties.get(key))) {
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return;
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}
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value = "";
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} else if (value.length() > SYSTEM_PROPERTY_MAX_LENGTH) {
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log(value + " exceeds system property max length.");
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return;
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}
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try {
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SystemProperties.set(key, value);
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} catch (Exception e) {
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// Failure to set a property can be caused by SELinux denial. This usually indicates
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// that the property wasn't whitelisted in sepolicy.
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// No need to report it on all user devices, only on debug builds.
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log("Unable to set property " + key + " value '" + value + "'", e);
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}
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}
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private static void log(String msg, Exception e) {
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if (Build.IS_DEBUGGABLE) {
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Slog.wtf(TAG, msg, e);
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} else {
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Slog.e(TAG, msg, e);
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}
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}
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private static void log(String msg) {
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if (Build.IS_DEBUGGABLE) {
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Slog.wtf(TAG, msg);
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} else {
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Slog.e(TAG, msg);
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}
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}
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@VisibleForTesting
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static String getResetFlagsFileContent() {
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String content = null;
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try {
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File reset_flag_file = new File(RESET_RECORD_FILE_PATH);
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BufferedReader br = new BufferedReader(new FileReader(reset_flag_file));
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content = br.readLine();
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br.close();
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} catch (IOException ioe) {
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log("failed to read file " + RESET_RECORD_FILE_PATH, ioe);
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}
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return content;
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}
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@VisibleForTesting
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void updatePropertyFromSetting(String settingName, String propName) {
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String settingValue = Settings.Global.getString(mContentResolver, settingName);
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setProperty(propName, settingValue);
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}
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}
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