services/core/java/com/android/server/rollback/RollbackStore.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 com.android.server.rollback;

 import android.annotation.NonNull;
 import android.content.pm.VersionedPackage;
 import android.content.rollback.PackageRollbackInfo;
 import android.content.rollback.PackageRollbackInfo.RestoreInfo;
 import android.content.rollback.RollbackInfo;
 import android.util.IntArray;
 import android.util.Log;

 import libcore.io.IoUtils;

 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;

 import java.io.File;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.nio.file.Files;
 import java.time.Instant;
 import java.time.format.DateTimeParseException;
 import java.util.ArrayList;
 import java.util.List;

 /**
  * Helper class for loading and saving rollback data to persistent storage.
  */
 class RollbackStore {
     private static final String TAG = "RollbackManager";

     // Assuming the rollback data directory is /data/rollback, we use the
     // following directory structure to store persisted data for available and
     // recently executed rollbacks:
     //   /data/rollback/
     //      available/
     //          XXX/
     //              rollback.json
     //              com.package.A/
     //                  base.apk
     //              com.package.B/
     //                  base.apk
     //          YYY/
     //              rollback.json
     //              com.package.C/
     //                  base.apk
     //      recently_executed.json
     //
     // * XXX, YYY are the rollbackIds for the corresponding rollbacks.
     // * rollback.json contains all relevant metadata for the rollback. This
     //   file is not written until the rollback is made available.
     //
     // TODO: Use AtomicFile for all the .json files?
     private final File mRollbackDataDir;
     private final File mAvailableRollbacksDir;
     private final File mRecentlyExecutedRollbacksFile;

     RollbackStore(File rollbackDataDir) {
         mRollbackDataDir = rollbackDataDir;
         mAvailableRollbacksDir = new File(mRollbackDataDir, "available");
         mRecentlyExecutedRollbacksFile = new File(mRollbackDataDir, "recently_executed.json");
     }

     /**
      * Reads the list of available rollbacks from persistent storage.
      */
     List<RollbackData> loadAvailableRollbacks() {
         List<RollbackData> availableRollbacks = new ArrayList<>();
         mAvailableRollbacksDir.mkdirs();
         for (File rollbackDir : mAvailableRollbacksDir.listFiles()) {
             if (rollbackDir.isDirectory()) {
                 try {
                     RollbackData data = loadRollbackData(rollbackDir);
                     availableRollbacks.add(data);
                 } catch (IOException e) {
                     // Note: Deleting the rollbackDir here will cause pending
                     // rollbacks to be deleted. This should only ever happen
                     // if reloadPersistedData is called while there are
                     // pending rollbacks. The reloadPersistedData method is
                     // currently only for testing, so that should be okay.
                     Log.e(TAG, "Unable to read rollback data at " + rollbackDir, e);
                     removeFile(rollbackDir);
                 }
             }
         }
         return availableRollbacks;
     }

     /**
      * Converts an {@code JSONArray} of integers to an {@code IntArray}.
      */
     private static @NonNull IntArray convertToIntArray(@NonNull JSONArray jsonArray)
             throws JSONException {
         if (jsonArray.length() == 0) {
             return new IntArray();
         }

         final int[] ret = new int[jsonArray.length()];
         for (int i = 0; i < ret.length; ++i) {
             ret[i] = jsonArray.getInt(i);
         }

         return IntArray.wrap(ret);
     }

     /**
      * Converts an {@code IntArray} into an {@code JSONArray} of integers.
      */
     private static @NonNull JSONArray convertToJsonArray(@NonNull IntArray intArray) {
         JSONArray jsonArray = new JSONArray();
         for (int i = 0; i < intArray.size(); ++i) {
             jsonArray.put(intArray.get(i));
         }

         return jsonArray;
     }

     private static @NonNull JSONArray convertToJsonArray(@NonNull List<RestoreInfo> list)
             throws JSONException {
         JSONArray jsonArray = new JSONArray();
         for (RestoreInfo ri : list) {
             JSONObject jo = new JSONObject();
             jo.put("userId", ri.userId);
             jo.put("appId", ri.appId);
             jo.put("seInfo", ri.seInfo);
             jsonArray.put(jo);
         }

         return jsonArray;
     }

     private static @NonNull ArrayList<RestoreInfo> convertToRestoreInfoArray(
             @NonNull JSONArray array) throws JSONException {
         ArrayList<RestoreInfo> restoreInfos = new ArrayList<>();

         for (int i = 0; i < array.length(); ++i) {
             JSONObject jo = array.getJSONObject(i);
             restoreInfos.add(new RestoreInfo(
                     jo.getInt("userId"),
                     jo.getInt("appId"),
                     jo.getString("seInfo")));
         }

         return restoreInfos;
     }

     /**
      * Reads the list of recently executed rollbacks from persistent storage.
      */
     List<RollbackInfo> loadRecentlyExecutedRollbacks() {
         List<RollbackInfo> recentlyExecutedRollbacks = new ArrayList<>();
         if (mRecentlyExecutedRollbacksFile.exists()) {
             try {
                 // TODO: How to cope with changes to the format of this file from
                 // when RollbackStore is updated in the future?
                 String jsonString = IoUtils.readFileAsString(
                         mRecentlyExecutedRollbacksFile.getAbsolutePath());
                 JSONObject object = new JSONObject(jsonString);
                 JSONArray array = object.getJSONArray("recentlyExecuted");
                 for (int i = 0; i < array.length(); ++i) {
                     JSONObject element = array.getJSONObject(i);
                     int rollbackId = element.getInt("rollbackId");
                     List<PackageRollbackInfo> packages = packageRollbackInfosFromJson(
                             element.getJSONArray("packages"));
                     List<VersionedPackage> causePackages = versionedPackagesFromJson(
                             element.getJSONArray("causePackages"));
                     RollbackInfo rollback = new RollbackInfo(rollbackId, packages, causePackages);
                     recentlyExecutedRollbacks.add(rollback);
                 }
             } catch (IOException | JSONException e) {
                 // TODO: What to do here? Surely we shouldn't just forget about
                 // everything after the point of exception?
                 Log.e(TAG, "Failed to read recently executed rollbacks", e);
             }
         }

         return recentlyExecutedRollbacks;
     }

     /**
      * Creates a new RollbackData instance with backupDir assigned.
      */
     RollbackData createAvailableRollback(int rollbackId) throws IOException {
         File backupDir = new File(mAvailableRollbacksDir, Integer.toString(rollbackId));
         return new RollbackData(rollbackId, backupDir);
     }

     /**
      * Creates a backup copy of the apk or apex for a package.
      */
     static void backupPackageCode(RollbackData data, String packageName, String codePath)
             throws IOException {
         File sourceFile = new File(codePath);
         File targetDir = new File(data.backupDir, packageName);
         targetDir.mkdirs();
         File targetFile = new File(targetDir, sourceFile.getName());

         // TODO: Copy by hard link instead to save on cpu and storage space?
         Files.copy(sourceFile.toPath(), targetFile.toPath());
     }

     /**
      * Returns the apk or apex file backed up for the given package.
      * Returns null if none found.
      */
     static File getPackageCode(RollbackData data, String packageName) {
         File targetDir = new File(data.backupDir, packageName);
         File[] files = targetDir.listFiles();
         if (files == null || files.length != 1) {
             return null;
         }
         return files[0];
     }

     /**
      * Writes the metadata for an available rollback to persistent storage.
      */
     void saveAvailableRollback(RollbackData data) throws IOException {
         try {
             JSONObject dataJson = new JSONObject();
             dataJson.put("rollbackId", data.rollbackId);
             dataJson.put("packages", toJson(data.packages));
             dataJson.put("timestamp", data.timestamp.toString());

             PrintWriter pw = new PrintWriter(new File(data.backupDir, "rollback.json"));
             pw.println(dataJson.toString());
             pw.close();
         } catch (JSONException e) {
             throw new IOException(e);
         }
     }

     /**
      * Removes all persistant storage associated with the given available
      * rollback.
      */
     void deleteAvailableRollback(RollbackData data) {
         // TODO(narayan): Make sure we delete the userdata snapshot along with the backup of the
         // actual app.
         removeFile(data.backupDir);
     }

     /**
      * Writes the list of recently executed rollbacks to storage.
      */
     void saveRecentlyExecutedRollbacks(List<RollbackInfo> recentlyExecutedRollbacks) {
         try {
             JSONObject json = new JSONObject();
             JSONArray array = new JSONArray();
             json.put("recentlyExecuted", array);

             for (int i = 0; i < recentlyExecutedRollbacks.size(); ++i) {
                 RollbackInfo rollback = recentlyExecutedRollbacks.get(i);
                 JSONObject element = new JSONObject();
                 element.put("rollbackId", rollback.getRollbackId());
                 element.put("packages", toJson(rollback.getPackages()));
                 element.put("causePackages", versionedPackagesToJson(rollback.getCausePackages()));
                 array.put(element);
             }

             PrintWriter pw = new PrintWriter(mRecentlyExecutedRollbacksFile);
             pw.println(json.toString());
             pw.close();
         } catch (IOException | JSONException e) {
             // TODO: What to do here?
             Log.e(TAG, "Failed to save recently executed rollbacks", e);
         }
     }

     /**
      * Reads the metadata for a rollback from the given directory.
      * @throws IOException in case of error reading the data.
      */
     private RollbackData loadRollbackData(File backupDir) throws IOException {
         try {
             File rollbackJsonFile = new File(backupDir, "rollback.json");
             JSONObject dataJson = new JSONObject(
                     IoUtils.readFileAsString(rollbackJsonFile.getAbsolutePath()));

             int rollbackId = dataJson.getInt("rollbackId");
             RollbackData data = new RollbackData(rollbackId, backupDir);
             data.packages.addAll(packageRollbackInfosFromJson(dataJson.getJSONArray("packages")));
             data.timestamp = Instant.parse(dataJson.getString("timestamp"));
             return data;
         } catch (JSONException | DateTimeParseException e) {
             throw new IOException(e);
         }
     }

     private JSONObject toJson(VersionedPackage pkg) throws JSONException {
         JSONObject json = new JSONObject();
         json.put("packageName", pkg.getPackageName());
         json.put("longVersionCode", pkg.getLongVersionCode());
         return json;
     }

     private VersionedPackage versionedPackageFromJson(JSONObject json) throws JSONException {
         String packageName = json.getString("packageName");
         long longVersionCode = json.getLong("longVersionCode");
         return new VersionedPackage(packageName, longVersionCode);
     }

     private JSONObject toJson(PackageRollbackInfo info) throws JSONException {
         JSONObject json = new JSONObject();
         json.put("versionRolledBackFrom", toJson(info.getVersionRolledBackFrom()));
         json.put("versionRolledBackTo", toJson(info.getVersionRolledBackTo()));

         IntArray pendingBackups = info.getPendingBackups();
         List<RestoreInfo> pendingRestores = info.getPendingRestores();
         json.put("pendingBackups", convertToJsonArray(pendingBackups));
         json.put("pendingRestores", convertToJsonArray(pendingRestores));

         return json;
     }

     private PackageRollbackInfo packageRollbackInfoFromJson(JSONObject json) throws JSONException {
         VersionedPackage versionRolledBackFrom = versionedPackageFromJson(
                 json.getJSONObject("versionRolledBackFrom"));
         VersionedPackage versionRolledBackTo = versionedPackageFromJson(
                 json.getJSONObject("versionRolledBackTo"));

         final IntArray pendingBackups = convertToIntArray(
                 json.getJSONArray("pendingBackups"));
         final ArrayList<RestoreInfo> pendingRestores = convertToRestoreInfoArray(
                 json.getJSONArray("pendingRestores"));

         return new PackageRollbackInfo(versionRolledBackFrom, versionRolledBackTo,
                 pendingBackups, pendingRestores);
     }

     private JSONArray versionedPackagesToJson(List<VersionedPackage> packages)
             throws JSONException {
         JSONArray json = new JSONArray();
         for (VersionedPackage pkg : packages) {
             json.put(toJson(pkg));
         }
         return json;
     }

     private List<VersionedPackage> versionedPackagesFromJson(JSONArray json) throws JSONException {
         List<VersionedPackage> packages = new ArrayList<>();
         for (int i = 0; i < json.length(); ++i) {
             packages.add(versionedPackageFromJson(json.getJSONObject(i)));
         }
         return packages;
     }

     private JSONArray toJson(List<PackageRollbackInfo> infos) throws JSONException {
         JSONArray json = new JSONArray();
         for (PackageRollbackInfo info : infos) {
             json.put(toJson(info));
         }
         return json;
     }

     private List<PackageRollbackInfo> packageRollbackInfosFromJson(JSONArray json)
             throws JSONException {
         List<PackageRollbackInfo> infos = new ArrayList<>();
         for (int i = 0; i < json.length(); ++i) {
             infos.add(packageRollbackInfoFromJson(json.getJSONObject(i)));
         }
         return infos;
     }

     /**
      * Deletes a file completely.
      * If the file is a directory, its contents are deleted as well.
      * Has no effect if the directory does not exist.
      */
     private void removeFile(File file) {
         if (file.isDirectory()) {
             for (File child : file.listFiles()) {
                 removeFile(child);
             }
         }
         if (file.exists()) {
             file.delete();
         }
     }
 }
	/*
	* 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 com.android.server.rollback;

	import android.annotation.NonNull;
	import android.content.pm.VersionedPackage;
	import android.content.rollback.PackageRollbackInfo;
	import android.content.rollback.PackageRollbackInfo.RestoreInfo;
	import android.content.rollback.RollbackInfo;
	import android.util.IntArray;
	import android.util.Log;

	import libcore.io.IoUtils;

	import org.json.JSONArray;
	import org.json.JSONException;
	import org.json.JSONObject;

	import java.io.File;
	import java.io.IOException;
	import java.io.PrintWriter;
	import java.nio.file.Files;
	import java.time.Instant;
	import java.time.format.DateTimeParseException;
	import java.util.ArrayList;
	import java.util.List;

	/**
	* Helper class for loading and saving rollback data to persistent storage.
	*/
	class RollbackStore {
	private static final String TAG = "RollbackManager";

	// Assuming the rollback data directory is /data/rollback, we use the
	// following directory structure to store persisted data for available and
	// recently executed rollbacks:
	// /data/rollback/
	// available/
	// XXX/
	// rollback.json
	// com.package.A/
	// base.apk
	// com.package.B/
	// base.apk
	// YYY/
	// rollback.json
	// com.package.C/
	// base.apk
	// recently_executed.json
	//
	// * XXX, YYY are the rollbackIds for the corresponding rollbacks.
	// * rollback.json contains all relevant metadata for the rollback. This
	// file is not written until the rollback is made available.
	//
	// TODO: Use AtomicFile for all the .json files?
	private final File mRollbackDataDir;
	private final File mAvailableRollbacksDir;
	private final File mRecentlyExecutedRollbacksFile;

	RollbackStore(File rollbackDataDir) {
	mRollbackDataDir = rollbackDataDir;
	mAvailableRollbacksDir = new File(mRollbackDataDir, "available");
	mRecentlyExecutedRollbacksFile = new File(mRollbackDataDir, "recently_executed.json");
	}

	/**
	* Reads the list of available rollbacks from persistent storage.
	*/
	List<RollbackData> loadAvailableRollbacks() {
	List<RollbackData> availableRollbacks = new ArrayList<>();
	mAvailableRollbacksDir.mkdirs();
	for (File rollbackDir : mAvailableRollbacksDir.listFiles()) {
	if (rollbackDir.isDirectory()) {
	try {
	RollbackData data = loadRollbackData(rollbackDir);
	availableRollbacks.add(data);
	} catch (IOException e) {
	// Note: Deleting the rollbackDir here will cause pending
	// rollbacks to be deleted. This should only ever happen
	// if reloadPersistedData is called while there are
	// pending rollbacks. The reloadPersistedData method is
	// currently only for testing, so that should be okay.
	Log.e(TAG, "Unable to read rollback data at " + rollbackDir, e);
	removeFile(rollbackDir);
	}
	}
	}
	return availableRollbacks;
	}

	/**
	* Converts an {@code JSONArray} of integers to an {@code IntArray}.
	*/
	private static @NonNull IntArray convertToIntArray(@NonNull JSONArray jsonArray)
	throws JSONException {
	if (jsonArray.length() == 0) {
	return new IntArray();
	}

	final int[] ret = new int[jsonArray.length()];
	for (int i = 0; i < ret.length; ++i) {
	ret[i] = jsonArray.getInt(i);
	}

	return IntArray.wrap(ret);
	}

	/**
	* Converts an {@code IntArray} into an {@code JSONArray} of integers.
	*/
	private static @NonNull JSONArray convertToJsonArray(@NonNull IntArray intArray) {
	JSONArray jsonArray = new JSONArray();
	for (int i = 0; i < intArray.size(); ++i) {
	jsonArray.put(intArray.get(i));
	}

	return jsonArray;
	}

	private static @NonNull JSONArray convertToJsonArray(@NonNull List<RestoreInfo> list)
	throws JSONException {
	JSONArray jsonArray = new JSONArray();
	for (RestoreInfo ri : list) {
	JSONObject jo = new JSONObject();
	jo.put("userId", ri.userId);
	jo.put("appId", ri.appId);
	jo.put("seInfo", ri.seInfo);
	jsonArray.put(jo);
	}

	return jsonArray;
	}

	private static @NonNull ArrayList<RestoreInfo> convertToRestoreInfoArray(
	@NonNull JSONArray array) throws JSONException {
	ArrayList<RestoreInfo> restoreInfos = new ArrayList<>();

	for (int i = 0; i < array.length(); ++i) {
	JSONObject jo = array.getJSONObject(i);
	restoreInfos.add(new RestoreInfo(
	jo.getInt("userId"),
	jo.getInt("appId"),
	jo.getString("seInfo")));
	}

	return restoreInfos;
	}

	/**
	* Reads the list of recently executed rollbacks from persistent storage.
	*/
	List<RollbackInfo> loadRecentlyExecutedRollbacks() {
	List<RollbackInfo> recentlyExecutedRollbacks = new ArrayList<>();
	if (mRecentlyExecutedRollbacksFile.exists()) {
	try {
	// TODO: How to cope with changes to the format of this file from
	// when RollbackStore is updated in the future?
	String jsonString = IoUtils.readFileAsString(
	mRecentlyExecutedRollbacksFile.getAbsolutePath());
	JSONObject object = new JSONObject(jsonString);
	JSONArray array = object.getJSONArray("recentlyExecuted");
	for (int i = 0; i < array.length(); ++i) {
	JSONObject element = array.getJSONObject(i);
	int rollbackId = element.getInt("rollbackId");
	List<PackageRollbackInfo> packages = packageRollbackInfosFromJson(
	element.getJSONArray("packages"));
	List<VersionedPackage> causePackages = versionedPackagesFromJson(
	element.getJSONArray("causePackages"));
	RollbackInfo rollback = new RollbackInfo(rollbackId, packages, causePackages);
	recentlyExecutedRollbacks.add(rollback);
	}
	} catch (IOException \| JSONException e) {
	// TODO: What to do here? Surely we shouldn't just forget about
	// everything after the point of exception?
	Log.e(TAG, "Failed to read recently executed rollbacks", e);
	}
	}

	return recentlyExecutedRollbacks;
	}

	/**
	* Creates a new RollbackData instance with backupDir assigned.
	*/
	RollbackData createAvailableRollback(int rollbackId) throws IOException {
	File backupDir = new File(mAvailableRollbacksDir, Integer.toString(rollbackId));
	return new RollbackData(rollbackId, backupDir);
	}

	/**
	* Creates a backup copy of the apk or apex for a package.
	*/
	static void backupPackageCode(RollbackData data, String packageName, String codePath)
	throws IOException {
	File sourceFile = new File(codePath);
	File targetDir = new File(data.backupDir, packageName);
	targetDir.mkdirs();
	File targetFile = new File(targetDir, sourceFile.getName());

	// TODO: Copy by hard link instead to save on cpu and storage space?
	Files.copy(sourceFile.toPath(), targetFile.toPath());
	}

	/**
	* Returns the apk or apex file backed up for the given package.
	* Returns null if none found.
	*/
	static File getPackageCode(RollbackData data, String packageName) {
	File targetDir = new File(data.backupDir, packageName);
	File[] files = targetDir.listFiles();
	if (files == null \|\| files.length != 1) {
	return null;
	}
	return files[0];
	}

	/**
	* Writes the metadata for an available rollback to persistent storage.
	*/
	void saveAvailableRollback(RollbackData data) throws IOException {
	try {
	JSONObject dataJson = new JSONObject();
	dataJson.put("rollbackId", data.rollbackId);
	dataJson.put("packages", toJson(data.packages));
	dataJson.put("timestamp", data.timestamp.toString());

	PrintWriter pw = new PrintWriter(new File(data.backupDir, "rollback.json"));
	pw.println(dataJson.toString());
	pw.close();
	} catch (JSONException e) {
	throw new IOException(e);
	}
	}

	/**
	* Removes all persistant storage associated with the given available
	* rollback.
	*/
	void deleteAvailableRollback(RollbackData data) {
	// TODO(narayan): Make sure we delete the userdata snapshot along with the backup of the
	// actual app.
	removeFile(data.backupDir);
	}

	/**
	* Writes the list of recently executed rollbacks to storage.
	*/
	void saveRecentlyExecutedRollbacks(List<RollbackInfo> recentlyExecutedRollbacks) {
	try {
	JSONObject json = new JSONObject();
	JSONArray array = new JSONArray();
	json.put("recentlyExecuted", array);

	for (int i = 0; i < recentlyExecutedRollbacks.size(); ++i) {
	RollbackInfo rollback = recentlyExecutedRollbacks.get(i);
	JSONObject element = new JSONObject();
	element.put("rollbackId", rollback.getRollbackId());
	element.put("packages", toJson(rollback.getPackages()));
	element.put("causePackages", versionedPackagesToJson(rollback.getCausePackages()));
	array.put(element);
	}

	PrintWriter pw = new PrintWriter(mRecentlyExecutedRollbacksFile);
	pw.println(json.toString());
	pw.close();
	} catch (IOException \| JSONException e) {
	// TODO: What to do here?
	Log.e(TAG, "Failed to save recently executed rollbacks", e);
	}
	}

	/**
	* Reads the metadata for a rollback from the given directory.
	* @throws IOException in case of error reading the data.
	*/
	private RollbackData loadRollbackData(File backupDir) throws IOException {
	try {
	File rollbackJsonFile = new File(backupDir, "rollback.json");
	JSONObject dataJson = new JSONObject(
	IoUtils.readFileAsString(rollbackJsonFile.getAbsolutePath()));

	int rollbackId = dataJson.getInt("rollbackId");
	RollbackData data = new RollbackData(rollbackId, backupDir);
	data.packages.addAll(packageRollbackInfosFromJson(dataJson.getJSONArray("packages")));
	data.timestamp = Instant.parse(dataJson.getString("timestamp"));
	return data;
	} catch (JSONException \| DateTimeParseException e) {
	throw new IOException(e);
	}
	}

	private JSONObject toJson(VersionedPackage pkg) throws JSONException {
	JSONObject json = new JSONObject();
	json.put("packageName", pkg.getPackageName());
	json.put("longVersionCode", pkg.getLongVersionCode());
	return json;
	}

	private VersionedPackage versionedPackageFromJson(JSONObject json) throws JSONException {
	String packageName = json.getString("packageName");
	long longVersionCode = json.getLong("longVersionCode");
	return new VersionedPackage(packageName, longVersionCode);
	}

	private JSONObject toJson(PackageRollbackInfo info) throws JSONException {
	JSONObject json = new JSONObject();
	json.put("versionRolledBackFrom", toJson(info.getVersionRolledBackFrom()));
	json.put("versionRolledBackTo", toJson(info.getVersionRolledBackTo()));

	IntArray pendingBackups = info.getPendingBackups();
	List<RestoreInfo> pendingRestores = info.getPendingRestores();
	json.put("pendingBackups", convertToJsonArray(pendingBackups));
	json.put("pendingRestores", convertToJsonArray(pendingRestores));

	return json;
	}

	private PackageRollbackInfo packageRollbackInfoFromJson(JSONObject json) throws JSONException {
	VersionedPackage versionRolledBackFrom = versionedPackageFromJson(
	json.getJSONObject("versionRolledBackFrom"));
	VersionedPackage versionRolledBackTo = versionedPackageFromJson(
	json.getJSONObject("versionRolledBackTo"));

	final IntArray pendingBackups = convertToIntArray(
	json.getJSONArray("pendingBackups"));
	final ArrayList<RestoreInfo> pendingRestores = convertToRestoreInfoArray(
	json.getJSONArray("pendingRestores"));

	return new PackageRollbackInfo(versionRolledBackFrom, versionRolledBackTo,
	pendingBackups, pendingRestores);
	}

	private JSONArray versionedPackagesToJson(List<VersionedPackage> packages)
	throws JSONException {
	JSONArray json = new JSONArray();
	for (VersionedPackage pkg : packages) {
	json.put(toJson(pkg));
	}
	return json;
	}

	private List<VersionedPackage> versionedPackagesFromJson(JSONArray json) throws JSONException {
	List<VersionedPackage> packages = new ArrayList<>();
	for (int i = 0; i < json.length(); ++i) {
	packages.add(versionedPackageFromJson(json.getJSONObject(i)));
	}
	return packages;
	}

	private JSONArray toJson(List<PackageRollbackInfo> infos) throws JSONException {
	JSONArray json = new JSONArray();
	for (PackageRollbackInfo info : infos) {
	json.put(toJson(info));
	}
	return json;
	}

	private List<PackageRollbackInfo> packageRollbackInfosFromJson(JSONArray json)
	throws JSONException {
	List<PackageRollbackInfo> infos = new ArrayList<>();
	for (int i = 0; i < json.length(); ++i) {
	infos.add(packageRollbackInfoFromJson(json.getJSONObject(i)));
	}
	return infos;
	}

	/**
	* Deletes a file completely.
	* If the file is a directory, its contents are deleted as well.
	* Has no effect if the directory does not exist.
	*/
	private void removeFile(File file) {
	if (file.isDirectory()) {
	for (File child : file.listFiles()) {
	removeFile(child);
	}
	}
	if (file.exists()) {
	file.delete();
	}
	}
	}