First baby steps towards settings backup

This change adds a sketched outline of the backup system architecture, with
all of the major pieces represented other than client-side helpers for
specific types of data.  IBackupManager and BackupService are public so that
we can write test apps against SDK-domain symbols from the outset.

What code exists in this change hasn't been tested and may crash.  It's the
beginnings of the real implementation but of course is barely begun.

4 files changed, 200 insertions, 0 deletions

diff --git a/core/java/android/backup/BackupService.java b/core/java/android/backup/BackupService.java
new file mode 100644
index 0000000..5cfa4f2
--- /dev/null
+++ b/core/java/android/backup/BackupService.java
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2009 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.backup;
+
+import android.annotation.SdkConstant;
+import android.annotation.SdkConstant.SdkConstantType;
+import android.app.Service;
+import android.backup.IBackupService;
+import android.content.Intent;
+import android.os.IBinder;
+import android.os.RemoteException;
+import android.util.Log;
+
+/**
+ * This is the central interface between an application and Android's
+ * settings backup mechanism.
+ * 
+ * <p><em>Not hidden but API subject to change and should not be published</em>
+ */
+
+public abstract class BackupService extends Service {
+    /**
+     * Service Action: Participate in the backup infrastructure.  Applications
+     * that wish to use the Android backup mechanism must provide an exported
+     * subclass of BackupService and give it an {@link android.content.IntentFilter
+     * IntentFilter} that accepts this action. 
+     */
+    @SdkConstant(SdkConstantType.SERVICE_ACTION)
+    public static final String SERVICE_ACTION = "android.service.action.BACKUP";
+
+    /**
+     * The application is being asked to write any data changed since the
+     * last time it performed a backup operation.  The state data recorded
+     * during the last backup pass is provided in the oldStateFd file descriptor.
+     * If oldStateFd is negative, no old state is available and the application
+     * should perform a full backup.  In both cases, a representation of the
+     * final backup state after this pass should be written to the file pointed
+     * to by the newStateFd file descriptor.
+     * 
+     * @param oldStateFd An open, read-only file descriptor pointing to the last
+     *                   backup state provided by the application.  May be negative,
+     *                   in which case no prior state is being provided and the
+     *                   application should perform a full backup.
+     * @param dataFd An open, read/write file descriptor pointing to the backup data
+     *               destination.  Typically the application will use backup helper
+     *               classes to write to this file.
+     * @param newStateFd An open, read/write file descriptor pointing to an empty
+     *                   file.  The application should record the final backup state
+     *                   here after writing the requested data to dataFd.
+     */
+    public abstract void onBackup(int oldStateFd, int dataFd, int newStateFd);
+    
+    /**
+     * The application is being restored from backup, and should replace any
+     * existing data with the contents of the backup.  The backup data is
+     * provided in the file pointed to by the dataFd file descriptor.  Once
+     * the restore is finished, the application should write a representation
+     * of the final state to the newStateFd file descriptor, 
+     * 
+     * @param dataFd An open, read-only file descriptor pointing to a full snapshot
+     *               of the application's data.
+     * @param newStateFd An open, read/write file descriptor pointing to an empty
+     *                   file.  The application should record the final backup state
+     *                   here after restoring its data from dataFd.
+     */
+    public abstract void onRestore(int dataFd, int newStateFd);
+
+
+    // ----- Core implementation -----
+    
+    public IBinder onBind(Intent intent) {
+        return mBinder;
+    }
+
+    private final IBinder mBinder = new BackupServiceBinder().asBinder();
+
+    // ----- IBackupService binder interface -----
+    private class BackupServiceBinder extends IBackupService.Stub {
+        public void doBackup(int oldStateFd, int dataFd, int newStateFd)
+                throws RemoteException {
+            // !!! TODO - real implementation; for now just invoke the callbacks directly
+            Log.v("BackupServiceBinder", "doBackup() invoked");
+            BackupService.this.onBackup(oldStateFd, dataFd, newStateFd);
+        }
+
+        public void doRestore(int dataFd, int newStateFd) throws RemoteException {
+            // !!! TODO - real implementation; for now just invoke the callbacks directly
+            Log.v("BackupServiceBinder", "doRestore() invoked");
+            BackupService.this.onRestore(dataFd, newStateFd);
+        }
+    }
+}
diff --git a/core/java/android/backup/IBackupManager.aidl b/core/java/android/backup/IBackupManager.aidl
new file mode 100644
index 0000000..40cebdd
--- /dev/null
+++ b/core/java/android/backup/IBackupManager.aidl
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2009 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.backup;
+
+/**
+ * Direct interface to the Backup Manager Service that applications invoke on.  The only
+ * operation currently needed is a simple notification that the app has made changes to
+ * data it wishes to back up, so the system should run a backup pass.
+ *
+ * {@hide pending API solidification}
+ */
+interface IBackupManager {
+    /**
+     * Tell the system service that the caller has made changes to its
+     * data, and therefore needs to undergo a backup pass.
+     */
+    oneway void dataChanged();
+}
diff --git a/core/java/android/backup/IBackupService.aidl b/core/java/android/backup/IBackupService.aidl
new file mode 100644
index 0000000..24544bd
--- /dev/null
+++ b/core/java/android/backup/IBackupService.aidl
@@ -0,0 +1,53 @@
+/*
+ * Copyright 2009, 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.backup;
+
+/**
+ * Interface presented by applications being asked to participate in the
+ * backup & restore mechanism.  End user code does not typically implement
+ * this interface; they subclass BackupService instead.
+ *
+ * {@hide}
+ */
+interface IBackupService {
+    /**
+     * Request that the app perform an incremental backup.
+     *
+     * @param oldStateFd Read-only file containing the description blob of the
+     *        app's data state as of the last backup operation's completion.
+     *
+     * @param dataFd Read-write file, empty when onBackup() is called, that
+     *        is the data destination for this backup pass's incrementals.
+     *
+     * @param newStateFd Read-write file, empty when onBackup() is called,
+     *        where the new state blob is to be recorded.
+     */
+    void doBackup(int oldStateFd, int dataFd, int newStateFd);
+
+    /**
+     * Restore an entire data snapshot to the application.
+     *
+     * @param dataFd Read-only file containing the full data snapshot of the
+     *        app's backup.  This is to be a <i>replacement</i> of the app's
+     *        current data, not to be merged into it.
+     *
+     * @param newStateFd Read-write file, empty when onRestore() is called,
+     *        that is to be written with the state description that holds after
+     *        the restore has been completed.
+     */
+    void doRestore(int dataFd, int newStateFd);
+}
diff --git a/core/java/android/content/Context.java b/core/java/android/content/Context.java
index a301449..f2ad248 100644
--- a/core/java/android/content/Context.java
+++ b/core/java/android/content/Context.java
@@ -1269,6 +1269,15 @@ public abstract class Context {
     public static final String APPWIDGET_SERVICE = "appwidget";
     
     /**
+     * Use with {@link #getSystemService} to retrieve an
+     * {@blink android.backup.IBackupManager IBackupManager} for communicating
+     * with the backup mechanism.
+     *
+     * @see #getSystemService
+     */
+    public static final String BACKUP_SERVICE = "backup";
+    
+    /**
      * Determine whether the given permission is allowed for a particular
      * process and user ID running in the system.
      *