Add system API for querying the available restore dataset for a package

Bug 20123585

Change-Id: Ife6e77a224b5d4175178aacdb7c285e9944b9eab

api/system-current.txt

@@ -5912,6 +5912,7 @@ package android.app.backup {
     method public android.app.backup.RestoreSession beginRestoreSession();
     method public void dataChanged();
     method public static void dataChanged(java.lang.String);
+    method public long getAvailableRestoreToken(java.lang.String);
     method public java.lang.String getCurrentTransport();
     method public boolean isBackupEnabled();
     method public java.lang.String[] listAllTransports();

core/java/android/app/backup/BackupManager.java

@@ -339,4 +339,30 @@ public class BackupManager {
             }
         }
     }
+
+    /**
+     * Ask the framework which dataset, if any, the given package's data would be
+     * restored from if we were to install it right now.
+     *
+     * <p>Callers must hold the android.permission.BACKUP permission to use this method.
+     *
+     * @param packageName The name of the package whose most-suitable dataset we
+     *     wish to look up
+     * @return The dataset token from which a restore should be attempted, or zero if
+     *     no suitable data is available.
+     *
+     * @hide
+     */
+    @SystemApi
+    public long getAvailableRestoreToken(String packageName) {
+        checkServiceBinder();
+        if (sService != null) {
+            try {
+                return sService.getAvailableRestoreToken(packageName);
+            } catch (RemoteException e) {
+                Log.e(TAG, "getAvailableRestoreToken() couldn't connect");
+            }
+        }
+        return 0;
+    }
 }

core/java/android/app/backup/IBackupManager.aidl

@@ -313,4 +313,17 @@ interface IBackupManager {
      *     is being queried.
      */
     boolean isBackupServiceActive(int whichUser);
+
+    /**
+     * Ask the framework which dataset, if any, the given package's data would be
+     * restored from if we were to install it right now.
+     *
+     * <p>Callers must hold the android.permission.BACKUP permission to use this method.
+     *
+     * @param packageName The name of the package whose most-suitable dataset we
+     *     wish to look up
+     * @return The dataset token from which a restore should be attempted, or zero if
+     *     no suitable data is available.
+     */
+    long getAvailableRestoreToken(String packageName);
 }

services/backup/java/com/android/server/backup/BackupManagerService.java

@@ -2209,7 +2209,10 @@ public class BackupManagerService {
 
     // Get the restore-set token for the best-available restore set for this package:
     // the active set if possible, else the ancestral one.  Returns zero if none available.
-    long getAvailableRestoreToken(String packageName) {
+    public long getAvailableRestoreToken(String packageName) {
+        mContext.enforceCallingOrSelfPermission(android.Manifest.permission.BACKUP,
+                "getAvailableRestoreToken");
+
         long token = mAncestralToken;
         synchronized (mQueueLock) {
             if (mEverStoredApps.contains(packageName)) {

services/backup/java/com/android/server/backup/Trampoline.java

@@ -316,6 +316,12 @@ public class Trampoline extends IBackupManager.Stub {
         }
     }
 
+    @Override
+    public long getAvailableRestoreToken(String packageName) {
+        BackupManagerService svc = mService;
+        return (svc != null) ? svc.getAvailableRestoreToken(packageName) : 0;
+    }
+
     @Override
     public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
         mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DUMP, TAG);