Recents backup helper

Handles backup/restore of recent tasks for the system.  Currently the
thumbnails are not saved.

At restore time the historical task records are placed in a designated
separate location rather than directly in the live bookkeeping; this
avoids ID duplication issues and makes it easier to deal with lazy
adoption of the historical task state as apps are installed on the
device post-restore.

Bug 17303286
Bug 15986349

Change-Id: Ie156c1e2ab9c9a7e7ac0447b27016fdcef55dded

1 files changed, 114 insertions, 0 deletions

diff --git a/core/java/android/app/backup/RecentsBackupHelper.java b/core/java/android/app/backup/RecentsBackupHelper.java
new file mode 100644
index 0000000..fd69d20
--- /dev/null
+++ b/core/java/android/app/backup/RecentsBackupHelper.java
@@ -0,0 +1,114 @@
+package android.app.backup;
+
+import android.content.Context;
+import android.os.Environment;
+import android.os.ParcelFileDescriptor;
+import android.util.Slog;
+
+import java.io.File;
+
+/**
+ * Helper for saving/restoring 'recent tasks' infrastructure.
+ * @hide
+ */
+public class RecentsBackupHelper implements BackupHelper {
+    private static final String TAG = "RecentsBackup";
+    private static final boolean DEBUG = false;
+
+    // This must match TaskPersister.TASKS_DIRNAME, but that class is not accessible from here
+    private static final String RECENTS_TASK_DIR = "recent_tasks";
+
+    // Must match TaskPersister.IMAGES_DIRNAME, as above
+    private static final String RECENTS_IMAGE_DIR = "recent_images";
+
+    // At restore time, tasks/thumbnails are placed in these directories alongside
+    // the "live" recents dirs named above.
+    private static final String RECENTS_TASK_RESTORE_DIR = "restored_" + RECENTS_TASK_DIR;
+    private static final String RECENTS_IMAGE_RESTORE_DIR = "restored_" + RECENTS_IMAGE_DIR;
+
+    // Prefixes for tagging the two kinds of recents backup records that we might generate
+    private static final String RECENTS_TASK_KEY = "task:";
+    private static final String RECENTS_IMAGE_KEY = "image:";
+
+    FileBackupHelperBase mTaskFileHelper;
+
+    final File mSystemDir;
+    final File mTasksDir;
+    final File mRestoredTasksDir;
+    final File mRestoredImagesDir;
+    final String[] mRecentFiles;
+    final String[] mRecentKeys;
+
+    /**
+     * @param context The agent context in which this helper instance will run
+     */
+    public RecentsBackupHelper(Context context) {
+        mTaskFileHelper = new FileBackupHelperBase(context);
+
+        mSystemDir = new File(Environment.getDataDirectory(), "system");
+        mTasksDir = new File(mSystemDir, RECENTS_TASK_DIR);
+        mRestoredTasksDir = new File(mSystemDir, RECENTS_TASK_RESTORE_DIR);
+        mRestoredImagesDir = new File(mSystemDir, RECENTS_IMAGE_RESTORE_DIR);
+
+        // Currently we back up only the recent-task descriptions, not the thumbnails
+        File[] recentFiles = mTasksDir.listFiles();
+        if (recentFiles != null) {
+            // We explicitly proceed even if this is a zero-size array
+            final int N = recentFiles.length;
+            mRecentKeys = new String[N];
+            mRecentFiles = new String[N];
+            if (DEBUG) {
+                Slog.i(TAG, "Identifying recents for backup: " + N);
+            }
+            for (int i = 0; i < N; i++) {
+                mRecentKeys[i] = new String(RECENTS_TASK_KEY + recentFiles[i].getName());
+                mRecentFiles[i] = recentFiles[i].getAbsolutePath();
+                if (DEBUG) {
+                    Slog.i(TAG, "   " + mRecentKeys[i]);
+                }
+            }
+        } else {
+            mRecentFiles = mRecentKeys = new String[0];
+        }
+    }
+
+    /**
+     * Task-file key:  RECENTS_TASK_KEY + leaf filename
+     * Thumbnail-file key: RECENTS_IMAGE_KEY + leaf filename
+     */
+    @Override
+    public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
+            ParcelFileDescriptor newState) {
+        FileBackupHelperBase.performBackup_checked(oldState, data, newState,
+                mRecentFiles, mRecentKeys);
+    }
+
+    @Override
+    public void restoreEntity(BackupDataInputStream data) {
+        final String key = data.getKey();
+        File output = null;
+        if (key.startsWith(RECENTS_TASK_KEY)) {
+            String name = key.substring(RECENTS_TASK_KEY.length());
+            output = new File(mRestoredTasksDir, name);
+            mRestoredTasksDir.mkdirs();
+        } else if (key.startsWith(RECENTS_IMAGE_KEY)) {
+            String name = key.substring(RECENTS_IMAGE_KEY.length());
+            output = new File(mRestoredImagesDir, name);
+            mRestoredImagesDir.mkdirs();
+        }
+
+        if (output != null) {
+            if (DEBUG) {
+                Slog.i(TAG, "Restoring key='"
+                        + key + "' to " + output.getAbsolutePath());
+            }
+            mTaskFileHelper.writeFile(output, data);
+        }
+    }
+
+    @Override
+    public void writeNewStateDescription(ParcelFileDescriptor newState) {
+        mTaskFileHelper.writeNewStateDescription(newState);
+    }
+
+}