Offer to cache ContentResolver-related Bundles.

There are a handful of core system services that collect data from
third-party ContentProviders by spinning them up and then caching the
results locally in memory.  However, if those apps are killed due to
low-memory pressure, they lose that cached data and have to collect
it again from scratch.  It's impossible for those apps to maintain a
correct cache when not running, since they'll miss out on Uri change
notifications.

To work around this, this change introducing a narrowly-scoped
caching mechanism that maps from Uris to Bundles.  The cache is
isolated per-user and per-calling-package, and internally it's
optimized to keep the Uri notification flow as fast as possible.
Each Bundle is invalidated whenever a notification event for a Uri
key is sent, or when the package hosting the provider is changed.

This change also wires up DocumentsUI to use this new mechanism,
which improves cold-start performance from 3300ms to 1800ms.  The
more DocumentsProviders a system has, the more pronounced this
benefit is.  Use BOOT_COMPLETED to build the cache at boot.

Add more permission docs, send a missing extra in DATA_CLEARED
broadcast.

Bug: 18406595
Change-Id: If3eae14bb3c69a8b83a65f530e081efc3b34d4bc
diff --git a/core/java/android/content/ContentResolver.java b/core/java/android/content/ContentResolver.java
index 4e1b6e0..441f188 100644
--- a/core/java/android/content/ContentResolver.java
+++ b/core/java/android/content/ContentResolver.java
@@ -2440,6 +2440,28 @@
         }
     }
 
+    /** {@hide} */
+    public void putCache(Uri key, Bundle value) {
+        try {
+            getContentService().putCache(mContext.getPackageName(), key, value,
+                    mContext.getUserId());
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
+    /** {@hide} */
+    public Bundle getCache(Uri key) {
+        try {
+            final Bundle bundle = getContentService().getCache(mContext.getPackageName(), key,
+                    mContext.getUserId());
+            if (bundle != null) bundle.setClassLoader(mContext.getClassLoader());
+            return bundle;
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
     /**
      * Returns sampling percentage for a given duration.
      *
diff --git a/core/java/android/content/IContentService.aidl b/core/java/android/content/IContentService.aidl
index 8b471a0..d47e780 100644
--- a/core/java/android/content/IContentService.aidl
+++ b/core/java/android/content/IContentService.aidl
@@ -179,6 +179,8 @@
             int userId);
 
     void addStatusChangeListener(int mask, ISyncStatusObserver callback);
-
     void removeStatusChangeListener(ISyncStatusObserver callback);
+
+    void putCache(in String packageName, in Uri key, in Bundle value, int userId);
+    Bundle getCache(in String packageName, in Uri key, int userId);
 }
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index fbc96c2..6444c6c 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -1483,11 +1483,21 @@
 
     <!-- Allows an application to manage access to documents, usually as part
          of a document picker.
+         <p>This permission should <em>only</em> be requested by the platform
+         document management app.  This permission cannot be granted to
+         third-party apps.
          <p>Protection level: signature
     -->
     <permission android:name="android.permission.MANAGE_DOCUMENTS"
         android:protectionLevel="signature" />
 
+    <!-- @hide Allows an application to cache content.
+         <p>Not for use by third-party applications.
+         <p>Protection level: signature
+    -->
+    <permission android:name="android.permission.CACHE_CONTENT"
+        android:protectionLevel="signature" />
+
     <!-- ================================== -->
     <!-- Permissions for screenlock         -->
     <!-- ================================== -->
diff --git a/packages/DocumentsUI/AndroidManifest.xml b/packages/DocumentsUI/AndroidManifest.xml
index 6f38e25..6fe239e 100644
--- a/packages/DocumentsUI/AndroidManifest.xml
+++ b/packages/DocumentsUI/AndroidManifest.xml
@@ -5,6 +5,8 @@
     <uses-permission android:name="android.permission.MANAGE_DOCUMENTS" />
     <uses-permission android:name="android.permission.REMOVE_TASKS" />
     <uses-permission android:name="android.permission.WAKE_LOCK" />
+    <uses-permission android:name="android.permission.CACHE_CONTENT" />
+    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
 
     <application
         android:name=".DocumentsApplication"
@@ -105,6 +107,12 @@
             </intent-filter>
         </receiver>
 
+        <receiver android:name=".BootReceiver">
+            <intent-filter>
+                <action android:name="android.intent.action.BOOT_COMPLETED" />
+            </intent-filter>
+        </receiver>
+
         <service
             android:name=".services.FileOperationService"
             android:exported="false">
diff --git a/packages/DocumentsUI/src/com/android/documentsui/BootReceiver.java b/packages/DocumentsUI/src/com/android/documentsui/BootReceiver.java
new file mode 100644
index 0000000..cdea9d7
--- /dev/null
+++ b/packages/DocumentsUI/src/com/android/documentsui/BootReceiver.java
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2016 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.documentsui;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+
+/**
+ * Prime {@link RootsCache} when the system is booted.
+ */
+public class BootReceiver extends BroadcastReceiver {
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        // We already spun up our application object before getting here, which
+        // kicked off a task to load roots, so this broadcast is finished once
+        // that first pass is done.
+        DocumentsApplication.getRootsCache(context).setBootCompletedResult(goAsync());
+    }
+}
diff --git a/packages/DocumentsUI/src/com/android/documentsui/RootsCache.java b/packages/DocumentsUI/src/com/android/documentsui/RootsCache.java
index 2b7294a..6efe9c8 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/RootsCache.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/RootsCache.java
@@ -18,6 +18,7 @@
 
 import static com.android.documentsui.Shared.DEBUG;
 
+import android.content.BroadcastReceiver.PendingResult;
 import android.content.ContentProviderClient;
 import android.content.ContentResolver;
 import android.content.Context;
@@ -30,6 +31,7 @@
 import android.database.Cursor;
 import android.net.Uri;
 import android.os.AsyncTask;
+import android.os.Bundle;
 import android.os.Handler;
 import android.os.SystemClock;
 import android.provider.DocumentsContract;
@@ -40,11 +42,11 @@
 import com.android.documentsui.model.RootInfo;
 import com.android.internal.annotations.GuardedBy;
 
+import libcore.io.IoUtils;
+
 import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.Multimap;
 
-import libcore.io.IoUtils;
-
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -63,6 +65,8 @@
 
     private static final String TAG = "RootsCache";
 
+    private static final boolean ENABLE_SYSTEM_CACHE = true;
+
     private final Context mContext;
     private final ContentObserver mObserver;
     private OnCacheUpdateListener mCacheUpdateListener;
@@ -73,6 +77,11 @@
     private final CountDownLatch mFirstLoad = new CountDownLatch(1);
 
     @GuardedBy("mLock")
+    private boolean mFirstLoadDone;
+    @GuardedBy("mLock")
+    private PendingResult mBootCompletedResult;
+
+    @GuardedBy("mLock")
     private Multimap<String, RootInfo> mRoots = ArrayListMultimap.create();
     @GuardedBy("mLock")
     private HashSet<String> mStoppedAuthorities = new HashSet<>();
@@ -118,7 +127,7 @@
     public void updateAsync() {
 
         // NOTE: This method is called when the UI language changes.
-        // For that reason we upadte our RecentsRoot to reflect
+        // For that reason we update our RecentsRoot to reflect
         // the current language.
         mRecentsRoot.title = mContext.getString(R.string.root_recent);
 
@@ -152,7 +161,25 @@
         }
     }
 
-    private void waitForFirstLoad() {
+    public void setBootCompletedResult(PendingResult result) {
+        synchronized (mLock) {
+            // Quickly check if we've already finished loading, otherwise hang
+            // out until first pass is finished.
+            if (mFirstLoadDone) {
+                result.finish();
+            } else {
+                mBootCompletedResult = result;
+            }
+        }
+    }
+
+    /**
+     * Block until the first {@link UpdateTask} pass has finished.
+     *
+     * @return {@code true} if cached roots is ready to roll, otherwise
+     *         {@code false} if we timed out while waiting.
+     */
+    private boolean waitForFirstLoad() {
         boolean success = false;
         try {
             success = mFirstLoad.await(15, TimeUnit.SECONDS);
@@ -161,6 +188,7 @@
         if (!success) {
             Log.w(TAG, "Timeout waiting for first update");
         }
+        return success;
     }
 
     /**
@@ -222,9 +250,11 @@
             final long start = SystemClock.elapsedRealtime();
 
             if (mFilterPackage != null) {
-                // Need at least first load, since we're going to be using
-                // previously cached values for non-matching packages.
-                waitForFirstLoad();
+                // We must have previously cached values to fill in non-matching
+                // packages, so wait around for successful first load.
+                if (!waitForFirstLoad()) {
+                    return null;
+                }
             }
 
             mTaskRoots.put(mRecentsRoot.authority, mRecentsRoot);
@@ -243,6 +273,11 @@
             if (DEBUG)
                 Log.d(TAG, "Update found " + mTaskRoots.size() + " roots in " + delta + "ms");
             synchronized (mLock) {
+                mFirstLoadDone = true;
+                if (mBootCompletedResult != null) {
+                    mBootCompletedResult.finish();
+                    mBootCompletedResult = null;
+                }
                 mRoots = mTaskRoots;
                 mStoppedAuthorities = mTaskStoppedAuthorities;
             }
@@ -300,9 +335,18 @@
             }
         }
 
-        final List<RootInfo> roots = new ArrayList<>();
         final Uri rootsUri = DocumentsContract.buildRootsUri(authority);
+        if (ENABLE_SYSTEM_CACHE) {
+            // Look for roots data that we might have cached for ourselves in the
+            // long-lived system process.
+            final Bundle systemCache = resolver.getCache(rootsUri);
+            if (systemCache != null) {
+                if (DEBUG) Log.d(TAG, "System cache hit for " + authority);
+                return systemCache.getParcelableArrayList(TAG);
+            }
+        }
 
+        final ArrayList<RootInfo> roots = new ArrayList<>();
         ContentProviderClient client = null;
         Cursor cursor = null;
         try {
@@ -318,6 +362,16 @@
             IoUtils.closeQuietly(cursor);
             ContentProviderClient.releaseQuietly(client);
         }
+
+        if (ENABLE_SYSTEM_CACHE) {
+            // Cache these freshly parsed roots over in the long-lived system
+            // process, in case our process goes away. The system takes care of
+            // invalidating the cache if the package or Uri changes.
+            final Bundle systemCache = new Bundle();
+            systemCache.putParcelableArrayList(TAG, roots);
+            resolver.putCache(rootsUri, systemCache);
+        }
+
         return roots;
     }
 
diff --git a/packages/DocumentsUI/src/com/android/documentsui/model/RootInfo.java b/packages/DocumentsUI/src/com/android/documentsui/model/RootInfo.java
index 3eaf10a..3960475 100644
--- a/packages/DocumentsUI/src/com/android/documentsui/model/RootInfo.java
+++ b/packages/DocumentsUI/src/com/android/documentsui/model/RootInfo.java
@@ -55,7 +55,7 @@
     private static final int VERSION_DROP_TYPE = 2;
 
     // The values of these constants determine the sort order of various roots in the RootsFragment.
-    @IntDef(flag = true, value = {
+    @IntDef(flag = false, value = {
             TYPE_IMAGES,
             TYPE_VIDEO,
             TYPE_AUDIO,
diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 07f668b..f99d035 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -5347,6 +5347,7 @@
                 Intent intent = new Intent(Intent.ACTION_PACKAGE_DATA_CLEARED,
                         Uri.fromParts("package", packageName, null));
                 intent.putExtra(Intent.EXTRA_UID, pkgUid);
+                intent.putExtra(Intent.EXTRA_USER_HANDLE, UserHandle.getUserId(pkgUid));
                 broadcastIntentInPackage("android", Process.SYSTEM_UID, intent,
                         null, null, 0, null, null, null, null, false, false, userId);
             } catch (RemoteException e) {
diff --git a/services/core/java/com/android/server/content/ContentService.java b/services/core/java/com/android/server/content/ContentService.java
index 212e077..03191a0 100644
--- a/services/core/java/com/android/server/content/ContentService.java
+++ b/services/core/java/com/android/server/content/ContentService.java
@@ -18,12 +18,16 @@
 
 import android.Manifest;
 import android.accounts.Account;
+import android.annotation.Nullable;
 import android.app.ActivityManager;
+import android.app.AppOpsManager;
+import android.content.BroadcastReceiver;
 import android.content.ComponentName;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.content.IContentService;
 import android.content.Intent;
+import android.content.IntentFilter;
 import android.content.ISyncStatusObserver;
 import android.content.PeriodicSync;
 import android.content.SyncAdapterType;
@@ -32,6 +36,7 @@
 import android.content.SyncStatusInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManagerInternal;
+import android.content.pm.ProviderInfo;
 import android.database.IContentObserver;
 import android.database.sqlite.SQLiteException;
 import android.net.Uri;
@@ -44,30 +49,64 @@
 import android.os.SystemProperties;
 import android.os.UserHandle;
 import android.text.TextUtils;
+import android.util.ArrayMap;
 import android.util.Log;
+import android.util.Pair;
 import android.util.Slog;
+import android.util.SparseArray;
 import android.util.SparseIntArray;
+
+import com.android.internal.annotations.GuardedBy;
+import com.android.internal.util.IndentingPrintWriter;
+import com.android.internal.util.Preconditions;
 import com.android.server.LocalServices;
 
 import java.io.FileDescriptor;
 import java.io.PrintWriter;
 import java.security.InvalidParameterException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * {@hide}
  */
 public final class ContentService extends IContentService.Stub {
     private static final String TAG = "ContentService";
+
     private Context mContext;
     private boolean mFactoryTest;
+
     private final ObserverNode mRootNode = new ObserverNode("");
+
     private SyncManager mSyncManager = null;
     private final Object mSyncManagerLock = new Object();
 
+    /**
+     * Map from userId to providerPackageName to [clientPackageName, uri] to
+     * value. This structure is carefully optimized to keep invalidation logic
+     * as cheap as possible.
+     */
+    @GuardedBy("mCache")
+    private final SparseArray<ArrayMap<String, ArrayMap<Pair<String, Uri>, Bundle>>>
+            mCache = new SparseArray<>();
+
+    private BroadcastReceiver mCacheReceiver = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            final Uri data = intent.getData();
+            if (data != null) {
+                final int userId = intent.getIntExtra(Intent.EXTRA_USER_HANDLE,
+                        UserHandle.USER_NULL);
+                final String packageName = data.getSchemeSpecificPart();
+                invalidateCacheLocked(userId, packageName, null);
+            }
+        }
+    };
+
     private SyncManager getSyncManager() {
         if (SystemProperties.getBoolean("config.disable_network", false)) {
             return null;
@@ -85,13 +124,15 @@
     }
 
     @Override
-    protected synchronized void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
+    protected synchronized void dump(FileDescriptor fd, PrintWriter pw_, String[] args) {
         mContext.enforceCallingOrSelfPermission(Manifest.permission.DUMP,
                 "caller doesn't have the DUMP permission");
 
+        final IndentingPrintWriter pw = new IndentingPrintWriter(pw_, "  ");
+
         // This makes it so that future permission checks will be in the context of this
         // process rather than the caller's process. We will restore this before returning.
-        long identityToken = clearCallingIdentity();
+        final long identityToken = clearCallingIdentity();
         try {
             if (mSyncManager == null) {
                 pw.println("No SyncManager created!  (Disk full?)");
@@ -132,6 +173,19 @@
                 pw.print(" Total number of nodes: "); pw.println(counts[0]);
                 pw.print(" Total number of observers: "); pw.println(counts[1]);
             }
+
+            synchronized (mCache) {
+                pw.println();
+                pw.println("Cached content:");
+                pw.increaseIndent();
+                for (int i = 0; i < mCache.size(); i++) {
+                    pw.println("User " + mCache.keyAt(i) + ":");
+                    pw.increaseIndent();
+                    pw.println(mCache.valueAt(i));
+                    pw.decreaseIndent();
+                }
+                pw.decreaseIndent();
+            }
         } finally {
             restoreCallingIdentity(identityToken);
         }
@@ -167,6 +221,15 @@
                         return getSyncAdapterPackagesForAuthorityAsUser(authority, userId);
                     }
                 });
+
+        final IntentFilter packageFilter = new IntentFilter();
+        packageFilter.addAction(Intent.ACTION_PACKAGE_ADDED);
+        packageFilter.addAction(Intent.ACTION_PACKAGE_CHANGED);
+        packageFilter.addAction(Intent.ACTION_PACKAGE_REMOVED);
+        packageFilter.addAction(Intent.ACTION_PACKAGE_DATA_CLEARED);
+        packageFilter.addDataScheme("package");
+        mContext.registerReceiverAsUser(mCacheReceiver, UserHandle.ALL,
+                packageFilter, null, null);
     }
 
     public void systemReady() {
@@ -312,6 +375,11 @@
                             uri.getAuthority());
                 }
             }
+
+            synchronized (mCache) {
+                final String providerPackageName = getProviderPackageName(uri);
+                invalidateCacheLocked(userHandle, providerPackageName, uri);
+            }
         } finally {
             restoreCallingIdentity(identityToken);
         }
@@ -915,6 +983,86 @@
         }
     }
 
+    private @Nullable String getProviderPackageName(Uri uri) {
+        final ProviderInfo pi = mContext.getPackageManager()
+                .resolveContentProvider(uri.getAuthority(), 0);
+        return (pi != null) ? pi.packageName : null;
+    }
+
+    private ArrayMap<Pair<String, Uri>, Bundle> findOrCreateCacheLocked(int userId,
+            String providerPackageName) {
+        ArrayMap<String, ArrayMap<Pair<String, Uri>, Bundle>> userCache = mCache.get(userId);
+        if (userCache == null) {
+            userCache = new ArrayMap<>();
+            mCache.put(userId, userCache);
+        }
+        ArrayMap<Pair<String, Uri>, Bundle> packageCache = userCache.get(providerPackageName);
+        if (packageCache == null) {
+            packageCache = new ArrayMap<>();
+            userCache.put(providerPackageName, packageCache);
+        }
+        return packageCache;
+    }
+
+    private void invalidateCacheLocked(int userId, String providerPackageName, Uri uri) {
+        ArrayMap<String, ArrayMap<Pair<String, Uri>, Bundle>> userCache = mCache.get(userId);
+        if (userCache == null) return;
+
+        ArrayMap<Pair<String, Uri>, Bundle> packageCache = userCache.get(providerPackageName);
+        if (packageCache == null) return;
+
+        if (uri != null) {
+            for (int i = 0; i < packageCache.size();) {
+                final Uri key = packageCache.keyAt(i).second;
+                if (Objects.equals(key, uri)) {
+                    packageCache.removeAt(i);
+                } else {
+                    i++;
+                }
+            }
+        } else {
+            packageCache.clear();
+        }
+    }
+
+    @Override
+    public void putCache(String packageName, Uri key, Bundle value, int userId) {
+        enforceCrossUserPermission(userId, TAG);
+        mContext.enforceCallingOrSelfPermission(android.Manifest.permission.CACHE_CONTENT, TAG);
+        mContext.getSystemService(AppOpsManager.class).checkPackage(Binder.getCallingUid(),
+                packageName);
+
+        final String providerPackageName = getProviderPackageName(key);
+        final Pair<String, Uri> fullKey = Pair.create(packageName, key);
+
+        synchronized (mCache) {
+            final ArrayMap<Pair<String, Uri>, Bundle> cache = findOrCreateCacheLocked(userId,
+                    providerPackageName);
+            if (value != null) {
+                cache.put(fullKey, value);
+            } else {
+                cache.remove(fullKey);
+            }
+        }
+    }
+
+    @Override
+    public Bundle getCache(String packageName, Uri key, int userId) {
+        enforceCrossUserPermission(userId, TAG);
+        mContext.enforceCallingOrSelfPermission(android.Manifest.permission.CACHE_CONTENT, TAG);
+        mContext.getSystemService(AppOpsManager.class).checkPackage(Binder.getCallingUid(),
+                packageName);
+
+        final String providerPackageName = getProviderPackageName(key);
+        final Pair<String, Uri> fullKey = Pair.create(packageName, key);
+
+        synchronized (mCache) {
+            final ArrayMap<Pair<String, Uri>, Bundle> cache = findOrCreateCacheLocked(userId,
+                    providerPackageName);
+            return cache.get(fullKey);
+        }
+    }
+
     public static ContentService main(Context context, boolean factoryTest) {
         ContentService service = new ContentService(context, factoryTest);
         ServiceManager.addService(ContentResolver.CONTENT_SERVICE_NAME, service);