content: /*
   * 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.server.wm;
  
  import android.annotation.Nullable;
  import android.app.ActivityManager.TaskSnapshot;
  import android.util.ArrayMap;
  import android.util.LruCache;
  
  import java.io.PrintWriter;
  import java.util.Map;
  import java.util.Map.Entry;
  
  /**
   * Caches snapshots. See {@link TaskSnapshotController}.
   * <p>
   * Access to this class should be guarded by the global window manager lock.
   */
  class TaskSnapshotCache {
  
      private final WindowManagerService mService;
      private final TaskSnapshotLoader mLoader;
      private final ArrayMap<AppWindowToken, Integer> mAppTaskMap = new ArrayMap<>();
      private final ArrayMap<Integer, CacheEntry> mRunningCache = new ArrayMap<>();
  
      TaskSnapshotCache(WindowManagerService service, TaskSnapshotLoader loader) {
          mService = service;
          mLoader = loader;
      }
  
      void putSnapshot(Task task, TaskSnapshot snapshot) {
          final CacheEntry entry = mRunningCache.get(task.mTaskId);
          if (entry != null) {
              mAppTaskMap.remove(entry.topApp);
          }
          final AppWindowToken top = task.getTopChild();
          mAppTaskMap.put(top, task.mTaskId);
          mRunningCache.put(task.mTaskId, new CacheEntry(snapshot, task.getTopChild()));
      }
  
      /**
       * If {@param restoreFromDisk} equals {@code true}, DO NOT HOLD THE WINDOW MANAGER LOCK!
       */
      @Nullable TaskSnapshot getSnapshot(int taskId, int userId, boolean restoreFromDisk,
              boolean reducedResolution) {
  
          synchronized (mService.mGlobalLock) {
              // Try the running cache.
              final CacheEntry entry = mRunningCache.get(taskId);
              if (entry != null) {
                  return entry.snapshot;
              }
          }
  
          // Try to restore from disk if asked.
          if (!restoreFromDisk) {
              return null;
          }
          return tryRestoreFromDisk(taskId, userId, reducedResolution);
      }
  
      /**
       * DO NOT HOLD THE WINDOW MANAGER LOCK WHEN CALLING THIS METHOD!
       */
      private TaskSnapshot tryRestoreFromDisk(int taskId, int userId, boolean reducedResolution) {
          final TaskSnapshot snapshot = mLoader.loadTask(taskId, userId, reducedResolution);
          if (snapshot == null) {
              return null;
          }
          return snapshot;
      }
  
      /**
       * Called when an app token has been removed
       */
      void onAppRemoved(AppWindowToken wtoken) {
          final Integer taskId = mAppTaskMap.get(wtoken);
          if (taskId != null) {
              removeRunningEntry(taskId);
          }
      }
  
      /**
       * Callend when an app window token's process died.
       */
      void onAppDied(AppWindowToken wtoken) {
          final Integer taskId = mAppTaskMap.get(wtoken);
          if (taskId != null) {
              removeRunningEntry(taskId);
          }
      }
  
      void onTaskRemoved(int taskId) {
          removeRunningEntry(taskId);
      }
  
      private void removeRunningEntry(int taskId) {
          final CacheEntry entry = mRunningCache.get(taskId);
          if (entry != null) {
              mAppTaskMap.remove(entry.topApp);
              mRunningCache.remove(taskId);
          }
      }
  
      void dump(PrintWriter pw, String prefix) {
          final String doublePrefix = prefix + "  ";
          final String triplePrefix = doublePrefix + "  ";
          pw.println(prefix + "SnapshotCache");
          for (int i = mRunningCache.size() - 1; i >= 0; i--) {
              final CacheEntry entry = mRunningCache.valueAt(i);
              pw.println(doublePrefix + "Entry taskId=" + mRunningCache.keyAt(i));
              pw.println(triplePrefix + "topApp=" + entry.topApp);
              pw.println(triplePrefix + "snapshot=" + entry.snapshot);
          }
      }
  
      private static final class CacheEntry {
  
          /** The snapshot. */
          final TaskSnapshot snapshot;
  
          /** The app token that was on top of the task when the snapshot was taken */
          final AppWindowToken topApp;
  
          CacheEntry(TaskSnapshot snapshot, AppWindowToken topApp) {
              this.snapshot = snapshot;
              this.topApp = topApp;
          }
      }
  }
  