content: /*
   * 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 com.android.server;
  
  import android.app.ActivityManager;
  import android.app.AppOpsManager;
  import android.content.BroadcastReceiver;
  import android.content.ContentResolver;
  import android.content.Context;
  import android.content.Intent;
  import android.content.IntentFilter;
  import android.content.res.Resources;
  import android.database.ContentObserver;
  import android.net.Uri;
  import android.os.Binder;
  import android.os.Debug;
  import android.os.DropBoxManager;
  import android.os.FileUtils;
  import android.os.Handler;
  import android.os.Looper;
  import android.os.Message;
  import android.os.ResultReceiver;
  import android.os.ShellCallback;
  import android.os.ShellCommand;
  import android.os.StatFs;
  import android.os.SystemClock;
  import android.os.UserHandle;
  import android.provider.Settings;
  import android.text.TextUtils;
  import android.text.format.Time;
  import android.util.ArrayMap;
  import android.util.ArraySet;
  import android.util.Slog;
  
  import com.android.internal.R;
  import com.android.internal.annotations.GuardedBy;
  import com.android.internal.annotations.VisibleForTesting;
  import com.android.internal.os.IDropBoxManagerService;
  import com.android.internal.util.DumpUtils;
  import com.android.internal.util.ObjectUtils;
  
  import libcore.io.IoUtils;
  
  import java.io.BufferedOutputStream;
  import java.io.File;
  import java.io.FileDescriptor;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.OutputStream;
  import java.io.PrintWriter;
  import java.util.ArrayList;
  import java.util.SortedSet;
  import java.util.TreeSet;
  import java.util.zip.GZIPOutputStream;
  
  /**
   * Implementation of {@link IDropBoxManagerService} using the filesystem.
   * Clients use {@link DropBoxManager} to access this service.
   */
  public final class DropBoxManagerService extends SystemService {
      private static final String TAG = "DropBoxManagerService";
      private static final int DEFAULT_AGE_SECONDS = 3 * 86400;
      private static final int DEFAULT_MAX_FILES = 1000;
      private static final int DEFAULT_MAX_FILES_LOWRAM = 300;
      private static final int DEFAULT_QUOTA_KB = 5 * 1024;
      private static final int DEFAULT_QUOTA_PERCENT = 10;
      private static final int DEFAULT_RESERVE_PERCENT = 10;
      private static final int QUOTA_RESCAN_MILLIS = 5000;
  
      private static final boolean PROFILE_DUMP = false;
  
      // TODO: This implementation currently uses one file per entry, which is
      // inefficient for smallish entries -- consider using a single queue file
      // per tag (or even globally) instead.
  
      // The cached context and derived objects
  
      private final ContentResolver mContentResolver;
      private final File mDropBoxDir;
  
      // Accounting of all currently written log files (set in init()).
  
      private FileList mAllFiles = null;
      private ArrayMap<String, FileList> mFilesByTag = null;
  
      private long mLowPriorityRateLimitPeriod = 0;
      private ArraySet<String> mLowPriorityTags = null;
  
      // Various bits of disk information
  
      private StatFs mStatFs = null;
      private int mBlockSize = 0;
      private int mCachedQuotaBlocks = 0;  // Space we can use: computed from free space, etc.
      private long mCachedQuotaUptimeMillis = 0;
  
      private volatile boolean mBooted = false;
  
      // Provide a way to perform sendBroadcast asynchronously to avoid deadlocks.
      private final DropBoxManagerBroadcastHandler mHandler;
  
      private int mMaxFiles = -1; // -1 means uninitialized.
  
      /** Receives events that might indicate a need to clean up files. */
      private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
          @Override
          public void onReceive(Context context, Intent intent) {
              // For ACTION_DEVICE_STORAGE_LOW:
              mCachedQuotaUptimeMillis = 0;  // Force a re-check of quota size
  
              // Run the initialization in the background (not this main thread).
              // The init() and trimToFit() methods are synchronized, so they still
              // block other users -- but at least the onReceive() call can finish.
              new Thread() {
                  public void run() {
                      try {
                          init();
                          trimToFit();
                      } catch (IOException e) {
                          Slog.e(TAG, "Can't init", e);
                      }
                  }
              }.start();
          }
      };
  
      private final IDropBoxManagerService.Stub mStub = new IDropBoxManagerService.Stub() {
          @Override
          public void add(DropBoxManager.Entry entry) {
              DropBoxManagerService.this.add(entry);
          }
  
          @Override
          public boolean isTagEnabled(String tag) {
              return DropBoxManagerService.this.isTagEnabled(tag);
          }
  
          @Override
          public DropBoxManager.Entry getNextEntry(String tag, long millis, String callingPackage) {
              return DropBoxManagerService.this.getNextEntry(tag, millis, callingPackage);
          }
  
          @Override
          public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
              DropBoxManagerService.this.dump(fd, pw, args);
          }
  
          @Override
          public void onShellCommand(FileDescriptor in, FileDescriptor out,
                                     FileDescriptor err, String[] args, ShellCallback callback,
                                     ResultReceiver resultReceiver) {
              (new ShellCmd()).exec(this, in, out, err, args, callback, resultReceiver);
          }
      };
  
      private class ShellCmd extends ShellCommand {
          @Override
          public int onCommand(String cmd) {
              if (cmd == null) {
                  return handleDefaultCommands(cmd);
              }
              final PrintWriter pw = getOutPrintWriter();
              try {
                  switch (cmd) {
                      case "set-rate-limit":
                          final long period = Long.parseLong(getNextArgRequired());
                          DropBoxManagerService.this.setLowPriorityRateLimit(period);
                          break;
                      case "add-low-priority":
                          final String addedTag = getNextArgRequired();
                          DropBoxManagerService.this.addLowPriorityTag(addedTag);
                          break;
                      case "remove-low-priority":
                          final String removeTag = getNextArgRequired();
                          DropBoxManagerService.this.removeLowPriorityTag(removeTag);
                          break;
                      case "restore-defaults":
                          DropBoxManagerService.this.restoreDefaults();
                          break;
                      default:
                          return handleDefaultCommands(cmd);
                  }
              } catch (Exception e) {
                  pw.println(e);
              }
              return 0;
          }
  
          @Override
          public void onHelp() {
              PrintWriter pw = getOutPrintWriter();
              pw.println("Dropbox manager service commands:");
              pw.println("  help");
              pw.println("    Print this help text.");
              pw.println("  set-rate-limit PERIOD");
              pw.println("    Sets low priority broadcast rate limit period to PERIOD ms");
              pw.println("  add-low-priority TAG");
              pw.println("    Add TAG to dropbox low priority list");
              pw.println("  remove-low-priority TAG");
              pw.println("    Remove TAG from dropbox low priority list");
              pw.println("  restore-defaults");
              pw.println("    restore dropbox settings to defaults");
          }
      }
  
      private class DropBoxManagerBroadcastHandler extends Handler {
          private final Object mLock = new Object();
  
          static final int MSG_SEND_BROADCAST = 1;
          static final int MSG_SEND_DEFERRED_BROADCAST = 2;
  
          @GuardedBy("mLock")
          private final ArrayMap<String, Intent> mDeferredMap = new ArrayMap();
  
          DropBoxManagerBroadcastHandler(Looper looper) {
              super(looper);
          }
  
          @Override
          public void handleMessage(Message msg) {
              switch (msg.what) {
                  case MSG_SEND_BROADCAST:
                      prepareAndSendBroadcast((Intent) msg.obj);
                      break;
                  case MSG_SEND_DEFERRED_BROADCAST:
                      Intent deferredIntent;
                      synchronized (mLock) {
                          deferredIntent = mDeferredMap.remove((String) msg.obj);
                      }
                      if (deferredIntent != null) {
                          prepareAndSendBroadcast(deferredIntent);
                      }
                      break;
              }
          }
  
          private void prepareAndSendBroadcast(Intent intent) {
              if (!DropBoxManagerService.this.mBooted) {
                  intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
              }
              getContext().sendBroadcastAsUser(intent, UserHandle.SYSTEM,
                      android.Manifest.permission.READ_LOGS);
          }
  
          private Intent createIntent(String tag, long time) {
              final Intent dropboxIntent = new Intent(DropBoxManager.ACTION_DROPBOX_ENTRY_ADDED);
              dropboxIntent.putExtra(DropBoxManager.EXTRA_TAG, tag);
              dropboxIntent.putExtra(DropBoxManager.EXTRA_TIME, time);
              return dropboxIntent;
          }
  
          /**
           * Schedule a dropbox broadcast to be sent asynchronously.
           */
          public void sendBroadcast(String tag, long time) {
              sendMessage(obtainMessage(MSG_SEND_BROADCAST, createIntent(tag, time)));
          }
  
          /**
           * Possibly schedule a delayed dropbox broadcast. The broadcast will only be scheduled if
           * no broadcast is currently scheduled. Otherwise updated the scheduled broadcast with the
           * new intent information, effectively dropping the previous broadcast.
           */
          public void maybeDeferBroadcast(String tag, long time) {
              synchronized (mLock) {
                  final Intent intent = mDeferredMap.get(tag);
                  if (intent == null) {
                      // Schedule new delayed broadcast.
                      mDeferredMap.put(tag, createIntent(tag, time));
                      sendMessageDelayed(obtainMessage(MSG_SEND_DEFERRED_BROADCAST, tag),
                              mLowPriorityRateLimitPeriod);
                  } else {
                      // Broadcast is already scheduled. Update intent with new data.
                      intent.putExtra(DropBoxManager.EXTRA_TIME, time);
                      final int dropped = intent.getIntExtra(DropBoxManager.EXTRA_DROPPED_COUNT, 0);
                      intent.putExtra(DropBoxManager.EXTRA_DROPPED_COUNT, dropped + 1);
                      return;
                  }
              }
          }
      }
  
      /**
       * Creates an instance of managed drop box storage using the default dropbox
       * directory.
       *
       * @param context to use for receiving free space & gservices intents
       */
      public DropBoxManagerService(final Context context) {
          this(context, new File("/data/system/dropbox"), FgThread.get().getLooper());
      }
  
      /**
       * Creates an instance of managed drop box storage.  Normally there is one of these
       * run by the system, but others can be created for testing and other purposes.
       *
       * @param context to use for receiving free space & gservices intents
       * @param path to store drop box entries in
       */
      @VisibleForTesting
      public DropBoxManagerService(final Context context, File path, Looper looper) {
          super(context);
          mDropBoxDir = path;
          mContentResolver = getContext().getContentResolver();
          mHandler = new DropBoxManagerBroadcastHandler(looper);
      }
  
      @Override
      public void onStart() {
          publishBinderService(Context.DROPBOX_SERVICE, mStub);
  
          // The real work gets done lazily in init() -- that way service creation always
          // succeeds, and things like disk problems cause individual method failures.
      }
  
      @Override
      public void onBootPhase(int phase) {
          switch (phase) {
              case PHASE_SYSTEM_SERVICES_READY:
                  IntentFilter filter = new IntentFilter();
                  filter.addAction(Intent.ACTION_DEVICE_STORAGE_LOW);
                  getContext().registerReceiver(mReceiver, filter);
  
                  mContentResolver.registerContentObserver(
                      Settings.Global.CONTENT_URI, true,
                      new ContentObserver(new Handler()) {
                          @Override
                          public void onChange(boolean selfChange) {
                              mReceiver.onReceive(getContext(), (Intent) null);
                          }
                      });
  
                  getLowPriorityResourceConfigs();
                  break;
  
              case PHASE_BOOT_COMPLETED:
                  mBooted = true;
                  break;
          }
      }
  
      /** Retrieves the binder stub -- for test instances */
      public IDropBoxManagerService getServiceStub() {
          return mStub;
      }
  
      public void add(DropBoxManager.Entry entry) {
          File temp = null;
          InputStream input = null;
          OutputStream output = null;
          final String tag = entry.getTag();
          try {
              int flags = entry.getFlags();
              Slog.i(TAG, "add tag=" + tag + " isTagEnabled=" + isTagEnabled(tag)
                      + " flags=0x" + Integer.toHexString(flags));
              if ((flags & DropBoxManager.IS_EMPTY) != 0) throw new IllegalArgumentException();
  
              init();
              if (!isTagEnabled(tag)) return;
              long max = trimToFit();
              long lastTrim = System.currentTimeMillis();
  
              byte[] buffer = new byte[mBlockSize];
              input = entry.getInputStream();
  
              // First, accumulate up to one block worth of data in memory before
              // deciding whether to compress the data or not.
  
              int read = 0;
              while (read < buffer.length) {
                  int n = input.read(buffer, read, buffer.length - read);
                  if (n <= 0) break;
                  read += n;
              }
  
              // If we have at least one block, compress it -- otherwise, just write
              // the data in uncompressed form.
  
              temp = new File(mDropBoxDir, "drop" + Thread.currentThread().getId() + ".tmp");
              int bufferSize = mBlockSize;
              if (bufferSize > 4096) bufferSize = 4096;
              if (bufferSize < 512) bufferSize = 512;
              FileOutputStream foutput = new FileOutputStream(temp);
              output = new BufferedOutputStream(foutput, bufferSize);
              if (read == buffer.length && ((flags & DropBoxManager.IS_GZIPPED) == 0)) {
                  output = new GZIPOutputStream(output);
                  flags = flags | DropBoxManager.IS_GZIPPED;
              }
  
              do {
                  output.write(buffer, 0, read);
  
                  long now = System.currentTimeMillis();
                  if (now - lastTrim > 30 * 1000) {
                      max = trimToFit();  // In case data dribbles in slowly
                      lastTrim = now;
                  }
  
                  read = input.read(buffer);
                  if (read <= 0) {
                      FileUtils.sync(foutput);
                      output.close();  // Get a final size measurement
                      output = null;
                  } else {
                      output.flush();  // So the size measurement is pseudo-reasonable
                  }
  
                  long len = temp.length();
                  if (len > max) {
                      Slog.w(TAG, "Dropping: " + tag + " (" + temp.length() + " > "
                              + max + " bytes)");
                      temp.delete();
                      temp = null;  // Pass temp = null to createEntry() to leave a tombstone
                      break;
                  }
              } while (read > 0);
  
              long time = createEntry(temp, tag, flags);
              temp = null;
  
              // Call sendBroadcast after returning from this call to avoid deadlock. In particular
              // the caller may be holding the WindowManagerService lock but sendBroadcast requires a
              // lock in ActivityManagerService. ActivityManagerService has been caught holding that
              // very lock while waiting for the WindowManagerService lock.
              if (mLowPriorityTags != null && mLowPriorityTags.contains(tag)) {
                  // Rate limit low priority Dropbox entries
                  mHandler.maybeDeferBroadcast(tag, time);
              } else {
                  mHandler.sendBroadcast(tag, time);
              }
          } catch (IOException e) {
              Slog.e(TAG, "Can't write: " + tag, e);
          } finally {
              IoUtils.closeQuietly(output);
              IoUtils.closeQuietly(input);
              entry.close();
              if (temp != null) temp.delete();
          }
      }
  
      public boolean isTagEnabled(String tag) {
          final long token = Binder.clearCallingIdentity();
          try {
              return !"disabled".equals(Settings.Global.getString(
                      mContentResolver, Settings.Global.DROPBOX_TAG_PREFIX + tag));
          } finally {
              Binder.restoreCallingIdentity(token);
          }
      }
  
      private boolean checkPermission(int callingUid, String callingPackage) {
          // Callers always need this permission
          getContext().enforceCallingOrSelfPermission(
                  android.Manifest.permission.READ_LOGS, TAG);
  
          // Callers also need the ability to read usage statistics
          switch (getContext().getSystemService(AppOpsManager.class)
                  .noteOp(AppOpsManager.OP_GET_USAGE_STATS, callingUid, callingPackage)) {
              case AppOpsManager.MODE_ALLOWED:
                  return true;
              case AppOpsManager.MODE_DEFAULT:
                  getContext().enforceCallingOrSelfPermission(
                          android.Manifest.permission.PACKAGE_USAGE_STATS, TAG);
                  return true;
              default:
                  return false;
          }
      }
  
      public synchronized DropBoxManager.Entry getNextEntry(String tag, long millis,
              String callingPackage) {
          if (!checkPermission(Binder.getCallingUid(), callingPackage)) {
              return null;
          }
  
          try {
              init();
          } catch (IOException e) {
              Slog.e(TAG, "Can't init", e);
              return null;
          }
  
          FileList list = tag == null ? mAllFiles : mFilesByTag.get(tag);
          if (list == null) return null;
  
          for (EntryFile entry : list.contents.tailSet(new EntryFile(millis + 1))) {
              if (entry.tag == null) continue;
              if ((entry.flags & DropBoxManager.IS_EMPTY) != 0) {
                  return new DropBoxManager.Entry(entry.tag, entry.timestampMillis);
              }
              final File file = entry.getFile(mDropBoxDir);
              try {
                  return new DropBoxManager.Entry(
                          entry.tag, entry.timestampMillis, file, entry.flags);
              } catch (IOException e) {
                  Slog.wtf(TAG, "Can't read: " + file, e);
                  // Continue to next file
              }
          }
  
          return null;
      }
  
      private synchronized void setLowPriorityRateLimit(long period) {
          mLowPriorityRateLimitPeriod = period;
      }
  
      private synchronized void addLowPriorityTag(String tag) {
          mLowPriorityTags.add(tag);
      }
  
      private synchronized void removeLowPriorityTag(String tag) {
          mLowPriorityTags.remove(tag);
      }
  
      private synchronized void restoreDefaults() {
          getLowPriorityResourceConfigs();
      }
  
      public synchronized void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
          if (!DumpUtils.checkDumpAndUsageStatsPermission(getContext(), TAG, pw)) return;
  
          try {
              init();
          } catch (IOException e) {
              pw.println("Can't initialize: " + e);
              Slog.e(TAG, "Can't init", e);
              return;
          }
  
          if (PROFILE_DUMP) Debug.startMethodTracing("/data/trace/dropbox.dump");
  
          StringBuilder out = new StringBuilder();
          boolean doPrint = false, doFile = false;
          ArrayList<String> searchArgs = new ArrayList<String>();
          for (int i = 0; args != null && i < args.length; i++) {
              if (args[i].equals("-p") || args[i].equals("--print")) {
                  doPrint = true;
              } else if (args[i].equals("-f") || args[i].equals("--file")) {
                  doFile = true;
              } else if (args[i].equals("-h") || args[i].equals("--help")) {
                  pw.println("Dropbox (dropbox) dump options:");
                  pw.println("  [-h|--help] [-p|--print] [-f|--file] [timestamp]");
                  pw.println("    -h|--help: print this help");
                  pw.println("    -p|--print: print full contents of each entry");
                  pw.println("    -f|--file: print path of each entry's file");
                  pw.println("  [timestamp] optionally filters to only those entries.");
                  return;
              } else if (args[i].startsWith("-")) {
                  out.append("Unknown argument: ").append(args[i]).append("\n");
              } else {
                  searchArgs.add(args[i]);
              }
          }
  
          out.append("Drop box contents: ").append(mAllFiles.contents.size()).append(" entries\n");
          out.append("Max entries: ").append(mMaxFiles).append("\n");
  
          out.append("Low priority rate limit period: ");
          out.append(mLowPriorityRateLimitPeriod).append(" ms\n");
          out.append("Low priority tags: ").append(mLowPriorityTags).append("\n");
  
          if (!searchArgs.isEmpty()) {
              out.append("Searching for:");
              for (String a : searchArgs) out.append(" ").append(a);
              out.append("\n");
          }
  
          int numFound = 0, numArgs = searchArgs.size();
          Time time = new Time();
          out.append("\n");
          for (EntryFile entry : mAllFiles.contents) {
              time.set(entry.timestampMillis);
              String date = time.format("%Y-%m-%d %H:%M:%S");
              boolean match = true;
              for (int i = 0; i < numArgs && match; i++) {
                  String arg = searchArgs.get(i);
                  match = (date.contains(arg) || arg.equals(entry.tag));
              }
              if (!match) continue;
  
              numFound++;
              if (doPrint) out.append("========================================\n");
              out.append(date).append(" ").append(entry.tag == null ? "(no tag)" : entry.tag);
  
              final File file = entry.getFile(mDropBoxDir);
              if (file == null) {
                  out.append(" (no file)\n");
                  continue;
              } else if ((entry.flags & DropBoxManager.IS_EMPTY) != 0) {
                  out.append(" (contents lost)\n");
                  continue;
              } else {
                  out.append(" (");
                  if ((entry.flags & DropBoxManager.IS_GZIPPED) != 0) out.append("compressed ");
                  out.append((entry.flags & DropBoxManager.IS_TEXT) != 0 ? "text" : "data");
                  out.append(", ").append(file.length()).append(" bytes)\n");
              }
  
              if (doFile || (doPrint && (entry.flags & DropBoxManager.IS_TEXT) == 0)) {
                  if (!doPrint) out.append("    ");
                  out.append(file.getPath()).append("\n");
              }
  
              if ((entry.flags & DropBoxManager.IS_TEXT) != 0 && (doPrint || !doFile)) {
                  DropBoxManager.Entry dbe = null;
                  InputStreamReader isr = null;
                  try {
                      dbe = new DropBoxManager.Entry(
                               entry.tag, entry.timestampMillis, file, entry.flags);
  
                      if (doPrint) {
                          isr = new InputStreamReader(dbe.getInputStream());
                          char[] buf = new char[4096];
                          boolean newline = false;
                          for (;;) {
                              int n = isr.read(buf);
                              if (n <= 0) break;
                              out.append(buf, 0, n);
                              newline = (buf[n - 1] == '\n');
  
                              // Flush periodically when printing to avoid out-of-memory.
                              if (out.length() > 65536) {
                                  pw.write(out.toString());
                                  out.setLength(0);
                              }
                          }
                          if (!newline) out.append("\n");
                      } else {
                          String text = dbe.getText(70);
                          out.append("    ");
                          if (text == null) {
                              out.append("[null]");
                          } else {
                              boolean truncated = (text.length() == 70);
                              out.append(text.trim().replace('\n', '/'));
                              if (truncated) out.append(" ...");
                          }
                          out.append("\n");
                      }
                  } catch (IOException e) {
                      out.append("*** ").append(e.toString()).append("\n");
                      Slog.e(TAG, "Can't read: " + file, e);
                  } finally {
                      if (dbe != null) dbe.close();
                      if (isr != null) {
                          try {
                              isr.close();
                          } catch (IOException unused) {
                          }
                      }
                  }
              }
  
              if (doPrint) out.append("\n");
          }
  
          if (numFound == 0) out.append("(No entries found.)\n");
  
          if (args == null || args.length == 0) {
              if (!doPrint) out.append("\n");
              out.append("Usage: dumpsys dropbox [--print|--file] [YYYY-mm-dd] [HH:MM:SS] [tag]\n");
          }
  
          pw.write(out.toString());
          if (PROFILE_DUMP) Debug.stopMethodTracing();
      }
  
      ///////////////////////////////////////////////////////////////////////////
  
      /** Chronologically sorted list of {@link EntryFile} */
      private static final class FileList implements Comparable<FileList> {
          public int blocks = 0;
          public final TreeSet<EntryFile> contents = new TreeSet<EntryFile>();
  
          /** Sorts bigger FileList instances before smaller ones. */
          public final int compareTo(FileList o) {
              if (blocks != o.blocks) return o.blocks - blocks;
              if (this == o) return 0;
              if (hashCode() < o.hashCode()) return -1;
              if (hashCode() > o.hashCode()) return 1;
              return 0;
          }
      }
  
      /**
       * Metadata describing an on-disk log file.
       *
       * Note its instances do no have knowledge on what directory they're stored, just to save
       * 4/8 bytes per instance.  Instead, {@link #getFile} takes a directory so it can build a
       * fullpath.
       */
      @VisibleForTesting
      static final class EntryFile implements Comparable<EntryFile> {
          public final String tag;
          public final long timestampMillis;
          public final int flags;
          public final int blocks;
  
          /** Sorts earlier EntryFile instances before later ones. */
          public final int compareTo(EntryFile o) {
              int comp = Long.compare(timestampMillis, o.timestampMillis);
              if (comp != 0) return comp;
  
              comp = ObjectUtils.compare(tag, o.tag);
              if (comp != 0) return comp;
  
              comp = Integer.compare(flags, o.flags);
              if (comp != 0) return comp;
  
              return Integer.compare(hashCode(), o.hashCode());
          }
  
          /**
           * Moves an existing temporary file to a new log filename.
           *
           * @param temp file to rename
           * @param dir to store file in
           * @param tag to use for new log file name
           * @param timestampMillis of log entry
           * @param flags for the entry data
           * @param blockSize to use for space accounting
           * @throws IOException if the file can't be moved
           */
          public EntryFile(File temp, File dir, String tag,long timestampMillis,
                           int flags, int blockSize) throws IOException {
              if ((flags & DropBoxManager.IS_EMPTY) != 0) throw new IllegalArgumentException();
  
              this.tag = TextUtils.safeIntern(tag);
              this.timestampMillis = timestampMillis;
              this.flags = flags;
  
              final File file = this.getFile(dir);
              if (!temp.renameTo(file)) {
                  throw new IOException("Can't rename " + temp + " to " + file);
              }
              this.blocks = (int) ((file.length() + blockSize - 1) / blockSize);
          }
  
          /**
           * Creates a zero-length tombstone for a file whose contents were lost.
           *
           * @param dir to store file in
           * @param tag to use for new log file name
           * @param timestampMillis of log entry
           * @throws IOException if the file can't be created.
           */
          public EntryFile(File dir, String tag, long timestampMillis) throws IOException {
              this.tag = TextUtils.safeIntern(tag);
              this.timestampMillis = timestampMillis;
              this.flags = DropBoxManager.IS_EMPTY;
              this.blocks = 0;
              new FileOutputStream(getFile(dir)).close();
          }
  
          /**
           * Extracts metadata from an existing on-disk log filename.
           *
           * Note when a filename is not recognizable, it will create an instance that
           * {@link #hasFile()} would return false on, and also remove the file.
           *
           * @param file name of existing log file
           * @param blockSize to use for space accounting
           */
          public EntryFile(File file, int blockSize) {
  
              boolean parseFailure = false;
  
              String name = file.getName();
              int flags = 0;
              String tag = null;
              long millis = 0;
  
              final int at = name.lastIndexOf('@');
              if (at < 0) {
                  parseFailure = true;
              } else {
                  tag = Uri.decode(name.substring(0, at));
                  if (name.endsWith(".gz")) {
                      flags |= DropBoxManager.IS_GZIPPED;
                      name = name.substring(0, name.length() - 3);
                  }
                  if (name.endsWith(".lost")) {
                      flags |= DropBoxManager.IS_EMPTY;
                      name = name.substring(at + 1, name.length() - 5);
                  } else if (name.endsWith(".txt")) {
                      flags |= DropBoxManager.IS_TEXT;
                      name = name.substring(at + 1, name.length() - 4);
                  } else if (name.endsWith(".dat")) {
                      name = name.substring(at + 1, name.length() - 4);
                  } else {
                      parseFailure = true;
                  }
                  if (!parseFailure) {
                      try {
                          millis = Long.parseLong(name);
                      } catch (NumberFormatException e) {
                          parseFailure = true;
                      }
                  }
              }
              if (parseFailure) {
                  Slog.wtf(TAG, "Invalid filename: " + file);
  
                  // Remove the file and return an empty instance.
                  file.delete();
                  this.tag = null;
                  this.flags = DropBoxManager.IS_EMPTY;
                  this.timestampMillis = 0;
                  this.blocks = 0;
                  return;
              }
  
              this.blocks = (int) ((file.length() + blockSize - 1) / blockSize);
              this.tag = TextUtils.safeIntern(tag);
              this.flags = flags;
              this.timestampMillis = millis;
          }
  
          /**
           * Creates a EntryFile object with only a timestamp for comparison purposes.
           * @param millis to compare with.
           */
          public EntryFile(long millis) {
              this.tag = null;
              this.timestampMillis = millis;
              this.flags = DropBoxManager.IS_EMPTY;
              this.blocks = 0;
          }
  
          /**
           * @return whether an entry actually has a backing file, or it's an empty "tombstone"
           * entry.
           */
          public boolean hasFile() {
              return tag != null;
          }
  
          /** @return File extension for the flags. */
          private String getExtension() {
              if ((flags &  DropBoxManager.IS_EMPTY) != 0) {
                  return ".lost";
              }
              return ((flags & DropBoxManager.IS_TEXT) != 0 ? ".txt" : ".dat") +
                      ((flags & DropBoxManager.IS_GZIPPED) != 0 ? ".gz" : "");
          }
  
          /**
           * @return filename for this entry without the pathname.
           */
          public String getFilename() {
              return hasFile() ? Uri.encode(tag) + "@" + timestampMillis + getExtension() : null;
          }
  
          /**
           * Get a full-path {@link File} representing this entry.
           * @param dir Parent directly.  The caller needs to pass it because {@link EntryFile}s don't
           *            know in which directory they're stored.
           */
          public File getFile(File dir) {
              return hasFile() ? new File(dir, getFilename()) : null;
          }
  
          /**
           * If an entry has a backing file, remove it.
           */
          public void deleteFile(File dir) {
              if (hasFile()) {
                  getFile(dir).delete();
              }
          }
      }
  
      ///////////////////////////////////////////////////////////////////////////
  
      /** If never run before, scans disk contents to build in-memory tracking data. */
      private synchronized void init() throws IOException {
          if (mStatFs == null) {
              if (!mDropBoxDir.isDirectory() && !mDropBoxDir.mkdirs()) {
                  throw new IOException("Can't mkdir: " + mDropBoxDir);
              }
              try {
                  mStatFs = new StatFs(mDropBoxDir.getPath());
                  mBlockSize = mStatFs.getBlockSize();
              } catch (IllegalArgumentException e) {  // StatFs throws this on error
                  throw new IOException("Can't statfs: " + mDropBoxDir);
              }
          }
  
          if (mAllFiles == null) {
              File[] files = mDropBoxDir.listFiles();
              if (files == null) throw new IOException("Can't list files: " + mDropBoxDir);
  
              mAllFiles = new FileList();
              mFilesByTag = new ArrayMap<>();
  
              // Scan pre-existing files.
              for (File file : files) {
                  if (file.getName().endsWith(".tmp")) {
                      Slog.i(TAG, "Cleaning temp file: " + file);
                      file.delete();
                      continue;
                  }
  
                  EntryFile entry = new EntryFile(file, mBlockSize);
  
                  if (entry.hasFile()) {
                      // Enroll only when the filename is valid.  Otherwise the above constructor
                      // has removed the file already.
                      enrollEntry(entry);
                  }
              }
          }
      }
  
      /** Adds a disk log file to in-memory tracking for accounting and enumeration. */
      private synchronized void enrollEntry(EntryFile entry) {
          mAllFiles.contents.add(entry);
          mAllFiles.blocks += entry.blocks;
  
          // mFilesByTag is used for trimming, so don't list empty files.
          // (Zero-length/lost files are trimmed by date from mAllFiles.)
  
          if (entry.hasFile() && entry.blocks > 0) {
              FileList tagFiles = mFilesByTag.get(entry.tag);
              if (tagFiles == null) {
                  tagFiles = new FileList();
                  mFilesByTag.put(TextUtils.safeIntern(entry.tag), tagFiles);
              }
              tagFiles.contents.add(entry);
              tagFiles.blocks += entry.blocks;
          }
      }
  
      /** Moves a temporary file to a final log filename and enrolls it. */
      private synchronized long createEntry(File temp, String tag, int flags) throws IOException {
          long t = System.currentTimeMillis();
  
          // Require each entry to have a unique timestamp; if there are entries
          // >10sec in the future (due to clock skew), drag them back to avoid
          // keeping them around forever.
  
          SortedSet<EntryFile> tail = mAllFiles.contents.tailSet(new EntryFile(t + 10000));
          EntryFile[] future = null;
          if (!tail.isEmpty()) {
              future = tail.toArray(new EntryFile[tail.size()]);
              tail.clear();  // Remove from mAllFiles
          }
  
          if (!mAllFiles.contents.isEmpty()) {
              t = Math.max(t, mAllFiles.contents.last().timestampMillis + 1);
          }
  
          if (future != null) {
              for (EntryFile late : future) {
                  mAllFiles.blocks -= late.blocks;
                  FileList tagFiles = mFilesByTag.get(late.tag);
                  if (tagFiles != null && tagFiles.contents.remove(late)) {
                      tagFiles.blocks -= late.blocks;
                  }
                  if ((late.flags & DropBoxManager.IS_EMPTY) == 0) {
                      enrollEntry(new EntryFile(late.getFile(mDropBoxDir), mDropBoxDir,
                              late.tag, t++, late.flags, mBlockSize));
                  } else {
                      enrollEntry(new EntryFile(mDropBoxDir, late.tag, t++));
                  }
              }
          }
  
          if (temp == null) {
              enrollEntry(new EntryFile(mDropBoxDir, tag, t));
          } else {
              enrollEntry(new EntryFile(temp, mDropBoxDir, tag, t, flags, mBlockSize));
          }
          return t;
      }
  
      /**
       * Trims the files on disk to make sure they aren't using too much space.
       * @return the overall quota for storage (in bytes)
       */
      private synchronized long trimToFit() throws IOException {
          // Expunge aged items (including tombstones marking deleted data).
  
          int ageSeconds = Settings.Global.getInt(mContentResolver,
                  Settings.Global.DROPBOX_AGE_SECONDS, DEFAULT_AGE_SECONDS);
          mMaxFiles = Settings.Global.getInt(mContentResolver,
                  Settings.Global.DROPBOX_MAX_FILES,
                  (ActivityManager.isLowRamDeviceStatic()
                          ?  DEFAULT_MAX_FILES_LOWRAM : DEFAULT_MAX_FILES));
          long cutoffMillis = System.currentTimeMillis() - ageSeconds * 1000;
          while (!mAllFiles.contents.isEmpty()) {
              EntryFile entry = mAllFiles.contents.first();
              if (entry.timestampMillis > cutoffMillis && mAllFiles.contents.size() < mMaxFiles) {
                  break;
              }
  
              FileList tag = mFilesByTag.get(entry.tag);
              if (tag != null && tag.contents.remove(entry)) tag.blocks -= entry.blocks;
              if (mAllFiles.contents.remove(entry)) mAllFiles.blocks -= entry.blocks;
              entry.deleteFile(mDropBoxDir);
          }
  
          // Compute overall quota (a fraction of available free space) in blocks.
          // The quota changes dynamically based on the amount of free space;
          // that way when lots of data is available we can use it, but we'll get
          // out of the way if storage starts getting tight.
  
          long uptimeMillis = SystemClock.uptimeMillis();
          if (uptimeMillis > mCachedQuotaUptimeMillis + QUOTA_RESCAN_MILLIS) {
              int quotaPercent = Settings.Global.getInt(mContentResolver,
                      Settings.Global.DROPBOX_QUOTA_PERCENT, DEFAULT_QUOTA_PERCENT);
              int reservePercent = Settings.Global.getInt(mContentResolver,
                      Settings.Global.DROPBOX_RESERVE_PERCENT, DEFAULT_RESERVE_PERCENT);
              int quotaKb = Settings.Global.getInt(mContentResolver,
                      Settings.Global.DROPBOX_QUOTA_KB, DEFAULT_QUOTA_KB);
  
              String dirPath = mDropBoxDir.getPath();
              try {
                  mStatFs.restat(dirPath);
              } catch (IllegalArgumentException e) {  // restat throws this on error
                  throw new IOException("Can't restat: " + mDropBoxDir);
              }
              int available = mStatFs.getAvailableBlocks();
              int nonreserved = available - mStatFs.getBlockCount() * reservePercent / 100;
              int maximum = quotaKb * 1024 / mBlockSize;
              mCachedQuotaBlocks = Math.min(maximum, Math.max(0, nonreserved * quotaPercent / 100));
              mCachedQuotaUptimeMillis = uptimeMillis;
          }
  
          // If we're using too much space, delete old items to make room.
          //
          // We trim each tag independently (this is why we keep per-tag lists).
          // Space is "fairly" shared between tags -- they are all squeezed
          // equally until enough space is reclaimed.
          //
          // A single circular buffer (a la logcat) would be simpler, but this
          // way we can handle fat/bursty data (like 1MB+ bugreports, 300KB+
          // kernel crash dumps, and 100KB+ ANR reports) without swamping small,
          // well-behaved data streams (event statistics, profile data, etc).
          //
          // Deleted files are replaced with zero-length tombstones to mark what
          // was lost.  Tombstones are expunged by age (see above).
  
          if (mAllFiles.blocks > mCachedQuotaBlocks) {
              // Find a fair share amount of space to limit each tag
              int unsqueezed = mAllFiles.blocks, squeezed = 0;
              TreeSet<FileList> tags = new TreeSet<FileList>(mFilesByTag.values());
              for (FileList tag : tags) {
                  if (squeezed > 0 && tag.blocks <= (mCachedQuotaBlocks - unsqueezed) / squeezed) {
                      break;
                  }
                  unsqueezed -= tag.blocks;
                  squeezed++;
              }
              int tagQuota = (mCachedQuotaBlocks - unsqueezed) / squeezed;
  
              // Remove old items from each tag until it meets the per-tag quota.
              for (FileList tag : tags) {
                  if (mAllFiles.blocks < mCachedQuotaBlocks) break;
                  while (tag.blocks > tagQuota && !tag.contents.isEmpty()) {
                      EntryFile entry = tag.contents.first();
                      if (tag.contents.remove(entry)) tag.blocks -= entry.blocks;
                      if (mAllFiles.contents.remove(entry)) mAllFiles.blocks -= entry.blocks;
  
                      try {
                          entry.deleteFile(mDropBoxDir);
                          enrollEntry(new EntryFile(mDropBoxDir, entry.tag, entry.timestampMillis));
                      } catch (IOException e) {
                          Slog.e(TAG, "Can't write tombstone file", e);
                      }
                  }
              }
          }
  
          return mCachedQuotaBlocks * mBlockSize;
      }
  
      private void getLowPriorityResourceConfigs() {
          mLowPriorityRateLimitPeriod = Resources.getSystem().getInteger(
                  R.integer.config_dropboxLowPriorityBroadcastRateLimitPeriod);
  
          final String[] lowPrioritytags = Resources.getSystem().getStringArray(
                  R.array.config_dropboxLowPriorityTags);
          final int size = lowPrioritytags.length;
          if (size == 0) {
              mLowPriorityTags = null;
              return;
          }
          mLowPriorityTags = new ArraySet(size);
          for (int i = 0; i < size; i++) {
              mLowPriorityTags.add(lowPrioritytags[i]);
          }
      }
  }
  