Debug系列3：DropBoxManagerService

private void startOtherServices() {     try {         ServiceManager.addService(Context.DROPBOX_SERVICE,                 new DropBoxManagerService(context, new File("/data/system/dropbox")));     } catch (Throwable e) {         reportWtf("starting DropBoxManagerService", e);     }     ... } 

public final class DropBoxManagerService extends IDropBoxManagerService.Stub {     ...     public DropBoxManagerService(final Context context, File path) {         mDropBoxDir = path; //保存工作目录          mContext = context;         mContentResolver = context.getContentResolver();          IntentFilter filter = new IntentFilter();         //注册存储设备可用空间低的广播         filter.addAction(Intent.ACTION_DEVICE_STORAGE_LOW);         //注册开机完毕的广播         filter.addAction(Intent.ACTION_BOOT_COMPLETED);         context.registerReceiver(mReceiver, filter);          //当Settings数据库变化时，则回调广播接收者的onReceive方法         //此处CONTENT_URI=content://settings/global"         mContentResolver.registerContentObserver(             Settings.Global.CONTENT_URI, true,             new ContentObserver(new Handler()) {                 @Override                 public void onChange(boolean selfChange) {                     mReceiver.onReceive(context, (Intent) null);                 }             });          mHandler = new Handler() {             @Override             public void handleMessage(Message msg) {                 // 发送广播                 if (msg.what == MSG_SEND_BROADCAST) {                     mContext.sendBroadcastAsUser((Intent)msg.obj, UserHandle.OWNER,                             android.Manifest.permission.READ_LOGS);                 }             }         };     } } 

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {     @Override     public void onReceive(Context context, Intent intent) {         if (intent != null && Intent.ACTION_BOOT_COMPLETED.equals(intent.getAction())) {             mBooted = true;             return;         }          //收到ACTION_DEVICE_STORAGE_LOW，则强制重新check存储空间         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(); //【见小节1.3.1】                     trimToFit(); //【见小节1.3.2】                 } catch (IOException e) {                     Slog.e(TAG, "Can't init", e);                 }             }         }.start();     } }; 

private synchronized void init() throws IOException {     if (mStatFs == null) {         if (!mDropBoxDir.isDirectory() && !mDropBoxDir.mkdirs()) {             throw new IOException("Can't mkdir: " + mDropBoxDir);         }         mStatFs = new StatFs(mDropBoxDir.getPath());         mBlockSize = mStatFs.getBlockSize(); //mBlockSize=4096     }      if (mAllFiles == null) {         File[] files = mDropBoxDir.listFiles();         //创建mAllFiles对象，记录所有的dropbox文件         mAllFiles = new FileList();         mFilesByTag = new HashMap<String, FileList>();          for (File file : files) {             if (file.getName().endsWith(".tmp")) {                 file.delete(); //删除后缀为.tmp文件                 continue;             }             // 创建dropbox的实体文件对象             EntryFile entry = new EntryFile(file, mBlockSize);             if (entry.tag == null) {                 continue; //忽略tag为空的文件             } else if (entry.timestampMillis == 0) {                 file.delete(); //删除时间戳为0的文件                 continue;             }             //将entry加入到mAllFiles对象             enrollEntry(entry);         }     } } 

private synchronized long trimToFit() {      int ageSeconds = Settings.Global.getInt(mContentResolver,             Settings.Global.DROPBOX_AGE_SECONDS, DEFAULT_AGE_SECONDS);     int maxFiles = Settings.Global.getInt(mContentResolver,             Settings.Global.DROPBOX_MAX_FILES, DEFAULT_MAX_FILES);     long cutoffMillis = System.currentTimeMillis() - ageSeconds * 1000;     while (!mAllFiles.contents.isEmpty()) {         EntryFile entry = mAllFiles.contents.first();         //当最老的文件时间戳在3天之内，且文件个数低于1000，则跳出循环         if (entry.timestampMillis > cutoffMillis && mAllFiles.contents.size() < maxFiles) 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;         if (entry.file != null) entry.file.delete(); //删除文件     }      long uptimeMillis = SystemClock.uptimeMillis();     //除非接收设备存储低的广播，否则间隔5s才能再次执行restat     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);         //重新统计文件         mStatFs.restat(mDropBoxDir.getPath());         int available = mStatFs.getAvailableBlocks();         int nonreserved = available - mStatFs.getBlockCount() * reservePercent / 100;         int maximum = quotaKb * 1024 / mBlockSize;         //可用的块数量         mCachedQuotaBlocks = Math.min(maximum, Math.max(0, nonreserved * quotaPercent / 100));         mCachedQuotaUptimeMillis = uptimeMillis;     }      if (mAllFiles.blocks > mCachedQuotaBlocks) {         //公平地限制所有tag的空间         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;          //移除每个tags中的旧items         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 {                     if (entry.file != null) entry.file.delete();                     enrollEntry(new EntryFile(mDropBoxDir, entry.tag, entry.timestampMillis));                 } catch (IOException e) {                     Slog.e(TAG, "Can't write tombstone file", e);                 }             }         }     }      return mCachedQuotaBlocks * mBlockSize; } 

public void addErrorToDropBox(String eventType,         ProcessRecord process, String processName, ActivityRecord activity,         ActivityRecord parent, String subject,         final String report, final File logFile,         final ApplicationErrorReport.CrashInfo crashInfo) {      //如果是普通App崩溃，则dropboxTag为data_app_crash     final String dropboxTag = processClass(process) + "_" + eventType;     //获取dropbox服务的客户端     final DropBoxManager dbox = (DropBoxManager)             mContext.getSystemService(Context.DROPBOX_SERVICE);      //当不需要输出dropbox报告则直接返回     if (dbox == null || !dbox.isTagEnabled(dropboxTag)) return;      final StringBuilder sb = new StringBuilder(1024);     //输出Process,flags,以及进程中所有package     appendDropBoxProcessHeaders(process, processName, sb);     ...     sb.append("Build: ").append(Build.FINGERPRINT).append("/n");     sb.append("/n");      //创建新线程，避免将调用者阻塞在I/O     Thread worker = new Thread("Error dump: " + dropboxTag) {         @Override         public void run() {             if (report != null) {                 sb.append(report);             }             if (logFile != null) {                 //当logFile不为空，则添加log信息到dropbox，最大上限为256KB                 sb.append(FileUtils.readTextFile(logFile, DROPBOX_MAX_SIZE,                             "/n/n[[TRUNCATED]]"));             }             if (crashInfo != null && crashInfo.stackTrace != null) {                 //当栈信息不为空，则添加stacktrace到dropbox                 sb.append(crashInfo.stackTrace);             }              String setting = Settings.Global.ERROR_LOGCAT_PREFIX + dropboxTag;             int lines = Settings.Global.getInt(mContext.getContentResolver(), setting, 0);             //当dropboxTag所对应的settings项不等于0，则输出logcat             if (lines > 0) {                     java.lang.Process logcat = new ProcessBuilder("/system/bin/logcat",                             "-v", "time", "-b", "events", "-b", "system", "-b", "main",                             "-b", "crash",                             "-t", String.valueOf(lines)).redirectErrorStream(true).start();                      input = new InputStreamReader(logcat.getInputStream());                      int num;                     char[] buf = new char[8192];                     while ((num = input.read(buf)) > 0) sb.append(buf, 0, num);                 } catch (IOException e) {                     Slog.e(TAG, "Error running logcat", e);                 } finally {                     if (input != null) try { input.close(); } catch (IOException e) {}                 }             }             //将logcat的输出到DropBox 【见小节2.2】             dbox.addText(dropboxTag, sb.toString());         }     };      if (process == null) {         //当进程为空，意味着system_server进程崩溃，系统可能很快就要挂了,         //那么不再创建新线程，而是直接在system_server进程中同步运行         worker.run();     } else {         //启动新线程         worker.start();     } } 

 private static String processClass(ProcessRecord process) {      //MY_PID代表的是当前进程pid，正是system_server进程      if (process == null || process.pid == MY_PID) {          return "system_server";      } else if ((process.info.flags & ApplicationInfo.FLAG_SYSTEM) != 0) {          return "system_app";      } else {          return "data_app";      }  } 

public void addText(String tag, String data) {     //data数据封装到Entry对象实例，再调用DBMS中的方法。     try { mService.add(new Entry(tag, 0, data)); } catch (RemoteException e) {} } 

public void add(DropBoxManager.Entry entry) {     File temp = null;     OutputStream output = null;     final String tag = entry.getTag();     try {         int flags = entry.getFlags();         if ((flags & DropBoxManager.IS_EMPTY) != 0) throw new IllegalArgumentException();         init(); // 初始化【见小节1.3.1】         if (!isTagEnabled(tag)) return;         long max = trimToFit(); // 压缩空间【见小节1.3.2】         long lastTrim = System.currentTimeMillis();         //mBlockSize等于4096         byte[] buffer = new byte[mBlockSize];         InputStream input = entry.getInputStream();          int read = 0;         while (read < buffer.length) {             int n = input.read(buffer, read, buffer.length - read);             if (n <= 0) break;             read += n;         }         //创建临时文件，例如tid=1234的对应文件drop1234.tmp         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);         //创建gzip压缩文件         if (read == buffer.length && ((flags & DropBoxManager.IS_GZIPPED) == 0)) {             output = new GZIPOutputStream(output);             flags = flags | DropBoxManager.IS_GZIPPED;         }          //不断将temp文件数据写入buffer         do {             output.write(buffer, 0, read);             long now = System.currentTimeMillis();             if (now - lastTrim > 30 * 1000) {                 max = trimToFit(); //执行时间超过30s则执行trim                 lastTrim = now;             }              read = input.read(buffer);             if (read <= 0) {                 FileUtils.sync(foutput);                 output.close();                 output = null;             } else {                 output.flush();             }              long len = temp.length();             if (len > max) {                 Slog.w(TAG, "Dropping: " + tag + " (" + temp.length() + " > " + max + " bytes)");                 temp.delete();                 temp = null;                 break;             }         } while (read > 0);          long time = createEntry(temp, tag, flags);         temp = null;          final Intent dropboxIntent = new Intent(DropBoxManager.ACTION_DROPBOX_ENTRY_ADDED);         dropboxIntent.putExtra(DropBoxManager.EXTRA_TAG, tag);         dropboxIntent.putExtra(DropBoxManager.EXTRA_TIME, time);         if (!mBooted) {             dropboxIntent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);         }         //发送广播MSG_SEND_BROADCAST         mHandler.sendMessage(mHandler.obtainMessage(MSG_SEND_BROADCAST, dropboxIntent));     } catch (IOException e) {         Slog.e(TAG, "Can't write: " + tag, e);     } finally {         try { if (output != null) output.close(); } catch (IOException e) {}         entry.close();         if (temp != null) temp.delete();     } }