content: /*
   * Copyright (C) 2014 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.net;
  
  import android.os.Handler;
  import android.os.HandlerThread;
  import android.text.TextUtils;
  import android.util.Log;
  
  import java.io.BufferedOutputStream;
  import java.io.DataOutputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  
  public class DelayedDiskWrite {
      private HandlerThread mDiskWriteHandlerThread;
      private Handler mDiskWriteHandler;
      /* Tracks multiple writes on the same thread */
      private int mWriteSequence = 0;
      private final String TAG = "DelayedDiskWrite";
  
      public interface Writer {
          public void onWriteCalled(DataOutputStream out) throws IOException;
      }
  
      public void write(final String filePath, final Writer w) {
          write(filePath, w, true);
      }
  
      public void write(final String filePath, final Writer w, final boolean open) {
          if (TextUtils.isEmpty(filePath)) {
              throw new IllegalArgumentException("empty file path");
          }
  
          /* Do a delayed write to disk on a separate handler thread */
          synchronized (this) {
              if (++mWriteSequence == 1) {
                  mDiskWriteHandlerThread = new HandlerThread("DelayedDiskWriteThread");
                  mDiskWriteHandlerThread.start();
                  mDiskWriteHandler = new Handler(mDiskWriteHandlerThread.getLooper());
              }
          }
  
          mDiskWriteHandler.post(new Runnable() {
              @Override
              public void run() {
                  doWrite(filePath, w, open);
              }
          });
      }
  
      private void doWrite(String filePath, Writer w, boolean open) {
          DataOutputStream out = null;
          try {
              if (open) {
                  out = new DataOutputStream(new BufferedOutputStream(
                          new FileOutputStream(filePath)));
              }
              w.onWriteCalled(out);
          } catch (IOException e) {
              loge("Error writing data file " + filePath);
          } finally {
              if (out != null) {
                  try {
                      out.close();
                  } catch (Exception e) {}
              }
  
              // Quit if no more writes sent
              synchronized (this) {
                  if (--mWriteSequence == 0) {
                      mDiskWriteHandler.getLooper().quit();
                      mDiskWriteHandler = null;
                      mDiskWriteHandlerThread = null;
                  }
              }
          }
      }
  
      private void loge(String s) {
          Log.e(TAG, s);
      }
  }
  
  