AU: Speed up updates by using buffered writes.

download_action.h

 // Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_DOWNLOAD_ACTION_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_DOWNLOAD_ACTION_H__
 
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 
 #include <string>
 
+#include <base/scoped_ptr.h>
 #include <curl/curl.h>
 
-#include "base/scoped_ptr.h"
 #include "update_engine/action.h"
 #include "update_engine/decompressing_file_writer.h"
 #include "update_engine/delta_performer.h"
-#include "update_engine/file_writer.h"
+#include "update_engine/buffered_file_writer.h"
 #include "update_engine/http_fetcher.h"
 #include "update_engine/install_plan.h"
 #include "update_engine/omaha_hash_calculator.h"
 #include "update_engine/split_file_writer.h"
 
 // The Download Action downloads a specified url to disk. The url should
 // point to either a full or delta update. If a full update, the file will
 // be piped into a SplitFileWriter, which will direct it to the kernel
 // and rootfs partitions. If it's a delta update, the destination kernel
 // and rootfs should already contain the source-version that this delta
@@ skipping 67 matching lines @@
 
   // The FileWriter that downloaded data should be written to. It will
   // either point to *decompressing_file_writer_ or *delta_performer_.
   FileWriter* writer_;
 
   // These are used for full updates:
   scoped_ptr<GzipDecompressingFileWriter> decompressing_file_writer_;
   scoped_ptr<SplitFileWriter> split_file_writer_;
   scoped_ptr<DirectFileWriter> kernel_file_writer_;
   scoped_ptr<DirectFileWriter> rootfs_file_writer_;
+  scoped_ptr<BufferedFileWriter> kernel_buffered_file_writer_;
+  scoped_ptr<BufferedFileWriter> rootfs_buffered_file_writer_;
 
   // Used to apply a delta update:
   scoped_ptr<DeltaPerformer> delta_performer_;
 
   // Pointer to the HttpFetcher that does the http work.
   scoped_ptr<HttpFetcher> http_fetcher_;
 
   // Used to find the hash of the bytes downloaded
   OmahaHashCalculator omaha_hash_calculator_;
 
   // For reporting status to outsiders
   DownloadActionDelegate* delegate_;
   uint64_t bytes_received_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadAction);
 };
 
 // We want to be sure that we're compiled with large file support on linux,
 // just in case we find ourselves downloading large images.
 COMPILE_ASSERT(8 == sizeof(off_t), off_t_not_64_bit);
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DOWNLOAD_ACTION_H__