Glue parallel download job and download file together.

content/browser/download/download_file_impl.h

 // Copyright (c) 2012 The Chromium 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 CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_IMPL_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_IMPL_H_
 
 #include "content/browser/download/download_file.h"
 
 #include <stddef.h>
@@ skipping 40 matching lines @@
       const net::NetLogWithSource& net_log,
       bool is_sparse_file,
       base::WeakPtr<DownloadDestinationObserver> observer);
 
   ~DownloadFileImpl() override;
 
   // DownloadFile functions.
   void Initialize(const InitializeCallback& callback) override;
 
   void AddByteStream(std::unique_ptr<ByteStreamReader> stream_reader,
-                     int64_t offset) override;
+                     int64_t offset,
+                     int64_t length) override;
 
   void RenameAndUniquify(const base::FilePath& full_path,
                          const RenameCompletionCallback& callback) override;
   void RenameAndAnnotate(const base::FilePath& full_path,
                          const std::string& client_guid,
                          const GURL& source_url,
                          const GURL& referrer_url,
                          const RenameCompletionCallback& callback) override;
   void Detach() override;
   void Cancel() override;
@@ skipping 15 matching lines @@
  private:
   friend class DownloadFileTest;
 
   // Wrapper of a ByteStreamReader, and the meta data needed to write to a
   // slice of the target file.
   //
   // Does not require the stream reader ready when constructor is called.
   // |stream_reader_| can be set later when the network response is handled.
   //
   // Multiple SourceStreams can concurrently write to the same file sink.
-  //
-  // The file IO processing is finished when all SourceStreams are finished.
   class CONTENT_EXPORT SourceStream {
    public:
     SourceStream(int64_t offset, int64_t length);
     ~SourceStream();
 
     void SetByteStream(std::unique_ptr<ByteStreamReader> stream_reader);
 
     // Called after successfully writing a buffer to disk.
     void OnWriteBytesToDisk(int64_t bytes_write);
 
@@ skipping 87 matching lines @@
   // DownloadSaveInfo provided during construction. Since the DownloadFileImpl
   // can be created on any thread, this holds the save_info_ until it can be
   // used to initialize file_ on the FILE thread.
   std::unique_ptr<DownloadSaveInfo> save_info_;
 
   // The default directory for creating the download file.
   base::FilePath default_download_directory_;
 
   // Map of the offset and the source stream that represents the slice
   // starting from offset.
-  // Must be created on the same thread that constructs the DownloadFile.
-  // Should not add or remove elements after creation.
-  // Any byte stream should have a SourceStream before added to the download
-  // file.
-  // The disk IO is completed when all source streams are finished.
+  // Can be modified in constructor on any thread, later must be accessed on
+  // file thread.

[asanka, 2017/03/14 19:44:01]

Doesn't need to be restated here. The thread restriction applies to all
DownloadFileImpl members.

[xingliu, 2017/03/14 22:48:29]

Done.

   SourceStreams source_streams_;
 
   // Used to trigger progress updates.
   std::unique_ptr<base::RepeatingTimer> update_timer_;
 
   // Set to true when multiple byte streams write to the same file.
   // The file may contain null bytes(holes) in between of valid data slices.
   // TODO(xingliu): Pass a slice info vector to determine if the file is sparse.
   bool is_sparse_file_;
 
   // Statistics
   size_t bytes_seen_;
   base::TimeDelta disk_writes_time_;
   base::TimeTicks download_start_;
   RateEstimator rate_estimator_;
 
   std::vector<DownloadItem::ReceivedSlice> received_slices_;
 
   base::WeakPtr<DownloadDestinationObserver> observer_;
   base::WeakPtrFactory<DownloadFileImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadFileImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_IMPL_H_