Make DownloadFileImpl handle multiple byte streams.

content/browser/download/download_file.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_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_H_
 
 #include <stdint.h>
 
+#include <memory>
 #include <string>
 
 #include "base/callback_forward.h"
 #include "base/files/file_path.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 
 class GURL;
 
 namespace content {
 
+class ByteStreamReader;
+
 // These objects live exclusively on the file thread and handle the writing
 // operations for one download. These objects live only for the duration that
 // the download is 'in progress': once the download has been completed or
 // cancelled, the DownloadFile is destroyed.
 class CONTENT_EXPORT DownloadFile {
  public:
   // Callback used with Initialize.  On a successful initialize, |reason| will
   // be DOWNLOAD_INTERRUPT_REASON_NONE; on a failed initialize, it will be
   // set to the reason for the failure.
   typedef base::Callback<void(DownloadInterruptReason reason)>
       InitializeCallback;
 
   // Callback used with Rename*().  On a successful rename |reason| will be
   // DOWNLOAD_INTERRUPT_REASON_NONE and |path| the path the rename
   // was done to.  On a failed rename, |reason| will contain the
   // error.
   typedef base::Callback<void(DownloadInterruptReason reason,
                               const base::FilePath& path)>
       RenameCompletionCallback;
 
   virtual ~DownloadFile() {}
 
   // Upon completion, |callback| will be called on the UI
   // thread as per the comment above, passing DOWNLOAD_INTERRUPT_REASON_NONE
   // on success, or a network download interrupt reason on failure.
   virtual void Initialize(const InitializeCallback& callback) = 0;
 
+  // Add a byte stream reader to write into a slice of the file, used for
+  // parallel download. Called on the file thread.
+  virtual void AddByteStream(std::unique_ptr<ByteStreamReader> stream_reader,
+                             int64_t offset) = 0;
+
   // Rename the download file to |full_path|.  If that file exists
   // |full_path| will be uniquified by suffixing " (<number>)" to the
   // file name before the extension.
   virtual void RenameAndUniquify(const base::FilePath& full_path,
                                  const RenameCompletionCallback& callback) = 0;
 
   // Rename the download file to |full_path| and annotate it with
   // "Mark of the Web" information about its source.  No uniquification
   // will be performed.
   virtual void RenameAndAnnotate(const base::FilePath& full_path,
                                  const std::string& client_guid,
                                  const GURL& source_url,
                                  const GURL& referrer_url,
                                  const RenameCompletionCallback& callback) = 0;
 
   // Detach the file so it is not deleted on destruction.
   virtual void Detach() = 0;
 
   // Abort the download and automatically close the file.
   virtual void Cancel() = 0;
 
   virtual const base::FilePath& FullPath() const = 0;
   virtual bool InProgress() const = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_FILE_H_