Added member data to classes to support download resumption.

content/browser/download/download_item.h

 // Copyright (c) 2011 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.
 //
 // Each download is represented by a DownloadItem, and all DownloadItems
 // are owned by the DownloadManager which maintains a global list of all
 // downloads. DownloadItems are created when a user initiates a download,
 // and exist for the duration of the browser life time.
 //
 // Download observers:
@@ skipping 139 matching lines @@
   // Open the file associated with this download (wait for the download to
   // complete if it is in progress).
   void OpenDownload();
 
   // Show the download via the OS shell.
   void ShowDownloadInShell();
 
   // Called when the user has validated the download of a dangerous file.
   void DangerousDownloadValidated();
 
-  // Received a new chunk of data
-  void Update(int64 bytes_so_far);
+  // Received a new chunk of data.
+  // |bytes_so_far| is the number of bytes received so far.
+  // |partial_hash| is the hash up to this point.  It will be an empty string
+  // if we are not calculating hashes.
+  void Update(int64 bytes_so_far, const std::string& partial_hash);

[Randy Smith (Not in Mondays), 2011/10/31 18:46:43]

Currently, Update is just used to send across size data for display purposes
based on a timer on the file thread--it isn't synchronous with OnReadCompleted
or anything.  |hash| isn't for display, so I don't think it makes sense to
include it in the update--it'll come across in OnAllDataSaved or Interrupted.

[ahendrickson, 2011/11/13 21:15:20]

No, Update also sets received_bytes_, which is passed along to the persistent
store.  I want the hash to end up there as well.

Specifically, I want the hash to be periodically updated in the persistent
store, so we can use it when we resume a download after a crash (where we won't
necessarily record a download interruption).

Does that seem reasonable to you?

[Randy Smith (Not in Mondays), 2011/11/15 18:35:25]

Hmmm.  I understand it, but I don't like it; I want to get the hash less
interwoven with the core downloads system, not more.  Let me pull back a bit and
summarize the requirements, then see if I can come up with a different way to
satisfy them.

As I understand what you're saying, you want the hash stored in the persistent
store on a regular basis, and you want that hash associated with a specific
number of bytes received, so that when you resume downloads you can resume hash
computation from a known position and known partial hash.  That strikes me as a
reasonable requirement.  That requirement means that whenever we update
bytes_received in the persistent store, we also need to update the hash value,
atomically with bytes received.  I'm also good with that.

However, I think the regular, periodic update of the hash is so that we can
resume downloads after a crash.  For either shutdown or error cases we'll flush
the information out to the database when we Cancel/Interrupt.  So it seems like
the need for this extra argument is purely for supporting the resumption after
crash case.  I don't feel like supporting that case is very high priority; at
least, I hope we don't crash that often :-}.  

Having said that, we do need to make sure that we we update the hash and
bytes_so_far atomically.  And *avoiding* updating the bytes-so-far if we don't
have the hash is probably a larger hassle than doing what you've got above.  So
yeah, I'm ok with this.  But if it turns into a large hassle I'd probably go the
other way--simplicity :uber alles is going to be my motto here.

 
   // Cancel the download operation. We need to distinguish between cancels at
   // exit (DownloadManager destructor) from user interface initiated cancels
   // because at exit, the history system may not exist, and any updates to it
   // require AddRef'ing the DownloadManager in the destructor which results in
   // a DCHECK failure. Set |user_cancel| to false when canceling from at
   // exit to prevent this crash. This may result in a difference between the
   // downloaded file's size on disk, and what the history system's last record
   // of it is. At worst, we'll end up re-downloading a small portion of the file
   // when resuming a download (assuming the server supports byte ranges).
   void Cancel(bool user_cancel);
 
   // Called by external code (SavePackage) using the DownloadItem interface
   // to display progress when the DownloadItem should be considered complete.
   void MarkAsComplete();
 
   // Called by the delegate after it delayed completing the download in
   // DownloadManagerDelegate::ShouldCompleteDownload.
   void CompleteDelayedDownload();
 
   // Called when all data has been saved. Only has display effects.
-  void OnAllDataSaved(int64 size);
+  void OnAllDataSaved(int64 size, const std::string final_hash);
 
   // Called when the downloaded file is removed.
   void OnDownloadedFileRemoved();
 
   // Download operation had an error.
   // |size| is the amount of data received at interruption.
+  // |partial_hash| is the current hash value at interruption.
   // |reason| is the download interrupt reason code that the operation received.
-  void Interrupted(int64 size, InterruptReason reason);
+  void Interrupted(int64 size,
+                   const std::string partial_hash,
+                   InterruptReason reason);
 
   // Deletes the file from disk and removes the download from the views and
   // history.  |user| should be true if this is the result of the user clicking
   // the discard button, and false if it is being deleted for other reasons like
   // browser shutdown.
   void Delete(DeleteReason reason);
 
   // Removes the download from the views and history.
   void Remove();
 
@@ skipping 68 matching lines @@
   std::string suggested_filename() const { return suggested_filename_; }
   std::string content_disposition() const { return content_disposition_; }
   std::string mime_type() const { return mime_type_; }
   std::string original_mime_type() const { return original_mime_type_; }
   std::string referrer_charset() const { return referrer_charset_; }
   int64 total_bytes() const { return total_bytes_; }
   void set_total_bytes(int64 total_bytes) {
     total_bytes_ = total_bytes;
   }
   int64 received_bytes() const { return received_bytes_; }
+  const std::string& partial_hash() const { return partial_hash_; }
   int32 id() const { return download_id_; }
   DownloadId global_id() const;
   base::Time start_time() const { return start_time_; }
   base::Time end_time() const { return end_time_; }
   void set_db_handle(int64 handle) { db_handle_ = handle; }
   int64 db_handle() const { return db_handle_; }
   DownloadManager* download_manager() { return download_manager_; }
   bool is_paused() const { return is_paused_; }
   bool open_when_complete() const { return open_when_complete_; }
   void set_open_when_complete(bool open) { open_when_complete_ = open; }
   bool file_externally_removed() const { return file_externally_removed_; }
   SafetyState safety_state() const { return safety_state_; }
   // Why |safety_state_| is not SAFE.
   DangerType GetDangerType() const;
   bool IsDangerous() const;
   void MarkFileDangerous();
   void MarkUrlDangerous();
 
   bool auto_opened() { return auto_opened_; }
   const FilePath& target_name() const { return state_info_.target_name; }
   bool prompt_user_for_save_location() const {
     return state_info_.prompt_user_for_save_location;
   }
   bool is_otr() const { return is_otr_; }
   const FilePath& suggested_path() const { return state_info_.suggested_path; }
   bool is_temporary() const { return is_temporary_; }
   void set_opened(bool opened) { opened_ = opened; }
   bool opened() const { return opened_; }
 
+  const std::string& last_modified_time() const { return last_modified_time_; }
+  void set_last_modified_time(const std::string& time) {
+    last_modified_time_ = time;
+  }
+  const std::string& etag() const { return etag_; }
+  void set_etag(const std::string& tag) { etag_ = tag; }
+
   InterruptReason last_reason() const { return last_reason_; }
 
   DownloadPersistentStoreInfo GetPersistentStoreInfo() const;
   DownloadStateInfo state_info() const { return state_info_; }
   const DownloadRequestHandle& request_handle() const {
     return request_handle_;
   }
 
   // Returns the final target file path for the download.
   FilePath GetTargetFilePath() const;
@@ skipping 25 matching lines @@
   void MockDownloadOpenForTesting() { open_enabled_ = false; }
 
  private:
   // Construction common to all constructors. |active| should be true for new
   // downloads and false for downloads from the history.
   void Init(bool active);
 
   // Internal helper for maintaining consistent received and total sizes.
   void UpdateSize(int64 size);
 
+  // Internal helper for keeping track of the hash as we receive data.
+  void UpdateHash(const std::string& partial_hash);
+
   // Called when the entire download operation (including renaming etc)
   // is completed.
   void Completed();
 
   // Start/stop sending periodic updates to our observers
   void StartProgressTimer();
   void StopProgressTimer();
 
   // Call to transition state; all state transitions should go through this.
   void TransitionTo(DownloadState new_state);
@@ skipping 43 matching lines @@
 
   // The value of the content type header sent with the downloaded item.  It
   // may be different from |mime_type_|, which may be set based on heuristics
   // which may look at the file extension and first few bytes of the file.
   std::string original_mime_type_;
 
   // The charset of the referring page where the download request comes from.
   // It's used to construct a suggested filename.
   std::string referrer_charset_;
 
-  // Total bytes expected
+  // Total bytes expected.
   int64 total_bytes_;
 
-  // Current received bytes
+  // Current received bytes.
   int64 received_bytes_;
 
+  // Current hash value.
+  std::string partial_hash_;
+
+  // Server's time stamp for the file.
+  std::string last_modified_time_;
+
+  // Server's ETAG for the file.
+  std::string etag_;
+
   // Last reason.
   InterruptReason last_reason_;
 
-  // Start time for calculating remaining time
+  // Start time for calculating remaining time.
   base::TimeTicks start_tick_;
 
-  // The current state of this download
+  // The current state of this download.
   DownloadState state_;
 
-  // The views of this item in the download shelf and download tab
+  // The views of this item in the download shelf and download tab.
   ObserverList<Observer> observers_;
 
-  // Time the download was started
+  // Time the download was started.
   base::Time start_time_;
 
-  // Time the download completed
+  // Time the download completed.
   base::Time end_time_;
 
-  // Our persistent store handle
+  // Our persistent store handle.
   int64 db_handle_;
 
-  // Timer for regularly updating our observers
+  // Timer for regularly updating our observers.
   base::RepeatingTimer<DownloadItem> update_timer_;
 
-  // Our owning object
+  // Our owning object.
   DownloadManager* download_manager_;
 
-  // In progress downloads may be paused by the user, we note it here
+  // In progress downloads may be paused by the user, we note it here.
   bool is_paused_;
 
   // A flag for indicating if the download should be opened at completion.
   bool open_when_complete_;
 
   // A flag for indicating if the downloaded file is externally removed.
   bool file_externally_removed_;
 
   // Indicates if the download is considered potentially safe or dangerous
   // (executable files are typically considered dangerous).
@@ skipping 23 matching lines @@
   // only.
   bool open_enabled_;
 
   // Did the delegate delay calling Complete on this download?
   bool delegate_delayed_complete_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadItem);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_ITEM_H_