[Downloads] Retry renames after transient failures.

content/browser/download/base_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_BASE_FILE_H_
 #define CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_
 
 #include <string>
 
 #include "base/files/file.h"
@@ skipping 38 matching lines @@
   // |default_directory| and |full_path()| are empty, then a temporary file will
   // be created in the default download location as determined by
   // ContentBrowserClient.
   DownloadInterruptReason Initialize(const base::FilePath& default_directory);
 
   // Write a new chunk of data to the file. Returns a DownloadInterruptReason
   // indicating the result of the operation.
   DownloadInterruptReason AppendDataToFile(const char* data, size_t data_len);
 
   // Rename the download file. Returns a DownloadInterruptReason indicating the
-  // result of the operation.
+  // result of the operation. A return code of NONE indicates that the rename
+  // was successful. After a failure, the full_path() and in_progress() can be
+  // used to determine the last known filename and whether the file is available
+  // for writing or retrying the rename.
   virtual DownloadInterruptReason Rename(const base::FilePath& full_path);
 
   // Detach the file so it is not deleted on destruction.
   virtual void Detach();
 
   // Abort the download and automatically close the file.
   void Cancel();
 
   // Indicate that the download has finished. No new data will be received.
   void Finish();
 
   // Set the client guid which will be used to identify the app to the
   // system AV scanning function. Should be called before
   // AnnotateWithSourceInformation() to take effect.
   void SetClientGuid(const std::string& guid);
 
   // Informs the OS that this file came from the internet. Returns a
   // DownloadInterruptReason indicating the result of the operation.
   // Note: SetClientGuid() should be called before this function on
   // Windows to ensure the correct app client ID is available.
   DownloadInterruptReason AnnotateWithSourceInformation();
 
-  base::FilePath full_path() const { return full_path_; }
+  // Returns the last known path to the download file. Can be empty if there's
+  // no file.
+  const base::FilePath& full_path() const { return full_path_; }
+
+  // Returns true if the file is open. If true, the file can be written to or
+  // renamed.
   bool in_progress() const { return file_.IsValid(); }
+
+  // Returns the number of bytes in the file pointed to by full_path().
   int64 bytes_so_far() const { return bytes_so_far_; }
 
   // Fills |hash| with the hash digest for the file.
   // Returns true if digest is successfully calculated.
   virtual bool GetHash(std::string* hash);
 
   // Returns the current (intermediate) state of the hash as a byte string.
   virtual std::string GetHashState();
 
   // Returns true if the given hash is considered empty.  An empty hash is
@@ skipping 76 matching lines @@
   bool detached_;
 
   net::BoundNetLog bound_net_log_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseFile);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_