Added member data to classes to support download resumption.

content/browser/download/base_file.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.
 
 #ifndef CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_
 #define CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_
 #pragma once
 
 #include <string>
 
 #include "base/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/pickle.h"
 #include "content/browser/power_save_blocker.h"
 #include "content/common/content_export.h"
 #include "googleurl/src/gurl.h"
 #include "net/base/file_stream.h"
 #include "net/base/net_errors.h"
 
+class Pickle;

[Randy Smith (Not in Mondays), 2011/11/21 02:10:17]

I don't think Pickle belongs in the interface to *File; it's an implementation
detail of how we save and restore the hash.  The pickle class is used to
transform between an arbitrary data structure and a byte chunk of of a
particular size.  I believe (?) that that can be wrapped in a string, and I'd
much rather have a string or some other opaque object than a Pickle.  Pickle's
are for transformation, not for passing stuff around.

Having said that, the current situation makes it very clear that partial and
complete hashes are really different things (one's a serialized intermediate
state of a class we don't know much about, the other has some meaning to it). 
So I'd suggest (with sadness; it's complexity in the interface we don't need)
that you shift back to have separate getters for the intermediate and final
hash.  

Note that it's probably *not* safe to store the intermediate hash value (==
pickle output) as a string in the database; that probably has to be a blob.

[ahendrickson, 2011/11/21 20:34:47]

Done.
This is done.
Agreed, but that will be in a separate CL.

+
 namespace crypto {
 class SecureHash;
 }
 namespace net {
 class FileStream;
 }
 
 // File being downloaded and saved to disk. This is a base class
 // for DownloadFile and SaveFile, which keep more state information.
 class CONTENT_EXPORT BaseFile {
  public:
   BaseFile(const FilePath& full_path,
            const GURL& source_url,
            const GURL& referrer_url,
            int64 received_bytes,
+           const Pickle& hash_state,
            const linked_ptr<net::FileStream>& file_stream);
   virtual ~BaseFile();
 
   // If calculate_hash is true, sha256 hash will be calculated.
   // Returns net::OK on success, or a network error code on failure.
   net::Error Initialize(bool calculate_hash);
 
   // Write a new chunk of data to the file.
   // Returns net::OK on success (all bytes written to the file),
   // or a network error code on failure.
@@ skipping 12 matching lines @@
   // Indicate that the download has finished. No new data will be received.
   void Finish();
 
   // Informs the OS that this file came from the internet.
   void AnnotateWithSourceInformation();
 
   FilePath full_path() const { return full_path_; }
   bool in_progress() const { return file_stream_ != NULL; }
   int64 bytes_so_far() const { return bytes_so_far_; }
 
-  // Set |hash| with sha256 digest for the file.
+  // Fills |hash| with the sha256 digest for the file.  May be partial.
   // Returns true if digest is successfully calculated.
   virtual bool GetSha256Hash(std::string* hash);
 
+  // Retrieves the current (intermediate) state of the hash and puts it in
+  // |hash_state|.
+  virtual bool GetSha256HashState(Pickle* hash_state);
+
+  // Resets the current state of the hash to the contents of |hash_state|.
+  virtual bool SetSha256HashState(Pickle* hash_state);
+
   // Returns true if the given hash is considered empty.  An empty hash is
   // a string of size kSha256HashLen that contains only zeros (initial value
   // for the hash).
   static bool IsEmptySha256Hash(const std::string& hash);
 
   virtual std::string DebugString() const;
 
  protected:
   virtual void CreateFileStream();  // For testing.
   // Returns net::OK on success, or a network error code on failure.
@@ skipping 25 matching lines @@
   // RAII handle to keep the system from sleeping while we're downloading.
   PowerSaveBlocker power_save_blocker_;
 
   // Indicates if sha256 hash should be calculated for the file.
   bool calculate_hash_;
 
   // Used to calculate sha256 hash for the file when calculate_hash_
   // is set.
   scoped_ptr<crypto::SecureHash> secure_hash_;
 
+  // The hash state is stored here on creation.
+  Pickle initial_hash_state_;
+
   unsigned char sha256_hash_[kSha256HashLen];
 
   // Indicates that this class no longer owns the associated file, and so
   // won't delete it on destruction.
   bool detached_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseFile);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_BASE_FILE_H_