AU: Optimize checkpointing a bit and decide on new update vs. resume.

delta_performer.h

 // Copyright (c) 2010 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_PERFORMER_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_PERFORMER_H__
 
 #include <inttypes.h>
 
 #include <vector>
@@ skipping 13 matching lines @@
 
 class DeltaPerformer : public FileWriter {
  public:
   DeltaPerformer(PrefsInterface* prefs)
       : prefs_(prefs),
         fd_(-1),
         kernel_fd_(-1),
         manifest_valid_(false),
         next_operation_num_(0),
         buffer_offset_(0),
+        last_updated_buffer_offset_(kuint64max),
         block_size_(0) {}
 
   // Opens the kernel. Should be called before or after Open(), but before
   // Write(). The kernel file will be close()d when Close() is called.
   bool OpenKernel(const char* kernel_path);
 
   // flags and mode ignored. Once Close()d, a DeltaPerformer can't be
   // Open()ed again.
   int Open(const char* path, int flags, mode_t mode);
 
@@ skipping 21 matching lines @@
   // Also, an extent starting at kSparseHole, appears as -1 in the string.
   // For example, if the Extents are {1, 1}, {4, 2}, {kSparseHole, 1},
   // {0, 1}, block_size is 4096, and full_length is 5 * block_size - 13,
   // the resulting string will be: "4096:4096,16384:8192,-1:4096,0:4083"
   static bool ExtentsToBsdiffPositionsString(
       const google::protobuf::RepeatedPtrField<Extent>& extents,
       uint64_t block_size,
       uint64_t full_length,
       std::string* positions_string);
 
+  // Returns true if a previous update attempt can be continued based on the
+  // persistent preferences and the new update check response hash.
+  static bool CanResumeUpdate(PrefsInterface* prefs,
+                              std::string update_check_response_hash);
+
+  // Resets the persistent update progress state to indicate that an update
+  // can't be resumed. Returns true on success, false otherwise.
+  static bool ResetUpdateProgress(PrefsInterface* prefs);
+
  private:
   // Returns true if enough of the delta file has been passed via Write()
   // to be able to perform a given install operation.
   bool CanPerformInstallOperation(
       const DeltaArchiveManifest_InstallOperation& operation);
 
   // Returns true on success.
   bool PerformInstallOperation(
       const DeltaArchiveManifest_InstallOperation& operation);
 
@@ skipping 10 matching lines @@
 
   // Returns true if the payload signature message has been extracted from
   // |operation|, false otherwise.
   bool ExtractSignatureMessage(
       const DeltaArchiveManifest_InstallOperation& operation);
 
   // Discard |count| bytes from the beginning of buffer_. If |do_hash| is true,
   // updates the hash calculator with these bytes before discarding them.
   void DiscardBufferHeadBytes(size_t count, bool do_hash);
 
-  bool ResetUpdateProgress();
+  // Checkpoints the update progress into persistent storage to allow this
+  // update attempt to be resumed after reboot.
   bool CheckpointUpdateProgress();
 
   // Update Engine preference store.
   PrefsInterface* prefs_;
 
   // File descriptor of open device.
   int fd_;
 
   // File descriptor of the kernel device
   int kernel_fd_;
 
   std::string path_;  // Path that fd_ refers to.
   std::string kernel_path_;  // Path that kernel_fd_ refers to.
 
   DeltaArchiveManifest manifest_;
   bool manifest_valid_;
 
   // Index of the next operation to perform in the manifest.
   int next_operation_num_;
 
   // buffer_ is a window of the data that's been downloaded. At first,
   // it contains the beginning of the download, but after the protobuf
   // has been downloaded and parsed, it contains a sliding window of
   // data blobs.
   std::vector<char> buffer_;
   // Offset of buffer_ in the binary blobs section of the update.
   uint64_t buffer_offset_;
 
+  // Last |buffer_offset_| value updated as part of the progress update.
+  uint64_t last_updated_buffer_offset_;
+
   // The block size (parsed from the manifest).
   uint32_t block_size_;
 
   // Calculate the payload hash to verify against the signed hash.
   OmahaHashCalculator hash_calculator_;
 
   // Signatures message blob extracted directly from the payload.
   std::vector<char> signatures_message_data_;
 
   DISALLOW_COPY_AND_ASSIGN(DeltaPerformer);
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_PERFORMER_H__