Add support for bsdiff of file system metadata blocks

delta_diff_generator.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_DIFF_GENERATOR_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_DIFF_GENERATOR_H__
 
 #include <string>
 #include <vector>
 #include "base/basictypes.h"
@@ skipping 85 matching lines @@
   // operation. If there is a change, or the old file doesn't exist,
   // the smallest of REPLACE, REPLACE_BZ, or BSDIFF wins.
   // new_filename must contain at least one byte.
   // Returns true on success.
   static bool ReadFileToDiff(const std::string& old_filename,
                              const std::string& new_filename,
                              std::vector<char>* out_data,
                              DeltaArchiveManifest_InstallOperation* out_op,
                              bool gather_extents);
 
+  // Similar to ReadFileToDiff but instead of working with a regular file,
+  // this function processes all file system related metadata and adds the
+  // required operations to graph.
+  static bool DeltaReadMetadata(Graph* graph,
+                                std::vector<Block>* blocks,
+                                const std::string& old_image,
+                                const std::string& new_image,
+                                int data_fd,
+                                off_t* data_file_size);
+
   // Creates a dummy REPLACE_BZ node in the given |vertex|. This can be used
   // to provide scratch space. The node writes |num_blocks| blocks starting at
   // |start_block|The node should be marked invalid before writing all nodes to
   // the output file.
   static void CreateScratchNode(uint64_t start_block,
                                 uint64_t num_blocks,
                                 Vertex* vertex);
 
   // Modifies blocks read by 'op' so that any blocks referred to by
   // 'remove_extents' are replaced with blocks from 'replace_extents'.
@@ skipping 102 matching lines @@
   DISALLOW_IMPLICIT_CONSTRUCTORS(DeltaDiffGenerator);
 };
 
 extern const char* const kBsdiffPath;
 extern const char* const kBspatchPath;
 extern const char* const kDeltaMagic;
 
 };  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DELTA_DIFF_GENERATOR_H__