Add support for bsdiff of file system metadata blocks

metadata.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_METADATA_H__
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_METADATA_H__
+
+#include "update_engine/delta_diff_generator.h"
+#include "update_engine/graph_types.h"
+
+namespace chromeos_update_engine {
+
+// Reads metadata from old image and new image and determines
+// the smallest way to encode the metadata for the diff.
+// If there's no change in the metadata, it creates a MOVE
+// operation. If there is a change, the smallest of REPLACE, REPLACE_BZ,
+// or BSDIFF wins. It writes the diff to data_fd and updates data_file_size
+// accordingly. It also adds the required operation to the graph and adds the
+// metadata extents to blocks.
+// Returns true on success.
+bool DeltaReadMetadata(Graph* graph,

[petkov, 2010/12/15 18:40:32]

This should probably be a static member of a class. See full_update_generator.h,
for example.

[thieule, 2010/12/15 19:57:01]

Done.

+                       std::vector<DeltaDiffGenerator::Block>* blocks,
+                       const std::string& old_image,
+                       const std::string& new_image,
+                       int data_fd,
+                       off_t* data_file_size);
+
+};  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_METADATA_H__