AU: Speed up full update payload generation by running multiple threads.

full_update_generator.h

Index: full_update_generator.h
diff --git a/full_update_generator.h b/full_update_generator.h
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+// 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_FULL_UPDATE_GENERATOR_H__
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_FULL_UPDATE_GENERATOR_H__
+
+#include <glib.h>
+
+#include "update_engine/graph_types.h"
+
+namespace chromeos_update_engine {
+
+class FullUpdateGenerator {
+ public:
+  // Given a new rootfs and kernel (|new_image|, |new_kernel_part|), reads them
+  // sequentially, creating a full update of chunk_size chunks. Populates
+  // |graph|, |kernel_ops|, and |final_order|, with data about the update
+  // operations, and writes relevant data to |fd|, updating |data_file_size| as
+  // it does. Only the first |image_size| bytes are read from |new_image|
+  // assuming that this is the actual file system.
+  static bool Run(
+      Graph* graph,
+      const std::string& new_kernel_part,
+      const std::string& new_image,
+      off_t image_size,
+      int fd,
+      off_t* data_file_size,
+      off_t chunk_size,
+      off_t block_size,
+      std::vector<DeltaArchiveManifest_InstallOperation>* kernel_ops,
+      std::vector<Vertex::Index>* final_order);
+
+ private:
+  // This should never be constructed.
+  DISALLOW_IMPLICIT_CONSTRUCTORS(FullUpdateGenerator);
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_FULL_UPDATE_GENERATOR_H__