Releasing the former Stadia file transfer tools

The tools allow efficient and fast synchronization of large directory
trees from a Windows workstation to a Linux target machine.

cdc_rsync* support efficient copy of files by using content-defined
chunking (CDC) to identify chunks within files that can be reused.

asset_stream_manager + cdc_fuse_fs support efficient streaming of a
local directory to a remote virtual file system based on FUSE. It also
employs CDC to identify and reuse unchanged data chunks.

common/gamelet_component.h

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef COMMON_GAMELET_COMPONENT_H_
+#define COMMON_GAMELET_COMPONENT_H_
+
+#include <string>
+#include <vector>
+
+#include "absl/status/status.h"
+
+namespace cdc_ft {
+
+// Provides functionality to check the freshness of gamelet components.
+// The components are considered fresh if both the timestamp and the file size
+// match.
+struct GameletComponent {
+  std::string filename;
+  uint64_t size;
+  int64_t modified_time;
+
+  GameletComponent(std::string filename, uint64_t size, time_t modified_time);
+  ~GameletComponent();
+
+  bool operator==(const GameletComponent& other) const;
+  bool operator!=(const GameletComponent& other) const;
+
+  // Gets the list of gamelet |components| from the given |component_paths|.
+  // Returns false if any of the components does not exist or cannot be stat'ed.
+  static absl::Status Get(const std::vector<std::string> component_paths,
+                          std::vector<GameletComponent>* components);
+
+  // Serializes the list of gamelet |components| as command line options.
+  // This should be called on the workstation. The resulting command line
+  // should be passed to the gamelet process.
+  static std::string ToCommandLineArgs(
+      const std::vector<GameletComponent>& components);
+
+  // Deserializes the list of gamelet components from command line options.
+  // This should be called in the gamelet process to retrieve the workstation
+  // components, which can then be compared to the gamelet components to check
+  // freshness.
+  static std::vector<GameletComponent> FromCommandLineArgs(int argc,
+                                                           const char** argv);
+
+  // Deserializes the list of gamelet components from a |components_arg| string
+  // as it is returned by ToCommandLineArgs().
+  // This should be called in the gamelet process to retrieve the workstation
+  // components, which can then be compared to the gamelet components to check
+  // freshness.
+  static std::vector<GameletComponent> FromCommandLineArgs(
+      const std::string& components_arg);
+};
+
+}  // namespace cdc_ft
+
+#endif  // COMMON_GAMELET_COMPONENT_H_