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.

cdc_fuse_fs/asset_stream_client.h

@@ -0,0 +1,62 @@
+/*
+ * 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 CDC_FUSE_FS_ASSET_STREAM_CLIENT_H_
+#define CDC_FUSE_FS_ASSET_STREAM_CLIENT_H_
+
+#include <memory>
+#include <string>
+#include <thread>
+
+#include "absl/status/statusor.h"
+#include "grpcpp/channel.h"
+#include "manifest/manifest_proto_defs.h"
+#include "proto/asset_stream_service.grpc.pb.h"
+
+namespace grpc_impl {
+class Channel;
+}
+
+namespace cdc_ft {
+
+// gRpc client for streaming assets to a gamelets. The client runs inside the
+// CDC Fuse filesystem and requests chunks from the workstation.
+class AssetStreamClient {
+ public:
+  // |channel| is a grpc channel to use.
+  // |enable_stats| determines whether additional statistics are sent.
+  AssetStreamClient(std::shared_ptr<grpc::Channel> channel, bool enable_stats);
+  ~AssetStreamClient();
+
+  // Gets the content of the chunk with given |id|.
+  absl::StatusOr<std::string> GetContent(const ContentIdProto& id);
+  absl::StatusOr<RepeatedStringProto> GetContent(
+      RepeatedContentIdProto chunk_ids);
+
+  // Sends the IDs of all cached chunks to the workstation for statistical
+  // purposes.
+  absl::Status SendCachedContentIds(std::vector<ContentIdProto> content_ids);
+
+ private:
+  using AssetStreamService = proto::AssetStreamService;
+  std::unique_ptr<AssetStreamService::Stub> stub_;
+  bool enable_stats_;
+  std::hash<std::thread::id> thread_id_hash_;
+};
+
+}  // namespace cdc_ft
+
+#endif  // CDC_FUSE_FS_ASSET_STREAM_CLIENT_H_