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.

asset_stream_manager/asset_stream_config.h

@@ -0,0 +1,107 @@
+/*
+ * 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 ASSET_STREAM_MANAGER_ASSET_STREAM_CONFIG_H_
+#define ASSET_STREAM_MANAGER_ASSET_STREAM_CONFIG_H_
+
+#include <map>
+#include <set>
+#include <string>
+
+#include "absl/status/status.h"
+#include "asset_stream_manager/session_config.h"
+
+namespace cdc_ft {
+
+// Class containing all configuration settings for asset streaming.
+// Reads flags from the command line and optionally applies overrides from
+// a json file.
+class AssetStreamConfig {
+ public:
+  // Constructs the configuration by applying command line flags.
+  AssetStreamConfig();
+  ~AssetStreamConfig();
+
+  // Loads a configuration from the JSON file at |path| and overrides any config
+  // values that are set in this file. Sample json file:
+  // {
+  //   "src_dir":"C:\\path\\to\\assets",
+  //   "verbosity":3,
+  //   "debug":0,
+  //   "singlethreaded":0,
+  //   "stats":0,
+  //   "quiet":0,
+  //   "check":0,
+  //   "log_to_stdout":0,
+  //   "cache_capacity":"150G",
+  //   "cleanup_timeout":300,
+  //   "access_idle_timeout":5,
+  //   "manifest_updater_threads":4,
+  //   "file_change_wait_duration_ms":500
+  // }
+  // Returns NotFoundError if the file does not exist.
+  // Returns InvalidArgumentError if the file is not valid JSON.
+  absl::Status LoadFromFile(const std::string& path);
+
+  // Returns a string with all config values, suitable for logging.
+  std::string ToString();
+
+  // Gets a comma-separated list of flags that were read from the JSON file.
+  // These flags override command line flags.
+  std::string GetFlagsReadFromFile();
+
+  // Gets a newline-separated list of errors for each flag that could not be
+  // read from the JSON file.
+  std::string GetFlagReadErrors();
+
+  // Workstation directory to stream. Should usually be empty since mounts are
+  // triggered by the CLI or the partner portal via a gRPC call, but useful
+  // during development.
+  const std::string& src_dir() const { return src_dir_; }
+
+  // IP address of the instance to stream to. Should usually be empty since
+  // mounts are triggered by the CLI or the partner portal via a gRPC call, but
+  // useful during development.
+  const std::string& instance_ip() const { return instance_ip_; }
+
+  // IP address of the instance to stream to. Should usually be unset (0) since
+  // mounts are triggered by the CLI or the partner portal via a gRPC call, but
+  // useful during development.
+  const uint16_t instance_port() const { return instance_port_; }
+
+  // Session configuration.
+  const SessionConfig session_cfg() const { return session_cfg_; }
+
+  // Whether to log to a file or to stdout.
+  bool log_to_stdout() const { return log_to_stdout_; }
+
+ private:
+  std::string src_dir_;
+  std::string instance_ip_;
+  uint16_t instance_port_ = 0;
+  SessionConfig session_cfg_;
+  bool log_to_stdout_ = false;
+
+  // Use a set, so the flags are sorted alphabetically.
+  std::set<std::string> flags_read_from_file_;
+
+  // Maps flags to errors occurred while reading this flag.
+  std::map<std::string, std::string> flag_read_errors_;
+};
+
+};  // namespace cdc_ft
+
+#endif  // ASSET_STREAM_MANAGER_ASSET_STREAM_CONFIG_H_