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/session_manager.h

@@ -0,0 +1,100 @@
+/*
+ * 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_SESSION_MANAGER_H_
+#define ASSET_STREAM_MANAGER_SESSION_MANAGER_H_
+
+#include <memory>
+#include <unordered_map>
+
+#include "absl/status/status.h"
+#include "absl/status/statusor.h"
+#include "absl/synchronization/mutex.h"
+#include "asset_stream_manager/session_config.h"
+#include "metrics/metrics.h"
+
+namespace cdc_ft {
+
+class MultiSession;
+class ProcessFactory;
+
+// Implements a service to start and stop streaming sessions as a server.
+// The corresponding clients are implemented by the ggp CLI and SDK Proxy.
+// The CLI triggers StartSession() from `ggp instance mount --local-dir` and
+// StopSession() from `ggp instance unmount`. SDK Proxy invokes StartSession()
+// when a user starts a new game from the partner portal and sets an `Asset
+// streaming directory` in the `Advanced settings` in the `Play settings`
+// dialog.
+// This service is owned by SessionManagementServer.
+class SessionManager {
+ public:
+  SessionManager(SessionConfig cfg, ProcessFactory* process_factory,
+                 metrics::MetricsService* metrics_service);
+  ~SessionManager();
+
+  // Starts a session and populates |multi_session| and |metrics_status|.
+  absl::Status StartSession(const std::string& instance_id,
+                            const std::string& project_id,
+                            const std::string& organization_id,
+                            const std::string& instance_ip,
+                            uint16_t instance_port, const std::string& src_dir,
+                            MultiSession** multi_session,
+                            metrics::SessionStartStatus* metrics_status)
+      ABSL_LOCKS_EXCLUDED(sessions_mutex_);
+
+  // Stops the session for the given |instance|. Returns a NotFound error if no
+  // session exists.
+  absl::Status StopSession(const std::string& instance)
+      ABSL_LOCKS_EXCLUDED(sessions_mutex_);
+
+  // Shuts down all existing MultiSessions.
+  absl::Status Shutdown() ABSL_LOCKS_EXCLUDED(sessions_mutex_);
+
+ private:
+  // Stops the session for the given |instance|. Returns a NotFound error if no
+  // session exists.
+  absl::Status StopSessionInternal(const std::string& instance)
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(sessions_mutex_);
+
+  // Returns the MultiSession for the given workstation directory |src_dir| or
+  // nullptr if it does not exist.
+  MultiSession* GetMultiSession(const std::string& src_dir)
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(sessions_mutex_);
+
+  // Gets an existing MultiSession or creates a new one for the given
+  // workstation directory |src_dir|.
+  absl::StatusOr<MultiSession*> GetOrCreateMultiSession(
+      const std::string& src_dir)
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(sessions_mutex_);
+
+  // Sets session start status for a metrics event.
+  void SetSessionStartStatus(metrics::DeveloperLogEvent* evt,
+                             absl::Status absl_status,
+                             metrics::SessionStartStatus status) const;
+
+  const SessionConfig cfg_;
+  ProcessFactory* const process_factory_;
+  metrics::MetricsService* const metrics_service_;
+
+  absl::Mutex sessions_mutex_;
+  using SessionMap =
+      std::unordered_map<std::string, std::unique_ptr<MultiSession>>;
+  SessionMap sessions_ ABSL_GUARDED_BY(sessions_mutex_);
+};
+
+}  // namespace cdc_ft
+
+#endif  // ASSET_STREAM_MANAGER_SESSION_MANAGER_H_