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/cdc_fuse_fs.h

@@ -0,0 +1,86 @@
+/*
+ * 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_CDC_FUSE_FS_H_
+#define CDC_FUSE_FS_CDC_FUSE_FS_H_
+
+#ifndef R_OK
+#define R_OK 4
+#endif
+#ifndef W_OK
+#define W_OK 2
+#endif
+#ifndef X_OK
+#define X_OK 1
+#endif
+
+#include <memory>
+
+#include "absl/status/status.h"
+#include "cdc_fuse_fs/config_stream_client.h"
+#include "grpcpp/channel.h"
+#include "manifest/manifest_proto_defs.h"
+
+namespace cdc_ft {
+
+class DataStoreReader;
+
+// CdcFuse filesystem constants, exposed for testing.
+namespace internal {
+// Number of hardlinks is not important since the fs is read-only (I think).
+constexpr int kCdcFuseDefaultNLink = 1;
+
+// Cloudcast user and group id.
+constexpr int kCdcFuseCloudcastUid = 1000;
+constexpr int kCdcFuseCloudcastGid = 1000;
+
+// Root user and group id.
+constexpr int kCdcFuseRootUid = 0;
+constexpr int kCdcFuseRootGid = 0;
+
+// Default timeout after which the kernel will assume inodes are stale.
+constexpr double kCdcFuseInodeTimeoutSec = 1.0;
+}  // namespace internal
+
+namespace cdc_fuse_fs {
+
+// Initializes the CDC FUSE filesystem. Parses the command line, sets up a
+// channel and a session, and optionally forks the process. For valid arguments
+// see fuse_common.h.
+absl::Status Initialize(int argc, char** argv);
+
+// Starts a client to read configuration updates over gRPC |channel|.
+// |instance| is the gamelet instance id.
+absl::Status StartConfigClient(std::string instance,
+                               std::shared_ptr<grpc::Channel> channel);
+
+// Sets the |data_store_reader| to load data from, initializes FUSE with a
+// manifest for an empty directory, and starts the filesystem. The call does
+// not return until the filesystem finishes running.
+// |consistency_check| defines whether FUSE consistency should be inspected
+// after each manifest update.
+absl::Status Run(DataStoreReader* data_store_reader, bool consistency_check);
+
+// Releases resources. Should be called when the filesystem finished running.
+void Shutdown();
+
+// Sets |manifest_id| as a CDC FUSE root.
+absl::Status SetManifest(const ContentIdProto& manifest_id);
+
+}  // namespace cdc_fuse_fs
+}  // namespace cdc_ft
+
+#endif  // CDC_FUSE_FS_CDC_FUSE_FS_H_