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_rsync_server/main.cc

@@ -0,0 +1,105 @@
+// 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.
+
+#include "cdc_rsync/base/server_exit_code.h"
+#include "cdc_rsync_server/cdc_rsync_server.h"
+#include "common/gamelet_component.h"
+#include "common/log.h"
+#include "common/status.h"
+
+namespace {
+
+void SendErrorMessage(const char* msg) {
+  constexpr char marker = cdc_ft::kServerErrorMarker;
+  fprintf(stderr, "%c%s%c", marker, msg, marker);
+}
+
+}  // namespace
+
+namespace cdc_ft {
+
+// Returns custom error codes based on the tag associated with |status|. This is
+// used to display custom error messages on the client.
+// Example: A bind failure usually means two instances are in use
+//          simultaneously.
+ServerExitCode GetExitCode(const absl::Status& status) {
+  absl::optional<Tag> tag = GetTag(status);
+  if (!tag.has_value()) {
+    return kServerExitCodeGeneric;
+  }
+
+  // Some tags translate to a special error message on the client.
+  switch (tag.value()) {
+    case Tag::kAddressInUse:
+      // Can't bind port, probably two instances in use simultaneously.
+      return kServerExitCodeAddressInUse;
+
+    case Tag::kSocketEof:
+      // Usually means client disconnected and shut down already.
+    case Tag::kDeployServer:
+    case Tag::kInstancePickerNotAvailableInQuietMode:
+    case Tag::kConnectionTimeout:
+    case Tag::kCount:
+      // Should not happen in server.
+      break;
+  }
+
+  return kServerExitCodeGeneric;
+}
+
+}  // namespace cdc_ft
+
+int main(int argc, const char** argv) {
+  if (argc < 2) {
+    printf("Usage: cdc_rsync_server <port> cdc_rsync_server <size> <time> \n");
+    printf("       where <size> and <time> are the file size and modified\n");
+    printf("       timestamp (Unix epoch) of the corresponding component.\n");
+    return cdc_ft::kServerExitCodeGenericStartup;
+  }
+
+  int port = atoi(argv[1]);
+  if (port == 0) {
+    SendErrorMessage(absl::StrFormat("Invalid port '%s'", argv[1]).c_str());
+    return cdc_ft::kServerExitCodeGenericStartup;
+  }
+
+  // The rest is expected to be sets of gamelet component info consisting of
+  // (filename, filesize, modified_time). This is used check whether the
+  // components are up-to-date.
+  std::vector<cdc_ft::GameletComponent> components =
+      cdc_ft::GameletComponent::FromCommandLineArgs(argc - 2, argv + 2);
+
+  cdc_ft::Log::Initialize(
+      std::make_unique<cdc_ft::ConsoleLog>(cdc_ft::LogLevel::kWarning));
+  cdc_ft::GgpRsyncServer server;
+  if (!server.CheckComponents(components)) {
+    return cdc_ft::kServerExitCodeOutOfDate;
+  }
+
+  absl::Status status = server.Run(port);
+  if (status.ok()) {
+    return 0;
+  }
+
+  cdc_ft::ServerExitCode code = cdc_ft::GetExitCode(status);
+
+  // Print full error in verbose mode, so that it's not lost.
+  if (server.GetVerbosity() >= 2) {
+    fprintf(stderr, "Server error: %s\n", status.ToString().c_str());
+  }
+
+  // Send error message to the client and return code.
+  SendErrorMessage(std::string(status.message()).c_str());
+  return code;
+}