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.

common/scoped_handle_win.cc

@@ -0,0 +1,77 @@
+// 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 "common/scoped_handle_win.h"
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+#include <cassert>
+#include <memory>
+
+namespace cdc_ft {
+
+ScopedHandle::ScopedHandle() : handle_(nullptr) {}
+
+ScopedHandle::ScopedHandle(HANDLE handle) : handle_(nullptr) { Set(handle); }
+
+ScopedHandle::ScopedHandle(ScopedHandle&& other) : handle_(nullptr) {
+  Set(other.Release());
+}
+
+ScopedHandle::~ScopedHandle() { Close(); }
+
+bool ScopedHandle::IsValid() const { return IsHandleValid(handle_); }
+
+ScopedHandle& ScopedHandle::operator=(ScopedHandle&& other) {
+  Set(other.Release());
+  return *this;
+}
+
+void ScopedHandle::Set(HANDLE handle) {
+  if (handle_ != handle) {
+    // Preserve old error code.
+    uint32_t last_error = GetLastError();
+    Close();
+
+    if (IsHandleValid(handle)) {
+      handle_ = handle;
+    }
+    SetLastError(last_error);
+  }
+}
+
+HANDLE ScopedHandle::Get() const {
+  assert(IsValid());
+  return handle_;
+}
+
+HANDLE ScopedHandle::Release() {
+  HANDLE temp = handle_;
+  handle_ = nullptr;
+  return temp;
+}
+
+void ScopedHandle::Close() {
+  if (IsHandleValid(handle_)) {
+    CloseHandle(handle_);
+    handle_ = nullptr;
+  }
+}
+
+bool ScopedHandle::IsHandleValid(HANDLE handle) {
+  return handle != nullptr && handle != INVALID_HANDLE_VALUE;
+}
+
+}  // namespace cdc_ft