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/buffer.cc

@@ -0,0 +1,88 @@
+// 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/buffer.h"
+
+#include <cstring>
+#include <utility>
+
+namespace cdc_ft {
+
+Buffer::Buffer() = default;
+
+Buffer::Buffer(size_t size) : size_(size) {
+  reserve(size);
+  resize(size);
+}
+
+Buffer::Buffer(std::initializer_list<char> list) {
+  reserve(list.size());
+  resize(list.size());
+  memcpy(data_, list.begin(), list.size());
+}
+
+Buffer::Buffer(Buffer&& other) noexcept { *this = std::move(other); }
+
+Buffer& Buffer::operator=(Buffer&& other) noexcept {
+  if (data_) {
+    free(data_);
+  }
+
+  size_ = other.size_;
+  capacity_ = other.capacity_;
+  data_ = other.data_;
+
+  other.size_ = 0;
+  other.capacity_ = 0;
+  other.data_ = nullptr;
+
+  return *this;
+}
+
+Buffer::~Buffer() {
+  if (data_) {
+    free(data_);
+    data_ = nullptr;
+    capacity_ = 0;
+  }
+}
+
+bool Buffer::operator==(const Buffer& other) const {
+  return size_ == other.size_ && memcmp(data_, other.data_, size_) == 0;
+}
+
+bool Buffer::operator!=(const Buffer& other) const { return !(*this == other); }
+
+void Buffer::resize(size_t new_size) {
+  size_ = new_size;
+  if (capacity_ < size_) {
+    capacity_ = size_ + size_ / 2;
+    data_ = static_cast<char*>(realloc(data_, capacity_));
+  }
+}
+
+void Buffer::reserve(size_t capacity) {
+  if (capacity_ < capacity) {
+    capacity_ = capacity;
+    data_ = static_cast<char*>(realloc(data_, capacity_));
+  }
+}
+
+void Buffer::append(const void* data, size_t data_size) {
+  size_t prev_size = size_;
+  resize(prev_size + data_size);
+  memcpy(data_ + prev_size, data, data_size);
+}
+
+}  // namespace cdc_ft