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.

manifest/content_id.h

@@ -0,0 +1,90 @@
+/*
+ * 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 MANIFEST_CONTENT_ID_H_
+#define MANIFEST_CONTENT_ID_H_
+
+#include <string>
+
+#include "absl/strings/string_view.h"
+#include "manifest/manifest_proto_defs.h"
+
+namespace cdc_ft {
+
+// This helper class provides some utility functions to work with ContentIdProto
+// messages.
+class ContentId {
+ public:
+  // Hashes are 160 bit long.
+  static constexpr size_t kHashSize = 20;
+
+  // Returns content ID for the |data| passed in as a string.
+  static ContentIdProto FromDataString(const std::string& data);
+
+  // Returns the content ID for the |data| passed in as a string_view.
+  static ContentIdProto FromDataString(absl::string_view data);
+
+  // Returns the content ID for the |data| passed in as a pointer.
+  static ContentIdProto FromArray(const void* data, size_t len);
+
+  // Converts the given content ID into a hex string. The string will consist of
+  // the hex digits of the hash ('0'...'9', 'a'...'f'), so a 160 bit hash
+  // results in a string of length kHashSize * 2.
+  static std::string ToHexString(const ContentIdProto& content_id);
+
+  // Converts the given hex string into a content ID. The string is assumed to
+  // consist of the hex digits of the hash ('0'...'9', 'a'...'f'), so a 160 bit
+  // hash would have length kHashSize * 2. Returns false if |str| is malformed.
+  static bool FromHexString(const std::string& str, ContentIdProto* content_id);
+
+  // Returns the |pos| byte of |content_id|.
+  // Returns 0 if |content_id| is not set or |pos| is invalid.
+  static uint8_t GetByte(const ContentIdProto& content_id, size_t pos);
+};
+
+namespace proto {
+
+inline bool operator==(const ContentId& a, const ContentId& b) {
+  return a.blake3_sum_160() == b.blake3_sum_160();
+}
+
+inline bool operator!=(const ContentId& a, const ContentId& b) {
+  return !(a == b);
+}
+
+inline bool operator<(const ContentId& a, const ContentId& b) {
+  return a.blake3_sum_160() < b.blake3_sum_160();
+}
+
+}  // namespace proto
+}  // namespace cdc_ft
+
+namespace std {
+
+template <>
+struct hash<cdc_ft::ContentIdProto> {
+  size_t operator()(const cdc_ft::ContentIdProto& id) const {
+    // Pick the first 8 bytes of the hash (assuming 64 bit binary).
+    if (id.blake3_sum_160().size() < sizeof(size_t)) {
+      return 0;
+    }
+    return *reinterpret_cast<const size_t*>(id.blake3_sum_160().data());
+  }
+};
+
+}  // namespace std
+
+#endif  // MANIFEST_CONTENT_ID_H_