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/mock_libfuse.h

@@ -0,0 +1,123 @@
+/*
+ * 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_MOCK_LIBFUSE_H_
+#define CDC_FUSE_FS_MOCK_LIBFUSE_H_
+
+#include <fcntl.h>
+#include <sys/stat.h>
+
+#include <cstdint>
+#include <vector>
+
+namespace cdc_ft {
+
+//
+// The interface below mimics the part of the FUSE low level interface we need.
+// See include/fuse_lowlevel.h for more information.
+//
+
+// Definitions.
+using fuse_ino_t = uint64_t;
+using fuse_req_t = void*;
+using nlink_t = uint64_t;
+
+constexpr fuse_ino_t FUSE_ROOT_ID = 1;
+#ifndef O_DIRECT
+constexpr uint32_t O_DIRECT = 040000;
+#endif
+
+struct fuse_entry_param {
+  fuse_ino_t ino;
+  struct stat attr;
+  double attr_timeout;
+  double entry_timeout;
+};
+
+struct fuse_file_info {
+  int flags = O_RDONLY;
+  unsigned int direct_io : 1;
+  unsigned int keep_cache : 1;
+
+  fuse_file_info() : direct_io(0), keep_cache(0) {}
+  explicit fuse_file_info(int flags)
+      : flags(flags), direct_io(0), keep_cache(0) {}
+};
+
+struct fuse_forget_data {
+  uint64_t ino;
+  uint64_t nlookup;
+};
+
+struct fuse_context {
+  int uid;
+  int gid;
+};
+
+struct statvfs {
+  uint32_t f_bsize;
+  uint32_t f_namemax;
+};
+
+// FUSE reply/action functions.
+size_t fuse_add_direntry(fuse_req_t req, char* buf, size_t bufsize,
+                         const char* name, const struct stat* stbuf, off_t off);
+int fuse_reply_attr(fuse_req_t req, const struct stat* attr,
+                    double attr_timeout);
+int fuse_reply_buf(fuse_req_t req, const char* buf, size_t size);
+int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param* e);
+int fuse_reply_err(fuse_req_t req, int err);
+int fuse_reply_open(fuse_req_t req, const struct fuse_file_info* fi);
+void fuse_reply_none(fuse_req_t req);
+int fuse_reply_statfs(fuse_req_t req, const struct statvfs* stbuf);
+struct fuse_context* fuse_get_context();
+
+// FUSE mocking class. Basically just a recorder for the fuse_* callbacks above.
+struct MockLibFuse {
+ public:
+  MockLibFuse();
+  ~MockLibFuse();
+
+  struct Attr {
+    struct stat value;
+    double timeout;
+    Attr(struct stat value, double timeout)
+        : value(std::move(value)), timeout(timeout) {}
+  };
+  void SetUid(int uid);
+  void SetGid(int gid);
+
+  // Struct stored in the buffer |buf| by fuse_add_direntry().
+  // Uses a maximum name size for simplicity.
+  struct DirEntry {
+    fuse_ino_t ino;
+    uint32_t mode;
+    char name[32];
+    off_t off;
+  };
+
+  std::vector<fuse_entry_param> entries;
+  std::vector<Attr> attrs;
+  std::vector<int> errors;
+  std::vector<fuse_file_info> open_files;
+  std::vector<std::vector<char>> buffers;
+  unsigned int none_counter = 0;
+  fuse_context context;
+};
+
+}  // namespace cdc_ft
+
+#endif  // CDC_FUSE_FS_MOCK_LIBFUSE_H_