+val download_file : ?fail:exn callback -> source -> string -> string -> unit callback -> unit
+ (** [download_file src pathname localfile cb] downloads [pathname]
+ to the named local file, and then calls the callback function. *)
+
+type download_dir_tarball_format = Tar | TGZ | TXZ
+
+val download_dir_tarball : ?fail:exn callback -> source -> string -> download_dir_tarball_format -> string -> unit callback -> unit
+ (** [download_dir_tarball_format src pathname format localfile cb]
+ downloads directory [pathname] to the named local file (a
+ tarball), and then calls the callback function.
+
+ [format] controls the download format, which is one of
+ uncompressed tar, gzip-compressed tar, or xz-compressed tar. *)
+
+val download_dir_find0 : ?fail:exn callback -> source -> string -> string -> unit callback -> unit
+ (** [download_dir_find0 src pathname localfile cb] downloads the
+ list of filenames of directory [pathname] to the named local
+ file (a ASCII NUL-separated text file), and then calls the
+ callback function. *)
+
+val disk_usage : ?fail:exn callback -> source -> string -> int64 callback -> unit
+ (** [disk_usage src pathname cb] calculates the disk usage of
+ directory [pathname] and calls the callback with the answer
+ (size of {b kilobytes}). *)
+