Useful for things like partitions.
*)
+class blocksize_overlay : int -> device ->
+ object
+ method name : string
+ method size : int64
+ method read : int64 -> int -> string
+ method read_bitstring : int64 -> int -> Bitmatch.bitstring
+ method blocksize : int
+ method mapblock : int64 -> (device * int64) list
+ end
+ (** Change the blocksize of an existing device. *)
+
val null_device : device
(** The null device. Any attempt to read generates an error. *)