gistfile1.ml

(*
из описания

open Cstruct_codegen;

value example = cstruct "mystruct"
  [ uint8  "ui8"
  ; int64 "si64"
  ]
;

value () = codegen [example]
;

*)

module Mystruct
 :
  sig

    (* Abstract data type to represent values of C-like structure 'mystruct' *)
    type t

    (* size of structure [t] in bytes *)
    val sizeof : int

    (* Creates a value of type [t] on bigarray of size [sizeof].
       one can modify bigarray, and these modifications will
       affect fields of created value (they will be visible with
       get_<field> or [dump]).
       Raises [Failure] on size mismatch. *)
    val of_bigarray : (char, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t -> t

    (* getters and setters: *)
    val get_ui8 : t -> int
    val set_ui8 : t -> int -> unit
    val get_si64 : t -> int64
    val set_si64 : t -> int64 -> unit

    (* makes a value of type [t] and initializes it with
       field values passed as labelled arguments. *)
    val make : ui8:int -> si64:int64 -> t

    (* dumps a value of type [t] to string, result looks like
       '{ a=1 ; b=3456 }' *)
    val dump : t -> string
  end
 =
  struct
    type t = (char, Bigarray.int8_unsigned_elt, Bigarray.c_layout) Bigarray.Array1.t

    let get_ui8 t = ExtUnix.Specific.BA.LittleEndian.unsafe_get_uint8 t 0
    let set_ui8 t v = ExtUnix.Specific.BA.LittleEndian.unsafe_set_uint8 t 0 v
    let get_si64 t = ExtUnix.Specific.BA.LittleEndian.unsafe_get_int64 t 1
    let set_si64 t v = ExtUnix.Specific.BA.LittleEndian.unsafe_set_int64 t 1 v
    let sizeof = 9

    let of_bigarray t =
      if Bigarray.Array1.dim t <> sizeof
      then failwith "Mystruct.of_bigarray: size doesn't match"
      else t

    let make ~ui8 ~si64 =
      let t = Bigarray.Array1.create Bigarray.char Bigarray.c_layout sizeof in
      (
        set_ui8 t ui8;
        set_si64 t si64;
        t
      )

    let dump t =
      let b = Buffer.create 50 in
      (
        Buffer.add_string b "{ ui8=";
        Buffer.add_string b (string_of_int (get_ui8 t));
        Buffer.add_string b " ; si64=";
        Buffer.add_string b (Int64.to_string (get_si64 t));
        Buffer.add_string b " }";
        Buffer.contents b
      )
  end