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|
open Printf
type typ = Bool | Char | Short | Int
type field =
| Plain of typ
| Bitfield of typ * int
| Padding of typ * int
type struct_ = field list
(* Concise description of a struct *)
let print_typ oc = function
| Bool -> fprintf oc "b"
| Char -> fprintf oc "c"
| Short -> fprintf oc "s"
| Int -> fprintf oc "i"
let print_padding_typ oc = function
| Bool -> fprintf oc "B"
| Char -> fprintf oc "C"
| Short -> fprintf oc "S"
| Int -> fprintf oc "I"
let print_field oc = function
| Plain t -> print_typ oc t
| Bitfield(t, w) -> fprintf oc "%a%d" print_typ t w
| Padding(t, w) -> fprintf oc "%a%d" print_padding_typ t w
let rec print_struct oc = function
| [] -> ()
| f :: s -> print_field oc f; print_struct oc s
(* Printing a struct in C syntax *)
let c_typ oc = function
| Bool -> fprintf oc "_Bool"
| Char -> fprintf oc "char"
| Short -> fprintf oc "short"
| Int -> fprintf oc "int"
let c_name oc n = fprintf oc "%c" (Char.chr (Char.code 'a' + n))
let c_field oc n = function
| Plain t ->
fprintf oc " %a %a;\n" c_typ t c_name n;
n + 1
| Bitfield(t, w) ->
fprintf oc " %a %a:%d;\n" c_typ t c_name n w;
n + 1
| Padding(t, w) ->
fprintf oc " %a :%d;\n" c_typ t w;
n
let c_struct oc s =
fprintf oc "struct %a {\n" print_struct s;
let rec c_str n = function
| [] -> ()
| f :: s -> let n' = c_field oc n f in c_str n' s in
c_str 0 s;
fprintf oc "};\n"
(* Random generation of structs *)
let random_1_8 () =
let n1 = Random.bits() in
let n2 = n1 lsr 2 in
match n1 land 3 with
| 0 -> 1
| 1 -> 2 + (n2 land 1) (* 2-3 *)
| 2 -> 4 + (n2 land 1) (* 4-5 *)
| 3 -> 6 + (n2 mod 3) (* 6-8 *)
| _ -> assert false
let random_1_16 () =
let n1 = Random.bits() in
let n2 = n1 lsr 2 in
match n1 land 3 with
| 0 -> 1 + (n2 land 1) (* 1-2 *)
| 1 -> 3 + (n2 mod 3) (* 3-4-5 *)
| 2 -> 6 + (n2 land 3) (* 6-7-8-9 *)
| 3 -> 10 + (n2 mod 7) (* 10-16 *)
| _ -> assert false
let random_1_32 () =
let n1 = Random.bits() in
let n2 = n1 lsr 2 in
match n1 land 3 with
| 0 -> 1 + (n2 land 1) (* 1-2 *)
| 1 -> 3 + (n2 mod 5) (* 3-4-5-6-7 *)
| 2 -> 8 + (n2 mod 8) (* 8-15 *)
| 3 -> 16 + (n2 mod 17) (* 16-32 *)
| _ -> assert false
let random_field () =
let (t, w) =
match Random.int 9 with
| 0 -> (Bool, 1)
| 1|2 -> (Char, random_1_8())
| 3|4 -> (Short, random_1_16())
| _ -> (Int, random_1_32()) in
match Random.int 10 with
| 0 -> Padding(t, (if Random.int 3 = 0 then 0 else w))
| 1 | 2 -> Plain t
| _ -> Bitfield(t, w)
let rec random_struct len =
if len <= 0 then [] else begin
let f = random_field () in
f :: random_struct (match f with Padding _ -> len | _ -> len - 1)
end
(* Optional filtering of structs where padding fields can increase alignment.
ELF says that padding fields are ignored to determine struct alignment,
but ARM does otherwise. *)
let alignof = function Bool -> 1 | Char -> 1 | Short -> 2 | Int -> 4
let unstable_alignment str =
let rec alignments al_data al_padding = function
| [] ->
al_padding > al_data
| (Plain t | Bitfield(t, _)) :: l ->
alignments (max (alignof t) al_data) al_padding l
| Padding(t, _) :: l ->
alignments al_data (max (alignof t) al_padding) l
in
alignments 1 1 str
(* Random testing *)
let structsize = ref 4
let ntests = ref 1000
let stable = ref false
let _ =
Arg.parse [
"-size", Arg.Int (fun n -> structsize := n),
" <sz> produce structs with <sz> members (default: 4)";
"-n", Arg.Int (fun n -> ntests := n),
" <num> produce <num> random structs";
"-seed", Arg.Int Random.init,
" <seed> use the given seed for randomization";
"-stable", Arg.Set stable,
" don't generate padding fields that could cause differences in alignment"
]
(fun s -> raise (Arg.Bad ("don't know what to do with " ^ s)))
"Usage: genlayout [options]\n\nOptions are:";
for _i = 1 to !ntests do
let s = random_struct !structsize in
if not (!stable && unstable_alignment s) then begin
printf "{\n";
c_struct stdout s;
printf "TEST%d(%a)\n" !structsize print_struct s;
printf "}\n"
end
done
|
