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structure SparcCSizes =
struct
structure Ty = CType
fun roundup (i, a) = a * ((i + a - 1) div a)
(* calculate size and alignment for a C type *)
fun sizeOfTy (Ty.C_void | Ty.C_float | Ty.C_PTR |
Ty.C_signed (Ty.I_int | Ty.I_long) |
Ty.C_unsigned (Ty.I_int | Ty.I_long)) = {sz=4, align=4}
| sizeOfTy (Ty.C_double |
Ty.C_signed Ty.I_long_long |
Ty.C_unsigned Ty.I_long_long) = {sz=8, align=8}
| sizeOfTy (Ty.C_long_double) = {sz=16, align=8}
| sizeOfTy (Ty.C_signed Ty.I_char | Ty.C_unsigned Ty.I_char) = {sz=1, align=1}
| sizeOfTy (Ty.C_signed Ty.I_short | Ty.C_unsigned Ty.I_short) = {sz=2, align=2}
| sizeOfTy (Ty.C_ARRAY (t, n)) = let val {sz=s, align=a} = sizeOfTy t in {sz=n * s, align=a} end
| sizeOfTy (Ty.C_STRUCT l) =
let (* i: next free memory address (relative to struct start);
* a: current total alignment,
* l: list of struct member types *)
fun pack (i, a, []) =
(* when we are done with all elements, the total size
* of the struct must be padded out to its own alignment *)
{sz=roundup (i, a), align=a}
| pack (i, a, t :: tl) = let
val {sz=ts, align=ta} = sizeOfTy t (* size and alignment for member *)
in
(* member must be aligned according to its own
* alignment requirement; the next free position
* is then at "aligned member-address plus member-size";
* new total alignment is max of current alignment
* and member alignment (assuming all alignments are
* powers of 2) *)
pack (roundup (i, ta) + ts, Int.max (a, ta), tl)
end
in
pack (0, 1, l)
end
| sizeOfTy (Ty.C_UNION l) =
let (* m: current max size
* a: current total alignment *)
fun overlay (m, a, []) = {sz=roundup (m, a), align=a}
| overlay (m, a, t :: tl) =
let val {sz=ts, align=ta} = sizeOfTy t
in
overlay (Int.max (m, ts), Int.max (a, ta), tl)
end
in
overlay (0, 1, l)
end
end
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