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|
(* c-sizes.sml
*
* Determine the number of bytes needed to store a C type.
*)
structure CSizes =
struct
structure CTy = CType
(* size and natural alignment for integer types. *)
fun sizeOfInt CTy.I_char = {ty = 8, sz = 1, align = 1}
| sizeOfInt CTy.I_short = {ty = 16, sz = 2, align = 2}
| sizeOfInt CTy.I_int = {ty = 32, sz = 4, align = 4}
| sizeOfInt CTy.I_long = {ty = 32, sz = 4, align = 4}
| sizeOfInt CTy.I_long_long = {ty = 64, sz = 8, align = 8}
(* sizes of other C types *)
val sizeOfPtr = {ty = 64, sz = 8, align = 8}
(* align the address to the given alignment, which must be a power of 2 *)
fun alignAddr (addr, align) =
let val mask = Word.fromInt(align-1)
in
Word.toIntX(Word.andb(Word.fromInt addr + mask, Word.notb mask))
end
fun align8 addr = Word.toIntX(Word.andb(Word.fromInt addr + 0w4, Word.notb 0w4))
(* compute the size and alignment information for a struct; tys is the list
* of member types.
* The total size is padded to agree with the struct's alignment.
*)
fun sizeOfStruct tys =
let fun ssz ([], maxAlign, offset) =
{sz = alignAddr(offset, maxAlign), align = maxAlign}
| ssz (ty::tys, maxAlign, offset) =
let val {sz, align} = sizeOfTy ty
val offset = alignAddr(offset, align)
in
ssz (tys, Int.max(maxAlign, align), offset+sz)
end
in
ssz (tys, 1, 0)
end
(* the size alignment of a union type is the maximum of the sizes and alignments
* of the members. The final size is padded to agree with the alignment.
*)
and sizeOfUnion tys = let
fun usz ([], maxAlign, maxSz) =
{sz = alignAddr(maxSz, maxAlign), align = maxAlign}
| usz (ty::tys, maxAlign, maxSz) = let
val {sz, align} = sizeOfTy ty
in
usz (tys, Int.max(maxAlign, align), Int.max(sz, maxSz))
end
in
usz (tys, 1, 0)
end
and sizeOfTy CTy.C_void = raise Fail "unexpected void argument type"
| sizeOfTy CTy.C_float = {sz = 4, align = 4}
| sizeOfTy CTy.C_double = {sz = 8, align = 8}
| sizeOfTy CTy.C_long_double = {sz = 12, align = 8}
| sizeOfTy (CTy.C_unsigned isz) = let
val {sz, align, ...} = sizeOfInt isz
in
{sz = sz, align = align}
end
| sizeOfTy (CTy.C_signed isz) = let
val {sz, align, ...} = sizeOfInt isz
in
{sz = sz, align = align}
end
| sizeOfTy CTy.C_PTR = {sz = 8, align = 8}
| sizeOfTy (CTy.C_ARRAY(ty, n)) = let
val {sz, align} = sizeOfTy ty
in
{sz = n*sz, align = align}
end
| sizeOfTy (CTy.C_STRUCT tys) = sizeOfStruct tys
| sizeOfTy (CTy.C_UNION tys) = sizeOfUnion tys
end (* CSizes *)
|
