Le jeudi 05 avril 2012 07:57:45, Anthony Tavener a écrit :
> I'm trying to determine the size of a Bigarray, in bytes.
>
> I've tried several things... ending up with this as the only solution:
>
> --------------------------
> let ba_char = Hashtbl.hash Bigarray.char;;
> let ba_int8_signed = Hashtbl.hash int8_signed;;
> let ba_int8_unsigned = Hashtbl.hash int8_unsigned;;
> let ba_int16_signed = Hashtbl.hash int16_signed;;
> let ba_int16_unsigned = Hashtbl.hash int16_unsigned;;
> let ba_int32 = Hashtbl.hash Bigarray.int32;;
> let ba_float32 = Hashtbl.hash float32;;
> let ba_int64 = Hashtbl.hash Bigarray.int64;;
> let ba_float64 = Hashtbl.hash float64;;
> let ba_complex32 = Hashtbl.hash complex32;;
> let ba_complex64 = Hashtbl.hash complex64;;
> let ba_int = Hashtbl.hash Bigarray.int;;
> let ba_nativeint = Hashtbl.hash Bigarray.nativeint;;
>
> let bigarray_bytes ba =
> let elt_bytes = match Hashtbl.hash (Array1.kind ba) with
>
> | x when x=ba_char || x=ba_int8_signed || x=ba_int8_unsigned -> 1
> | x when x=ba_int16_signed || x=ba_int16_unsigned -> 2
> | x when x=ba_int32 || x=ba_float32 -> 4
> | x when x=ba_int64 || x=ba_float64 || x=ba_complex32 -> 8
> | x when x=ba_complex64 -> 16
> | x when x=ba_int || x=ba_nativeint ->
>
> Nativeint.size lsr 8
>
> | _ -> failwith "Unknown Bigarray kind."
>
> in (Array1.dim ba) * elt_bytes;;
> --------------------------
>
> Which is a rather ugly hack! It feels dirty like Obj.magic, while being
> completely inelegant, and even has a fail case! Can't get much worse. :)
> Of course, internally, bigarray will know it's own size... sometimes the
> price of abstraction... *sigh*
>
> I found a related Mantis entry from 6 years back:
> http://caml.inria.fr/mantis/view.php?id=3962
>
> Well... does anyone have some better suggestions? Please? :)
> Oh, I can make it look a little prettier by plugging in the constants eked
> out by Hashtbl.hash. ;D
>
> Why do I want this? Interfacing with OpenGL (glcaml).
>
> Thanks for looking, and more again if you have a good tip!
Hi Anthony,
Had the same problem with glMLite.
I use the function below, but if there is a better solution I would be
interested too:
val ba_sizeof: ba:('a, 'b, Bigarray.c_layout) Bigarray.Array1.t -> int
external elem_size: ba:('a, 'b, Bigarray.c_layout) Bigarray.Array1.t -> int
= "ml_ba_elem_size" "noalloc"
let ba_sizeof ~ba =
((Bigarray.Array1.dim ba) * (elem_size ba)) ;;
CAMLprim value ml_ba_elem_size( value _ba )
{
struct caml_bigarray *ba = Bigarray_val(_ba);
int size;
switch (ba->flags & BIGARRAY_KIND_MASK)
{
case BIGARRAY_SINT8:
case BIGARRAY_UINT8:
size = 1; break;
case BIGARRAY_SINT16:
case BIGARRAY_UINT16:
size = 2; break;
case BIGARRAY_INT32:
case BIGARRAY_FLOAT32:
case BIGARRAY_COMPLEX32:
size = 4; break;
case BIGARRAY_INT64:
case BIGARRAY_FLOAT64:
case BIGARRAY_COMPLEX64:
size = 8; break;
case BIGARRAY_CAML_INT:
case BIGARRAY_NATIVE_INT:
size = sizeof(value); break;
}
return Val_int(size);
}
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