Hi Andrew,
Could you please post a link to the library? Thanks. :)
On Wednesday, March 21, 2018 at 12:35:46 AM UTC+6, Andrew Knapp wrote:
>
> Hello,
>
> I'd like to be able to send dataviewtypes as messages in a low-latency ipc
> library I've written.
>
> In this scenario, any use of malloc is unacceptable. Everything must be
> allocated from a memory pool or the stack, but datavtype constructors
> always allocate on the heap.
>
> What is the best way to access to the size and flat memory of the
> datavtype's tagged union, preferably in a typesafe manner? You can do this
> by a hack like
>
> dataviewtype message =
> | Bar of (int, double)
> | Baz of (double, double)
>
> #define BAR 0
> #define BAZ 1
>
> typedef BAR_ = @{
> contag = int,
> atslab__0 = int,
> atslab__1 = double
> }
>
> typedef BAZ_ = @{
> contag = int,
> atslab__0 = double,
> atslab__1 = double
> }
>
> and then using $UNSAFE.cast{Foo} on a pointer to stack or pool allocated
> memory of size FOO_SIZE = max(sizeof<BAR_>, sizeof<BAZ_>), which has had
> its contag set to BAR or BAZ via another unsafe cast.
>
> Unfortunately there is really a lot of boilerplate here and it will be
> easy for things to get out of sync with datatype definitions, especially
> with a lot of constructors. Moreover, FOO_SIZE is not a static constant, so
> you can't just write something like var buf : @[char][FOO_SIZE*N]
>
> Also, is there an equivalent of the placement new operator in C++?
>
> Thanks,
> Andrew
>
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