Get actual size beforehand

[NefixEstrada]

Hello!

Is it possible to know the size that will have a struct beforehand?

So, having,

#[binrw]
struct A {
  first: u8,
  second: u16,
  third: u8,
}

Is it possible to know that the size that the struct will have will be 4 at comptime?

Could also be added as #[brw(calc(SOMETHING))] for another struct? Or the struct itself?

Thank you!

[csnover]

binrw does not currently calculate the size of a struct at compile time. You could annotate it yourself with e.g. impl A { const SIZE: usize = 4; }. What are you using this information for?

[NefixEstrada]

To calculate fields on structs.

I have a MessageA struct, and then a Header struct. The header has a field that is called size, which contains the size that MessageA is going to have.

Since a lot of times this information is already known at comptime, I think it would be useful if it could be added somehow in the library itself and not annotate each structure manually

Thanks!