Conditional DekuWrite

[whati001]

Conditional DekuWrite

[sharksforarms]

@whati001 I believe by combining skip and cond you can achieve what you're looking for?

You're right there isn't something like this for 'write side only' or 'read side only'

You can interpret it as "skip field (read or write) if cond"

Here's an example.

use deku::prelude::*;

#[derive(Debug, PartialEq, DekuRead, DekuWrite)]
struct MyStruct {
    should_next: bool,

    #[deku(skip, cond = "!*should_next")]
    // on read: if cond == true, we skip and the value is set to Default::default()
    // on write: if cond == true, we skip and the writing of the value
    optional: Option<u8>,

    other_field: u8,
}

fn main() {
    env_logger::init();

    {
        let input = &[0x01, 0x02, 0x03];
        let (_rest, r) = MyStruct::from_bytes((input, 0)).unwrap();
        assert_eq!(
            r,
            MyStruct {
                should_next: true,
                optional: Some(0x02),
                other_field: 0x03,
            }
        );

        assert_eq!(vec![0x01, 0x02, 0x03], r.to_bytes().unwrap())
    }

    {
        let input = &[0x00, 0x03];
        let (_rest, r) = MyStruct::from_bytes((input, 0)).unwrap();
        assert_eq!(
            r,
            MyStruct {
                should_next: false,
                optional: None,
                other_field: 0x03,
            }
        );

        assert_eq!(vec![0x00, 0x03], r.to_bytes().unwrap())
    }
}

[wcampbell0x2a]

Deku does not have a skip_serializing_if attribute, but could add this.

[whati001]

Hi @sharksforarms
Thank you very much for the quick feedback. You are right, seems like I have overseen to add the skip attribute.
Using the following deku #[deku(skip, cond = '...'] works now for me.