Trait TransitionMetadata

pub trait TransitionMetadata<Cur: Sandbox, Next: Sandbox> { }

Metadata about an evolution or devolution. Any Sandbox implementation that also implements EvolvableSandbox or DevolvableSandbox can decide the following things in a type-safe way:

1. That transition is possible
2. That transition requires a specific kind of metadata

For example, if you have the following structs:

struct MySandbox1 {}
struct MySandbox2 {}

impl Sandbox for MySandbox1 {...}
impl Sandbox for MySandbox2 {...}

…then you can define a metadata-free evolve transition between MySandbox1 and MySandbox2, and a devolve transition that requires a callback between MySandbox2 and MySandbox as follows:

impl EvolvableSandbox<
    MySandbox1,
    MySandbox2,
    Noop<MySandbox1, MySandbox2>
> for MySandbox1 {
    fn evolve(
        self,
        _: Noop<MySandbox1, MySandbox2>
    ) -> Result<MySandbox2> {
        Ok(MySandbox2{})
    }
}

Most transitions will likely involve Noop, but some may involve implementing their own.

Implementors

impl<'a, Cur: Sandbox, Next: Sandbox, F> TransitionMetadata<Cur, Next> for MultiUseContextCallback<'a, Cur, F>

where F: FnOnce(&mut MultiUseGuestCallContext) -> Result<()>,

impl<Cur: Sandbox, Next: Sandbox> TransitionMetadata<Cur, Next> for Noop<Cur, Next>