Add a version of rcu with projection

[Swoorup]

Currently the version of rcu doesn't allow projection, is it possible to instead add a version of the function that allows such?

    pub fn rcu_project<F, A>(&mut self, f: F) -> (bool, A) where F: FnOnce(&T) -> (T, A) {

This is useful when dealing with a Option type where you always want to set it to some when updating it.

[avl]

Thank you for your request!

I'm all for adding new useful methods!

Using the method signature suggested, A could not have references into T. I think?

Would it be better to have two closure parameters, one FnOnce(&T) -> T and one FnOnce(&'a T)->A where A:'a ?

I won't have time to work on arcshift the next couple of days, but I'm happy to add the suggested function next week!

[Swoorup]

Would it be better to have two closure parameters, one FnOnce(&T) -> T and one FnOnce(&'a T)->A where A:'a ?

Hmm yeah this is more sensical 😄

[avl]

I'm thinking we could have a signature like this:

fn rcu_project<'s, A>(&'s mut self, f: impl FnOnce(&T) -> Option<T>, projector: impl FnOnce(&'s T) -> A ) -> (bool, A)

This allows the second closure, 'projector', to safely return references that point into the 'T' created by 'f'.

[avl]

An 'rcu_project'-method has been added.

Let me know if it doesn't solve your problem!