Struct tor_dirmgr::SharedMutArc

pub struct SharedMutArc<T> {
    dir: RwLock<Option<Arc<T>>>,
}

Available on crate feature experimental-api only.

A shareable mutable-ish optional reference to a an Arc.

Because you can’t actually change a shared Arc, this type implements mutability by replacing the Arc itself with a new value. It tries to avoid needless clones by taking advantage of Arc::make_mut.

Fields

dir: RwLock<Option<Arc<T>>>

Locked reference to the current value.

(It’s okay to use RwLock here, because we never suspend while holding the lock.)

Implementations

impl<T> SharedMutArc<T>

pub fn new() -> Self

Construct a new empty SharedMutArc.

pub fn replace(&self, new_val: T)

Replace the current value with new_val.

pub(crate) fn clear(&self)

Remove the current value of this SharedMutArc.

pub fn get(&self) -> Option<Arc<T>>

Return a new reference to the current value, if there is one.

pub fn mutate<F, U>(&self, func: F) -> Result<U>

where F: FnOnce(&mut T) -> Result<U>, T: Clone,

Replace the contents of this SharedMutArc with the results of applying func to the inner value.

Gives an error if there is no inner value.

Other threads will not abe able to access the inner value while the function is running.

Limitation: No panic-safety

If func panics while it’s running, this object will become invalid and future attempts to use it will panic. (TODO: Fix this.)

Trait Implementations

impl<T: Debug> Debug for SharedMutArc<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for SharedMutArc<T>

fn default() -> Self

Returns the “default value” for a type.

impl PreviousNetDir for SharedMutArc<NetDir>

fn get_netdir(&self) -> Option<Arc<NetDir>>

Get the previous netdir, if there still is one.