Struct JoinMap 

pub struct JoinMap<K, V> { /* private fields */ }

A collection of keyed tasks spawned on a Tokio runtime. Hacky implementation of a join set that allows for a key to be associated with each task by having the task return a tuple of (key, value).

Implementations

impl<K, V> JoinMap<K, V>

pub fn new() -> Self

Create a new JoinSet.

pub fn len(&self) -> usize

Returns the number of tasks currently in the JoinSet.

pub fn is_empty(&self) -> bool

Returns whether the JoinSet is empty.

impl<K, V> JoinMap<K, V>

where K: Eq + Hash + Clone + Send + Sync + 'static, V: 'static,

pub fn spawn<F>(&mut self, key: K, future: F)

where F: Future<Output = (K, V)> + Send + 'static, V: Send,

Spawns a task onto the Tokio runtime that will execute the given future ONLY IF there is not already a task in the set with the same key.

pub fn contains_key(&self, key: &K) -> bool

Returns true if the JoinSet contains a task for the given key.

pub async fn join_next(&mut self) -> Option<Result<(K, V), JoinError>>

Waits until one of the tasks in the set completes and returns its output.

Returns None if the set is empty.

Cancel Safety

This method is cancel safe. If join_next is used as the event in a tokio::select! statement and some other branch completes first, it is guaranteed that no tasks were removed from this JoinSet.

pub fn poll_join_next( &mut self, cx: &mut Context<'_>, ) -> Poll<Option<Result<(K, V), JoinError>>>

Polls for one of the tasks in the set to complete.

If this returns Poll::Ready(Some(_)), then the task that completed is removed from the set.

When the method returns Poll::Pending, the Waker in the provided Context is scheduled to receive a wakeup when a task in the JoinSet completes. Note that on multiple calls to poll_join_next, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup.

Returns

This function returns:

• Poll::Pending if the JoinSet is not empty but there is no task whose output is available right now.
• Poll::Ready(Some(Ok(value))) if one of the tasks in this JoinSet has completed. The value is the return value of one of the tasks that completed.
• Poll::Ready(Some(Err(err))) if one of the tasks in this JoinSet has panicked or been aborted. The err is the JoinError from the panicked/aborted task.
• Poll::Ready(None) if the JoinSet is empty.

Note that this method may return Poll::Pending even if one of the tasks has completed. This can happen if the [coop budget] is reached.

Trait Implementations

impl<K: Debug, V: Debug> Debug for JoinMap<K, V>

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

Formats the value using the given formatter.

impl<K: Default, V: Default> Default for JoinMap<K, V>

fn default() -> JoinMap<K, V>

Returns the “default value” for a type.