Struct WaitQueue 

pub struct WaitQueue { /* private fields */ }

Available on crate feature std only.

Parties waiting, in arrival order, for capacity that others free.

A Party queues a Waiter with Self::push before it checks the capacity it waits for; whoever frees capacity calls Self::wake_one for one unit, or Self::wake_all for a change of unknown size, after freeing it. Both sides fence, so of a waiter queuing and capacity freeing at once, one sees the other. Every unit reaches a waiter, which spends it on a look or, as it leaves, passes it on in this queue. Nothing else is locked while its lock is held, but the wakers of the parties it wakes run under it, so a wake and a leave never interleave: a waker must not call back into the queue, and an async runtime’s does not.

Capacity several queues contend for goes to the oldest of their fronts: a party leaving it to an older waiter of another queue gives way to it.

Implementations

impl WaitQueue

pub fn new() -> WaitQueue

Available on crate features grpc and http only.

Create an empty queue.

pub fn push(&self, waiter: &Waiter)

Available on crate features grpc and http only.

Queue waiter behind the older parties. Check the capacity it waits for after.

pub fn remove(&self, waiter: &Waiter) -> usize

Available on crate features grpc and http only.

Leave the queue, returning the wakes it sent the waiter that are not spent: capacity they stand for and the waiter does not use is left to the others, so pass it on. Queues whose parties gave way to the waiter get a wake.

A party freeing capacity meets the leave under the queue’s lock: it wakes the waiter before, or reports nobody waiting after.

pub fn give_way(&self, than: u64, giver: &Waiter) -> bool

Available on crate features grpc and http only.

Whether a waiter older than than waits here, for capacity the party of giver, its place in another queue, contends for too: that party gives way to it. The waiter is woken to look, if it holds no wake, and giver once it leaves, if its party still waits: atomic with the leave, so that wake is not lost.

pub fn len(&self) -> usize

Available on crate features grpc and http only.

How many wait.

pub fn is_empty(&self) -> bool

Available on crate features grpc and http only.

Whether nobody waits.

pub fn front_order(&self) -> Option<u64>

Available on crate features grpc and http only.

The Party::order of the first waiter, if any waits.

pub fn front_is_woken(&self) -> bool

Available on crate features grpc and http only.

Whether the first waiter holds a wake: capacity is being handed down the queue.

pub fn unspent(&self) -> usize

Available on crate features grpc and http only.

The wakes this queue sent its waiters that they did not spend, saturating at usize::MAX.

pub fn admits(&self, waiter: Option<&Waiter>) -> bool

Available on crate features grpc and http only.

Whether a party may take capacity now: nobody waits ahead of it, or it holds a wake of this queue. None is a party that does not wait here.

pub fn wake_front(&self) -> bool

Available on crate features grpc and http only.

Make the first waiter look after this: a wake if it holds none, else a look more without a unit of capacity, so a look of it that began before runs once more. False if nobody waits.

pub fn wake_one(&self) -> bool

Available on crate features grpc and http only.

One unit of capacity: wake the first waiter without a wake of this queue or, if all of them hold one, the first again, since its look may have begun before the unit. False if nobody waits: the capacity is nobody’s.

pub fn wake_many(&self, n: usize) -> bool

Available on crate features grpc and http only.

n units of capacity at once: as Self::wake_one n times, in one pass over the queue. False if nobody waits.

pub fn wake_all(&self) -> bool

Available on crate features grpc and http only.

A change of unknown size: wake every waiter. False if nobody waits.

Trait Implementations

impl Debug for WaitQueue

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

Formats the value using the given formatter.

impl Default for WaitQueue

fn default() -> WaitQueue

Returns the “default value” for a type.