Struct cordyceps::mpsc_queue::Consumer
source · pub struct Consumer<'q, T: Linked<Links<T>>> { /* private fields */ }
Expand description
A handle that holds the right to dequeue elements from a MpscQueue
.
This can be used when one thread wishes to dequeue many elements at a time,
to avoid the overhead of ensuring mutual exclusion on every dequeue
or
try_dequeue
call.
This type is returned by the MpscQueue::consume
and MpscQueue::try_consume
methods.
If the right to dequeue elements needs to be reserved for longer than a
single scope, an owned variant (OwnedConsumer
) is also available, when
the MpscQueue
is stored in an Arc
. Since the MpscQueue
must be stored
in an Arc
, the OwnedConsumer
type requires the “alloc” feature flag.
Implementations§
source§impl<'q, T: Send + Linked<Links<T>>> Consumer<'q, T>
impl<'q, T: Send + Linked<Links<T>>> Consumer<'q, T>
sourcepub fn dequeue(&self) -> Option<T::Handle>
pub fn dequeue(&self) -> Option<T::Handle>
Dequeue an element from the queue.
This method will wait by spinning with an exponential backoff if the queue is in an inconsistent state.
The Consumer::try_dequeue
will return an error rather than waiting when
the queue is in an inconsistent state.
Returns
Some(
T::Handle
)
if an element was successfully dequeuedNone
if the queue is empty
sourcepub fn try_dequeue(&self) -> Result<T::Handle, TryDequeueError>
pub fn try_dequeue(&self) -> Result<T::Handle, TryDequeueError>
Try to dequeue an element from the queue, without waiting if the queue is in an inconsistent state.
As discussed in the algorithm description on 1024cores.net, it
is possible for this queue design to enter an inconsistent state if the
consumer tries to dequeue an element while a producer is in the middle
of enqueueing a new element. If this occurs, the consumer must briefly
wait before dequeueing an element. This method returns
TryDequeueError::Inconsistent
when the queue is in an inconsistent
state.
The Consumer::dequeue
method will instead wait (by spinning with an
exponential backoff) when the queue is in an inconsistent state.
Returns
T::Handle
if an element was successfully dequeuedTryDequeueError::Empty
if there are no elements in the queueTryDequeueError::Inconsistent
if the queue is currently in an inconsistent state
Returns
Some(T::Handle)
if an element was successfully dequeuedNone
if the queue is empty
Trait Implementations§
source§impl<T> Iterator for Consumer<'_, T>where
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impl<T> Iterator for Consumer<'_, T>where T: Send + Linked<Links<T>>,
source§fn next(&mut self) -> Option<Self::Item>
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