pub struct MutexTicket<'a, T> { /* private fields */ }
Expand description

Helper to poll a mutex.

Since Mutex::lock futures keep track of where in queue the lock request is, this is different to mutex.lock().poll(ctx) as that construction will create a new lock request at each poll. This can often be useful when we need to poll something that is contained under this mutex.

Typical usage: let mut ticket = MutexTicket::new(); poll_fn(|ctx| { let mutex_guard = ready!(ticket.poll(ctx)); mutex_guard.some_child_future.poll(ctx) }).await;

What this means: Attempt to acquire the mutex. If it’s not available, wait until it’s available. With the mutex acquired, check some_child_future. If it’s completed, complete the poll_fn. If it’s not completed drop the mutex guard (unblock other tasks) and wait for some_child_future to be awoken.

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impl<'a, T> MutexTicket<'a, T>

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pub fn new(mutex: &'a Mutex<T>) -> MutexTicket<'a, T>

Create a new MutexTicket

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pub fn poll(&mut self, ctx: &mut Context<'_>) -> Poll<MutexGuard<'a, T>>

Poll once to see if the lock has been acquired. This is not Future::poll because it’s intended to be a helper used during a Future::poll implementation, but never as a Future itself – one can simply call Mutex::lock.await in that case!

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pub async fn lock(&mut self) -> MutexGuard<'a, T>

Finish locking. This should be used instead of the Mutex.lock function if there is a MutexTicket constructed already - it may be that said MutexTicket has already been granted ownership of the Mutex - if this is the case, the Mutex.lock call will never succeed.

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impl<'a, T: Debug> Debug for MutexTicket<'a, T>

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

Formats the value using the given formatter. Read more

Auto Trait Implementations§

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impl<'a, T> !RefUnwindSafe for MutexTicket<'a, T>

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impl<'a, T> Send for MutexTicket<'a, T>
where T: Send,

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impl<'a, T> Sync for MutexTicket<'a, T>
where T: Send,

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impl<'a, T> Unpin for MutexTicket<'a, T>

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impl<'a, T> !UnwindSafe for MutexTicket<'a, T>

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> Encode<Ambiguous1> for T

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unsafe fn encode( self, _encoder: &mut Encoder<'_>, _offset: usize, _depth: Depth ) -> Result<(), Error>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID. Read more
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impl<T> Encode<Ambiguous2> for T

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unsafe fn encode( self, _encoder: &mut Encoder<'_>, _offset: usize, _depth: Depth ) -> Result<(), Error>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided [Span], returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> Pointable for T

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const ALIGN: usize = _

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a [WithDispatch] wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a [WithDispatch] wrapper. Read more
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impl<St> WithTag for St

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fn tagged<T>(self, tag: T) -> Tagged<T, St>

Produce a new stream from this one which yields item tupled with a constant tag