Trait Sink

Source

pub trait Sink<Item> {
    type Error;

    // Required methods
    fn poll_ready(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::Error>>;
    fn start_send(self: Pin<&mut Self>, item: Item) -> Result<(), Self::Error>;
    fn poll_flush(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::Error>>;
    fn poll_close(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::Error>>;
}

Expand description

A Sink is a value into which other values can be sent, asynchronously.

Basic examples of sinks include the sending side of:

Channels
Sockets
Pipes

In addition to such “primitive” sinks, it’s typical to layer additional functionality, such as buffering, on top of an existing sink.

Sending to a sink is “asynchronous” in the sense that the value may not be sent in its entirety immediately. Instead, values are sent in a two-phase way: first by initiating a send, and then by polling for completion. This two-phase setup is analogous to buffered writing in synchronous code, where writes often succeed immediately, but internally are buffered and are actually written only upon flushing.

In addition, the Sink may be full, in which case it is not even possible to start the sending process.

As with Future and Stream, the Sink trait is built from a few core required methods, and a host of default methods for working in a higher-level way. The Sink::send_all combinator is of particular importance: you can use it to send an entire stream to a sink, which is the simplest way to ultimately consume a stream.

Required Associated Types§

Source

type Error

The type of value produced by the sink when an error occurs.

Required Methods§

Source

fn poll_ready( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Attempts to prepare the Sink to receive a value.

This method must be called and return Poll::Ready(Ok(())) prior to each call to start_send.

This method returns Poll::Ready once the underlying sink is ready to receive data. If this method returns Poll::Pending, the current task is registered to be notified (via cx.waker().wake_by_ref()) when poll_ready should be called again.

In most cases, if the sink encounters an error, the sink will permanently be unable to receive items.

Source

fn start_send(self: Pin<&mut Self>, item: Item) -> Result<(), Self::Error>

Begin the process of sending a value to the sink. Each call to this function must be preceded by a successful call to poll_ready which returned Poll::Ready(Ok(())).

As the name suggests, this method only begins the process of sending the item. If the sink employs buffering, the item isn’t fully processed until the buffer is fully flushed. Since sinks are designed to work with asynchronous I/O, the process of actually writing out the data to an underlying object takes place asynchronously. You must use poll_flush or poll_close in order to guarantee completion of a send.

Implementations of poll_ready and start_send will usually involve flushing behind the scenes in order to make room for new messages. It is only necessary to call poll_flush if you need to guarantee that all of the items placed into the Sink have been sent.

In most cases, if the sink encounters an error, the sink will permanently be unable to receive items.

Source

fn poll_flush( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Flush any remaining output from this sink.

Returns Poll::Ready(Ok(())) when no buffered items remain. If this value is returned then it is guaranteed that all previous values sent via start_send have been flushed.

Returns Poll::Pending if there is more work left to do, in which case the current task is scheduled (via cx.waker().wake_by_ref()) to wake up when poll_flush should be called again.

In most cases, if the sink encounters an error, the sink will permanently be unable to receive items.

Source

fn poll_close( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Flush any remaining output and close this sink, if necessary.

Returns Poll::Ready(Ok(())) when no buffered items remain and the sink has been successfully closed.

Returns Poll::Pending if there is more work left to do, in which case the current task is scheduled (via cx.waker().wake_by_ref()) to wake up when poll_close should be called again.

If this function encounters an error, the sink should be considered to have failed permanently, and no more Sink methods should be called.

Sink

Trait Sink Copy item path

Required Associated Types§

type Error

Required Methods§

fn poll_ready( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

fn start_send(self: Pin<&mut Self>, item: Item) -> Result<(), Self::Error>

fn poll_flush( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

fn poll_close( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<(), Self::Error>>

Implementations on Foreign Types§

impl<A, B, Item> Sink<Item> for Either<A, B>where A: Sink<Item>, B: Sink<Item, Error = <A as Sink<Item>>::Error>,

type Error = <A as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut Either<A, B>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Either<A, B> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut Either<A, B>>, item: Item, ) -> Result<(), <Either<A, B> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut Either<A, B>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Either<A, B> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut Either<A, B>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Either<A, B> as Sink<Item>>::Error>>

impl<P, Item> Sink<Item> for Pin<P>where P: DerefMut + Unpin, <P as Deref>::Target: Sink<Item>,

type Error = <<P as Deref>::Target as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut Pin<P>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Pin<P> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut Pin<P>>, item: Item, ) -> Result<(), <Pin<P> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut Pin<P>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Pin<P> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut Pin<P>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Pin<P> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for Filter<S, Fut, F>where S: Stream + Sink<Item>, F: FnMut(&<S as Stream>::Item) -> Fut, Fut: Future<Output = bool>,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut Filter<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Filter<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut Filter<S, Fut, F>>, item: Item, ) -> Result<(), <Filter<S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut Filter<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Filter<S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut Filter<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Filter<S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for FilterMap<S, Fut, F>where S: Stream + Sink<Item>, F: FnMut1<<S as Stream>::Item, Output = Fut>, Fut: Future,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut FilterMap<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <FilterMap<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut FilterMap<S, Fut, F>>, item: Item, ) -> Result<(), <FilterMap<S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut FilterMap<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <FilterMap<S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut FilterMap<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <FilterMap<S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for Scan<S, S, Fut, F>where S: Stream + Sink<Item>,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut Scan<S, S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Scan<S, S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut Scan<S, S, Fut, F>>, item: Item, ) -> Result<(), <Scan<S, S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut Scan<S, S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Scan<S, S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut Scan<S, S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Scan<S, S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for SkipWhile<S, Fut, F>where S: Stream + Sink<Item>, F: FnMut(&<S as Stream>::Item) -> Fut, Fut: Future<Output = bool>,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut SkipWhile<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <SkipWhile<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut SkipWhile<S, Fut, F>>, item: Item, ) -> Result<(), <SkipWhile<S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut SkipWhile<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <SkipWhile<S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut SkipWhile<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <SkipWhile<S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for TakeWhile<S, Fut, F>where S: Stream + Sink<Item>,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut TakeWhile<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <TakeWhile<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut TakeWhile<S, Fut, F>>, item: Item, ) -> Result<(), <TakeWhile<S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut TakeWhile<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <TakeWhile<S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut TakeWhile<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <TakeWhile<S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for Then<S, Fut, F>where S: Sink<Item>,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut Then<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Then<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut Then<S, Fut, F>>, item: Item, ) -> Result<(), <Then<S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut Then<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Then<S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut Then<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <Then<S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for AndThen<S, Fut, F>where S: Sink<Item>,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut AndThen<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <AndThen<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut AndThen<S, Fut, F>>, item: Item, ) -> Result<(), <AndThen<S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut AndThen<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <AndThen<S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut AndThen<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <AndThen<S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for OrElse<S, Fut, F>where S: Sink<Item>,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut OrElse<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <OrElse<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut OrElse<S, Fut, F>>, item: Item, ) -> Result<(), <OrElse<S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut OrElse<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <OrElse<S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut OrElse<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <OrElse<S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item> Sink<Item> for TryFilterMap<S, Fut, F>where S: Sink<Item>,

type Error = <S as Sink<Item>>::Error

fn poll_ready( self: Pin<&mut TryFilterMap<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <TryFilterMap<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut TryFilterMap<S, Fut, F>>, item: Item, ) -> Result<(), <TryFilterMap<S, Fut, F> as Sink<Item>>::Error>

fn poll_flush( self: Pin<&mut TryFilterMap<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <TryFilterMap<S, Fut, F> as Sink<Item>>::Error>>

fn poll_close( self: Pin<&mut TryFilterMap<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <TryFilterMap<S, Fut, F> as Sink<Item>>::Error>>

impl<S, Fut, F, Item, E> Sink<Item> for TryFilter<S, Fut, F>where S: TryStream + Sink<Item, Error = E>,

type Error = E

fn poll_ready( self: Pin<&mut TryFilter<S, Fut, F>>, cx: &mut Context<'_>, ) -> Poll<Result<(), <TryFilter<S, Fut, F> as Sink<Item>>::Error>>

fn start_send( self: Pin<&mut TryFilter<S, Fut, F>>, item: Item, ) -> Result<(), <TryFilter<S, Fut, F> as Sink<Item>>::Error>

Trait Sink

impl<A, B, Item> Sink<Item> for Either<A, B>
where A: Sink<Item>, B: Sink<Item, Error = <A as Sink<Item>>::Error>,

impl<P, Item> Sink<Item> for Pin<P>
where P: DerefMut + Unpin, <P as Deref>::Target: Sink<Item>,

impl<S, Fut, F, Item> Sink<Item> for Filter<S, Fut, F>
where S: Stream + Sink<Item>, F: FnMut(&<S as Stream>::Item) -> Fut, Fut: Future<Output = bool>,

impl<S, Fut, F, Item> Sink<Item> for FilterMap<S, Fut, F>
where S: Stream + Sink<Item>, F: FnMut1<<S as Stream>::Item, Output = Fut>, Fut: Future,

impl<S, Fut, F, Item> Sink<Item> for Scan<S, S, Fut, F>
where S: Stream + Sink<Item>,

impl<S, Fut, F, Item> Sink<Item> for SkipWhile<S, Fut, F>
where S: Stream + Sink<Item>, F: FnMut(&<S as Stream>::Item) -> Fut, Fut: Future<Output = bool>,

impl<S, Fut, F, Item> Sink<Item> for TakeWhile<S, Fut, F>
where S: Stream + Sink<Item>,

impl<S, Fut, F, Item> Sink<Item> for Then<S, Fut, F>
where S: Sink<Item>,

impl<S, Fut, F, Item> Sink<Item> for AndThen<S, Fut, F>
where S: Sink<Item>,

impl<S, Fut, F, Item> Sink<Item> for OrElse<S, Fut, F>
where S: Sink<Item>,

impl<S, Fut, F, Item> Sink<Item> for TryFilterMap<S, Fut, F>
where S: Sink<Item>,

impl<S, Fut, F, Item, E> Sink<Item> for TryFilter<S, Fut, F>
where S: TryStream + Sink<Item, Error = E>,

impl<S, Fut, F, Item, E> Sink<Item> for TrySkipWhile<S, Fut, F>
where S: TryStream + Sink<Item, Error = E>,

impl<S, Fut, F, Item, E> Sink<Item> for TryTakeWhile<S, Fut, F>
where S: TryStream + Sink<Item, Error = E>,

impl<S, Fut, Item> Sink<Item> for TakeUntil<S, Fut>
where S: Stream + Sink<Item>, Fut: Future,

impl<S, Item> Sink<Item> for &mut S
where S: Sink<Item> + Unpin + ?Sized,

impl<S, Item> Sink<Item> for Box<S>
where S: Sink<Item> + Unpin + ?Sized,

impl<S, Item> Sink<Item> for BufferUnordered<S>
where S: Stream + Sink<Item>, <S as Stream>::Item: Future,

impl<S, Item> Sink<Item> for Buffered<S>
where S: Stream + Sink<Item>, <S as Stream>::Item: Future,

impl<S, Item> Sink<Item> for Chunks<S>
where S: Stream + Sink<Item>,

impl<S, Item> Sink<Item> for Enumerate<S>
where S: Stream + Sink<Item>,

impl<S, Item> Sink<Item> for Fuse<S>
where S: Stream + Sink<Item>,

impl<S, Item> Sink<Item> for Peekable<S>
where S: Sink<Item> + Stream,