Enum futures::future::Either

pub enum Either<A, B> {
    Left(A),
    Right(B),
}

Combines two different futures, streams, or sinks having the same associated types into a single type.

This is useful when conditionally choosing between two distinct future types:

use futures::future::Either;

let cond = true;

let fut = if cond {
    Either::Left(async move { 12 })
} else {
    Either::Right(async move { 44 })
};

assert_eq!(fut.await, 12);

Variants

Left(A)

First branch of the type

Right(B)

Second branch of the type

Implementations

impl<A, B, T> Either<(T, A), (T, B)>

pub fn factor_first(self) -> (T, Either<A, B>)

Factor out a homogeneous type from an either of pairs.

Here, the homogeneous type is the first element of the pairs.

impl<A, B, T> Either<(A, T), (B, T)>

pub fn factor_second(self) -> (Either<A, B>, T)

Factor out a homogeneous type from an either of pairs.

Here, the homogeneous type is the second element of the pairs.

impl<T> Either<T, T>

pub fn into_inner(self) -> T

Extract the value of an either over two equivalent types.

Trait Implementations

impl<A, B> AsyncBufRead for Either<A, B> where
    A: AsyncBufRead,
    B: AsyncBufRead, 

pub fn poll_fill_buf(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>
) -> Poll<Result<&[u8], Error>>

Attempt to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

pub fn consume(self: Pin<&mut Either<A, B>>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read.

impl<A, B> AsyncRead for Either<A, B> where
    A: AsyncRead,
    B: AsyncRead, 

pub fn poll_read(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>,
    buf: &mut [u8]
) -> Poll<Result<usize, Error>>

Attempt to read from the AsyncRead into buf.

pub fn poll_read_vectored(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>,
    bufs: &mut [IoSliceMut<'_>]
) -> Poll<Result<usize, Error>>

Attempt to read from the AsyncRead into bufs using vectored IO operations.

impl<A, B> AsyncSeek for Either<A, B> where
    A: AsyncSeek,
    B: AsyncSeek, 

pub fn poll_seek(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>,
    pos: SeekFrom
) -> Poll<Result<u64, Error>>

Attempt to seek to an offset, in bytes, in a stream.

impl<A, B> AsyncWrite for Either<A, B> where
    A: AsyncWrite,
    B: AsyncWrite, 

pub fn poll_write(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>,
    buf: &[u8]
) -> Poll<Result<usize, Error>>

Attempt to write bytes from buf into the object.

pub fn poll_write_vectored(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>,
    bufs: &[IoSlice<'_>]
) -> Poll<Result<usize, Error>>

Attempt to write bytes from bufs into the object using vectored IO operations.

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

Attempt to flush the object, ensuring that any buffered data reach their destination.

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

Attempt to close the object.

impl<A, B> Clone for Either<A, B> where
    A: Clone,
    B: Clone, 

pub fn clone(&self) -> Either<A, B>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<A, B> Debug for Either<A, B> where
    A: Debug,
    B: Debug, 

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

Formats the value using the given formatter.

impl<A, B> FusedFuture for Either<A, B> where
    A: FusedFuture,
    B: FusedFuture<Output = <A as Future>::Output>, 

pub fn is_terminated(&self) -> bool

Returns true if the underlying future should no longer be polled.

impl<A, B> FusedStream for Either<A, B> where
    A: FusedStream,
    B: FusedStream<Item = <A as Stream>::Item>, 

pub fn is_terminated(&self) -> bool

Returns true if the stream should no longer be polled.

impl<A, B> Future for Either<A, B> where
    A: Future,
    B: Future<Output = <A as Future>::Output>, 

type Output = <A as Future>::Output

The type of value produced on completion.

pub fn poll(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>
) -> Poll<<Either<A, B> as Future>::Output>

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available.

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

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

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

Attempts to prepare the Sink to receive a value.

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

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

Flush any remaining output from this sink.

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

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

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

type Item = <A as Stream>::Item

Values yielded by the stream.

pub fn poll_next(
    self: Pin<&mut Either<A, B>>,
    cx: &mut Context<'_>
) -> Poll<Option<<Either<A, B> as Stream>::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

pub fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.