tokio_util::either

Enum Either

source
pub enum Either<L, R> {
    Left(L),
    Right(R),
}
Expand description

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

This type implements common asynchronous traits such as Future and those in Tokio.

§Example

The following code will not work:

#[tokio::main]
async fn main() {
    let result = if some_condition() {
        some_async_function()
    } else {
        other_async_function() // <- Will print: "`if` and `else` have incompatible types"
    };

    println!("Result is {}", result.await);
}

When the output type is the same, we can wrap each future in Either to avoid the issue:

use tokio_util::either::Either;

#[tokio::main]
async fn main() {
    let result = if some_condition() {
        Either::Left(some_async_function())
    } else {
        Either::Right(other_async_function())
    };

    let value = result.await;
    println!("Result is {}", value);
}

Variants§

§

Left(L)

§

Right(R)

Trait Implementations§

source§

impl<L, R> AsyncBufRead for Either<L, R>

source§

fn poll_fill_buf( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<&[u8]>>

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

fn consume(self: Pin<&mut Self>, 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. Read more
source§

impl<L, R> AsyncRead for Either<L, R>
where L: AsyncRead, R: AsyncRead,

source§

fn poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut ReadBuf<'_>, ) -> Poll<Result<()>>

Attempts to read from the AsyncRead into buf. Read more
source§

impl<L, R> AsyncSeek for Either<L, R>
where L: AsyncSeek, R: AsyncSeek,

source§

fn start_seek(self: Pin<&mut Self>, position: SeekFrom) -> Result<()>

Attempts to seek to an offset, in bytes, in a stream. Read more
source§

fn poll_complete( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Result<u64>>

Waits for a seek operation to complete. Read more
source§

impl<L, R> AsyncWrite for Either<L, R>
where L: AsyncWrite, R: AsyncWrite,

source§

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

Attempt to write bytes from buf into the object. Read more
source§

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

Attempts to flush the object, ensuring that any buffered data reach their destination. Read more
source§

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

Initiates or attempts to shut down this writer, returning success when the I/O connection has completely shut down. Read more
source§

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

Like poll_write, except that it writes from a slice of buffers. Read more
source§

fn is_write_vectored(&self) -> bool

Determines if this writer has an efficient poll_write_vectored implementation. Read more
source§

impl<L: Clone, R: Clone> Clone for Either<L, R>

source§

fn clone(&self) -> Either<L, R>

Returns a copy of the value. Read more
1.0.0 · source§

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

Performs copy-assignment from source. Read more
source§

impl<L: Debug, R: Debug> Debug for Either<L, R>

source§

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

Formats the value using the given formatter. Read more
source§

impl<L, R, O> Future for Either<L, R>
where L: Future<Output = O>, R: Future<Output = O>,

source§

type Output = O

The type of value produced on completion.
source§

fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>

Attempts to resolve the future to a final value, registering the current task for wakeup if the value is not yet available. Read more
source§

impl<L, R, Item, Error> Sink<Item> for Either<L, R>
where L: Sink<Item, Error = Error>, R: Sink<Item, Error = Error>,

source§

type Error = Error

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

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

Attempts to prepare the Sink to receive a value. Read more
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(())). Read more
source§

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

Flush any remaining output from this sink. Read more
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. Read more
source§

impl<L, R> Stream for Either<L, R>
where L: Stream, R: Stream<Item = L::Item>,

source§

type Item = <L as Stream>::Item

Values yielded by the stream.
source§

fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<Self::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. Read more
source§

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

Returns the bounds on the remaining length of the stream. Read more

Auto Trait Implementations§

§

impl<L, R> Freeze for Either<L, R>
where L: Freeze, R: Freeze,

§

impl<L, R> RefUnwindSafe for Either<L, R>

§

impl<L, R> Send for Either<L, R>
where L: Send, R: Send,

§

impl<L, R> Sync for Either<L, R>
where L: Sync, R: Sync,

§

impl<L, R> Unpin for Either<L, R>
where L: Unpin, R: Unpin,

§

impl<L, R> UnwindSafe for Either<L, R>
where L: UnwindSafe, R: UnwindSafe,

Blanket Implementations§

source§

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

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<T> Borrow<T> for T
where T: ?Sized,

source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for T
where T: ?Sized,

source§

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

Mutably borrows from an owned value. Read more
source§

impl<T> CloneToUninit for T
where T: Clone,

source§

unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
source§

impl<T> From<T> for T

source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

impl<T, U> Into<U> for T
where U: From<T>,

source§

fn into(self) -> U

Calls U::from(self).

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

source§

impl<F> IntoFuture for F
where F: Future,

source§

type Output = <F as Future>::Output

The output that the future will produce on completion.
source§

type IntoFuture = F

Which kind of future are we turning this into?
source§

fn into_future(self) -> <F as IntoFuture>::IntoFuture

Creates a future from a value. Read more
source§

impl<T> ToOwned for T
where T: Clone,

source§

type Owned = T

The resulting type after obtaining ownership.
source§

fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
source§

fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
source§

impl<T, U> TryFrom<U> for T
where U: Into<T>,

source§

type Error = Infallible

The type returned in the event of a conversion error.
source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<F, T, E> TryFuture for F
where F: Future<Output = Result<T, E>> + ?Sized,

source§

type Ok = T

The type of successful values yielded by this future
source§

type Error = E

The type of failures yielded by this future
source§

fn try_poll( self: Pin<&mut F>, cx: &mut Context<'_>, ) -> Poll<<F as Future>::Output>

Poll this TryFuture as if it were a Future. Read more
source§

impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

source§

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

The type returned in the event of a conversion error.
source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
source§

impl<S, T, E> TryStream for S
where S: Stream<Item = Result<T, E>> + ?Sized,

source§

type Ok = T

The type of successful values yielded by this future
source§

type Error = E

The type of failures yielded by this future
source§

fn try_poll_next( self: Pin<&mut S>, cx: &mut Context<'_>, ) -> Poll<Option<Result<<S as TryStream>::Ok, <S as TryStream>::Error>>>

Poll this TryStream as if it were a Stream. Read more