Trait AsyncWrite

pub trait AsyncWrite {
    // Required methods
    fn poll_write(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &[u8],
    ) -> Poll<Result<usize, Error>>;
    fn poll_flush(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Error>>;
    fn poll_close(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Error>>;

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

Available on crate feature io only.

Write bytes asynchronously.

This trait is analogous to the std::io::Write trait, but integrates with the asynchronous task system. In particular, the poll_write method, unlike Write::write, will automatically queue the current task for wakeup and return if the writer cannot take more data, rather than blocking the calling thread.

Required Methods

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

Attempt to write bytes from buf into the object.

On success, returns Poll::Ready(Ok(num_bytes_written)).

If the object is not ready for writing, the method returns Poll::Pending and arranges for the current task (via cx.waker().wake_by_ref()) to receive a notification when the object becomes writable or is closed.

Implementation

This function may not return errors of kind WouldBlock or Interrupted. Implementations must convert WouldBlock into Poll::Pending and either internally retry or convert Interrupted into another error kind.

poll_write must try to make progress by flushing the underlying object if that is the only way the underlying object can become writable again.

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

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

On success, returns Poll::Ready(Ok(())).

If flushing cannot immediately complete, this method returns Poll::Pending and arranges for the current task (via cx.waker().wake_by_ref()) to receive a notification when the object can make progress towards flushing.

Implementation

This function may not return errors of kind WouldBlock or Interrupted. Implementations must convert WouldBlock into Poll::Pending and either internally retry or convert Interrupted into another error kind.

It only makes sense to do anything here if you actually buffer data.

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

Attempt to close the object.

On success, returns Poll::Ready(Ok(())).

If closing cannot immediately complete, this function returns Poll::Pending and arranges for the current task (via cx.waker().wake_by_ref()) to receive a notification when the object can make progress towards closing.

Implementation

This function may not return errors of kind WouldBlock or Interrupted. Implementations must convert WouldBlock into Poll::Pending and either internally retry or convert Interrupted into another error kind.

Provided Methods

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

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

This method is similar to poll_write, but allows data from multiple buffers to be written using a single operation.

On success, returns Poll::Ready(Ok(num_bytes_written)).

If the object is not ready for writing, the method returns Poll::Pending and arranges for the current task (via cx.waker().wake_by_ref()) to receive a notification when the object becomes writable or is closed.

By default, this method delegates to using poll_write on the first nonempty buffer in bufs, or an empty one if none exists. Objects which support vectored IO should override this method.

Implementation

This function may not return errors of kind WouldBlock or Interrupted. Implementations must convert WouldBlock into Poll::Pending and either internally retry or convert Interrupted into another error kind.

Implementations on Foreign Types

impl AsyncWrite for Vec<u8>

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

fn poll_write_vectored( self: Pin<&mut Vec<u8>>, _: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

fn poll_flush( self: Pin<&mut Vec<u8>>, _: &mut Context<'_>, ) -> Poll<Result<(), Error>>

fn poll_close( self: Pin<&mut Vec<u8>>, cx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

impl<P> AsyncWrite for Pin<P>

where P: DerefMut + Unpin, <P as Deref>::Target: AsyncWrite,

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

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

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

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

impl<T> AsyncWrite for &mut T

where T: AsyncWrite + Unpin + ?Sized,

fn poll_write( self: Pin<&mut &mut T>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll<Result<usize, Error>>

fn poll_write_vectored( self: Pin<&mut &mut T>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

fn poll_flush( self: Pin<&mut &mut T>, cx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

fn poll_close( self: Pin<&mut &mut T>, cx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

impl<T> AsyncWrite for Box<T>

where T: AsyncWrite + Unpin + ?Sized,

fn poll_write( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, buf: &[u8], ) -> Poll<Result<usize, Error>>

fn poll_write_vectored( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, bufs: &[IoSlice<'_>], ) -> Poll<Result<usize, Error>>

fn poll_flush( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

fn poll_close( self: Pin<&mut Box<T>>, cx: &mut Context<'_>, ) -> Poll<Result<(), Error>>

Implementors

impl AsyncWrite for Cursor<&mut Vec<u8>>

impl AsyncWrite for Cursor<&mut [u8]>

impl AsyncWrite for Cursor<Box<[u8]>>

impl AsyncWrite for Cursor<Vec<u8>>

impl AsyncWrite for Sink

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

where A: AsyncWrite, B: AsyncWrite,

impl<R: AsyncWrite> AsyncWrite for BufReader<R>

impl<St> AsyncWrite for IntoAsyncRead<St>

where St: TryStream<Error = Error> + AsyncWrite, St::Ok: AsRef<[u8]>,

impl<T> AsyncWrite for AllowStdIo<T>

where T: Write,

impl<W: AsyncWrite01> AsyncWrite for Compat01As03<W>

Available on crate features io-compat and compat only.

impl<W: AsyncWrite> AsyncWrite for BufWriter<W>

impl<W: AsyncWrite> AsyncWrite for LineWriter<W>

impl<W: AsyncWrite> AsyncWrite for WriteHalf<W>