Trait virtual_fs::AsyncRead

pub trait AsyncRead {
    // Required method
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut ReadBuf<'_>,
    ) -> Poll<Result<(), Error>>;
}

Reads bytes from a source.

This trait is analogous to the std::io::Read trait, but integrates with the asynchronous task system. In particular, the poll_read method, unlike Read::read, will automatically queue the current task for wakeup and return if data is not yet available, rather than blocking the calling thread.

Specifically, this means that the poll_read function will return one of the following:

• Poll::Ready(Ok(())) means that data was immediately read and placed into the output buffer. The amount of data read can be determined by the increase in the length of the slice returned by ReadBuf::filled. If the difference is 0, EOF has been reached.

• Poll::Pending means that no data was read into the buffer provided. The I/O object is not currently readable but may become readable in the future. Most importantly, the current future’s task is scheduled to get unparked when the object is readable. This means that like Future::poll you’ll receive a notification when the I/O object is readable again.

• Poll::Ready(Err(e)) for other errors are standard I/O errors coming from the underlying object.

This trait importantly means that the read method only works in the context of a future’s task. The object may panic if used outside of a task.

Utilities for working with AsyncRead values are provided by AsyncReadExt.

Required Methods

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

Attempts to read from the AsyncRead into buf.

On success, returns Poll::Ready(Ok(())) and places data in the unfilled portion of buf. If no data was read (buf.filled().len() is unchanged), it implies that EOF has been reached.

If no data is available for reading, the method returns Poll::Pending and arranges for the current task (via cx.waker()) to receive a notification when the object becomes readable or is closed.

Implementations on Foreign Types

impl AsyncRead for &[u8]

fn poll_read( self: Pin<&mut &[u8]>, _cx: &mut Context<'_>, buf: &mut ReadBuf<'_>, ) -> Poll<Result<(), Error>>

impl<P> AsyncRead for Pin<P>

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

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

impl<T> AsyncRead for &mut T

where T: AsyncRead + Unpin + ?Sized,

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

impl<T> AsyncRead for Box<T>

where T: AsyncRead + Unpin + ?Sized,

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

impl<T> AsyncRead for Cursor<T>

where T: AsRef<[u8]> + Unpin,

fn poll_read( self: Pin<&mut Cursor<T>>, _cx: &mut Context<'_>, buf: &mut ReadBuf<'_>, ) -> Poll<Result<(), Error>>

Implementors

impl AsyncRead for ArcBoxFile

impl AsyncRead for BufferFile

impl AsyncRead for CombineFile

impl AsyncRead for CopyOnWriteFile

impl AsyncRead for DualWriteFile

impl AsyncRead for virtual_fs::host_fs::File

Available on crate feature host-fs only.

impl AsyncRead for virtual_fs::host_fs::Stderr

Available on crate feature host-fs only.

impl AsyncRead for virtual_fs::host_fs::Stdin

Available on crate feature host-fs only.

impl AsyncRead for virtual_fs::host_fs::Stdout

Available on crate feature host-fs only.

impl AsyncRead for tokio::fs::file::File

impl AsyncRead for tokio::io::stdin::Stdin

impl AsyncRead for Empty

impl AsyncRead for DuplexStream

impl AsyncRead for Repeat

impl AsyncRead for virtual_fs::mem_fs::Stderr

impl AsyncRead for virtual_fs::mem_fs::Stdin

impl AsyncRead for virtual_fs::mem_fs::Stdout

impl AsyncRead for NullFile

impl AsyncRead for Pipe

impl AsyncRead for PipeRx

impl AsyncRead for RandomFile

impl AsyncRead for DeviceFile

impl AsyncRead for WebCFile

Available on crate feature static-fs only.

impl AsyncRead for StaticFile

impl AsyncRead for ZeroFile

impl<R> AsyncRead for BufReader<R>

where R: AsyncRead,

impl<R> AsyncRead for Take<R>

where R: AsyncRead,

impl<R, W> AsyncRead for Join<R, W>

where R: AsyncRead,

impl<RW> AsyncRead for BufStream<RW>

where RW: AsyncRead + AsyncWrite,

impl<T> AsyncRead for ArcFile<T>

where T: VirtualFile + Send + Sync + 'static,

impl<T> AsyncRead for ReadHalf<T>

where T: AsyncRead,

impl<W> AsyncRead for BufWriter<W>

where W: AsyncWrite + AsyncRead,