Trait futures_util::io::AsyncRead
source · pub trait AsyncRead {
// Required method
fn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<Result<usize, Error>>;
// Provided method
fn poll_read_vectored(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &mut [IoSliceMut<'_>],
) -> Poll<Result<usize, Error>> { ... }
}Expand description
Read bytes asynchronously.
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.
Required Methods§
sourcefn poll_read(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<Result<usize, Error>>
fn poll_read( self: Pin<&mut Self>, cx: &mut Context<'_>, buf: &mut [u8], ) -> Poll<Result<usize, Error>>
Attempt to read from the AsyncRead into buf.
On success, returns Poll::Ready(Ok(num_bytes_read)).
If no data is available for reading, 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
readable 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.
Provided Methods§
sourcefn poll_read_vectored(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &mut [IoSliceMut<'_>],
) -> Poll<Result<usize, Error>>
fn poll_read_vectored( self: Pin<&mut Self>, cx: &mut Context<'_>, bufs: &mut [IoSliceMut<'_>], ) -> Poll<Result<usize, Error>>
Attempt to read from the AsyncRead into bufs using vectored
IO operations.
This method is similar to poll_read, but allows data to be read
into multiple buffers using a single operation.
On success, returns Poll::Ready(Ok(num_bytes_read)).
If no data is available for reading, 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
readable or is closed.
By default, this method delegates to using poll_read 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.