Trait futures_util::io::AsyncWrite
source · 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>> { ... }
}Expand description
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§
sourcefn poll_write(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8],
) -> Poll<Result<usize, Error>>
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.
sourcefn poll_flush(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), Error>>
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.
sourcefn poll_close(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
) -> Poll<Result<(), Error>>
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§
sourcefn poll_write_vectored(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &[IoSlice<'_>],
) -> Poll<Result<usize, Error>>
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.