Trait async_std::io::Write [−][src]
pub trait Write {
fn poll_write(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
buf: &[u8]
) -> Poll<Result<usize>>;
fn poll_flush(
self: Pin<&mut Self>,
cx: &mut Context<'_>
) -> Poll<Result<()>>;
fn poll_close(
self: Pin<&mut Self>,
cx: &mut Context<'_>
) -> Poll<Result<()>>;
fn poll_write_vectored(
self: Pin<&mut Self>,
cx: &mut Context<'_>,
bufs: &[IoSlice<'_>]
) -> Poll<Result<usize>> { ... }
fn write<'a>(&'a mut self, buf: &'a [u8]) -> ImplFuture<Result<usize>>
where
Self: Unpin,
{ ... }
fn flush(&mut self) -> ImplFuture<Result<()>>
where
Self: Unpin,
{ ... }
fn write_vectored<'a>(
&'a mut self,
bufs: &'a [IoSlice<'a>]
) -> ImplFuture<Result<usize>>
where
Self: Unpin,
{ ... }
fn write_all<'a>(&'a mut self, buf: &'a [u8]) -> ImplFuture<Result<()>>
where
Self: Unpin,
{ ... }
fn write_fmt<'a>(&'a mut self, fmt: Arguments<'_>) -> ImplFuture<Result<()>>
where
Self: Unpin,
{ ... }
}
Expand description
Allows writing to a byte stream.
This trait is a re-export of futures::io::AsyncWrite
and is an async version of
std::io::Write
.
Methods other than poll_write
, poll_write_vectored
, poll_flush
, and
poll_close
do not really exist in the trait itself, but they become available when
WriteExt
from the prelude is imported:
use async_std::prelude::*;
Required methods
Attempt to write bytes from buf
into the object.
Attempt to flush the object, ensuring that any buffered data reach their destination.
Provided methods
Attempt to write bytes from bufs
into the object using vectored IO operations.
Writes some bytes into the byte stream.
Returns the number of bytes written from the start of the buffer.
If the return value is Ok(n)
then it must be guaranteed that
0 <= n <= buf.len()
. A return value of 0
typically means that the underlying
object is no longer able to accept bytes and will likely not be able to in the
future as well, or that the buffer provided is empty.
Examples
use async_std::fs::File;
use async_std::prelude::*;
let mut file = File::create("a.txt").await?;
let n = file.write(b"hello world").await?;
Flushes the stream to ensure that all buffered contents reach their destination.
Examples
use async_std::fs::File;
use async_std::prelude::*;
let mut file = File::create("a.txt").await?;
file.write_all(b"hello world").await?;
file.flush().await?;
Like write
, except that it writes from a slice of buffers.
Data is copied from each buffer in order, with the final buffer read from possibly
being only partially consumed. This method must behave as a call to write
with
the buffers concatenated would.
The default implementation calls write
with either the first nonempty buffer
provided, or an empty one if none exists.
Writes an entire buffer into the byte stream.
This method will continuously call write
until there is no more data to be
written or an error is returned. This method will not return until the entire
buffer has been successfully written or such an error occurs.
Examples
use async_std::fs::File;
use async_std::prelude::*;
let mut file = File::create("a.txt").await?;
file.write_all(b"hello world").await?;
Writes a formatted string into this writer, returning any error encountered.
This method will continuously call write
until there is no more data to be
written or an error is returned. This future will not resolve until the entire
buffer has been successfully written or such an error occurs.
Examples
use async_std::io::prelude::*;
use async_std::fs::File;
let mut buffer = File::create("foo.txt").await?;
// this call
write!(buffer, "{:.*}", 2, 1.234567).await?;
// turns into this:
buffer.write_fmt(format_args!("{:.*}", 2, 1.234567)).await?;