Trait tokio::io::AsyncBufRead
source · [−]pub trait AsyncBufRead: AsyncRead {
fn poll_fill_buf(
self: Pin<&mut Self>,
cx: &mut Context<'_>
) -> Poll<Result<&[u8]>>;
fn consume(self: Pin<&mut Self>, amt: usize);
}
Expand description
Reads bytes asynchronously.
This trait is analogous to std::io::BufRead
, but integrates with
the asynchronous task system. In particular, the poll_fill_buf
method,
unlike BufRead::fill_buf
, will automatically queue the current task for wakeup
and return if data is not yet available, rather than blocking the calling
thread.
Utilities for working with AsyncBufRead
values are provided by
AsyncBufReadExt
.
Required methods
Attempts to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.
On success, returns Poll::Ready(Ok(buf))
.
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.
This function is a lower-level call. It needs to be paired with the
consume
method to function properly. When calling this
method, none of the contents will be “read” in the sense that later
calling poll_read
may return the same contents. As such, consume
must
be called with the number of bytes that are consumed from this buffer to
ensure that the bytes are never returned twice.
An empty buffer returned indicates that the stream has reached EOF.
Tells this buffer that amt
bytes have been consumed from the buffer,
so they should no longer be returned in calls to poll_read
.
This function is a lower-level call. It needs to be paired with the
poll_fill_buf
method to function properly. This function does
not perform any I/O, it simply informs this object that some amount of
its buffer, returned from poll_fill_buf
, has been consumed and should
no longer be returned. As such, this function may do odd things if
poll_fill_buf
isn’t called before calling it.
The amt
must be <=
the number of bytes in the buffer returned by
poll_fill_buf
.