Struct futures_util::io::Take

#[must_use = "readers do nothing unless you `.await` or poll them"]
pub struct Take<R> { /* fields omitted */ }

Reader for the take method.

Methods

impl<R: AsyncRead> Take<R>

pub fn limit(&self) -> u64

Returns the remaining number of bytes that can be read before this instance will return EOF.

Note

This instance may reach EOF after reading fewer bytes than indicated by this method if the underlying AsyncRead instance reaches EOF.

Examples

use futures::io::{AsyncReadExt, Cursor};

let reader = Cursor::new(&b"12345678"[..]);
let mut buffer = [0; 2];

let mut take = reader.take(4);
let n = take.read(&mut buffer).await?;

assert_eq!(take.limit(), 2);

pub fn set_limit(&mut self, limit: u64)

Sets the number of bytes that can be read before this instance will return EOF. This is the same as constructing a new Take instance, so the amount of bytes read and the previous limit value don't matter when calling this method.

Examples

use futures::io::{AsyncReadExt, Cursor};

let reader = Cursor::new(&b"12345678"[..]);
let mut buffer = [0; 4];

let mut take = reader.take(4);
let n = take.read(&mut buffer).await?;

assert_eq!(n, 4);
assert_eq!(take.limit(), 0);

take.set_limit(10);
let n = take.read(&mut buffer).await?;
assert_eq!(n, 4);

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

pub fn get_ref(&self) -> &R

Gets a reference to the underlying reader.

Examples

use futures::io::{AsyncReadExt, Cursor};

let reader = Cursor::new(&b"12345678"[..]);
let mut buffer = [0; 4];

let mut take = reader.take(4);
let n = take.read(&mut buffer).await?;

let cursor_ref = take.get_ref();
assert_eq!(cursor_ref.position(), 4);

Important traits for &'_ mut F

impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

pub fn get_mut(&mut self) -> &mut R

Gets a mutable reference to the underlying reader.

Care should be taken to avoid modifying the internal I/O state of the underlying reader as doing so may corrupt the internal limit of this Take.

Examples

use futures::io::{AsyncReadExt, Cursor};

let reader = Cursor::new(&b"12345678"[..]);
let mut buffer = [0; 4];

let mut take = reader.take(4);
let n = take.read(&mut buffer).await?;

let cursor_mut = take.get_mut();

Important traits for Pin<P>

impl<P> Future for Pin<P> where
    P: Unpin + DerefMut,
    <P as Deref>::Target: Future,  type Output = <<P as Deref>::Target as Future>::Output;

pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut R>

Gets a pinned mutable reference to the underlying reader.

Care should be taken to avoid modifying the internal I/O state of the underlying reader as doing so may corrupt the internal limit of this Take.

pub fn into_inner(self) -> R

Consumes the Take, returning the wrapped reader.

Examples

use futures::io::{AsyncReadExt, Cursor};

let reader = Cursor::new(&b"12345678"[..]);
let mut buffer = [0; 4];

let mut take = reader.take(4);
let n = take.read(&mut buffer).await?;

let cursor = take.into_inner();
assert_eq!(cursor.position(), 4);

Trait Implementations

impl<R: Unpin> Unpin for Take<R>

impl<R: Debug> Debug for Take<R>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<R: AsyncRead> AsyncRead for Take<R>

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.

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.

impl<R: AsyncBufRead> AsyncBufRead for Take<R>

fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Result<&[u8]>>

Attempt to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty.

fn consume(self: Pin<&mut Self>, amt: usize)

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to [poll_read].