Struct futures_util::io::Take

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

This is supported on crate feature io only.

Reader for the take method.

Implementations

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);

pub fn get_ref(&self) -> &R

Acquires a reference to the underlying sink or stream that this combinator is pulling from.

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

Acquires a mutable reference to the underlying sink or stream that this combinator is pulling from.

Note that care must be taken to avoid tampering with the state of the sink or stream which may otherwise confuse this combinator.

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

Acquires a pinned mutable reference to the underlying sink or stream that this combinator is pulling from.

Note that care must be taken to avoid tampering with the state of the sink or stream which may otherwise confuse this combinator.

pub fn into_inner(self) -> R

Consumes this combinator, returning the underlying sink or stream.

Note that this may discard intermediate state of this combinator, so care should be taken to avoid losing resources when this is called.

Trait Implementations

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.

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.

unsafe fn initializer(&self) -> Initializer

Determines if this AsyncReader can work with buffers of uninitialized memory.

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: Debug> Debug for Take<R>

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

Formats the value using the given formatter.

impl<'__pin, R> Unpin for Take<R> where
    __Origin<'__pin, R>: Unpin,