Trait AsyncReadExt

pub trait AsyncReadExt: AsyncRead {
    // Provided methods
    fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadFuture<'a, Self>
       where Self: Unpin { ... }
    fn read_vectored<'a>(
        &'a mut self,
        bufs: &'a mut [IoSliceMut<'a>],
    ) -> ReadVectoredFuture<'a, Self>
       where Self: Unpin { ... }
    fn read_to_end<'a>(
        &'a mut self,
        buf: &'a mut Vec<u8>,
    ) -> ReadToEndFuture<'a, Self>
       where Self: Unpin { ... }
    fn read_to_string<'a>(
        &'a mut self,
        buf: &'a mut String,
    ) -> ReadToStringFuture<'a, Self>
       where Self: Unpin { ... }
    fn read_exact<'a>(
        &'a mut self,
        buf: &'a mut [u8],
    ) -> ReadExactFuture<'a, Self>
       where Self: Unpin { ... }
    fn take(self, limit: u64) -> Take<Self>
       where Self: Sized { ... }
    fn bytes(self) -> Bytes<Self>
       where Self: Sized { ... }
    fn chain<R>(self, next: R) -> Chain<Self, R>
       where R: AsyncRead,
             Self: Sized { ... }
    fn boxed_reader<'a>(self) -> Pin<Box<dyn AsyncRead + Send + 'a>>
       where Self: Sized + Send + 'a { ... }
}

Extension trait for AsyncRead.

Provided Methods

fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadFuture<'a, Self>

where Self: Unpin,

Reads some bytes from the byte stream.

On success, returns the total number of bytes read.

If the return value is Ok(n), then it must be guaranteed that 0 <= n <= buf.len(). A nonzero n value indicates that the buffer has been filled with n bytes of data. If n is 0, then it can indicate one of two scenarios:

1. This reader has reached its “end of file” and will likely no longer be able to produce bytes. Note that this does not mean that the reader will always no longer be able to produce bytes.
2. The buffer specified was 0 bytes in length.

Examples

use futures_lite::io::{AsyncReadExt, BufReader};

let input: &[u8] = b"hello";
let mut reader = BufReader::new(input);

let mut buf = vec![0; 1024];
let n = reader.read(&mut buf).await?;

fn read_vectored<'a>( &'a mut self, bufs: &'a mut [IoSliceMut<'a>], ) -> ReadVectoredFuture<'a, Self>

where Self: Unpin,

Like read(), except it reads into a slice of buffers.

Data is copied to fill each buffer in order, with the final buffer possibly being only partially filled. This method must behave same as a single call to read() with the buffers concatenated would.

fn read_to_end<'a>( &'a mut self, buf: &'a mut Vec<u8>, ) -> ReadToEndFuture<'a, Self>

where Self: Unpin,

Reads the entire contents and appends them to a Vec.

On success, returns the total number of bytes read.

Examples

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

let mut reader = Cursor::new(vec![1, 2, 3]);
let mut contents = Vec::new();

let n = reader.read_to_end(&mut contents).await?;
assert_eq!(n, 3);
assert_eq!(contents, [1, 2, 3]);

fn read_to_string<'a>( &'a mut self, buf: &'a mut String, ) -> ReadToStringFuture<'a, Self>

where Self: Unpin,

Reads the entire contents and appends them to a String.

On success, returns the total number of bytes read.

Examples

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

let mut reader = Cursor::new(&b"hello");
let mut contents = String::new();

let n = reader.read_to_string(&mut contents).await?;
assert_eq!(n, 5);
assert_eq!(contents, "hello");

fn read_exact<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadExactFuture<'a, Self>

where Self: Unpin,

Reads the exact number of bytes required to fill buf.

On success, returns the total number of bytes read.

Examples

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

let mut reader = Cursor::new(&b"hello");
let mut contents = vec![0; 3];

reader.read_exact(&mut contents).await?;
assert_eq!(contents, b"hel");

fn take(self, limit: u64) -> Take<Self>

where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

This method returns a new instance of AsyncRead which will read at most limit bytes, after which it will always return Ok(0) indicating EOF.

Examples

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

let mut reader = Cursor::new(&b"hello");
let mut contents = String::new();

let n = reader.take(3).read_to_string(&mut contents).await?;
assert_eq!(n, 3);
assert_eq!(contents, "hel");

fn bytes(self) -> Bytes<Self>

where Self: Sized,

Converts this AsyncRead into a Stream of bytes.

The returned type implements Stream where Item is io::Result<u8>.

use futures_lite::io::{AsyncReadExt, Cursor};
use futures_lite::stream::StreamExt;

let reader = Cursor::new(&b"hello");
let mut bytes = reader.bytes();

while let Some(byte) = bytes.next().await {
    println!("byte: {}", byte?);
}

fn chain<R>(self, next: R) -> Chain<Self, R>

where R: AsyncRead, Self: Sized,

Creates an adapter which will chain this stream with another.

The returned AsyncRead instance will first read all bytes from this reader until EOF is found, and then continue with next.

Examples

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

let r1 = Cursor::new(&b"hello");
let r2 = Cursor::new(&b"world");
let mut reader = r1.chain(r2);

let mut contents = String::new();
reader.read_to_string(&mut contents).await?;
assert_eq!(contents, "helloworld");

fn boxed_reader<'a>(self) -> Pin<Box<dyn AsyncRead + Send + 'a>>

where Self: Sized + Send + 'a,

Available on crate feature alloc only.

Boxes the reader and changes its type to dyn AsyncRead + Send + 'a.

Examples

use futures_lite::io::AsyncReadExt;

let reader = [1, 2, 3].boxed_reader();

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<R> AsyncReadExt for R

where R: AsyncRead + ?Sized,