AsyncReadExt in futures_lite::io - Rust (original) (raw)

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: AsyncRead>(self, next: R) -> Chain<Self, R>
       where Self: Sized { ... }
    fn boxed_reader<'a>(self) -> Pin<Box<dyn AsyncRead + Send + 'a>>
       where Self: Sized + Send + 'a { ... }
}

Expand description

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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 that0 <= 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?;

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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 toread() with the buffers concatenated would.

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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]);

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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");

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Reads the exact number of bytes required to fill buf.

§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");

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

This method returns a new instance of AsyncRead which will read at mostlimit 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");

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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?);
}

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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");

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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();

This trait is not dyn compatible.

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

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