Trait AsyncSeekExt

pub trait AsyncSeekExt: AsyncSeek {
    // Provided methods
    fn seek(&mut self, pos: SeekFrom) -> Seek<'_, Self>
       where Self: Unpin { ... }
    fn rewind(&mut self) -> Seek<'_, Self>
       where Self: Unpin { ... }
    fn stream_position(&mut self) -> Seek<'_, Self>
       where Self: Unpin { ... }
}

Available on crate feature io-util only.

An extension trait that adds utility methods to AsyncSeek types.

Examples

use std::io::{self, Cursor, SeekFrom};
use tokio::io::{AsyncSeekExt, AsyncReadExt};

#[tokio::main]
async fn main() -> io::Result<()> {
    let mut cursor = Cursor::new(b"abcdefg");

    // the `seek` method is defined by this trait
    cursor.seek(SeekFrom::Start(3)).await?;

    let mut buf = [0; 1];
    let n = cursor.read(&mut buf).await?;
    assert_eq!(n, 1);
    assert_eq!(buf, [b'd']);

    Ok(())
}

See module documentation for more details.

Provided Methods

fn seek(&mut self, pos: SeekFrom) -> Seek<'_, Self>

where Self: Unpin,

Creates a future which will seek an IO object, and then yield the new position in the object and the object itself.

Equivalent to:

async fn seek(&mut self, pos: SeekFrom) -> io::Result<u64>;

In the case of an error the buffer and the object will be discarded, with the error yielded.

Examples

use tokio::fs::File;
use tokio::io::{AsyncSeekExt, AsyncReadExt};

use std::io::SeekFrom;

let mut file = File::open("foo.txt").await?;
file.seek(SeekFrom::Start(6)).await?;

let mut contents = vec![0u8; 10];
file.read_exact(&mut contents).await?;

fn rewind(&mut self) -> Seek<'_, Self>

where Self: Unpin,

Creates a future which will rewind to the beginning of the stream.

This is convenience method, equivalent to self.seek(SeekFrom::Start(0)).

fn stream_position(&mut self) -> Seek<'_, Self>

where Self: Unpin,

Creates a future which will return the current seek position from the start of the stream.

This is equivalent to self.seek(SeekFrom::Current(0)).

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<S: AsyncSeek + ?Sized> AsyncSeekExt for S