Trait AsyncSeekExt

pub trait AsyncSeekExt: AsyncSeek

An extension trait that adds utility methods to AsyncSeek types.

Examples

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

# #[tokio::main(flavor = "current_thread")]
# 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][crate::io] 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

# #[cfg(not(target_family = "wasm"))]
# {
use tokio::fs::File;
use tokio::io::{AsyncSeekExt, AsyncReadExt};

use std::io::SeekFrom;

# async fn dox() -> std::io::Result<()> {
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?;
# Ok(())
# }
# }

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)).

Implementors