Trait async_std::io::prelude::BufReadExt

pub trait BufReadExt: BufRead {
    // Provided methods
    fn read_until<'a>(
        &'a mut self,
        byte: u8,
        buf: &'a mut Vec<u8>,
    ) -> ReadUntilFuture<'a, Self>
       where Self: Unpin { ... }
    fn read_line<'a>(
        &'a mut self,
        buf: &'a mut String,
    ) -> ReadLineFuture<'a, Self>
       where Self: Unpin { ... }
    fn lines(self) -> Lines<Self>
       where Self: Unpin + Sized { ... }
    fn split(self, byte: u8) -> Split<Self>
       where Self: Sized { ... }
}

Extension methods for BufRead.

Provided Methods

fn read_until<'a>( &'a mut self, byte: u8, buf: &'a mut Vec<u8>, ) -> ReadUntilFuture<'a, Self>

where Self: Unpin,

Reads all bytes into buf until the delimiter byte or EOF is reached.

This function will read bytes from the underlying stream until the delimiter or EOF is found. Once found, all bytes up to, and including, the delimiter (if found) will be appended to buf.

If successful, this function will return the total number of bytes read.

Examples

use async_std::fs::File;
use async_std::io::BufReader;
use async_std::prelude::*;

let mut file = BufReader::new(File::open("a.txt").await?);

let mut buf = Vec::with_capacity(1024);
let n = file.read_until(b'\n', &mut buf).await?;

Multiple successful calls to read_until append all bytes up to and including to buf:

use async_std::io::BufReader;
use async_std::prelude::*;

let from: &[u8] = b"append\nexample\n";
let mut reader = BufReader::new(from);
let mut buf = vec![];

let mut size = reader.read_until(b'\n', &mut buf).await?;
assert_eq!(size, 7);
assert_eq!(buf, b"append\n");

size += reader.read_until(b'\n', &mut buf).await?;
assert_eq!(size, from.len());

assert_eq!(buf, from);

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

where Self: Unpin,

Reads all bytes and appends them into buf until a newline (the 0xA byte) is reached.

This function will read bytes from the underlying stream until the newline delimiter (the 0xA byte) or EOF is found. Once found, all bytes up to, and including, the delimiter (if found) will be appended to buf.

If successful, this function will return the total number of bytes read.

If this function returns Ok(0), the stream has reached EOF.

Errors

This function has the same error semantics as read_until and will also return an error if the read bytes are not valid UTF-8. If an I/O error is encountered then buf may contain some bytes already read in the event that all data read so far was valid UTF-8.

Examples

use async_std::fs::File;
use async_std::io::BufReader;
use async_std::prelude::*;

let mut file = BufReader::new(File::open("a.txt").await?);

let mut buf = String::new();
file.read_line(&mut buf).await?;

fn lines(self) -> Lines<Self>

where Self: Unpin + Sized,

Returns a stream over the lines of this byte stream.

The stream returned from this function will yield instances of io::Result<String>. Each string returned will not have a newline byte (the 0xA byte) or CRLF (0xD, 0xA bytes) at the end.

Examples

use async_std::fs::File;
use async_std::io::BufReader;
use async_std::prelude::*;

let file = File::open("a.txt").await?;
let mut lines = BufReader::new(file).lines();
let mut count = 0;

while let Some(line) = lines.next().await {
    line?;
    count += 1;
}

fn split(self, byte: u8) -> Split<Self>

where Self: Sized,

Returns a stream over the contents of this reader split on the byte byte.

The stream returned from this function will return instances of io::Result<Vec<u8>>. Each vector returned will not have the delimiter byte at the end.

This function will yield errors whenever read_until would have also yielded an error.

Examples

std::io::Cursor is a type that implements BufRead. In this example, we use Cursor to iterate over all hyphen delimited segments in a byte slice

use async_std::prelude::*;
use async_std::io;

let cursor = io::Cursor::new(b"lorem-ipsum-dolor");

let mut split_iter = cursor.split(b'-').map(|l| l.unwrap());
assert_eq!(split_iter.next().await, Some(b"lorem".to_vec()));
assert_eq!(split_iter.next().await, Some(b"ipsum".to_vec()));
assert_eq!(split_iter.next().await, Some(b"dolor".to_vec()));
assert_eq!(split_iter.next().await, None);

Object Safety

This trait is not object safe.

Implementors

impl<T: BufRead + ?Sized> BufReadExt for T