[−][src]Trait futures_util::io::AsyncBufReadExt

pub trait AsyncBufReadExt: AsyncBufRead {
    fn copy_buf_into<W: ?Sized>(self, writer: &mut W) -> CopyBufInto<Self, W>
    where
        Self: Sized,
        W: AsyncWrite + Unpin,
    { ... }

    fn read_until<'a>(
        &'a mut self, 
        byte: u8, 
        buf: &'a mut Vec<u8>
    ) -> ReadUntil<'a, Self>
    where
        Self: Unpin,
    { ... }

    fn read_line<'a>(&'a mut self, buf: &'a mut String) -> ReadLine<'a, Self>
    where
        Self: Unpin,
    { ... }

    fn lines(self) -> Lines<Self>
    where
        Self: Sized,
    { ... }
}

An extension trait which adds utility methods to AsyncBufRead types.

Provided methods

ⓘImportant traits for CopyBufInto<'_, R, W>
fn copy_buf_into<W: ?Sized>(self, writer: &mut W) -> CopyBufInto<Self, W> where
    Self: Sized,
    W: AsyncWrite + Unpin, 

Creates a future which copies all the bytes from one object to another.

The returned future will copy all the bytes read from this AsyncBufRead into the writer specified. This future will only complete once the reader has hit EOF and all bytes have been written to and flushed from the writer provided.

On success the number of bytes is returned.

Examples

#![feature(async_await)]
use futures::io::{AsyncBufReadExt, AsyncWriteExt};
use std::io::Cursor;

let reader = Cursor::new([1, 2, 3, 4]);
let mut writer = Cursor::new([0u8; 5]);

let bytes = reader.copy_buf_into(&mut writer).await?;
writer.close().await?;

assert_eq!(bytes, 4);
assert_eq!(writer.into_inner(), [1, 2, 3, 4, 0]);

ⓘImportant traits for ReadUntil<'_, R>
fn read_until<'a>(
    &'a mut self,
    byte: u8,
    buf: &'a mut Vec<u8>
) -> ReadUntil<'a, Self> where
    Self: Unpin, 

Creates a future which will read all the bytes associated with this I/O object into buf until the delimiter byte or EOF is reached. This method is the async equivalent to BufRead::read_until.

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.

The returned future will resolve to the number of bytes read once the read operation is completed.

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

Examples

#![feature(async_await)]
use futures::io::AsyncBufReadExt;
use std::io::Cursor;

let mut cursor = Cursor::new(b"lorem-ipsum");
let mut buf = vec![];

// cursor is at 'l'
let num_bytes = cursor.read_until(b'-', &mut buf).await?;
assert_eq!(num_bytes, 6);
assert_eq!(buf, b"lorem-");
buf.clear();

// cursor is at 'i'
let num_bytes = cursor.read_until(b'-', &mut buf).await?;
assert_eq!(num_bytes, 5);
assert_eq!(buf, b"ipsum");
buf.clear();

// cursor is at EOF
let num_bytes = cursor.read_until(b'-', &mut buf).await?;
assert_eq!(num_bytes, 0);
assert_eq!(buf, b"");

ⓘImportant traits for ReadLine<'_, R>
fn read_line<'a>(&'a mut self, buf: &'a mut String) -> ReadLine<'a, Self> where
    Self: Unpin, 

Creates a future which will read all the bytes associated with this I/O object into buf until a newline (the 0xA byte) or EOF is reached, This method is the async equivalent to BufRead::read_line.

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.

The returned future will resolve to the number of bytes read once the read operation is completed.

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

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

#![feature(async_await)]
use futures::io::AsyncBufReadExt;
use std::io::Cursor;

let mut cursor = Cursor::new(b"foo\nbar");
let mut buf = String::new();

// cursor is at 'f'
let num_bytes = cursor.read_line(&mut buf).await?;
assert_eq!(num_bytes, 4);
assert_eq!(buf, "foo\n");
buf.clear();

// cursor is at 'b'
let num_bytes = cursor.read_line(&mut buf).await?;
assert_eq!(num_bytes, 3);
assert_eq!(buf, "bar");
buf.clear();

// cursor is at EOF
let num_bytes = cursor.read_line(&mut buf).await?;
assert_eq!(num_bytes, 0);
assert_eq!(buf, "");

fn lines(self) -> Lines<Self> where
    Self: Sized, 

Returns a stream over the lines of this reader. This method is the async equivalent to BufRead::lines.

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.

Errors

Each line of the stream has the same error semantics as AsyncBufReadExt::read_line.

Examples

#![feature(async_await)]
use futures::io::AsyncBufReadExt;
use futures::stream::StreamExt;
use std::io::Cursor;

let cursor = Cursor::new(b"lorem\nipsum\r\ndolor");

let mut lines_stream = cursor.lines().map(|l| l.unwrap());
assert_eq!(lines_stream.next().await, Some(String::from("lorem")));
assert_eq!(lines_stream.next().await, Some(String::from("ipsum")));
assert_eq!(lines_stream.next().await, Some(String::from("dolor")));
assert_eq!(lines_stream.next().await, None);
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Implementors

impl<R: AsyncBufRead + ?Sized> AsyncBufReadExt for R[src]

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