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Struct async_std::io::BufReader

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pub struct BufReader<R> { /* private fields */ }
Expand description

Adds buffering to any reader.

It can be excessively inefficient to work directly with a Read instance. A BufReader performs large, infrequent reads on the underlying Read and maintains an in-memory buffer of the incoming byte stream.

BufReader can improve the speed of programs that make small and repeated read calls to the same file or network socket. It does not help when reading very large amounts at once, or reading just one or a few times. It also provides no advantage when reading from a source that is already in memory, like a Vec<u8>.

When the BufReader is dropped, the contents of its buffer will be discarded. Creating multiple instances of a BufReader on the same stream can cause data loss.

This type is an async version of std::io::BufReader.

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

Implementations

Creates a buffered reader with default buffer capacity.

The default capacity is currently 8 KB, but may change in the future.

Examples
use async_std::fs::File;
use async_std::io::BufReader;

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

Creates a new buffered reader with the specified capacity.

Examples
use async_std::fs::File;
use async_std::io::BufReader;

let f = BufReader::with_capacity(1024, File::open("a.txt").await?);

Gets a reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

Examples
use async_std::fs::File;
use async_std::io::BufReader;

let f = BufReader::new(File::open("a.txt").await?);
let inner = f.get_ref();

Gets a mutable reference to the underlying reader.

It is inadvisable to directly read from the underlying reader.

Examples
use async_std::fs::File;
use async_std::io::BufReader;

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

Returns a reference to the internal buffer.

This function will not attempt to fill the buffer if it is empty.

Examples
use async_std::fs::File;
use async_std::io::BufReader;

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

Unwraps the buffered reader, returning the underlying reader.

Note that any leftover data in the internal buffer is lost.

Examples
use async_std::fs::File;
use async_std::io::BufReader;

let f = BufReader::new(File::open("a.txt").await?);
let inner = f.into_inner();

Trait Implementations

Attempt to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read. Read more

Attempt to read from the AsyncRead into buf. Read more

Attempt to read from the AsyncRead into bufs using vectored IO operations. Read more

Seeks to an offset, in bytes, in the underlying reader.

The position used for seeking with SeekFrom::Current(_) is the position the underlying reader would be at if the BufReader had no internal buffer.

Seeking always discards the internal buffer, even if the seek position would otherwise fall within it. This guarantees that calling .into_inner() immediately after a seek yields the underlying reader at the same position.

See Seek for more details.

Note: In the edge case where you’re seeking with SeekFrom::Current(n) where n minus the internal buffer length overflows an i64, two seeks will be performed instead of one. If the second seek returns Err, the underlying reader will be left at the same position it would have if you called seek with SeekFrom::Current(0).

Formats the value using the given formatter. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Returns the contents of the internal buffer, filling it with more data if empty. Read more

Consumes amt buffered bytes. Read more

Reads all bytes and appends them into buf until the delimiter byte or EOF is found. Read more

Reads all bytes and appends them into buf until a newline (the 0xA byte) or EOF is found. Read more

Returns a stream over the lines of this byte stream. Read more

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

Reads some bytes from the byte stream. Read more

Like read(), except it reads into a slice of buffers. Read more

Reads the entire contents and appends them to a Vec. Read more

Reads the entire contents and appends them to a String. Read more

Reads the exact number of bytes required to fill buf. Read more

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

Converts this AsyncRead into a Stream of bytes. Read more

Creates an adapter which will chain this stream with another. Read more

Boxes the reader and changes its type to dyn AsyncRead + Send + 'a. Read more

Seeks to a new position in a byte stream. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.