std::io::* 2. Struct std::io::BufReader

https://doc.rust-lang.org/std/io/struct.BufReader.html
サマリ
small and repeated read calls to the same file or network socket.

when reading very large amounts at once, or reading just one or a few times. >> 何の役にも立たない.

マルチスレッドデータ損失リスク(BufReader::into_inner度)

use std::io::prelude::*;
use std::io::BufReader;
use std::fs::File;
fn main() -> std::io::Result<()>{
    let f= File::open("log.txt")?;
    let mut reader= BufReader::new(f);

    let mut line= String::new();
    let len= reader.read_line(&mut line)?;

    println!("First line is {} bytes long", len);
    Ok(())
}

Implementations
impl BufReader
pub fn new(inner: R) -> BufReader
pub fn with_capacity(capacity: usize, inner: R) -> BufReader
impl BufReader
pub fn get_ref(&self) -> &R
pub fn get_mut(&mut self) -> &mut R
pub fn buffer(&self) -> &[u8]
pub fn capacity(&self) -> usize
pub fn into_inner(self) -> R
impl BufReader
pub fn seek_relative(&mut self, offset: i64) -> Result<()>