BufReader in std::io - Rust
source link: https://doc.rust-lang.org/stable/std/io/struct.BufReader.html
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Struct std::io::BufReader1.0.0[−][src]
pub struct BufReader<R> { /* fields omitted */ }The BufReader<R> struct adds buffering to any reader.
It can be excessively inefficient to work directly with a Read instance.
For example, every call to read on TcpStream
results in a system call. A BufReader<R> performs large, infrequent reads on
the underlying Read and maintains an in-memory buffer of the results.
BufReader<R> 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<R> is dropped, the contents of its buffer will be
discarded. Creating multiple instances of a BufReader<R> on the same
stream can cause data loss. Reading from the underlying reader after
unwrapping the BufReader<R> with BufReader::into_inner can also cause
data loss.
Examples
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(())
}RunRecommend
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