G.FIO.01 文件读取建议使用 BufReader/BufWriter 来代替 Reader/Write - Rust 编码规范 V 1.0 beta

G.FIO.01 文件读取建议使用 `BufReader/BufWriter` 来代替 `Reader/Write`

【描述】

BufReader/BufWriter 使用缓冲区来减少 I/O 请求的次数，提升性能。访问磁盘一次读取 256 个字节显然比访问磁盘256次每次一个字节效率要更高。

【示例】

use std::fs::File;
use std::io::{BufReader, Read};

fn main() {
    let mut data = String::new();
    let f = File::open("/etc/hosts").expect("Unable to open file");
    let mut br = BufReader::new(f);
    br.read_to_string(&mut data).expect("Unable to read string");
    println!("{}", data);
}

写 I/O：

use std::fs::File;
use std::io::{BufWriter, Write};

fn main() {
    let data = "Some data!";
    let f = File::create("/tmp/foo").expect("Unable to create file");
    let mut f = BufWriter::new(f);
    f.write_all(data.as_bytes()).expect("Unable to write data");
}

逐行读：注意返回的每行字符串都不含有换行字符。


#![allow(unused)]
fn main() {
use std::fs::File;
use std::io::{BufRead, BufReader};

pub fn scan() -> Result<(), io::Error> {
    let mut file = BufReader::new(try!(File::open("foo.txt")));

    let mut line = String::new();
    while try!(file.read_line(&mut line)) != 0 {
        if line.starts_with("x") {
            try!(file.seek(SeekFrom::Start(1000)));
        }
        do_stuff(&line);
        line.clear();
    }

    Ok(())
}
}