简洁的写法

fn load_blacklist(filename: &str) -> Result
    
     
      > {    File::open(Path::new(filename)).and_then(|mut f| {        let mut buffer = String::new();        f.read_to_string( &mut buffer ).and_then(|_| {            Ok(buffer.as_str().lines().map(|s| s.trim().to_owned()).filter(|s| s.len() > 0).collect::
      
       <_>>())        })    }).map_err(|e| e.into())}
      
     
    

如果文件体积不大，可以用这种一步读取全文的方式进行处理。

另外，简洁的写法，会牺牲行数、时间等调试和统计数据的获取。

下面这种写法似乎更直观，更清晰；但是没有了.map, .and_then 之类方法的起承转合，似乎缺少了一些 Rust 的感觉。

fn load_category(filename: &str) -> Result
    
     
      > {    let mut f = File::open(Path::new(filename))?;    let mut buffer = String::new();    f.read_to_string( &mut buffer )?;    let cats : HashSet<_> = buffer.as_str().lines().map(|s| s.trim().to_owned()).filter(|s| s.len() > 0).collect();    Ok(cats)}
     
    

引入 BufReader，增加读缓冲

#[allow(dead_code)]fn load_blacklist(filename: &str) -> Result
    
     
      > {    let fp = File::open(Path::new(filename)).unwrap();    let clock = Instant::now();    let mut cats = HashSet::new();    let mut n_in = 0;    let mut n_bytes = 0;    let reader = BufReader::with_capacity( 1024*1024*4, fp );    for mut l in reader.lines().map(|r| r.unwrap()) {        if !l.is_empty() && l.chars().rev().next().unwrap() == '\n' {            l.pop();        }        let line = l.trim();        if line.len() < 1 {            continue;        }        n_in += 1;        n_bytes += line.len();        cats.insert( line.to_owned() );    }    let n_out = cats.len();    let time_elapsed = clock.elapsed();    let time_last = (time_elapsed.as_secs() as f64) + (time_elapsed.subsec_nanos() as f64 * 1e-9);    let tps = if time_last > 0.0 { n_in as f64 / time_last as f64 } else { n_in as f64 };    let bw  = (if time_last > 0.0 { n_bytes as f64 / time_last as f64 } else { n_bytes as f64 }) / 1048576_f64;    info!("[STAT] parse {} last {:.2} seconds, in={} out={} tps={:.2} bw={:.2} MB/s\n", filename, time_last, n_in, n_out, tps, bw);    Ok(cats)}
     
    

使用 enumerate()，记录输入数据的行号

#[allow(dead_code)]fn load_blacklist(filename: &str) -> Result
    
     
      > {    let fp = File::open(Path::new(filename)).unwrap();    let clock = Instant::now();    let mut cats = HashSet::new();    let mut n_in = 0;    let mut n_bytes = 0;    let reader = BufReader::with_capacity( 1024*1024*4, fp );    for (ln, lo) in reader.lines().enumerate() {        let mut l = match lo {            Ok(s) => s,            Err(e) => {                stderr().write_all(format!("BAD LINE#{} error -- {:?}\n", ln, e).as_bytes()).unwrap();                continue;            },          };          if !l.is_empty() && l.chars().rev().next().unwrap() == '\n' {            l.pop();        }           let line = l.trim();        if line.len() < 1 {            continue;        }        n_in += 1;        n_bytes += line.len();        cats.insert( line.to_owned() );    }    let n_out = cats.len();    let time_elapsed = clock.elapsed();    let time_last = (time_elapsed.as_secs() as f64) + (time_elapsed.subsec_nanos() as f64 * 1e-9);    let tps = if time_last > 0.0 { n_in as f64 / time_last as f64 } else { n_in as f64 };    let bw  = (if time_last > 0.0 { n_bytes as f64 / time_last as f64 } else { n_bytes as f64 }) / 1048576_f64;    info!("[STAT] parse {} last {:.2} seconds, in={} out={} tps={:.2} bw={:.2} MB/s\n", filename, time_last, n_in, n_out, tps, bw);    Ok(cats)}
     
    

当 filename == '-' 时，从标准输入（STDIN）读取

#[allow(dead_code)]fn load_blacklist(filename: &str) -> Result
    
     
      > {    let fp = match filename {        "-" => Box::new(stdin()) as Box
      
       ,        filename => {            let path = Path::new(filename);            let fp = File::open(path).unwrap();            Box::new(fp) as Box
       
                },    };    let clock = Instant::now();    let mut cats = HashSet::new();    let mut n_in = 0;    let mut n_bytes = 0;    let reader = BufReader::with_capacity( 1024*1024*4, fp );    for mut l in reader.lines().map(|r| r.unwrap()) {        if !l.is_empty() && l.chars().rev().next().unwrap() == '\n' {            l.pop();        }        let line = l.trim();        if line.len() < 1 {            continue;        }        n_in += 1;        n_bytes += line.len();        cats.insert( line.to_owned() );    }    if filename != "-" {        let n_out = cats.len();        let time_elapsed = clock.elapsed();        let time_last = (time_elapsed.as_secs() as f64) + (time_elapsed.subsec_nanos() as f64 * 1e-9);        let tps = if time_last > 0.0 { n_in as f64 / time_last as f64 } else { n_in as f64 };        let bw  = (if time_last > 0.0 { n_bytes as f64 / time_last as f64 } else { n_bytes as f64 }) / 1048576_f64;        stderr().write_all(format!("[STAT] parse {} last {:.2} seconds, in={} out={} tps={:.2} bw={:.2} MB/s\n", filename, time_last, n_in, n_out, tps, bw).as_bytes()).unwrap();    }    Ok(cats)}