some ways to read files in rust, mmap is fastest

files.rs

    use std::time::Instant;
    use std::fs::File;
    use std::io::{self, prelude::*, BufReader};

    let file = File::open("examples/WDC_tickbidask.csv")?;
    let mut reader = BufReader::new(file);
    let mut line = String::new();
    let mut lines = 0;
    let start = Instant::now();
    while reader.read_line(&mut line).unwrap() > 0 {
        //println!("{}", line);
        line.clear();
        lines += 1;
    }
    println!("{lines} {:?}", start.elapsed());

    use memmap2::Mmap;
    let mut file = File::open("examples/WDC_tickbidask.csv")?;
    let mmap = unsafe { Mmap::map(&file)? };
    let mut lines = 0;
    let start = Instant::now();
    for line in mmap.split(|c| *c as char == '\n') {
        //println!("{}", line);
        lines += 1;
    }
    println!("{:?}", start.elapsed());

    let file = File::open("examples/WDC_tickbidask.csv")?;
    let reader = BufReader::new(file);
    let start = Instant::now();
    for line in reader.lines() {
        //println!("{}", line?);
    }
    println!("{:?}", start.elapsed());

    let mut rdr = csv::ReaderBuilder::new()
        .buffer_capacity(2*1024*1024)
        .quoting(false)
        .from_path("examples/WDC_tickbidask.csv").unwrap();
    let headers = rdr.byte_headers()?.clone();
    let mut raw_record = csv::ByteRecord::new();
    let start = Instant::now();
    while rdr.read_byte_record(&mut raw_record)? {
        //let record: TickerData = raw_record.deserialize(Some(&headers))?;
        //println!("{:?}", raw_record);
    }
    println!("{:?}", start.elapsed());