write_file.rs

use std::{env::args, fs::{self, remove_file}, io::Write};

fn main() {
    let argv = args();
    let f: Vec<String> = argv.collect();
    let (path, size_str, turn_str) = (&f[1].clone(), f[2].clone(), f[3].clone());

    let turn = if let Ok(turn) = turn_str.parse::<u64>(){
        turn
    } else {
        1
    };
    
    let (num, ll) = size_str.split_at(size_str.len()-1);
    let get_num = |x: &str| {x.parse::<f64>().unwrap_or(0.0)};
    let the_num = ||{get_num(num)};

    let float_lshift = |x: f64, y:u8| {
        let b = x.floor();
        ((b as u64) << y) + ((x-b) * ((1<<y) as f64)) as u64
    };
    let size: u64 = match ll {
        "k" | "K" => float_lshift(the_num(), 10),
        "M" | "m" => float_lshift(the_num(), 20),
        "g" | "G" => float_lshift(the_num(), 30),
        _ => get_num(num).floor() as u64,
    };

    let buf = if size <= 16<<20 {
        &[0;16<<10][..]
    } else {
        &[0;16<<20][..]
    };
    
    for i in 1..=turn {
        println!("Turn: {}", i);
        let mut file = fs::File::create(path).unwrap();
        let mut written: u64 = 0;
        while written < size {
            file.write_all(buf).expect("write error");
            written += buf.len() as u64;
        }
        if remove_file(path).is_err() {
            println!("remove failed");
        }
    }

}