crc32sum.rs

use std::env;
use std::fs::File;
use std::io::{stdin, Read};

use crc_all::CrcAlgo;
use lazy_static::lazy_static;

const BUFFER_SIZE: usize = 1024 * 16;

fn crc32sum<R: Read>(r: &mut R) -> u32 {
    lazy_static! {
        static ref CRC32: CrcAlgo<u32> =
            CrcAlgo::<u32>::new(0x04c11db7, 32, 0xffffffff, 0xffffffff, true);
    }

    let crc = &mut 0;
    CRC32.init_crc(crc);

    let mut buf = Vec::with_capacity(BUFFER_SIZE);
    unsafe {
        buf.set_len(BUFFER_SIZE);
    }

    let mut n;
    while {
        n = r.read(buf.as_mut()).unwrap();
        n > 0
    } {
        CRC32.update_crc(crc, &buf[..n]);
    }

    CRC32.finish_crc(crc)
}

fn main() {
    let args = env::args();

    if args.len() > 1 {
        for path in args.skip(1) {
            println!(
                "{:08x}  {}",
                crc32sum(&mut File::open(&path).unwrap()),
                &path
            );
        }
    } else {
        println!("{:08x}  {}", crc32sum(&mut stdin().lock()), "-");
    }
}