use sha2::{Digest, Sha256};

const N: usize = 10;
const SIZE: usize = 128 * 1024;

fn main() {
    println!("sequential");
    for checksum in Blobs::new(SIZE, N).map(|x| sha256(&x)) {
        println!("{}", checksum);
    }

    // println!("rayon");
    // for checksum in blobs.take(N).par_iter().map(|x| sha256(x)) {
    //     println!("{}", checksum);
    // }
}

struct Blobs {
    size: usize,
    n: usize,
}

impl Blobs {
    fn new(size: usize, n: usize) -> Self {
        Self { size, n }
    }
}

impl Iterator for Blobs {
    type Item = Vec<u8>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.n > 0 {
            self.n -= 1;
            Some(vec![0; self.size])
        } else {
            None
        }
    }
}

fn sha256(data: &[u8]) -> String {
    let mut hasher = Sha256::new();
    hasher.update(data);
    let hash = hasher.finalize();
    format!("{:x}", hash)
}