write_rand

Cargo.toml

[package]
name = "write_rand"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
rand = "0.8.5"
rand_xoshiro = "0.6.0"

[profile.release]
lto = true

main.rs

extern crate rand;
extern crate rand_xoshiro;

use std::fs::File;
use std::io::Write;
use rand_xoshiro::Xoshiro256PlusPlus;
use rand_xoshiro::rand_core::{RngCore, SeedableRng};

const CHUNK_SIZE: i64 = 2_i64.pow(16);
const NUMBER: i64 = 0x100000000;
//const NUMBER: i64 = 0x400000000; // 4*2^32  copies are erroneous from md5sum, file length 17179869184
//const NUMBER: i64 = 0x200000000  // 2*2^32  copies are erroneous from md5sum, file length 8589934592
//const NUMBER: i64 = 0x100000001  // 2^32+1  copies without md5 detected error, file length 4294967297
//const NUMBER: i64 = 0x180000000  //         copies without md5 detected error, file length 6442450944
//const NUMBER: i64 = 0x1FFFFFFFF

fn write_file(length: i64) {
    let mut rng = Xoshiro256PlusPlus::from_entropy();
    let mut file_ref = File::create("bigfile").expect("Create failed!");
    let mut buf = vec![0u8; CHUNK_SIZE as usize].into_boxed_slice();
    for _ in 0..(length / CHUNK_SIZE) {
        rng.fill_bytes(buf.as_mut());
        file_ref.write_all(&buf).expect("Write failed!");
    }
}

fn main() {
    write_file(NUMBER);
}