hash calc by ChatGPT (FIPS-140 compliant)

hash.rs

extern crate clap;
extern crate openssl;

use clap::{App, Arg};
use openssl::hash::{Hasher, MessageDigest};
use std::error::Error;
use std::fs::File;
use std::io::{BufReader, Read};

fn main() -> Result<(), Box<Error>> {
    // Parse the command-line arguments
    let matches = App::new("sha256")
        .arg(
            Arg::with_name("file")
                .short("f")
                .long("file")
                .value_name("FILE")
                .help("The file to calculate the hash of")
                .takes_value(true),
        )
        .get_matches();

    // Open the file (or use stdin if no file was specified)
    let file = matches.value_of("file").map_or(
        Box::new(BufReader::new(std::io::stdin())) as Box<dyn Read>,
        |file_name| {
            Box::new(BufReader::new(File::open(file_name)?)) as Box<dyn Read>
        },
    );

    // Turn on FIPS mode
    openssl::fips::Fips::activate()?;

    // Create a hasher with the SHA-256 algorithm
    let mut hasher = Hasher::new(MessageDigest::sha256())?;

    // Read the file and update the hasher with its contents
    let mut buffer = [0; 1024];
    loop {
        let count = file.read(&mut buffer)?;
        if count == 0 {
            break;
        }
        hasher.update(&buffer[..count])?;
    }

    // Calculate the hash and print it as a hexadecimal string
    let hash = hasher.finish()?;
    println!("{:x}", hash);

    Ok(())
}