literate-crypto 0.0.3

Literate Cryptography by 12hbender
Documentation 
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//! Tests for padding schemes. The tests ensure that
//! ```
//! len(pad(data)) % N == 0 && unpad(pad(data)) == data
//! ```
//! for any random data.

use {
    crate::{util::CollectVec, Padding, Pkcs7},
    rand::Rng,
};

#[test]
fn pkcs7() {
    test(Pkcs7::default(), 16, 13);
    test(Pkcs7::default(), 16, 16);
    test(Pkcs7::default(), 16, 17);
    test(Pkcs7::default(), 16, 18);
}

/// Ensure that
/// ```
/// len(pad(data)) % N == 0 && unpad(pad(data)) == data
/// ```
/// for any random data of length `data_len`.
fn test<Pad: Padding>(pad: Pad, n: usize, data_len: usize)
where
    Pad::Err: std::fmt::Debug,
{
    let data = (0..data_len)
        .map(|_| rand::thread_rng().gen())
        .collect_vec();

    let padded = pad.pad(data.clone(), n);
    assert!(
        padded.len() % n == 0,
        "padding does not align to block size\ndata: {data:?}\npadded: {padded:?}\nblock size: {n}",
    );

    let unpadded = pad.unpad(padded.clone(), n).unwrap();
    assert_eq!(
        unpadded, data,
        "unpadded data does not match original\ndata: {data:?}\npadded: {padded:?}\nunpadded: \
         {unpadded:?}"
    );
}