use alloc::vec::Vec;
use num_bigint::BigUint;
use zeroize::Zeroizing;
use crate::errors::{Error, Result};
#[inline]
fn left_pad(input: &[u8], padded_len: usize) -> Result<Vec<u8>> {
if input.len() > padded_len {
return Err(Error::InvalidPadLen);
}
let mut out = vec![0u8; padded_len];
out[padded_len - input.len()..].copy_from_slice(input);
Ok(out)
}
#[inline]
pub(crate) fn uint_to_be_pad(input: BigUint, padded_len: usize) -> Result<Vec<u8>> {
left_pad(&input.to_bytes_be(), padded_len)
}
#[inline]
pub(crate) fn uint_to_zeroizing_be_pad(input: BigUint, padded_len: usize) -> Result<Vec<u8>> {
let m = Zeroizing::new(input);
let m = Zeroizing::new(m.to_bytes_be());
left_pad(&m, padded_len)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_left_pad() {
const INPUT_LEN: usize = 3;
let input = vec![0u8; INPUT_LEN];
let padded = left_pad(&input, INPUT_LEN + 1).unwrap();
assert_eq!(padded.len(), INPUT_LEN + 1);
let padded = left_pad(&input, INPUT_LEN).unwrap();
assert_eq!(padded.len(), INPUT_LEN);
let padded = left_pad(&input, INPUT_LEN - 1);
assert!(padded.is_err());
}
}