use digest::{Digest, DynDigest, FixedOutputReset};
pub(crate) fn mgf1_xor(out: &mut [u8], digest: &mut dyn DynDigest, seed: &[u8]) {
let mut counter = [0u8; 4];
let mut i = 0;
const MAX_LEN: u64 = core::u32::MAX as u64 + 1;
assert!(out.len() as u64 <= MAX_LEN);
while i < out.len() {
let mut digest_input = vec![0u8; seed.len() + 4];
digest_input[0..seed.len()].copy_from_slice(seed);
digest_input[seed.len()..].copy_from_slice(&counter);
digest.update(digest_input.as_slice());
let digest_output = &*digest.finalize_reset();
let mut j = 0;
loop {
if j >= digest_output.len() || i >= out.len() {
break;
}
out[i] ^= digest_output[j];
j += 1;
i += 1;
}
inc_counter(&mut counter);
}
}
pub(crate) fn mgf1_xor_digest<D>(out: &mut [u8], digest: &mut D, seed: &[u8])
where
D: Digest + FixedOutputReset,
{
let mut counter = [0u8; 4];
let mut i = 0;
const MAX_LEN: u64 = core::u32::MAX as u64 + 1;
assert!(out.len() as u64 <= MAX_LEN);
while i < out.len() {
Digest::update(digest, seed);
Digest::update(digest, counter);
let digest_output = digest.finalize_reset();
let mut j = 0;
loop {
if j >= digest_output.len() || i >= out.len() {
break;
}
out[i] ^= digest_output[j];
j += 1;
i += 1;
}
inc_counter(&mut counter);
}
}
fn inc_counter(counter: &mut [u8; 4]) {
for i in (0..4).rev() {
counter[i] = counter[i].wrapping_add(1);
if counter[i] != 0 {
return;
}
}
}