rind 0.1.7

Pure-Rust cryptography for MoQ, forked from graviola
Documentation 
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// SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT-0

use crate::low::AesKey;
use crate::low::generic::ctr;

/// XORs AES-CTR keystream into `inout`.
///
/// The counter blocks are `nonce` followed by the big-endian `counter`,
/// `counter + 1`, and so on, wrapping within 32 bits.
pub(crate) fn apply(key: &AesKey, nonce: &[u8; 12], counter: u32, inout: &mut [u8]) {
    if let AesKey::Hw(key) = key {
        return ctr::blocks(nonce, counter, inout, |ivec, blocks| {
            key.ctr32(ivec, blocks)
        });
    }

    ctr::blocks(nonce, counter, inout, |ivec, blocks| {
        let counter = u32::from_be_bytes(ivec[12..].try_into().unwrap());
        for (i, block) in (0u32..).zip(blocks) {
            let mut keystream = *ivec;
            keystream[12..].copy_from_slice(&counter.wrapping_add(i).to_be_bytes());
            key.encrypt_block(&mut keystream);
            for (b, k) in block.iter_mut().zip(keystream) {
                *b ^= k;
            }
        }
    })
}