use super::Block;
use crate::{endian::*, error};
use core::convert::TryInto;
use core::marker::PhantomData;
pub struct Nonce([u8; NONCE_LEN]);
impl Nonce {
#[inline]
pub fn try_assume_unique_for_key(value: &[u8]) -> Result<Self, error::Unspecified> {
let value: &[u8; NONCE_LEN] = value.try_into()?;
Ok(Self::assume_unique_for_key(*value))
}
#[inline]
pub fn assume_unique_for_key(value: [u8; NONCE_LEN]) -> Self {
Self(value)
}
}
impl AsRef<[u8; NONCE_LEN]> for Nonce {
fn as_ref(&self) -> &[u8; NONCE_LEN] {
&self.0
}
}
pub const NONCE_LEN: usize = 96 / 8;
#[repr(C)]
pub union Counter<U32: Layout<u32>>
where
u32: From<U32>,
{
block: Block,
u32s: [U32; 4],
encoding: PhantomData<U32>,
}
impl<U32: Layout<u32>> Counter<U32>
where
u32: From<U32>,
{
pub fn zero(nonce: Nonce) -> Self {
Self::new(nonce, 0)
}
pub fn one(nonce: Nonce) -> Self {
Self::new(nonce, 1)
}
#[cfg(test)]
pub fn from_test_vector(nonce: &[u8], initial_counter: u32) -> Self {
Self::new(
Nonce::try_assume_unique_for_key(nonce).unwrap(),
initial_counter,
)
}
fn new(Nonce(nonce): Nonce, initial_counter: u32) -> Self {
let mut r = Self {
block: Block::zero(),
};
let block = unsafe { &mut r.block };
block.as_mut()[U32::NONCE_BYTE_INDEX..][..NONCE_LEN].copy_from_slice(nonce.as_ref());
r.increment_by_less_safe(initial_counter);
r
}
#[inline]
pub fn increment(&mut self) -> Iv {
let block = unsafe { &self.block };
let r = Iv(block.clone());
self.increment_by_less_safe(1);
r
}
#[inline]
pub fn increment_by_less_safe(&mut self, increment_by: u32) {
let u32s = unsafe { &mut self.u32s };
let value = &mut u32s[U32::COUNTER_U32_INDEX];
*value = (u32::from(*value) + increment_by).into();
}
}
#[repr(C)]
pub struct Iv(Block);
impl<U32: Layout<u32>> From<Counter<U32>> for Iv
where
u32: From<U32>,
{
fn from(counter: Counter<U32>) -> Self {
Self(unsafe { counter.block })
}
}
impl Iv {
#[inline]
pub fn assume_unique_for_key(a: Block) -> Self {
Self(a)
}
#[inline]
pub fn into_block_less_safe(self) -> Block {
self.0
}
}
pub trait Layout<T>: Encoding<T>
where
T: From<Self>,
{
const COUNTER_U32_INDEX: usize;
const NONCE_BYTE_INDEX: usize;
}
impl<T> Layout<T> for BigEndian<T>
where
BigEndian<T>: Encoding<T>,
T: Copy + From<Self>,
{
const COUNTER_U32_INDEX: usize = 3;
const NONCE_BYTE_INDEX: usize = 0;
}
impl<T> Layout<T> for LittleEndian<T>
where
LittleEndian<T>: Encoding<T>,
T: Copy + From<Self>,
{
const COUNTER_U32_INDEX: usize = 0;
const NONCE_BYTE_INDEX: usize = 4;
}