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#![no_std]
#![doc(html_logo_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo_small.png")]
#![warn(missing_docs, rust_2018_idioms)]
pub use polyval::universal_hash;
use core::convert::TryInto;
use polyval::{field::Block, Polyval};
use universal_hash::generic_array::{typenum::U16, GenericArray};
use universal_hash::{Output, UniversalHash};
#[derive(Clone)]
#[repr(align(16))]
pub struct GHash(Polyval);
impl UniversalHash for GHash {
type KeySize = U16;
type OutputSize = U16;
fn new(h: &GenericArray<u8, U16>) -> Self {
let mut h: Block = h.clone().into();
h.reverse();
GHash(Polyval::new(&mulX_POLYVAL(h).into()))
}
fn update_block(&mut self, x: &GenericArray<u8, U16>) {
let mut x: Block = x.clone().into();
x.reverse();
self.0.update_block(&x.into());
}
fn reset(&mut self) {
self.0.reset();
}
fn result(self) -> Output<U16> {
let mut output: Block = self.0.result().into_bytes().into();
output.reverse();
Output::new(output.into())
}
}
#[allow(non_snake_case)]
fn mulX_POLYVAL(block: Block) -> Block {
let mut v0 = u64::from_le_bytes(block[..8].try_into().unwrap());
let mut v1 = u64::from_le_bytes(block[8..].try_into().unwrap());
let v0h = v0 >> 63;
let v1h = v1 >> 63;
v0 <<= 1;
v1 <<= 1;
v0 ^= v1h;
v1 ^= v0h ^ (v1h << 63) ^ (v1h << 62) ^ (v1h << 57);
(u128::from(v0) | (u128::from(v1) << 64)).to_le_bytes()
}