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use tiny_keccak::XofReader;
use ::cshake::CShake;
use ::utils::{ left_encode, right_encode };
#[derive(Clone)]
pub struct KMac(CShake);
impl KMac {
#[inline]
pub fn new_kmac128(key: &[u8], custom: &[u8]) -> Self {
let mut kmac = KMac(CShake::new_cshake128(b"KMAC", custom));
kmac.init(key, 168);
kmac
}
#[inline]
pub fn new_kmac256(key: &[u8], custom: &[u8]) -> Self {
let mut kmac = KMac(CShake::new_cshake256(b"KMAC", custom));
kmac.init(key, 136);
kmac
}
fn init(&mut self, key: &[u8], rate: usize) {
let mut encbuf = [0; 9];
let pos = left_encode(&mut encbuf, rate as u64);
self.0.update(&encbuf[pos..]);
let pos = left_encode(&mut encbuf, key.len() as u64 * 8);
self.0.update(&encbuf[pos..]);
self.0.update(key);
(self.0).0.fill_block();
}
#[inline]
pub fn update(&mut self, buf: &[u8]) {
self.0.update(buf)
}
#[inline]
pub fn finalize(mut self, buf: &mut [u8]) {
self.with_bitlength(buf.len() as u64 * 8);
self.0.finalize(buf);
}
#[inline]
pub fn xof(mut self) -> XofReader {
self.with_bitlength(0);
self.0.xof()
}
#[inline]
fn with_bitlength(&mut self, bitlength: u64) {
let mut encbuf = [0; 9];
let pos = right_encode(&mut encbuf, bitlength);
self.0.update(&encbuf[pos..]);
}
}