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// Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

// Copyright 2021 Conflux Foundation. All rights reserved.
// Conflux is free software and distributed under GNU General Public License.
// See http://www.gnu.org/licenses/

//! Wrapper structs for types that need [RustCrypto](https://github.com/RustCrypto)
//! traits implemented.

use digest::{
    consts::{U136, U32},
    generic_array::GenericArray,
    BlockInput, Digest, FixedOutput, Reset, Update,
};
use tiny_keccak::{Hasher, Sha3};

/// A wrapper for [`tiny_keccak::Sha3::v256`] that
/// implements RustCrypto [`digest`] traits [`BlockInput`], [`Update`],
/// [`Reset`], and [`FixedOutput`]. Consequently, this wrapper can be used in
/// RustCrypto APIs that require a hash function (usually something that impls
/// [`Digest`]).
#[derive(Clone)]
pub struct Sha3_256(Sha3);

// ensure that we impl all of the sub-traits required for the Digest trait alias
static_assertions::assert_impl_all!(Sha3_256: Digest);

impl Default for Sha3_256 {
    #[inline]
    fn default() -> Self { Self(Sha3::v256()) }
}

impl BlockInput for Sha3_256 {
    type BlockSize = U136;
}

impl Update for Sha3_256 {
    #[inline]
    fn update(&mut self, data: impl AsRef<[u8]>) {
        self.0.update(data.as_ref());
    }
}

impl Reset for Sha3_256 {
    #[inline]
    fn reset(&mut self) { *self = Self::default(); }
}

impl FixedOutput for Sha3_256 {
    type OutputSize = U32;

    #[inline]
    fn finalize_into(self, out: &mut GenericArray<u8, Self::OutputSize>) {
        self.0.finalize(out.as_mut());
    }

    #[inline]
    fn finalize_into_reset(
        &mut self, out: &mut GenericArray<u8, Self::OutputSize>,
    ) {
        self.clone().finalize_into(out);
        Reset::reset(self)
    }
}