// Copyright (c) 2020-present The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_CRYPTO_SHA3_H

#define BITCOIN_CRYPTO_SHA3_H

#include <span.h>

#include <cstdint>

#include <cstdlib>

//! The Keccak-f[1600] transform.

void KeccakF(uint64_t (&st)[25]);

class SHA3_256

{

private:

    uint64_t m_state[25] = {0};

    unsigned char m_buffer[8];

    unsigned m_bufsize = 0;

    unsigned m_pos = 0;

    //! Sponge rate in bits.

    static constexpr unsigned RATE_BITS = 1088;

    //! Sponge rate expressed as a multiple of the buffer size.

    static constexpr unsigned RATE_BUFFERS = RATE_BITS / (8 * sizeof(m_buffer));

    static_assert(RATE_BITS % (8 * sizeof(m_buffer)) == 0, "Rate must be a multiple of 8 bytes");

public:

    static constexpr size_t OUTPUT_SIZE = 32;

    SHA3_256() = default;

    SHA3_256& Write(std::span<const unsigned char> data);

    SHA3_256& Finalize(std::span<unsigned char> output);

    SHA3_256& Reset();

};

#endif // BITCOIN_CRYPTO_SHA3_H