/*

 * Copyright (c) 2020-2022, the SerenityOS developers.

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <AK/Array.h>

#include <AK/Span.h>

#include <AK/Types.h>

#include <LibCrypto/Checksum/CRC32.h>

namespace Crypto::Checksum {

static constexpr auto generate_table()

{

    Array<u32, 256> data {};

    for (auto i = 0u; i < data.size(); i++) {

        u32 value = i;

        for (auto j = 0; j < 8; j++) {

            if (value & 1) {

                value = 0xEDB88320 ^ (value >> 1);

            } else {

                value = value >> 1;

            }

        }

        data[i] = value;

    }

    return data;

}

static constexpr auto table = generate_table();

void CRC32::update(ReadonlyBytes data)

{

    for (size_t i = 0; i < data.size(); i++) {

        m_state = table[(m_state ^ data.at(i)) & 0xFF] ^ (m_state >> 8);

    }

};

u32 CRC32::digest()

{

    return ~m_state;

}

}