/*
 * Copyright (c) 2020, Peter Elliott <pelliott@serenityos.org>
 * Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include "Tar.h"

namespace Archive {

unsigned TarFileHeader::expected_checksum() const
{
    auto checksum = 0u;
    const u8* u8_this = reinterpret_cast<const u8*>(this);
    const u8* u8_m_checksum = reinterpret_cast<const u8*>(&m_checksum);
    for (auto i = 0u; i < sizeof(TarFileHeader); ++i) {
        if (u8_this + i >= u8_m_checksum && u8_this + i < u8_m_checksum + sizeof(m_checksum)) {
            checksum += ' ';
        } else {
            checksum += u8_this[i];
        }
    }
    return checksum;
}

void TarFileHeader::calculate_checksum()
{
    memset(m_checksum, ' ', sizeof(m_checksum));
    VERIFY(String::formatted("{:06o}", expected_checksum()).copy_characters_to_buffer(m_checksum, sizeof(m_checksum)));
}

}