/*

 * 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;

    u8 const* u8_this = reinterpret_cast<u8 const*>(this);

    u8 const* u8_m_checksum = reinterpret_cast<u8 const*>(&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;

}

ErrorOr<void> TarFileHeader::calculate_checksum()

{

    memset(m_checksum, ' ', sizeof(m_checksum));

    auto octal = TRY(String::formatted("{:06o}", expected_checksum()));

    bool copy_successful = octal.bytes_as_string_view().copy_characters_to_buffer(m_checksum, sizeof(m_checksum));

    VERIFY(copy_successful);

    return {};

}

bool TarFileHeader::is_zero_block() const

{

    u8 const* buffer = reinterpret_cast<u8 const*>(this);

    for (size_t i = 0; i < sizeof(TarFileHeader); ++i) {

        if (buffer[i] != 0)

            return false;

    }

    return true;

}

bool TarFileHeader::content_is_like_extended_header() const

{

    return type_flag() == TarFileType::ExtendedHeader || type_flag() == TarFileType::GlobalExtendedHeader;

}

void TarFileHeader::set_filename_and_prefix(StringView filename)

{

    // FIXME: Add support for extended tar headers for longer filenames.

    VERIFY(filename.length() <= sizeof(m_filename) + sizeof(m_prefix));

    if (filename.length() <= sizeof(m_filename)) {

        set_prefix(""sv);

        set_filename(filename);

        return;

    }

    Optional<size_t> slash = filename.find('/', filename.length() - sizeof(m_filename));

    VERIFY(slash.has_value());

    set_prefix(filename.substring_view(0, slash.value() + 1));

    set_filename(filename.substring_view(slash.value() + 1));

}

}