DiskImageUtils.cc

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#include "DiskImageUtils.hh"
#include "DiskPartition.hh"
#include "CommandException.hh"
#include "BootBlocks.hh"
#include "endian.hh"
#include "enumerate.hh"
#include "one_of.hh"
#include "random.hh"
#include "ranges.hh"
#include "view.hh"
#include "xrange.hh"
#include <algorithm>
#include <bit>
#include <cassert>
#include <ctime>
 
namespace openmsx::DiskImageUtils {
 
static constexpr unsigned DOS1_MAX_CLUSTER_COUNT = 0x3FE;  // Max 3 sectors per FAT
static constexpr unsigned FAT12_MAX_CLUSTER_COUNT = 0xFF4;
static constexpr unsigned FAT16_MAX_CLUSTER_COUNT = 0xFFF4;
static constexpr unsigned SECTOR_SIZE = sizeof(SectorBuffer);
static constexpr unsigned DIR_ENTRIES_PER_SECTOR = SECTOR_SIZE / sizeof(MSXDirEntry);
 
enum class PartitionTableType {
        SUNRISE_IDE,
        NEXTOR
};
 
static constexpr std::array<char, 11> SUNRISE_PARTITION_TABLE_HEADER = {
        '\353', '\376', '\220', 'M', 'S', 'X', '_', 'I', 'D', 'E', ' '
};
static constexpr std::array<char, 11> NEXTOR_PARTITION_TABLE_HEADER = {
        '\353', '\376', '\220', 'N', 'E', 'X', 'T', 'O', 'R', '2', '0'
};
[[nodiscard]] static std::optional<PartitionTableType> getPartitionTableType(const SectorBuffer& buf)
{
        if (buf.ptSunrise.header == SUNRISE_PARTITION_TABLE_HEADER) {
                return PartitionTableType::SUNRISE_IDE;
        } else if (buf.ptNextor.header == NEXTOR_PARTITION_TABLE_HEADER &&
                   buf.ptNextor.part[0].sys_ind != 0 && // Extra checks to distinguish MBR from VBR
                   buf.ptNextor.part[0].start == 1) {   // since they have the same OEM signature.
                return PartitionTableType::NEXTOR;
        }
        return {};
}
 
bool hasPartitionTable(SectorAccessibleDisk& disk)
{
        SectorBuffer buf;
        disk.readSector(0, buf);
        return getPartitionTableType(buf).has_value();
}
 
// Get partition from Nextor extended boot record (standard EBR) chain.
static Partition& getPartitionNextorExtended(
        SectorAccessibleDisk& disk, unsigned partition, SectorBuffer& buf,
        unsigned remaining, unsigned ebrOuterSector)
{
        unsigned ebrSector = ebrOuterSector;
        while (true) {
                disk.readSector(ebrSector, buf);
 
                if (remaining == 0) {
                        // EBR partition entry. Start is relative to *this* EBR sector.
                        auto& p = buf.ptNextor.part[0];
                        if (p.start == 0) {
                                break;
                        }
                        // Adjust to absolute address before returning.
                        p.start = ebrSector + p.start;
                        return p;
                }
 
                // EBR link entry. Start is relative to *outermost* EBR sector.
                auto& link = buf.ptNextor.part[1];
                if (link.start == 0) {
                        break;
                } else if (link.sys_ind != one_of(0x05, 0x0F)) {
                        throw CommandException("Invalid extended boot record.");
                }
                ebrSector = ebrOuterSector + link.start;
                remaining--;
        }
        throw CommandException("No partition number ", partition);
}
 
// Get partition from Nextor master boot record (standard MBR).
static Partition& getPartitionNextor(
        SectorAccessibleDisk& disk, unsigned partition, SectorBuffer& buf)
{
        unsigned remaining = partition - 1;
        for (auto& p : buf.ptNextor.part) {
                if (p.start == 0) {
                        break;
                } else if (p.sys_ind == one_of(0x05, 0x0F)) {
                        return getPartitionNextorExtended(disk, partition, buf, remaining, p.start);
                } else if (remaining == 0) {
                        return p;
                }
                remaining--;
        }
        throw CommandException("No partition number ", partition);
}
 
// Get partition from Sunrise IDE master boot record.
static Partition& getPartitionSunrise(unsigned partition, SectorBuffer& buf)
{
        // check number in range
        if (partition < 1 || partition > buf.ptSunrise.part.size()) {
                throw CommandException(
                        "Invalid partition number specified (must be 1-",
                        buf.ptSunrise.part.size(), ").");
        }
        // check valid partition number
        auto& p = buf.ptSunrise.part[buf.ptSunrise.part.size() - partition];
        if (p.start == 0) {
                throw CommandException("No partition number ", partition);
        }
        return p;
}
 
Partition& getPartition(SectorAccessibleDisk& disk, unsigned partition, SectorBuffer& buf)
{
        // check drive has a partition table
        // check valid partition number and return the entry
        disk.readSector(0, buf);
        auto partitionTableType = getPartitionTableType(buf);
        if (partitionTableType == PartitionTableType::SUNRISE_IDE) {
                return getPartitionSunrise(partition, buf);
        } else if (partitionTableType == PartitionTableType::NEXTOR) {
                return getPartitionNextor(disk, partition, buf);
        } else {
                throw CommandException("No (or invalid) partition table.");
        }
}
 
void checkSupportedPartition(SectorAccessibleDisk& disk, unsigned partition)
{
        SectorBuffer buf;
        Partition& p = getPartition(disk, partition, buf);
 
        // check partition type
        if (p.sys_ind != one_of(0x01, 0x04, 0x06, 0x0E)) {
                throw CommandException("Only FAT12 and FAT16 partitions are supported.");
        }
}
 
 
// Create a correct boot sector depending on the required size of the filesystem
struct SetBootSectorResult {
        unsigned sectorsPerFat;
        unsigned fatCount;
        unsigned fatStart;
        unsigned rootDirStart;
        unsigned dataStart;
        uint8_t descriptor;
        bool fat16;
};
static SetBootSectorResult setBootSector(
        MSXBootSector& boot, MSXBootSectorType bootType, size_t nbSectors)
{
        // start from the default boot block ..
        if (bootType == MSXBootSectorType::DOS1) {
                boot = BootBlocks::dos1BootBlock.bootSector;
        } else if (bootType == MSXBootSectorType::DOS2) {
                boot = BootBlocks::dos2BootBlock.bootSector;
        } else if (bootType == MSXBootSectorType::NEXTOR && nbSectors > 0x10000) {
                boot = BootBlocks::nextorBootBlockFAT16.bootSector;
        } else if (bootType == MSXBootSectorType::NEXTOR) {
                boot = BootBlocks::nextorBootBlockFAT12.bootSector;
        } else {
                UNREACHABLE;
        }
 
        // .. and fill-in image-size dependent parameters ..
        // these are the same for most formats
        uint8_t nbReservedSectors = 1;
        uint8_t nbHiddenSectors = 1;
        uint32_t vol_id = random_32bit() & 0x7F7F7F7F; // why are bits masked?;
 
        // all these are set below (but initialize here to avoid warning)
        uint16_t nbSides = 2;
        uint8_t nbFats = 2;
        uint16_t nbSectorsPerFat = 3;
        uint8_t nbSectorsPerCluster = 2;
        uint16_t nbDirEntry = 112;
        uint8_t descriptor = 0xF9;
        bool fat16 = false;
 
        // now set correct info according to size of image (in sectors!)
        if (bootType == MSXBootSectorType::NEXTOR && nbSectors > 0x10000) {
                // using the same layout as Nextor 2.1.1’s FDISK
                nbSides = 0;
                nbFats = 2;
                nbDirEntry = 512;
                descriptor = 0xF0;
                nbHiddenSectors = 0;
                fat16 = true;
 
                // <= 128 MB: 4, <= 256 MB: 8, ..., <= 4 GB: 128
                nbSectorsPerCluster = narrow<uint8_t>(std::clamp(std::bit_ceil(nbSectors) >> 16, size_t(4), size_t(128)));
 
                // Calculate fat size based on cluster count estimate
                unsigned fatStart = nbReservedSectors + nbDirEntry / DIR_ENTRIES_PER_SECTOR;
                unsigned estSectorCount = narrow<unsigned>(nbSectors - fatStart);
                unsigned estClusterCount = std::min(estSectorCount / nbSectorsPerCluster, FAT16_MAX_CLUSTER_COUNT);
                unsigned fatSize = 2 * (estClusterCount + 2);
                nbSectorsPerFat = narrow<uint16_t>((fatSize + SECTOR_SIZE - 1) / SECTOR_SIZE);  // round up
 
                // Adjust sectors count down to match cluster count
                unsigned dataStart = fatStart + nbFats * nbSectorsPerFat;
                unsigned dataSectorCount = narrow<unsigned>(nbSectors - dataStart);
                unsigned clusterCount = std::min(dataSectorCount / nbSectorsPerCluster, FAT16_MAX_CLUSTER_COUNT);
                nbSectors = dataStart + clusterCount * nbSectorsPerCluster;
        } else if (bootType == MSXBootSectorType::NEXTOR) {
                // using the same layout as Nextor 2.1.1’s FDISK
                nbSides = 0;
                nbFats = 2;
                nbDirEntry = 112;
                descriptor = 0xF0;
                nbHiddenSectors = 0;
 
                // <= 2 MB: 1, <= 4 MB: 2, ..., <= 32 MB: 16
                nbSectorsPerCluster = narrow<uint8_t>(std::clamp(std::bit_ceil(nbSectors) >> 12, size_t(1), size_t(16)));
 
                // Partitions <= 16 MB are defined to have at most 3 sectors per FAT,
                // so that they can boot DOS 1. This limits the cluster count to 1022.
                // And for some unknown reason, Nextor limits it to one less than that.
                unsigned maxClusterCount = FAT12_MAX_CLUSTER_COUNT;
                if (nbSectors <= 0x8000) {
                        maxClusterCount = DOS1_MAX_CLUSTER_COUNT - 1;
                        nbSectorsPerCluster *= 4; // <= 2 MB: 4, <= 4 MB: 8, ..., <= 16 MB: 32
                }
 
                // Calculate fat size based on cluster count estimate
                unsigned fatStart = nbReservedSectors + nbDirEntry / DIR_ENTRIES_PER_SECTOR;
                unsigned estSectorCount = narrow<unsigned>(nbSectors - fatStart);
                unsigned estClusterCount = std::min(estSectorCount / nbSectorsPerCluster, maxClusterCount);
                unsigned fatSize = (3 * (estClusterCount + 2) + 1) / 2;  // round up
                nbSectorsPerFat = narrow<uint16_t>((fatSize + SECTOR_SIZE - 1) / SECTOR_SIZE);  // round up
 
                // Adjust sectors count down to match cluster count
                unsigned dataStart = fatStart + nbFats * nbSectorsPerFat;
                unsigned dataSectorCount = narrow<unsigned>(nbSectors - dataStart);
                unsigned clusterCount = std::min(dataSectorCount / nbSectorsPerCluster, maxClusterCount);
                nbSectors = dataStart + clusterCount * nbSectorsPerCluster;
        } else if (bootType == MSXBootSectorType::DOS1 && nbSectors > 1440) {
                // DOS1 supports up to 3 sectors per FAT, limiting the cluster count to 1022.
                nbSides = 0;
                nbFats = 2;
                nbDirEntry = 112;
                descriptor = 0xF0;
                nbHiddenSectors = 0;
 
                // <= 1 MB: 2, <= 2 MB: 4, ..., <= 32 MB: 64
                nbSectorsPerCluster = narrow<uint8_t>(std::clamp(std::bit_ceil(nbSectors) >> 10, size_t(2), size_t(64)));
 
                // Calculate fat size based on cluster count estimate
                unsigned fatStart = nbReservedSectors + nbDirEntry / DIR_ENTRIES_PER_SECTOR;
                unsigned estSectorCount = narrow<unsigned>(nbSectors - fatStart);
                unsigned estClusterCount = std::min(estSectorCount / nbSectorsPerCluster, DOS1_MAX_CLUSTER_COUNT);
                unsigned fatSize = (3 * (estClusterCount + 2) + 1) / 2;  // round up
                nbSectorsPerFat = narrow<uint16_t>((fatSize + SECTOR_SIZE - 1) / SECTOR_SIZE);  // round up
 
                // Adjust sectors count down to match cluster count
                unsigned dataStart = fatStart + nbFats * nbSectorsPerFat;
                unsigned dataSectorCount = narrow<unsigned>(nbSectors - dataStart);
                unsigned clusterCount = std::min(dataSectorCount / nbSectorsPerCluster, DOS1_MAX_CLUSTER_COUNT);
                nbSectors = dataStart + clusterCount * nbSectorsPerCluster;
        } else if (nbSectors > 32732) {
                // using the same layout as used by Jon in IDEFDISK v 3.1
                // 32732 < nbSectors
                // note: this format is only valid for nbSectors <= 65536
                nbSides = 32;           // copied from a partition from an IDE HD
                nbFats = 2;
                nbSectorsPerFat = 12;   // copied from a partition from an IDE HD
                nbSectorsPerCluster = 16;
                nbDirEntry = 256;
                descriptor = 0xF0;
                nbHiddenSectors = 16;   // override default from above
                // for a 32MB disk or greater the sectors would be >= 65536
                // since MSX use 16 bits for this, in case of sectors = 65536
                // the truncated word will be 0 -> formatted as 320 Kb disk!
                if (nbSectors > 65535) nbSectors = 65535; // this is the max size for fat12 :-)
        } else if (nbSectors > 16388) {
                // using the same layout as used by Jon in IDEFDISK v 3.1
                // 16388 < nbSectors <= 32732
                nbSides = 2;            // unknown yet
                nbFats = 2;
                nbSectorsPerFat = 12;
                nbSectorsPerCluster = 8;
                nbDirEntry = 256;
                descriptor = 0XF0;
        } else if (nbSectors > 8212) {
                // using the same layout as used by Jon in IDEFDISK v 3.1
                // 8212 < nbSectors <= 16388
                nbSides = 2;            // unknown yet
                nbFats = 2;
                nbSectorsPerFat = 12;
                nbSectorsPerCluster = 4;
                nbDirEntry = 256;
                descriptor = 0xF0;
        } else if (nbSectors > 4126) {
                // using the same layout as used by Jon in IDEFDISK v 3.1
                // 4126 < nbSectors <= 8212
                nbSides = 2;            // unknown yet
                nbFats = 2;
                nbSectorsPerFat = 12;
                nbSectorsPerCluster = 2;
                nbDirEntry = 256;
                descriptor = 0xF0;
        } else if (nbSectors > 2880) {
                // using the same layout as used by Jon in IDEFDISK v 3.1
                // 2880 < nbSectors <= 4126
                nbSides = 2;            // unknown yet
                nbFats = 2;
                nbSectorsPerFat = 6;
                nbSectorsPerCluster = 2;
                nbDirEntry = 224;
                descriptor = 0xF0;
        } else if (nbSectors > 1440) {
                // using the same layout as used by Jon in IDEFDISK v 3.1
                // 1440 < nbSectors <= 2880
                nbSides = 2;            // unknown yet
                nbFats = 2;
                nbSectorsPerFat = 5;
                nbSectorsPerCluster = 2;
                nbDirEntry = 112;
                descriptor = 0xF0;
        } else if (nbSectors > 720) {
                // normal double sided disk
                // 720 < nbSectors <= 1440
                nbSides = 2;
                nbFats = 2;
                nbSectorsPerFat = 3;
                nbSectorsPerCluster = 2;
                nbDirEntry = 112;
                descriptor = 0xF9;
                nbSectors = 1440;       // force nbSectors to 1440, why?
        } else {
                // normal single sided disk
                // nbSectors <= 720
                nbSides = 1;
                nbFats = 2;
                nbSectorsPerFat = 2;
                nbSectorsPerCluster = 2;
                nbDirEntry = 112;
                descriptor = 0xF8;
                nbSectors = 720;        // force nbSectors to 720, why?
        }
 
        assert(nbDirEntry % 16 == 0);  // Non multiples of 16 not supported.
 
        if (nbSectors < 0x10000) {
                boot.nrSectors = narrow<uint16_t>(nbSectors);
        } else if (bootType == MSXBootSectorType::NEXTOR && fat16) {
                boot.nrSectors = 0;
        } else {
                throw CommandException("Too many sectors for FAT12 ", nbSectors);
        }
 
        boot.nrSides = nbSides;
        boot.spCluster = nbSectorsPerCluster;
        boot.nrFats = nbFats;
        boot.sectorsFat = nbSectorsPerFat;
        boot.dirEntries = nbDirEntry;
        boot.descriptor = descriptor;
        boot.resvSectors = nbReservedSectors;
 
        if (bootType == MSXBootSectorType::DOS1) {
                auto& params = boot.params.dos1;
                params.hiddenSectors = nbHiddenSectors;
        } else if (bootType == MSXBootSectorType::DOS2 || (bootType == MSXBootSectorType::NEXTOR && !fat16)) {
                auto& params = boot.params.dos2;
                params.hiddenSectors = nbHiddenSectors;
                params.vol_id = vol_id;
        } else if (bootType == MSXBootSectorType::NEXTOR && fat16) {
                auto& params = boot.params.extended;
                if (nbSectors <= 0x800000) {
                        params.nrSectors = narrow<unsigned>(nbSectors);
                } else {
                        throw CommandException("Too many sectors for FAT16 ", nbSectors);
                }
                params.hiddenSectors = nbHiddenSectors;
                params.vol_id = vol_id;
        } else {
                UNREACHABLE;
        }
 
        SetBootSectorResult result;
        result.sectorsPerFat = nbSectorsPerFat;
        result.fatCount = nbFats;
        result.fatStart = nbReservedSectors;
        result.rootDirStart = result.fatStart + nbFats * nbSectorsPerFat;
        result.dataStart = result.rootDirStart + nbDirEntry / 16;
        result.descriptor = descriptor;
        result.fat16 = fat16;
        return result;
}
 
void format(SectorAccessibleDisk& disk, MSXBootSectorType bootType)
{
        format(disk, bootType, disk.getNbSectors());
}
 
void format(SectorAccessibleDisk& disk, MSXBootSectorType bootType, size_t nbSectors)
{
        // first create a boot sector for given partition size
        nbSectors = std::min(nbSectors, disk.getNbSectors());
        SectorBuffer buf;
        SetBootSectorResult result = setBootSector(buf.bootSector, bootType, nbSectors);
        disk.writeSector(0, buf);
 
        // write empty FAT sectors (except for first sector, see below)
        ranges::fill(buf.raw, 0);
        for (auto fat : xrange(result.fatCount)) {
                for (auto i : xrange(1u, result.sectorsPerFat)) {
                        disk.writeSector(i + result.fatStart + fat * result.sectorsPerFat, buf);
                }
        }
 
        // write empty directory sectors
        for (auto i : xrange(result.rootDirStart, result.dataStart)) {
                disk.writeSector(i, buf);
        }
 
        // first FAT sector is special:
        //  - first byte contains the media descriptor
        //  - first two clusters must be marked as EOF
        buf.raw[0] = result.descriptor;
        buf.raw[1] = 0xFF;
        buf.raw[2] = 0xFF;
        if (result.fat16) {
                buf.raw[3] = 0xFF;
        }
        for (auto fat : xrange(result.fatCount)) {
                disk.writeSector(result.fatStart + fat * result.sectorsPerFat, buf);
        }
 
        // write 'empty' data sectors
        ranges::fill(buf.raw, 0xE5);
        for (auto i : xrange(result.dataStart, nbSectors)) {
                disk.writeSector(i, buf);
        }
}
 
struct CHS {
        unsigned cylinder;
        uint8_t head; // 0-15
        uint8_t sector; // 1-32
};
[[nodiscard]] static constexpr CHS logicalToCHS(unsigned logical)
{
        // This is made to fit the openMSX hard disk configuration:
        //  32 sectors/track   16 heads
        unsigned tmp = logical + 1;
        uint8_t sector = tmp % 32;
        if (sector == 0) sector = 32;
        tmp = (tmp - sector) / 32;
        uint8_t head = tmp % 16;
        unsigned cylinder = tmp / 16;
        return {cylinder, head, sector};
}
 
static std::vector<unsigned> clampPartitionSizes(std::span<const unsigned> sizes,
        size_t diskSize, unsigned initialOffset, unsigned perPartitionOffset)
{
        std::vector<unsigned> clampedSizes;
        size_t sizeRemaining = std::min(diskSize, size_t(std::numeric_limits<unsigned>::max()));
 
        if (sizeRemaining >= initialOffset) {
                sizeRemaining -= initialOffset;
        } else {
                return clampedSizes;
        }
 
        for (auto size : sizes) {
                if (sizeRemaining <= perPartitionOffset) {
                        break;
                }
                sizeRemaining -= perPartitionOffset;
                if (size <= perPartitionOffset) {
                        throw CommandException("Partition size too small: ", size);
                }
                size -= perPartitionOffset;
                if (sizeRemaining > size) {
                        clampedSizes.push_back(size);
                        sizeRemaining -= size;
                } else {
                        clampedSizes.push_back(narrow<unsigned>(sizeRemaining));
                        break;
                }
        }
        return clampedSizes;
}
 
// Partition with standard master / extended boot record (MBR / EBR) for Nextor.
static std::vector<unsigned> partitionNextor(SectorAccessibleDisk& disk, std::span<const unsigned> sizes)
{
        SectorBuffer buf;
        auto& pt = buf.ptNextor;
 
        std::vector<unsigned> clampedSizes = clampPartitionSizes(sizes, disk.getNbSectors(), 0, 1);
 
        if (clampedSizes.empty()) {
                ranges::fill(buf.raw, 0);
                pt.header = NEXTOR_PARTITION_TABLE_HEADER;
                pt.end = 0xAA55;
                disk.writeSector(0, buf);
                return clampedSizes;
        }
 
        unsigned ptSector = 0;
        for (auto [i, size] : enumerate(clampedSizes)) {
                ranges::fill(buf.raw, 0);
                if (i == 0) {
                        pt.header = NEXTOR_PARTITION_TABLE_HEADER;
                }
                pt.end = 0xAA55;
 
                // Add partition entry
                auto& p = pt.part[0];
                p.boot_ind = (i == 0) ? 0x80 : 0x00; // boot flag
                p.sys_ind = size > 0x10000 ? 0x0E : 0x01; // FAT16B (LBA), or FAT12
                p.start = 1;
                p.size = size;
 
                // Add link if not the last partition
                if (i != clampedSizes.size() - 1) {
                        auto& link = pt.part[1];
                        link.sys_ind = 0x05; // EBR
                        if (i == 0) {
                                link.start = ptSector + 1 + size;
                                link.size = sum(view::drop(sizes, 1), [](unsigned s) { return 1 + s; });
                        } else {
                                link.start = ptSector + 1 + size - (1 + clampedSizes[0]);
                                link.size = 1 + clampedSizes[i + 1];
                        }
                }
 
                disk.writeSector(ptSector, buf);
 
                ptSector += 1 + size;
        }
        return clampedSizes;
}
 
// Partition with Sunrise IDE master boot record.
static std::vector<unsigned> partitionSunrise(SectorAccessibleDisk& disk, std::span<const unsigned> sizes)
{
        SectorBuffer buf;
        auto& pt = buf.ptSunrise;
 
        std::vector<unsigned> clampedSizes = clampPartitionSizes(sizes, disk.getNbSectors(), 1, 0);
        if (clampedSizes.size() > pt.part.size()) {
                clampedSizes.resize(pt.part.size());
        }
 
        ranges::fill(buf.raw, 0);
        pt.header = SUNRISE_PARTITION_TABLE_HEADER;
        pt.end = 0xAA55;
 
        unsigned partitionOffset = 1;
        for (auto [i, size] : enumerate(clampedSizes)) {
                unsigned partitionNbSectors = size;
                auto& p = pt.part[30 - i];
                auto [startCylinder, startHead, startSector] =
                        logicalToCHS(partitionOffset);
                auto [endCylinder, endHead, endSector] =
                        logicalToCHS(partitionOffset + partitionNbSectors - 1);
                p.boot_ind = (i == 0) ? 0x80 : 0x00; // boot flag
                p.head = startHead;
                p.sector = startSector;
                p.cyl = narrow_cast<uint8_t>(startCylinder); // wraps for size larger than 64MB
                p.sys_ind = 0x01; // FAT12
                p.end_head = endHead;
                p.end_sector = endSector;
                p.end_cyl = narrow_cast<uint8_t>(endCylinder);
                p.start = partitionOffset;
                p.size = partitionNbSectors;
                partitionOffset += partitionNbSectors;
        }
        disk.writeSector(0, buf);
        return clampedSizes;
}
 
// Partition with standard master boot record (MBR) for Beer IDE 1.9.
static std::vector<unsigned> partitionBeer(SectorAccessibleDisk& disk, std::span<const unsigned> sizes)
{
        SectorBuffer buf;
        auto& pt = buf.ptNextor;
 
        std::vector<unsigned> clampedSizes = clampPartitionSizes(sizes, disk.getNbSectors(), 1, 0);
        if (clampedSizes.size() > pt.part.size()) {
                clampedSizes.resize(pt.part.size());
        }
 
        ranges::fill(buf.raw, 0);
        pt.header = NEXTOR_PARTITION_TABLE_HEADER; // TODO: Find out BEER IDE signature
        pt.end = 0xAA55;
 
        unsigned partitionOffset = 1;
        for (auto [i, size] : enumerate(clampedSizes)) {
                auto& p = pt.part[i];
                p.boot_ind = (i == 0) ? 0x80 : 0x00; // boot flag
                p.sys_ind = 0x01; // FAT12
                p.start = partitionOffset;
                p.size = size;
                partitionOffset += size;
        }
 
        disk.writeSector(0, buf);
        return clampedSizes;
}
 
unsigned partition(SectorAccessibleDisk& disk, std::span<const unsigned> sizes, MSXBootSectorType bootType)
{
        std::vector<unsigned> clampedSizes = [&] {
                if (bootType == MSXBootSectorType::NEXTOR) {
                        return partitionNextor(disk, sizes);
                } else if (bootType == MSXBootSectorType::DOS2) {
                        return partitionSunrise(disk, sizes);
                } else if (bootType == MSXBootSectorType::DOS1) {
                        return partitionBeer(disk, sizes);
                } else {
                        UNREACHABLE;
                }
        }();
 
        for (auto [i, size] : enumerate(clampedSizes)) {
                DiskPartition diskPartition(disk, narrow<unsigned>(i + 1));
                format(diskPartition, bootType, size);
        }
 
        return narrow<unsigned>(clampedSizes.size());
}
 
} // namespace openmsx::DiskImageUtils