private ExFatPartition(Stream partitionStream, ExFatOptions options, bool readBootsector)
{
if (!partitionStream.CanSeek)
{
throw new ArgumentException("Given stream must be seekable");
}
if (!partitionStream.CanRead)
{
throw new ArgumentException("Given stream must be readable");
}
_partitionStream = partitionStream;
_options = options;
if (readBootsector)
{
BootSector = ReadBootSector(_partitionStream);
}
}
/// <summary>
/// Reads the boot sector.
/// </summary>
/// <param name="partitionStream">The partition stream.</param>
/// <returns></returns>
public static ExFatBootSector ReadBootSector(Stream partitionStream)
{
partitionStream.Seek(0, SeekOrigin.Begin);
var defaultBootSector = new ExFatBootSector(new byte[512]);
defaultBootSector.Read(partitionStream);
var sectorSize = defaultBootSector.BytesPerSector.Value;
// it probably not a valid exFAT boot sector, so don't dig any further
if (sectorSize < 512 || sectorSize > 4096)
{
return(defaultBootSector);
}
var fullData = new byte[sectorSize * 12];
partitionStream.Seek(0, SeekOrigin.Begin);
var bootSector = new ExFatBootSector(fullData);
bootSector.Read(partitionStream);
return(bootSector);
}
/// <summary>
/// Formats the specified partition stream.
/// </summary>
/// <param name="partitionStream">The partition stream.</param>
/// <param name="options">The options.</param>
/// <param name="volumeLabel">The volume label.</param>
/// <returns></returns>
public static ExFatPartition Format(Stream partitionStream, ExFatFormatOptions options, string volumeLabel = null)
{
var partition = new ExFatPartition(partitionStream, 0, false);
partitionStream.Seek(0, SeekOrigin.Begin);
var volumeSpace = options?.VolumeSpace ?? (ulong)partitionStream.Length;
var bytesPerSector = options?.BytesPerSector ?? 512;
var totalSectors = volumeSpace / bytesPerSector;
var sectorsPerCluster = options?.SectorsPerCluster ?? ComputeSectorsPerCluster(totalSectors);
if (sectorsPerCluster > 1 << 25)
{
throw new ArgumentException("Sectors per cluster can not exceed 2^25");
}
const uint fats = 1;
const uint usedFats = fats;
const uint bootSectors = 12;
const uint bpbSectors = 2 * bootSectors;
// create bootsector
var bootSectorBytes = new byte[bytesPerSector * 12];
var bootSector = new ExFatBootSector(bootSectorBytes);
var totalClusters = (uint)(totalSectors - bpbSectors) / (usedFats * 4 / bytesPerSector + sectorsPerCluster);
var sectorsPerFat = totalClusters * 4 / bytesPerSector;
bootSector.JmpBoot.Set(ExFatBootSector.DefaultJmpBoot);
bootSector.OemName.Value = ExFatBootSector.ExFatOemName;
bootSector.VolumeLengthSectors.Value = totalSectors;
bootSector.FatOffsetSector.Value = Align(bpbSectors, bytesPerSector);
bootSector.FatLengthSectors.Value = Align(sectorsPerFat, bytesPerSector);
bootSector.ClusterOffsetSector.Value = Align(bootSector.FatOffsetSector.Value + usedFats * bootSector.FatLengthSectors.Value, bytesPerSector);
totalClusters = (uint)((volumeSpace / bytesPerSector - bootSector.ClusterOffsetSector.Value) / sectorsPerCluster);
if (totalClusters > 0xFFFFFFF0)
{
throw new ArgumentException("clusters are too small to address full disk");
}
bootSector.ClusterCount.Value = totalClusters;
bootSector.VolumeSerialNumber.Value = (uint)new Random().Next();
bootSector.FileSystemRevision.Value = 256;
bootSector.VolumeFlags.Value = 0;
bootSector.BytesPerSector.Value = bytesPerSector;
bootSector.SectorsPerCluster.Value = sectorsPerCluster;
bootSector.NumberOfFats.Value = (byte)fats;
bootSector.DriveSelect.Value = 0x80;
bootSector.PercentInUse.Value = 0xFF;
for (int sectorIndex = 0; sectorIndex <= 8; sectorIndex++)
{
bootSectorBytes[sectorIndex * bytesPerSector + bytesPerSector - 2] = 0x55;
bootSectorBytes[sectorIndex * bytesPerSector + bytesPerSector - 1] = 0xAA;
}
partition.BootSector = bootSector;
// prepare FAT
partition.ClearFat();
partition.SetNextCluster(0, Cluster.Marker);
partition.SetNextCluster(1, Cluster.Last);
// create allocation bitmap
var allocationBitmapEntry = CreateAllocationBitmap(partition, totalClusters);
// create root directory
var directoryDataDescriptor = new DataDescriptor(0, false, ulong.MaxValue, ulong.MaxValue);
using (var s = partition.OpenClusterStream(directoryDataDescriptor, FileAccess.ReadWrite,
d => directoryDataDescriptor = new DataDescriptor(d.FirstCluster, d.Contiguous, long.MaxValue, long.MaxValue)))
{
s.SetDataLength(bytesPerSector * sectorsPerCluster);
}
bootSector.RootDirectoryCluster.Value = directoryDataDescriptor.FirstCluster.ToUInt32();
// boot sector is now complete
var checksum = bootSector.ComputeChecksum();
for (var offset = 11 * bytesPerSector; offset < 12 * bytesPerSector; offset += 4)
{
bootSectorBytes[offset] = checksum[0];
bootSectorBytes[offset + 1] = checksum[1];
bootSectorBytes[offset + 2] = checksum[2];
bootSectorBytes[offset + 3] = checksum[3];
}
partition.WriteSectors(0, bootSectorBytes, (int)bootSectors);
partition.WriteSectors(bootSectors, bootSectorBytes, (int)bootSectors);
using (var directoryStream = partition.OpenClusterStream(directoryDataDescriptor, FileAccess.ReadWrite))
{
allocationBitmapEntry.Write(directoryStream);
CreateUpCaseTable(partition, directoryStream);
CreateVolumeLabel(directoryStream, volumeLabel);
}
partition.Flush();
return(partition);
}
