public static BootSector Read(IBlockDevice device)
{
var b = new byte[512];
var bb = new MemoryStream(b);
device.Read(0, bb);
bb.Position = 510;
if (bb.ReadByte() != 0x55)
{
throw new IOException(
"missing boot sector signature");
}
bb.Position = 511;
if (bb.ReadByte() != 0xaa)
{
throw new IOException(
"missing boot sector signature");
}
bb.Position = SECTORS_PER_CLUSTER_OFFSET;
var sectorsPerCluster = (byte)bb.ReadByte();
if (sectorsPerCluster <= 0)
{
throw new IOException(
"suspicious sectors per cluster count " + sectorsPerCluster);
}
var rootDirEntriesB = new byte[2];
bb.Position = Fat16BootSector.ROOT_DIR_ENTRIES_OFFSET;
bb.Read(rootDirEntriesB, 0, 2);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(rootDirEntriesB, 0, 2);
}
int rootDirEntries = BitConverter.ToUInt16(rootDirEntriesB, 0);
var rootDirSectors = ((rootDirEntries * 32) +
(device.GetSectorSize() - 1)) / device.GetSectorSize();
var total16B = new byte[2];
bb.Position = TOTAL_SECTORS_16_OFFSET;
bb.Read(total16B, 0, 2);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(total16B, 0, 2);
}
int total16 = BitConverter.ToUInt16(total16B, 0);
var total32B = new byte[4];
bb.Position = TOTAL_SECTORS_32_OFFSET;
bb.Read(total32B, 0, 4);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(total32B, 0, 4);
}
long total32 = BitConverter.ToUInt32(total32B, 0);
var totalSectors = total16 == 0 ? total32 : total16;
var fatSz16B = new byte[2];
bb.Position = Fat16BootSector.SECTORS_PER_FAT_OFFSET;
bb.Read(fatSz16B, 0, 2);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(fatSz16B, 0, 2);
}
int fatSz16 = BitConverter.ToUInt16(fatSz16B, 0);
var fatSz32B = new byte[4];
bb.Position = Fat32BootSector.SECTORS_PER_FAT_OFFSET;
bb.Read(fatSz32B, 0, 4);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(fatSz32B, 0, 4);
}
long fatSz32 = BitConverter.ToUInt32(fatSz32B, 0);
var fatSz = fatSz16 == 0 ? fatSz32 : fatSz16;
var reservedSectorsB = new byte[2];
bb.Position = RESERVED_SECTORS_OFFSET;
bb.Read(reservedSectorsB, 0, 2);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(reservedSectorsB, 0, 2);
}
int reservedSectors = BitConverter.ToUInt16(reservedSectorsB, 0);
bb.Position = FAT_COUNT_OFFSET;
var fatCount = bb.ReadByte();
var dataSectors = totalSectors - (reservedSectors +
(fatCount * fatSz) + rootDirSectors);
var clusterCount = dataSectors / sectorsPerCluster;
var result =
(clusterCount > Fat16BootSector.MAX_FAT16_CLUSTERS) ?
(BootSector) new Fat32BootSector(device) : (BootSector) new Fat16BootSector(device);
result.Read();
return(result);
}
/// <summary>
/// Initializes the boot sector and file system for the device. The file
/// system created by this method will always be in read-write mode.
/// </summary>
/// <returns>the file system that was created</returns>
/// <exception cref="System.IO.IOException">IOException on write error</exception>
public FatFileSystem Format()
{
var sectorSize = device.GetSectorSize();
var totalSectors = (int)(device.GetSize() / sectorSize);
FsInfoSector fsi;
BootSector bs;
if (sectorsPerCluster == 0)
{
throw new Exception();
}
if (fatType == FatType.BaseFat32)
{
bs = new Fat32BootSector(device);
InitBootSector(bs);
var f32Bs = (Fat32BootSector)bs;
f32Bs.SetFsInfoSectorNr(1);
f32Bs.SetSectorsPerFat(SectorsPerFat(0, totalSectors));
var rnd = new Random();
f32Bs.SetFileSystemId(rnd.Next());
f32Bs.SetVolumeLabel(label);
/* create FS info sector */
fsi = FsInfoSector.Create(f32Bs);
}
else
{
bs = new Fat16BootSector(device);
InitBootSector(bs);
var f16Bs = (Fat16BootSector)bs;
var rootDirEntries = RootDirectorySize(
device.GetSectorSize(), totalSectors);
f16Bs.SetRootDirEntryCount(rootDirEntries);
f16Bs.SetSectorsPerFat(SectorsPerFat(rootDirEntries, totalSectors));
if (label != null)
{
f16Bs.SetVolumeLabel(label);
}
fsi = null;
}
// bs.write();
if (fatType == FatType.BaseFat32)
{
var f32Bs = (Fat32BootSector)bs;
/* possibly writes the boot sector copy */
f32Bs.WriteCopy(device);
}
var fat = Fat.Create(bs, 0);
AbstractDirectory rootDirStore;
if (fatType == FatType.BaseFat32)
{
rootDirStore = ClusterChainDirectory.CreateRoot(fat);
fsi.SetFreeClusterCount(fat.GetFreeClusterCount());
fsi.SetLastAllocatedCluster(fat.GetLastAllocatedCluster());
fsi.Write();
}
else
{
rootDirStore = Fat16RootDirectory.Create((Fat16BootSector)bs);
}
var rootDir =
new FatLfnDirectory(rootDirStore, fat, false);
rootDir.Flush();
for (var i = 0; i < bs.GetNrFats(); i++)
{
fat.WriteCopy(FatUtils.GetFatOffset(bs, i));
}
bs.Write();
var fs = FatFileSystem.Read(device, false);
if (label != null)
{
fs.SetVolumeLabel(label);
}
fs.Flush();
return(fs);
}
