//Formats a volume with FAT12 file system - currently assumes it's a floppy disk...
public static Fat12FileSystem Create(Stream stream, BiosParameterBlock bpb, bool writeBPB)
{
if (stream == null)
{
throw new ArgumentNullException(nameof(stream), "stream cannot be null!");
}
if (bpb == null)
{
throw new ArgumentNullException(nameof(bpb), "bpb cannot be null!");
}
if (!bpb.Validate())
{
throw new InvalidDataException("bpb is invalid!");
}
var fat = new Fat12FileSystem(stream, bpb);
uint totalSize = (uint)stream.Length;
uint rootDirSize = (uint)(bpb.RootDirectoryEntries << 5);
uint fatSize = (uint)(bpb.LogicalSectorsPerFAT * bpb.BytesPerLogicalSector);
uint fat1Offset = (uint)(bpb.ReservedLogicalSectors * bpb.BytesPerLogicalSector);
uint fat2Offset = fat1Offset + fatSize;
uint dataAreaOffset = fat2Offset + fatSize + rootDirSize;
using (var writer = new BinaryWriter(stream, Encoding.ASCII, true))
{
stream.Seek(0, SeekOrigin.Begin);
for (uint i = 0; i < totalSize; i++)
{
writer.Write((byte)0);
}
//Fille the data area with 0xF6
stream.Seek(dataAreaOffset, SeekOrigin.Begin);
for (uint i = 0; i < totalSize - dataAreaOffset; i++)
{
writer.Write((byte)0xF6);
}
stream.Seek(0, SeekOrigin.Begin);
writer.Write(bpb.BootJump, 0, 3);
writer.Write(bpb.OemId.PadRight(8, ' ').ToCharArray());
if (writeBPB)
{
writer.Write(bpb.BytesPerLogicalSector);
writer.Write(bpb.LogicalSectorsPerCluster);
writer.Write(bpb.ReservedLogicalSectors);
writer.Write(bpb.NumberOfFATs);
writer.Write(bpb.RootDirectoryEntries);
writer.Write(bpb.TotalLogicalSectors <= ushort.MaxValue ? (ushort)bpb.TotalLogicalSectors : (ushort)0);
writer.Write(bpb.MediaDescriptor);
writer.Write(bpb.Version != BiosParameterBlockVersion.Fat32 ? (ushort)bpb.LogicalSectorsPerFAT : (ushort)0);
writer.Write(bpb.PhysicalSectorsPerTrack);
writer.Write(bpb.NumberOfHeads);
writer.Write(bpb.HiddenSectors);
writer.Write(bpb.TotalLogicalSectors > ushort.MaxValue ? bpb.TotalLogicalSectors : 0);
//DOS 3.4+ specific values
if (bpb.Version == BiosParameterBlockVersion.Dos34 || bpb.Version == BiosParameterBlockVersion.Dos40)
{
var ebpb = (ExtendedBiosParameterBlock)bpb;
writer.Write(ebpb.PhysicalDriveNumber);
writer.Write(ebpb.Flags);
writer.Write((byte)ebpb.ExtendedBootSignature);
writer.Write(ebpb.VolumeSerialNumber.Value);
//DOS 4.0 adds volume label and FS type as well
if (bpb.Version == BiosParameterBlockVersion.Dos40)
{
if (string.IsNullOrWhiteSpace(ebpb.VolumeLabel))
{
writer.Write("NO NAME ".ToCharArray());
}
else
{
writer.Write(ebpb.VolumeLabel.PadRight(11, ' ').ToCharArray());
}
writer.Write(ebpb.FileSystemType.PadRight(8, ' ').ToCharArray());
}
}
}
//Boot signature
stream.Seek(0x1FE, SeekOrigin.Begin);
writer.Write((byte)0x55);
writer.Write((byte)0xAA);
/* Media descriptor needs to be written to each FAT as well, upper 4 bits must all be set.
* It takes up the first cluster entry (0), and the second entry (1) is also reserved */
stream.Seek(fat1Offset, SeekOrigin.Begin);
writer.Write(bpb.MediaDescriptor);
writer.Write((byte)0xFF);
writer.Write((byte)0xFF);
stream.Seek(fat2Offset, SeekOrigin.Begin);
writer.Write(bpb.MediaDescriptor);
writer.Write((byte)0xFF);
writer.Write((byte)0xFF);
//Volume label needs to be written to the root directory as well
stream.Seek(fat2Offset + fatSize, SeekOrigin.Begin);
//First 11 bytes (8.3 space-padded filename without the period) are the label itself
{
if (bpb is ExtendedBiosParameterBlock bpb40 && !string.IsNullOrEmpty(bpb40.VolumeLabel))
{
writer.Write(bpb40.VolumeLabel.PadRight(11, ' ').ToCharArray());
writer.Write((byte)0x08); //Volume label attribute
}
}
}
return(fat);
}
