private Fat(BootSector bs, long offset)
{
this.bs = bs;
fatType = bs.GetFatType();
if (bs.GetSectorsPerFat() > int.MaxValue)
{
throw new ArgumentException("FAT too large");
}
if (bs.GetSectorsPerFat() <= 0)
{
throw new IOException(
"boot sector says there are " + bs.GetSectorsPerFat() +
" sectors per FAT");
}
if (bs.GetBytesPerSector() <= 0)
{
throw new IOException(
"boot sector says there are " + bs.GetBytesPerSector() +
" bytes per sector");
}
sectorCount = (int)bs.GetSectorsPerFat();
sectorSize = bs.GetBytesPerSector();
device = bs.GetDevice();
this.offset = offset;
lastAllocatedCluster = FIRST_CLUSTER;
if (bs.GetDataClusterCount() > int.MaxValue)
{
throw
new IOException("too many data clusters");
}
if (bs.GetDataClusterCount() == 0)
{
throw
new IOException("no data clusters");
}
lastClusterIndex = (int)bs.GetDataClusterCount() + FIRST_CLUSTER;
entries = new long[(int)((sectorCount * sectorSize) /
fatType.GetEntrySize())];
if (lastClusterIndex > entries.Length)
{
throw new IOException(
"file system has " + lastClusterIndex +
"clusters but only " + entries.Length + " FAT entries");
}
}
/// <summary>
/// Creates a new <see cref="Fat"/> as specified by a <see cref="BootSector"/>.
/// </summary>
/// <param name="bs">the boot sector specifying the <see cref="Fat"/> layout</param>
/// <param name="fatNr">the number of the <see cref="Fat"/> to create</param>
/// <returns>the <see cref="Fat"/> that was created</returns>
/// <exception cref="IOException">IOException on write error</exception>
/// <exception cref="ArgumentException">ArgumentException if fatNr is greater than
/// <see cref="BootSector.GetNrFats"/></exception>
public static Fat Create(BootSector bs, int fatNr)
{
if (fatNr > bs.GetNrFats())
{
throw new ArgumentException(
"boot sector says there are only " + bs.GetNrFats() +
" FATs when creating FAT #" + fatNr);
}
var fatOffset = FatUtils.GetFatOffset(bs, fatNr);
var result = new Fat(bs, fatOffset);
if (bs.GetDataClusterCount() > result.entries.Length)
{
throw new IOException("FAT too small for device");
}
result.Init(bs.GetMediumDescriptor());
result.Write();
return(result);
}
/// <summary>
/// This method is currently not implemented for <see cref="FatFileSystem"/> and
/// always returns -1.
/// </summary>
/// <returns>always -1</returns>
public override long GetTotalSpace()
{
return(bs.GetDataClusterCount() * bs.GetBytesPerCluster());
}