// Note: there could be up to 2^64 clusters ( http://technet.microsoft.com/en-us/library/cc938432.aspx )
private void Extend(ulong currentNumberOfClusters, ulong additionalNumberOfClusters)
{
// Each bit in the $Bitmap file represents a cluster.
// The size of the $Bitmap file is always a multiple of 8 bytes, extra bits are always set to 1.
//
// Note:
// 1TB of additional allocation will result in a bitmap of 32 MB (assuming 4KB clusters)
// 128TB of additional allocation will result in a bitmap of 512 MB (assuming 8KB clusters)
byte[] bitmap;
ulong nextClusterIndexInBitmap = 0; // the next cluster that will be allocated
ulong writeOffset = m_bitmap.Length;
if (currentNumberOfClusters % 64 > 0)
{
ulong numberOfClustersToAllocate = additionalNumberOfClusters - (64 - (currentNumberOfClusters % 64));
ulong numberOfBytesToAllocate = (ulong)Math.Ceiling((double)numberOfClustersToAllocate / 8);
numberOfBytesToAllocate = (ulong)Math.Ceiling((double)numberOfBytesToAllocate / 8) * 8;
// The last 8 bytes may contain extra bits that were previously set as used, and now have to be free.
// We extend the file before reading the last 8 bytes of the bitmap, because it's possible that during the extension,
// clusters will be allocated from the last 8 bytes of the $bitmap file. for this reason, we must first extend the file, and then read the bitmap
m_bitmap.ExtendFile(numberOfBytesToAllocate);
bitmap = new byte[8 + numberOfBytesToAllocate];
// We have to modify the last 8 bytes in the current bitmap (which will be the first in 'bitmap')
writeOffset = writeOffset - 8;
byte[] temp = m_bitmap.ReadFromFile(writeOffset, 8);
Array.Copy(temp, bitmap, 8);
nextClusterIndexInBitmap = currentNumberOfClusters % 64;
while (nextClusterIndexInBitmap < 64)
{
ClusterUsageBitmap.UpdateClusterStatus(bitmap, nextClusterIndexInBitmap, false);
nextClusterIndexInBitmap++;
}
nextClusterIndexInBitmap += numberOfClustersToAllocate;
}
else
{
ulong additionalNumberOfBytes = (ulong)Math.Ceiling((double)additionalNumberOfClusters / 8);
additionalNumberOfBytes = (ulong)Math.Ceiling((double)additionalNumberOfBytes / 8) * 8;
bitmap = new byte[additionalNumberOfBytes];
nextClusterIndexInBitmap = additionalNumberOfClusters;
}
// mark extra bits as used:
while (nextClusterIndexInBitmap < (ulong)bitmap.Length * 8)
{
ClusterUsageBitmap.UpdateClusterStatus(bitmap, nextClusterIndexInBitmap, true);
nextClusterIndexInBitmap++;
}
m_bitmap.WriteToFile(writeOffset, bitmap);
}
public NTFSVolume(Volume volume, bool useMftMirror)
{
m_volume = volume;
byte[] bootSector = m_volume.ReadSector(0);
m_bootRecord = NTFSBootRecord.ReadRecord(bootSector);
if (m_bootRecord != null)
{
m_mft = new MasterFileTable(this, useMftMirror);
m_bitmap = new ClusterUsageBitmap(this);
}
}
