public override void EraseOldFileSystemResidentFiles(VolumeInfo volume,
DirectoryInfo tempDirectory, IErasureMethod method,
FileSystemEntriesEraseProgress callback)
{
//Squeeze files smaller than one MFT record until the volume and the MFT is full.
long MFTRecordSize = NtfsApi.GetMftRecordSegmentSize(volume);
long lastFileSize = MFTRecordSize;
try
{
for ( ; ;)
{
//Open this stream
string fileName = GenerateRandomFileName(tempDirectory, 18);
FileStream strm = new FileStream(fileName, FileMode.CreateNew, FileAccess.Write,
FileShare.None, 8, FileOptions.WriteThrough);
try
{
//Stretch the file size to use up some of the resident space.
strm.SetLength(lastFileSize);
//Then run the erase task
method.Erase(strm, long.MaxValue, Host.Instance.Prngs.ActivePrng, null);
//Call the callback function if one is provided. We'll provide a dummy
//value since we really have no idea how much of the MFT we can clean.
if (callback != null)
{
callback((int)(MFTRecordSize - lastFileSize), (int)MFTRecordSize);
}
}
catch (IOException)
{
if (lastFileSize-- == 0)
{
break;
}
}
finally
{
//Close the stream handle
strm.Close();
//Then reset the time the file was created.
ResetFileTimes(new FileInfo(fileName));
}
}
}
catch (IOException)
{
//OK, enough squeezing: there isn't enough space to even create a new MFT record.
}
}
public override void EraseFileSystemObject(StreamInfo info, IErasureMethod method,
ErasureMethodProgressFunction callback)
{
//Check if the file fits in one cluster - if it does it may be MFT resident
//TODO: any more deterministic way of finding out?
VolumeInfo volume = VolumeInfo.FromMountPoint(info.DirectoryName);
if (info.Length < NtfsApi.GetMftRecordSegmentSize(volume))
{
//Yes it does, erase exactly to the file length
using (FileStream strm = info.Open(FileMode.Open, FileAccess.Write,
FileShare.None))
{
method.Erase(strm, long.MaxValue, Host.Instance.Prngs.ActivePrng,
null);
}
}
//Create the file stream, and call the erasure method to write to
//the stream.
long fileArea = GetFileArea(info);
//If the stream is empty, there's nothing to overwrite. Continue
//to the next entry
if (fileArea == 0)
{
return;
}
using (FileStream strm = info.Open(FileMode.Open, FileAccess.Write,
FileShare.None, FileOptions.WriteThrough))
{
//Set the end of the stream after the wrap-round the cluster size
strm.SetLength(fileArea);
//Then erase the file.
method.Erase(strm, long.MaxValue, Host.Instance.Prngs.ActivePrng, callback);
//Set the length of the file to 0.
strm.Seek(0, SeekOrigin.Begin);
strm.SetLength(0);
}
}
public override void EraseDirectoryStructures(VolumeInfo info,
FileSystemEntriesEraseProgress callback)
{
//Create a directory to hold all the temporary files
DirectoryInfo tempDir = new DirectoryInfo(GenerateRandomFileName(
info.MountPoints[0], 32));
tempDir.Create();
try
{
//Get the size of the MFT
long mftSize = NtfsApi.GetMftValidSize(info);
long mftRecordSegmentSize = NtfsApi.GetMftRecordSegmentSize(info);
int pollingInterval = (int)Math.Min(Math.Max(1, mftSize / info.ClusterSize / 20), 128);
int totalFiles = (int)Math.Max(1L, mftSize / mftRecordSegmentSize);
int filesCreated = 0;
while (true)
{
++filesCreated;
string fileName = GenerateRandomFileName(tempDir, 220);
File.Create(fileName).Close();
ResetFileTimes(new FileInfo(fileName));
if (filesCreated % pollingInterval == 0)
{
//Call back to our progress function: this is the first half of the
//procedure so divide the effective progress by 2.
if (callback != null)
{
int halfFilesCreated = filesCreated / 2;
callback(halfFilesCreated, Math.Max(halfFilesCreated, totalFiles));
}
//Check if the MFT has grown.
if (mftSize < NtfsApi.GetMftValidSize(info))
{
break;
}
}
}
}
catch (IOException)
{
}
finally
{
//Clear up all the temporary files
FileInfo[] files = tempDir.GetFiles("*", SearchOption.AllDirectories);
for (int i = 0; i < files.Length; ++i)
{
if (callback != null && i % 50 == 0)
{
callback(files.Length + i, files.Length * 2);
}
files[i].Delete();
}
DeleteFolder(tempDir, true);
}
}
