private void BuildFirstClusterIndex()
{
if (_firstClusterIndex == null)
{
// Iterate over all files on the drive and record their first cluster.
// Newer files overwrite older files.
_firstClusterIndex = new Dictionary <long, IFATNode>();
SearchByTree(new NodeVisitCallback(delegate(INodeMetadata metadata, ulong progress, ulong total) {
// Handle files
FileFAT file = metadata as FileFAT;
if (file != null)
{
if (!_firstClusterIndex.ContainsKey(file.FirstCluster) ||
_firstClusterIndex[file.FirstCluster].LastModified < file.LastModified)
{
_firstClusterIndex[file.FirstCluster] = file;
}
}
// Handle folders
FolderFAT folder = metadata as FolderFAT;
if (folder != null)
{
if (!_firstClusterIndex.ContainsKey(folder.FirstCluster) ||
_firstClusterIndex[folder.FirstCluster].LastModified < folder.LastModified)
{
_firstClusterIndex[folder.FirstCluster] = folder;
}
}
return(true);
}), null);
}
}
internal override FileRecoveryStatus GetChanceOfRecovery(FileSystemNode node)
{
FileFAT file = node as FileFAT;
if (file == null)
{
return(FileRecoveryStatus.Unknown);
}
else
{
int numZeroLinks;
if (IsFatChainOverwritten(file, out numZeroLinks))
{
return(numZeroLinks == 0 ? FileRecoveryStatus.Overwritten : FileRecoveryStatus.PartiallyOverwritten);
}
else
{
BuildFirstClusterIndex();
// Check to see if the first cluster is also allocated to something more recent
if (_firstClusterIndex.ContainsKey(file.FirstCluster))
{
return(_firstClusterIndex[file.FirstCluster].Name == file.Name ? FileRecoveryStatus.Recoverable : FileRecoveryStatus.Overwritten);
}
else
{
Console.Error.WriteLine("ERROR: File {0} at cluster {1} was missing from the first cluster index.", file.Name, file.FirstCluster);
return(FileRecoveryStatus.Unknown);
}
}
}
}
private bool IsFatChainOverwritten(FileFAT file, out int numZeroLinks)
{
// Iterate through the FAT links to see if any of them are non-zero.
long remainingLength = file.Length;
var currentCluster = file.FirstCluster;
numZeroLinks = 0;
while (remainingLength > 0)
{
if (_fileAllocationTable.GetEntry(currentCluster) != 0)
{
return(true);
}
remainingLength -= BytesPerCluster;
currentCluster++;
numZeroLinks++;
}
return(false);
}