/// <summary>
/// Reads the file descriptor sector for a given file and verified that all sectors in the file segment list (and the file descriptor sector itself)
/// are marked as free in the passed cluster allocation map. It then marks the clusters as marked.
/// </summary>
/// <param name="map">Cluster allocation map.</param>
/// <param name="filedesc">Logical sector number of the file descriptor sector for the file.</param>
/// <param name="clustersize">Cluster size for this filesystem.</param>
/// <exception cref="FilesystemConsistencyException">Thrown if any cluster used for this file is already allocated.</exception>
private void VerifyAndUpdateAllocationMap(OS9AllocationMap map, int filedesc, int clustersize)
{
var fileinfo = OS9FileInfo.Parse(ReadSector(filedesc), null);
/* Verify that all sectors used by this file are marked as free in the cluster allocation map. */
if (map.IsAllocated(filedesc / clustersize))
{
throw new FilesystemConsistencyException(String.Format("Sector {0} is in use by multiple files", filedesc));
}
foreach (var segment in fileinfo.Segments)
{
int sector = segment.Lsn;
for (int i = 0; i < segment.Size; i++)
{
if (map.IsAllocated(sector / clustersize))
{
throw new FilesystemConsistencyException(String.Format("Sector {0} is in use by multiple files", sector));
}
sector++;
}
}
/* Mark all sectors as allocated. */
map.SetAllocated(filedesc / clustersize, true);
foreach (var segment in fileinfo.Segments)
{
int sector = segment.Lsn;
for (int i = 0; i < segment.Size; i++)
{
map.SetAllocated(sector / clustersize, true);
sector++;
}
}
}
internal void ReadDiskHeader()
{
if (DiskInfo == null || AllocationMap == null)
{
DiskInfo = new OS9DiskInfo(ReadSector(IdentificationSector));
AllocationMap = new OS9AllocationMap(ReadSector(AllocationMapSector), DiskInfo.AllocationMapSize);
}
}
/// <summary>
/// Event handler for the SectorWritten event of the associated disk object.
/// </summary>
/// <param name="obj"></param>
/// <param name="e"></param>
private void SectorWrittenHandler(Object obj, SectorWrittenEventArgs e)
{
int lsn = SectorToLsn(e.Head, e.Track, e.Sector);
if (lsn == IdentificationSector || lsn == AllocationMapSector)
{
DiskInfo = null;
AllocationMap = null;
}
}
/// <summary>
/// Checks the filesystem consistency.
/// </summary>
/// <exception cref="FilesystemConsistencyException">Thrown if the filesystem is not consistent in a manner that makes write operations unsafe.</exception>
public void Check()
{
if (IsDisposed)
{
throw new ObjectDisposedException(GetType().FullName);
}
ReadDiskHeader();
var allocmap = new OS9AllocationMap(DiskInfo.AllocationMapSize); // mirror the allocation map
allocmap.SetAllocated(IdentificationSector / DiskInfo.ClusterSize, true);
allocmap.SetAllocated(AllocationMapSector / DiskInfo.ClusterSize, true);
var dirs = new Queue <int>(); // LSN of all directories found while traversing the file structure
dirs.Enqueue(DiskInfo.RootDirectory);
VerifyAndUpdateAllocationMap(allocmap, DiskInfo.RootDirectory, DiskInfo.ClusterSize);
/* Traverse the directory hierarchy and update the cluster allocation map for all files encountered. */
while (dirs.Count > 0)
{
int lsn = dirs.Dequeue();
var files = ReadDirectory(lsn);
foreach (var file in files)
{
if (file.IsValid && !String.Equals(file.Filename, ".") && !String.Equals(file.Filename, ".."))
{
VerifyAndUpdateAllocationMap(allocmap, file.Sector, DiskInfo.ClusterSize);
var fileinfo = OS9FileInfo.Parse(ReadSector(file.Sector), file.Filename);
if (fileinfo.IsDirectory)
{
dirs.Enqueue(file.Sector);
}
}
}
}
/* Finally, verify that all clusters used by files found are actually marked as allocated in the disk cluster allocation map. */
for (int i = 0; i < AllocationMap.AllocationMapSize; i++)
{
if (allocmap.IsAllocated(i) && !AllocationMap.IsAllocated(i))
{
throw new FilesystemConsistencyException(String.Format("Cluster {0} is in use by a file but not marked as allocated", i));
}
}
}
/// <summary>
/// Reads the file descriptor sector for a given file and verified that all sectors in the file segment list (and the file descriptor sector itself)
/// are marked as free in the passed cluster allocation map. It then marks the clusters as marked.
/// </summary>
/// <param name="map">Cluster allocation map.</param>
/// <param name="filedesc">Logical sector number of the file descriptor sector for the file.</param>
/// <param name="clustersize">Cluster size for this filesystem.</param>
/// <exception cref="FilesystemConsistencyException">Thrown if any cluster used for this file is already allocated.</exception>
private void VerifyAndUpdateAllocationMap(OS9AllocationMap map, int filedesc, int clustersize)
{
var fileinfo = OS9FileInfo.Parse(ReadSector(filedesc), null);
/* Verify that all sectors used by this file are marked as free in the cluster allocation map. */
if (map.IsAllocated(filedesc/clustersize)) throw new FilesystemConsistencyException(String.Format("Sector {0} is in use by multiple files", filedesc));
foreach (var segment in fileinfo.Segments)
{
int sector = segment.Lsn;
for (int i=0; i<segment.Size; i++)
{
if (map.IsAllocated(sector/clustersize)) throw new FilesystemConsistencyException(String.Format("Sector {0} is in use by multiple files", sector));
sector++;
}
}
/* Mark all sectors as allocated. */
map.SetAllocated(filedesc/clustersize, true);
foreach (var segment in fileinfo.Segments)
{
int sector = segment.Lsn;
for (int i=0; i<segment.Size; i++)
{
map.SetAllocated(sector/clustersize, true);
sector++;
}
}
}
/// <summary>
/// Event handler for the SectorWritten event of the associated disk object.
/// </summary>
/// <param name="obj"></param>
/// <param name="e"></param>
private void SectorWrittenHandler(Object obj, SectorWrittenEventArgs e)
{
int lsn = SectorToLsn(e.Head, e.Track, e.Sector);
if (lsn == IdentificationSector || lsn == AllocationMapSector)
{
DiskInfo = null;
AllocationMap = null;
}
}
internal void ReadDiskHeader()
{
if (DiskInfo == null || AllocationMap == null)
{
DiskInfo = new OS9DiskInfo(ReadSector(IdentificationSector));
AllocationMap = new OS9AllocationMap(ReadSector(AllocationMapSector), DiskInfo.AllocationMapSize);
}
}
/// <summary>
/// Checks the filesystem consistency.
/// </summary>
/// <exception cref="FilesystemConsistencyException">Thrown if the filesystem is not consistent in a manner that makes write operations unsafe.</exception>
public void Check()
{
if (IsDisposed) throw new ObjectDisposedException(GetType().FullName);
ReadDiskHeader();
var allocmap = new OS9AllocationMap(DiskInfo.AllocationMapSize); // mirror the allocation map
allocmap.SetAllocated(IdentificationSector/DiskInfo.ClusterSize, true);
allocmap.SetAllocated(AllocationMapSector/DiskInfo.ClusterSize, true);
var dirs = new Queue<int>(); // LSN of all directories found while traversing the file structure
dirs.Enqueue(DiskInfo.RootDirectory);
VerifyAndUpdateAllocationMap(allocmap, DiskInfo.RootDirectory, DiskInfo.ClusterSize);
/* Traverse the directory hierarchy and update the cluster allocation map for all files encountered. */
while (dirs.Count > 0)
{
int lsn = dirs.Dequeue();
var files = ReadDirectory(lsn);
foreach (var file in files)
{
if (file.IsValid && !String.Equals(file.Filename, ".") && !String.Equals(file.Filename, ".."))
{
VerifyAndUpdateAllocationMap(allocmap, file.Sector, DiskInfo.ClusterSize);
var fileinfo = OS9FileInfo.Parse(ReadSector(file.Sector), file.Filename);
if (fileinfo.IsDirectory)
{
dirs.Enqueue(file.Sector);
}
}
}
}
/* Finally, verify that all clusters used by files found are actually marked as allocated in the disk cluster allocation map. */
for (int i = 0; i < AllocationMap.AllocationMapSize; i++ )
{
if (allocmap.IsAllocated(i) && !AllocationMap.IsAllocated(i))
{
throw new FilesystemConsistencyException(String.Format("Cluster {0} is in use by a file but not marked as allocated", i));
}
}
}
