private void CheckHeader()
{
_fileStream.Position = 0;
byte[] headerSector = Utilities.ReadFully(_fileStream, Utilities.SectorSize);
Footer header = Footer.FromBytes(headerSector, 0);
if (!header.IsValid())
{
ReportError("Invalid VHD footer at start of file");
}
_fileStream.Position = _fileStream.Length - Utilities.SectorSize;
byte[] footerSector = Utilities.ReadFully(_fileStream, Utilities.SectorSize);
if (!Utilities.AreEqual(footerSector, headerSector))
{
ReportError("Header and footer are different");
}
if (_footer == null || !_footer.IsValid())
{
_footer = header;
}
}
private void CheckFooter()
{
_fileStream.Position = _fileStream.Length - Utilities.SectorSize;
byte[] sector = Utilities.ReadFully(_fileStream, Utilities.SectorSize);
_footer = Footer.FromBytes(sector, 0);
if (!_footer.IsValid())
{
ReportError("Invalid VHD footer at end of file");
}
}
public DynamicStream(Stream fileStream, DynamicHeader dynamicHeader, long length, SparseStream parentStream, Ownership ownsParentStream)
{
if (fileStream == null)
{
throw new ArgumentNullException("fileStream");
}
if (dynamicHeader == null)
{
throw new ArgumentNullException("dynamicHeader");
}
if (parentStream == null)
{
throw new ArgumentNullException("parentStream");
}
if (length < 0)
{
throw new ArgumentOutOfRangeException("length", length, "Negative lengths not allowed");
}
_fileStream = fileStream;
_dynamicHeader = dynamicHeader;
_length = length;
_parentStream = parentStream;
_ownsParentStream = ownsParentStream;
_blockBitmaps = new byte[_dynamicHeader.MaxTableEntries][];
_blockBitmapSize = (int)Utilities.RoundUp((_dynamicHeader.BlockSize / Utilities.SectorSize) / 8, Utilities.SectorSize);
ReadBlockAllocationTable();
// Detect where next block should go (cope if the footer is missing)
_fileStream.Position = Utilities.RoundDown(_fileStream.Length, Utilities.SectorSize) - Utilities.SectorSize;
byte[] footerBytes = Utilities.ReadFully(_fileStream, Utilities.SectorSize);
Footer footer = Footer.FromBytes(footerBytes, 0);
_nextBlockStart = _fileStream.Position - (footer.IsValid() ? Utilities.SectorSize : 0);
}
private void ReadFooter(bool fallbackToFront)
{
_fileStream.Position = _fileStream.Length - Utilities.SectorSize;
byte[] sector = Utilities.ReadFully(_fileStream, Utilities.SectorSize);
_footer = Footer.FromBytes(sector, 0);
if (!_footer.IsValid())
{
if (!fallbackToFront)
{
throw new IOException("Corrupt VHD file - invalid footer at end (did not check front of file)");
}
_fileStream.Position = 0;
Utilities.ReadFully(_fileStream, sector, 0, Utilities.SectorSize);
_footer = Footer.FromBytes(sector, 0);
if (!_footer.IsValid())
{
throw new IOException("Failed to find a valid VHD footer at start or end of file - VHD file is corrupt");
}
}
}
