private void LoadDescriptor(Stream s)
{
s.Position = 0;
byte[] header = Utilities.ReadFully(s, (int)Math.Min(Sizes.Sector, s.Length));
if (header.Length < Sizes.Sector || Utilities.ToUInt32LittleEndian(header, 0) != HostedSparseExtentHeader.VmdkMagicNumber)
{
s.Position = 0;
_descriptor = new DescriptorFile(s);
if (_access != FileAccess.Read)
{
_descriptor.ContentId = (uint)_rng.Next();
s.Position = 0;
_descriptor.Write(s);
s.SetLength(s.Position);
}
}
else
{
// This is a sparse disk extent, hopefully with embedded descriptor...
HostedSparseExtentHeader hdr = HostedSparseExtentHeader.Read(header, 0);
if (hdr.DescriptorOffset != 0)
{
Stream descriptorStream = new SubStream(s, hdr.DescriptorOffset * Sizes.Sector, hdr.DescriptorSize * Sizes.Sector);
_descriptor = new DescriptorFile(descriptorStream);
if (_access != FileAccess.Read)
{
_descriptor.ContentId = (uint)_rng.Next();
descriptorStream.Position = 0;
_descriptor.Write(descriptorStream);
byte[] blank = new byte[descriptorStream.Length - descriptorStream.Position];
descriptorStream.Write(blank, 0, blank.Length);
}
}
}
}
public HostedSparseExtentStream(Stream file, Ownership ownsFile, long diskOffset, SparseStream parentDiskStream, Ownership ownsParentDiskStream)
{
_fileStream = file;
_ownsFileStream = ownsFile;
_diskOffset = diskOffset;
_parentDiskStream = parentDiskStream;
_ownsParentDiskStream = ownsParentDiskStream;
file.Position = 0;
byte[] headerSector = Utilities.ReadFully(file, Sizes.Sector);
_hostedHeader = HostedSparseExtentHeader.Read(headerSector, 0);
if (_hostedHeader.GdOffset == -1)
{
// Fall back to secondary copy that (should) be at the end of the stream, just before the end-of-stream sector marker
file.Position = file.Length - Sizes.OneKiB;
headerSector = Utilities.ReadFully(file, Sizes.Sector);
_hostedHeader = HostedSparseExtentHeader.Read(headerSector, 0);
if (_hostedHeader.MagicNumber != HostedSparseExtentHeader.VmdkMagicNumber)
{
throw new IOException("Unable to locate valid VMDK header or footer");
}
}
_header = _hostedHeader;
if (_hostedHeader.CompressAlgorithm != 0 && _hostedHeader.CompressAlgorithm != 1)
{
throw new NotSupportedException("Only uncompressed and DEFLATE compressed disks supported");
}
_gtCoverage = _header.NumGTEsPerGT * _header.GrainSize * Sizes.Sector;
LoadGlobalDirectory();
}
