/// <summary>
/// Makes a best guess at the geometry of a disk.
/// </summary>
/// <param name="disk">String containing the disk image to detect the geometry from.</param>
/// <returns>The detected geometry.</returns>
public static Geometry DetectGeometry(Stream disk)
{
if (disk.Length >= Sizes.Sector)
{
disk.Position = 0;
byte[] bootSector = StreamUtilities.ReadExact(disk, Sizes.Sector);
if (bootSector[510] == 0x55 && bootSector[511] == 0xAA)
{
long lastSector = 0;
disk.Position = Sizes.Sector;
var sector = StreamUtilities.ReadExact(disk, Sizes.Sector);
var header = new GptHeader(Sizes.Sector);
if (!header.ReadFrom(sector, 0))
{
throw new InvalidDataException("Failed to read primary GPT header");
}
disk.Position = header.PartitionEntriesLba * Sizes.Sector;
var entryBuffer = StreamUtilities.ReadExact(disk,
(int)(header.PartitionEntrySize * header.PartitionEntryCount));
if (header.EntriesCrc != Crc32LittleEndian.Compute(Crc32Algorithm.Common,
entryBuffer, 0, entryBuffer.Length))
{
throw new InvalidDataException("Invalid GPT header");
}
for (int i = 0; i < header.PartitionEntryCount; ++i)
{
GptEntry entry = new GptEntry();
entry.ReadFrom(entryBuffer, i * header.PartitionEntrySize);
if (entry.PartitionType != Guid.Empty)
{
lastSector = entry.LastUsedLogicalBlock + 1;
}
}
if (lastSector > 0)
{
return(Geometry.FromCapacity(lastSector * Sizes.Sector, Sizes.Sector));
}
}
}
return(Geometry.FromCapacity(disk.Length));
}
private void Init(Stream disk, Geometry diskGeometry)
{
BiosPartitionTable bpt;
try
{
bpt = new BiosPartitionTable(disk, diskGeometry);
}
catch (IOException ioe)
{
throw new IOException("Invalid GPT disk, protective MBR table not present or invalid", ioe);
}
if (bpt.Count != 1 || bpt[0].BiosType != BiosPartitionTypes.GptProtective)
{
throw new IOException("Invalid GPT disk, protective MBR table is not valid");
}
_diskData = disk;
_diskGeometry = diskGeometry;
disk.Position = diskGeometry.BytesPerSector;
byte[] sector = StreamUtilities.ReadFully(disk, diskGeometry.BytesPerSector);
_primaryHeader = new GptHeader(diskGeometry.BytesPerSector);
if (!_primaryHeader.ReadFrom(sector, 0) || !ReadEntries(_primaryHeader))
{
disk.Position = disk.Length - diskGeometry.BytesPerSector;
disk.Read(sector, 0, sector.Length);
_secondaryHeader = new GptHeader(diskGeometry.BytesPerSector);
if (!_secondaryHeader.ReadFrom(sector, 0) || !ReadEntries(_secondaryHeader))
{
throw new IOException("No valid GUID Partition Table found");
}
// Generate from the primary table from the secondary one
_primaryHeader = new GptHeader(_secondaryHeader);
_primaryHeader.HeaderLba = _secondaryHeader.AlternateHeaderLba;
_primaryHeader.AlternateHeaderLba = _secondaryHeader.HeaderLba;
_primaryHeader.PartitionEntriesLba = 2;
// If the disk is writeable, fix up the primary partition table based on the
// (valid) secondary table.
if (disk.CanWrite)
{
WritePrimaryHeader();
}
}
if (_secondaryHeader == null)
{
_secondaryHeader = new GptHeader(diskGeometry.BytesPerSector);
disk.Position = disk.Length - diskGeometry.BytesPerSector;
disk.Read(sector, 0, sector.Length);
if (!_secondaryHeader.ReadFrom(sector, 0) || !ReadEntries(_secondaryHeader))
{
// Generate from the secondary table from the primary one
_secondaryHeader = new GptHeader(_primaryHeader);
_secondaryHeader.HeaderLba = _secondaryHeader.AlternateHeaderLba;
_secondaryHeader.AlternateHeaderLba = _secondaryHeader.HeaderLba;
_secondaryHeader.PartitionEntriesLba = _secondaryHeader.HeaderLba -
MathUtilities.RoundUp(
_secondaryHeader.PartitionEntryCount *
_secondaryHeader.PartitionEntrySize,
diskGeometry.BytesPerSector);
// If the disk is writeable, fix up the secondary partition table based on the
// (valid) primary table.
if (disk.CanWrite)
{
WriteSecondaryHeader();
}
}
}
}
