/// <summary>
/// Reads the volume descriptors for
/// </summary>
/// <param name="extentVds">The anchor volume extent information.</param>
/// <returns>Returns true if the volume descriptors were read from the image successfully.</returns>
private bool ReadVolumeDescriptors(UdfFileExtent extentVds)
{
byte[] buffer = new byte[SectorSize];
long location = extentVds.Position;
while (location < extentVds.Length && location < this.imageSize)
{
this.stream.Seek(location << SectorSizeLog, (int)SeekOrigin.Begin, IntPtr.Zero);
if (!this.stream.ReadSafe(buffer, buffer.Length))
{
return(false);
}
VolumeTag tag = new VolumeTag();
tag.Parse(0, buffer, buffer.Length);
switch ((VolumeDescriptorType)tag.Identifier)
{
case VolumeDescriptorType.Terminating:
// Found terminating descriptor. Image is valid.
return(true);
case VolumeDescriptorType.Partition:
if (this.Partitions.Count >= MaxPartitions)
{
return(false);
}
this.ReadPartitionDescriptor(buffer);
break;
case VolumeDescriptorType.LogicalVolume:
if (this.LogicalVolumes.Count >= MaxLogicalVolumes || !this.ReadLogicalDescriptor(buffer))
{
return(false);
}
break;
}
location++;
}
// Did not find the terminating descriptor. Not a valid image.
return(false);
}
/// <summary>
/// Opens the file and attempts to read the contents of the ISO image.
/// </summary>
/// <returns>Returns true if the image was opened successfully.</returns>
public bool Open()
{
try
{
using (var fileStream = this.ImageFile.OpenRead())
{
// Initialize the stream
this.InitializeStream(fileStream);
// Must have at least one sector in the image.
if (this.imageSize < SectorSize)
{
return(false);
}
// Parse the anchor pointer to find the location of the volume descriptors.
UdfFileExtent extentVds = this.ReadAnchorVolumePointer();
if (extentVds == null)
{
return(false);
}
// Parse the volume and paritiotion information from the image.
if (!this.ReadVolumeDescriptors(extentVds))
{
return(false);
}
// Finally, read the file structure.
return(this.ReadFileStructure());
}
}
catch (Exception ex)
{
if (!(ex is UnauthorizedAccessException || ex is DirectoryNotFoundException || ex is IOException))
{
throw;
}
}
return(false);
}
/// <summary>
/// Reads the Anchor Volume pointer from the image.
/// </summary>
/// <returns>Returns true if the pointer was found.</returns>
private UdfFileExtent ReadAnchorVolumePointer()
{
UdfFileExtent result = null;
byte[] buffer = new byte[SectorSize];
this.stream.Seek(-buffer.Length, (int)SeekOrigin.End, IntPtr.Zero);
if (!this.stream.ReadSafe(buffer, buffer.Length))
{
return(result);
}
VolumeTag tag = new VolumeTag();
if (tag.Parse(0, buffer, buffer.Length) &&
tag.Identifier == (short)VolumeDescriptorType.AnchorVolumePtr)
{
result = new UdfFileExtent();
result.Parse(16, buffer);
}
return(result);
}