zisofs is a compression format for files on ISO9660 file system. It has limited support across operating systems, mainly Linux kernel. Typically a directory tree is first preprocessed by mkzftree (from the zisofs-tools package before being turned into an ISO9660 image by mkisofs, genisoimage or similar tool. The data is zlib compressed.
The specification here describes the structure of a file that has been preprocessed by mkzftree, not of a full ISO9660 ziso. Data is not decompressed, as blocks with length 0 have a special meaning. Decompression and deconstruction of this data should be done outside of Kaitai Struct.
This page hosts a formal specification of zisofs using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for C# generated by Kaitai Struct depends on the C# runtime library. You have to install it before you can parse data.
The C# runtime library is available in the NuGet Gallery. Installation instructions can also be found there.
Parse a local file and get structure in memory:
var data = Zisofs.FromFile("path/to/local/file.bin");
Or parse structure from a byte array:
byte[] someArray = new byte[] { ... };
var data = new Zisofs(new KaitaiStream(someArray));
After that, one can get various attributes from the structure by accessing properties like:
data.BlockPointers // => The final pointer (`block_pointers[header.num_blocks]`) indicates the end
of the last block. Typically this is also the end of the file data.
// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
using System.Collections.Generic;
namespace Kaitai
{
/// <summary>
/// zisofs is a compression format for files on ISO9660 file system. It has
/// limited support across operating systems, mainly Linux kernel. Typically a
/// directory tree is first preprocessed by mkzftree (from the zisofs-tools
/// package before being turned into an ISO9660 image by mkisofs, genisoimage
/// or similar tool. The data is zlib compressed.
///
/// The specification here describes the structure of a file that has been
/// preprocessed by mkzftree, not of a full ISO9660 ziso. Data is not
/// decompressed, as blocks with length 0 have a special meaning. Decompression
/// and deconstruction of this data should be done outside of Kaitai Struct.
/// </summary>
/// <remarks>
/// Reference: <a href="https://web.archive.org/web/20200612093441/https://dev.lovelyhq.com/libburnia/web/-/wikis/zisofs">Source</a>
/// </remarks>
public partial class Zisofs : KaitaiStruct
{
public static Zisofs FromFile(string fileName)
{
return new Zisofs(new KaitaiStream(fileName));
}
public Zisofs(KaitaiStream p__io, KaitaiStruct p__parent = null, Zisofs p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root ?? this;
f_blocks = false;
_read();
}
private void _read()
{
__raw_header = m_io.ReadBytes(16);
var io___raw_header = new KaitaiStream(__raw_header);
_header = new Header(io___raw_header, this, m_root);
_blockPointers = new List<uint>();
for (var i = 0; i < (Header.NumBlocks + 1); i++)
{
_blockPointers.Add(m_io.ReadU4le());
}
}
public partial class Header : KaitaiStruct
{
public static Header FromFile(string fileName)
{
return new Header(new KaitaiStream(fileName));
}
public Header(KaitaiStream p__io, Zisofs p__parent = null, Zisofs p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root;
f_blockSize = false;
f_numBlocks = false;
_read();
}
private void _read()
{
_magic = m_io.ReadBytes(8);
if (!((KaitaiStream.ByteArrayCompare(Magic, new byte[] { 55, 228, 83, 150, 201, 219, 214, 7 }) == 0)))
{
throw new ValidationNotEqualError(new byte[] { 55, 228, 83, 150, 201, 219, 214, 7 }, Magic, M_Io, "/types/header/seq/0");
}
_uncompressedSize = m_io.ReadU4le();
_lenHeader = m_io.ReadU1();
if (!(LenHeader == 4))
{
throw new ValidationNotEqualError(4, LenHeader, M_Io, "/types/header/seq/2");
}
_blockSizeLog2 = m_io.ReadU1();
if (!( ((BlockSizeLog2 == 15) || (BlockSizeLog2 == 16) || (BlockSizeLog2 == 17)) ))
{
throw new ValidationNotAnyOfError(BlockSizeLog2, M_Io, "/types/header/seq/3");
}
_reserved = m_io.ReadBytes(2);
if (!((KaitaiStream.ByteArrayCompare(Reserved, new byte[] { 0, 0 }) == 0)))
{
throw new ValidationNotEqualError(new byte[] { 0, 0 }, Reserved, M_Io, "/types/header/seq/4");
}
}
private bool f_blockSize;
private int _blockSize;
public int BlockSize
{
get
{
if (f_blockSize)
return _blockSize;
_blockSize = (int) ((1 << BlockSizeLog2));
f_blockSize = true;
return _blockSize;
}
}
private bool f_numBlocks;
private int _numBlocks;
/// <summary>
/// ceil(uncompressed_size / block_size)
/// </summary>
public int NumBlocks
{
get
{
if (f_numBlocks)
return _numBlocks;
_numBlocks = (int) (((UncompressedSize / BlockSize) + (KaitaiStream.Mod(UncompressedSize, BlockSize) != 0 ? 1 : 0)));
f_numBlocks = true;
return _numBlocks;
}
}
private byte[] _magic;
private uint _uncompressedSize;
private byte _lenHeader;
private byte _blockSizeLog2;
private byte[] _reserved;
private Zisofs m_root;
private Zisofs m_parent;
public byte[] Magic { get { return _magic; } }
/// <summary>
/// Size of the original uncompressed file
/// </summary>
public uint UncompressedSize { get { return _uncompressedSize; } }
/// <summary>
/// header_size >> 2 (currently 4)
/// </summary>
public byte LenHeader { get { return _lenHeader; } }
public byte BlockSizeLog2 { get { return _blockSizeLog2; } }
public byte[] Reserved { get { return _reserved; } }
public Zisofs M_Root { get { return m_root; } }
public Zisofs M_Parent { get { return m_parent; } }
}
public partial class Block : KaitaiStruct
{
public Block(uint p_ofsStart, uint p_ofsEnd, KaitaiStream p__io, Zisofs p__parent = null, Zisofs p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root;
_ofsStart = p_ofsStart;
_ofsEnd = p_ofsEnd;
f_lenData = false;
f_data = false;
_read();
}
private void _read()
{
}
private bool f_lenData;
private int _lenData;
public int LenData
{
get
{
if (f_lenData)
return _lenData;
_lenData = (int) ((OfsEnd - OfsStart));
f_lenData = true;
return _lenData;
}
}
private bool f_data;
private byte[] _data;
public byte[] Data
{
get
{
if (f_data)
return _data;
KaitaiStream io = M_Root.M_Io;
long _pos = io.Pos;
io.Seek(OfsStart);
_data = io.ReadBytes(LenData);
io.Seek(_pos);
f_data = true;
return _data;
}
}
private uint _ofsStart;
private uint _ofsEnd;
private Zisofs m_root;
private Zisofs m_parent;
public uint OfsStart { get { return _ofsStart; } }
public uint OfsEnd { get { return _ofsEnd; } }
public Zisofs M_Root { get { return m_root; } }
public Zisofs M_Parent { get { return m_parent; } }
}
private bool f_blocks;
private List<Block> _blocks;
public List<Block> Blocks
{
get
{
if (f_blocks)
return _blocks;
_blocks = new List<Block>();
for (var i = 0; i < Header.NumBlocks; i++)
{
_blocks.Add(new Block(BlockPointers[i], BlockPointers[(i + 1)], m_io, this, m_root));
}
f_blocks = true;
return _blocks;
}
}
private Header _header;
private List<uint> _blockPointers;
private Zisofs m_root;
private KaitaiStruct m_parent;
private byte[] __raw_header;
public Header Header { get { return _header; } }
/// <summary>
/// The final pointer (`block_pointers[header.num_blocks]`) indicates the end
/// of the last block. Typically this is also the end of the file data.
/// </summary>
public List<uint> BlockPointers { get { return _blockPointers; } }
public Zisofs M_Root { get { return m_root; } }
public KaitaiStruct M_Parent { get { return m_parent; } }
public byte[] M_RawHeader { get { return __raw_header; } }
}
}