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 JavaScript generated by Kaitai Struct depends on the JavaScript runtime library. You have to install it before you can parse data.
The JavaScript runtime library is available at npm:
npm install kaitai-structSee the usage examples in the JavaScript notes.
Parse structure from an ArrayBuffer:
var arrayBuffer = ...;
var data = new Zisofs(new KaitaiStream(arrayBuffer));
After that, one can get various attributes from the structure by accessing fields or 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
(function (root, factory) {
if (typeof define === 'function' && define.amd) {
define(['kaitai-struct/KaitaiStream'], factory);
} else if (typeof module === 'object' && module.exports) {
module.exports = factory(require('kaitai-struct/KaitaiStream'));
} else {
root.Zisofs = factory(root.KaitaiStream);
}
}(typeof self !== 'undefined' ? self : this, function (KaitaiStream) {
/**
* 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.
* @see {@link https://web.archive.org/web/20200612093441/https://dev.lovelyhq.com/libburnia/web/-/wikis/zisofs|Source}
*/
var Zisofs = (function() {
function Zisofs(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this._read();
}
Zisofs.prototype._read = function() {
this._raw_header = this._io.readBytes(16);
var _io__raw_header = new KaitaiStream(this._raw_header);
this.header = new Header(_io__raw_header, this, this._root);
this.blockPointers = [];
for (var i = 0; i < (this.header.numBlocks + 1); i++) {
this.blockPointers.push(this._io.readU4le());
}
}
var Header = Zisofs.Header = (function() {
function Header(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this._read();
}
Header.prototype._read = function() {
this.magic = this._io.readBytes(8);
if (!((KaitaiStream.byteArrayCompare(this.magic, [55, 228, 83, 150, 201, 219, 214, 7]) == 0))) {
throw new KaitaiStream.ValidationNotEqualError([55, 228, 83, 150, 201, 219, 214, 7], this.magic, this._io, "/types/header/seq/0");
}
this.uncompressedSize = this._io.readU4le();
this.lenHeader = this._io.readU1();
if (!(this.lenHeader == 4)) {
throw new KaitaiStream.ValidationNotEqualError(4, this.lenHeader, this._io, "/types/header/seq/2");
}
this.blockSizeLog2 = this._io.readU1();
if (!( ((this.blockSizeLog2 == 15) || (this.blockSizeLog2 == 16) || (this.blockSizeLog2 == 17)) )) {
throw new KaitaiStream.ValidationNotAnyOfError(this.blockSizeLog2, this._io, "/types/header/seq/3");
}
this.reserved = this._io.readBytes(2);
if (!((KaitaiStream.byteArrayCompare(this.reserved, [0, 0]) == 0))) {
throw new KaitaiStream.ValidationNotEqualError([0, 0], this.reserved, this._io, "/types/header/seq/4");
}
}
Object.defineProperty(Header.prototype, 'blockSize', {
get: function() {
if (this._m_blockSize !== undefined)
return this._m_blockSize;
this._m_blockSize = (1 << this.blockSizeLog2);
return this._m_blockSize;
}
});
/**
* ceil(uncompressed_size / block_size)
*/
Object.defineProperty(Header.prototype, 'numBlocks', {
get: function() {
if (this._m_numBlocks !== undefined)
return this._m_numBlocks;
this._m_numBlocks = (Math.floor(this.uncompressedSize / this.blockSize) + (KaitaiStream.mod(this.uncompressedSize, this.blockSize) != 0 ? 1 : 0));
return this._m_numBlocks;
}
});
/**
* Size of the original uncompressed file
*/
/**
* header_size >> 2 (currently 4)
*/
return Header;
})();
var Block = Zisofs.Block = (function() {
function Block(_io, _parent, _root, ofsStart, ofsEnd) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this.ofsStart = ofsStart;
this.ofsEnd = ofsEnd;
this._read();
}
Block.prototype._read = function() {
}
Object.defineProperty(Block.prototype, 'lenData', {
get: function() {
if (this._m_lenData !== undefined)
return this._m_lenData;
this._m_lenData = (this.ofsEnd - this.ofsStart);
return this._m_lenData;
}
});
Object.defineProperty(Block.prototype, 'data', {
get: function() {
if (this._m_data !== undefined)
return this._m_data;
var io = this._root._io;
var _pos = io.pos;
io.seek(this.ofsStart);
this._m_data = io.readBytes(this.lenData);
io.seek(_pos);
return this._m_data;
}
});
return Block;
})();
Object.defineProperty(Zisofs.prototype, 'blocks', {
get: function() {
if (this._m_blocks !== undefined)
return this._m_blocks;
this._m_blocks = [];
for (var i = 0; i < this.header.numBlocks; i++) {
this._m_blocks.push(new Block(this._io, this, this._root, this.blockPointers[i], this.blockPointers[(i + 1)]));
}
return this._m_blocks;
}
});
/**
* 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.
*/
return Zisofs;
})();
return Zisofs;
}));