vfat: JavaScript parsing library

KS implementation details

License: CC0-1.0
Minimal Kaitai Struct required: 0.9

References

This page hosts a formal specification of vfat using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime 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-struct

Code

See the usage examples in the JavaScript notes.

Parse structure from an ArrayBuffer:

var arrayBuffer = ...;
var data = new Vfat(new KaitaiStream(arrayBuffer));

After that, one can get various attributes from the structure by accessing fields or properties like:

data.bootSector // => get boot sector

JavaScript source code to parse vfat

Vfat.js

// 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', './DosDatetime'], factory);
  } else if (typeof module === 'object' && module.exports) {
    module.exports = factory(require('kaitai-struct/KaitaiStream'), require('./DosDatetime'));
  } else {
    root.Vfat = factory(root.KaitaiStream, root.DosDatetime);
  }
}(this, function (KaitaiStream, DosDatetime) {
/**
 * @see {@link https://download.microsoft.com/download/0/8/4/084c452b-b772-4fe5-89bb-a0cbf082286a/fatgen103.doc|Source}
 */

var Vfat = (function() {
  function Vfat(_io, _parent, _root) {
    this._io = _io;
    this._parent = _parent;
    this._root = _root || this;

    this._read();
  }
  Vfat.prototype._read = function() {
    this.bootSector = new BootSector(this._io, this, this._root);
  }

  /**
   * Extended BIOS Parameter Block for FAT32
   */

  var ExtBiosParamBlockFat32 = Vfat.ExtBiosParamBlockFat32 = (function() {
    function ExtBiosParamBlockFat32(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    ExtBiosParamBlockFat32.prototype._read = function() {
      this.lsPerFat = this._io.readU4le();
      this.hasActiveFat = this._io.readBitsIntLe(1) != 0;
      this.reserved1 = this._io.readBitsIntLe(3);
      this.activeFatId = this._io.readBitsIntLe(4);
      this._io.alignToByte();
      this.reserved2 = this._io.readBytes(1);
      if (!((KaitaiStream.byteArrayCompare(this.reserved2, [0]) == 0))) {
        throw new KaitaiStream.ValidationNotEqualError([0], this.reserved2, this._io, "/types/ext_bios_param_block_fat32/seq/4");
      }
      this.fatVersion = this._io.readU2le();
      this.rootDirStartClus = this._io.readU4le();
      this.lsFsInfo = this._io.readU2le();
      this.bootSectorsCopyStartLs = this._io.readU2le();
      this.reserved3 = this._io.readBytes(12);
      this.physDriveNum = this._io.readU1();
      this.reserved4 = this._io.readU1();
      this.extBootSign = this._io.readU1();
      this.volumeId = this._io.readBytes(4);
      this.partitionVolumeLabel = KaitaiStream.bytesToStr(KaitaiStream.bytesStripRight(this._io.readBytes(11), 32), "ASCII");
      this.fsTypeStr = KaitaiStream.bytesToStr(KaitaiStream.bytesStripRight(this._io.readBytes(8), 32), "ASCII");
    }

    /**
     * Logical sectors per file allocation table (corresponds with
     * the old entry `ls_per_fat` in the DOS 2.0 BPB).
     */

    /**
     * If true, then there is "active" FAT, which is designated in
     * `active_fat` attribute. If false, all FATs are mirrored as
     * usual.
     */

    /**
     * Zero-based number of active FAT, if `has_active_fat`
     * attribute is true.
     */

    /**
     * Cluster number of root directory start, typically 2 if it
     * contains no bad sector. (Microsoft's FAT32 implementation
     * imposes an artificial limit of 65,535 entries per directory,
     * whilst many third-party implementations do not.)
     */

    /**
     * Logical sector number of FS Information Sector, typically 1,
     * i.e., the second of the three FAT32 boot sectors. Values
     * like 0 and 0xFFFF are used by some FAT32 implementations to
     * designate abscence of FS Information Sector.
     */

    /**
     * First logical sector number of a copy of the three FAT32
     * boot sectors, typically 6.
     */

    /**
     * Physical drive number (0x00 for (first) removable media,
     * 0x80 for (first) fixed disk as per INT 13h).
     */

    /**
     * Should be 0x29 to indicate that an EBPB with the following 3
     * entries exists.
     */

    /**
     * Volume ID (serial number).
     * 
     * Typically the serial number "xxxx-xxxx" is created by a
     * 16-bit addition of both DX values returned by INT 21h/AH=2Ah
     * (get system date) and INT 21h/AH=2Ch (get system time) for
     * the high word and another 16-bit addition of both CX values
     * for the low word of the serial number. Alternatively, some
     * DR-DOS disk utilities provide a /# option to generate a
     * human-readable time stamp "mmdd-hhmm" build from BCD-encoded
     * 8-bit values for the month, day, hour and minute instead of
     * a serial number.
     */

    return ExtBiosParamBlockFat32;
  })();

  var BootSector = Vfat.BootSector = (function() {
    function BootSector(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    BootSector.prototype._read = function() {
      this.jmpInstruction = this._io.readBytes(3);
      this.oemName = KaitaiStream.bytesToStr(KaitaiStream.bytesStripRight(this._io.readBytes(8), 32), "ASCII");
      this.bpb = new BiosParamBlock(this._io, this, this._root);
      if (!(this.isFat32)) {
        this.ebpbFat16 = new ExtBiosParamBlockFat16(this._io, this, this._root);
      }
      if (this.isFat32) {
        this.ebpbFat32 = new ExtBiosParamBlockFat32(this._io, this, this._root);
      }
    }

    /**
     * Offset of FATs in bytes from start of filesystem
     */
    Object.defineProperty(BootSector.prototype, 'posFats', {
      get: function() {
        if (this._m_posFats !== undefined)
          return this._m_posFats;
        this._m_posFats = (this.bpb.bytesPerLs * this.bpb.numReservedLs);
        return this._m_posFats;
      }
    });
    Object.defineProperty(BootSector.prototype, 'lsPerFat', {
      get: function() {
        if (this._m_lsPerFat !== undefined)
          return this._m_lsPerFat;
        this._m_lsPerFat = (this.isFat32 ? this.ebpbFat32.lsPerFat : this.bpb.lsPerFat);
        return this._m_lsPerFat;
      }
    });

    /**
     * Size of root directory in logical sectors
     * @see FAT: General Overview of On-Disk Format, section "FAT Data Structure"
     */
    Object.defineProperty(BootSector.prototype, 'lsPerRootDir', {
      get: function() {
        if (this._m_lsPerRootDir !== undefined)
          return this._m_lsPerRootDir;
        this._m_lsPerRootDir = Math.floor((((this.bpb.maxRootDirRec * 32) + this.bpb.bytesPerLs) - 1) / this.bpb.bytesPerLs);
        return this._m_lsPerRootDir;
      }
    });

    /**
     * Determines if filesystem is FAT32 (true) or FAT12/16 (false)
     * by analyzing some preliminary conditions in BPB. Used to
     * determine whether we should parse post-BPB data as
     * `ext_bios_param_block_fat16` or `ext_bios_param_block_fat32`.
     */
    Object.defineProperty(BootSector.prototype, 'isFat32', {
      get: function() {
        if (this._m_isFat32 !== undefined)
          return this._m_isFat32;
        this._m_isFat32 = this.bpb.maxRootDirRec == 0;
        return this._m_isFat32;
      }
    });

    /**
     * Size of one FAT in bytes
     */
    Object.defineProperty(BootSector.prototype, 'sizeFat', {
      get: function() {
        if (this._m_sizeFat !== undefined)
          return this._m_sizeFat;
        this._m_sizeFat = (this.bpb.bytesPerLs * this.lsPerFat);
        return this._m_sizeFat;
      }
    });

    /**
     * Offset of root directory in bytes from start of filesystem
     */
    Object.defineProperty(BootSector.prototype, 'posRootDir', {
      get: function() {
        if (this._m_posRootDir !== undefined)
          return this._m_posRootDir;
        this._m_posRootDir = (this.bpb.bytesPerLs * (this.bpb.numReservedLs + (this.lsPerFat * this.bpb.numFats)));
        return this._m_posRootDir;
      }
    });

    /**
     * Size of root directory in bytes
     */
    Object.defineProperty(BootSector.prototype, 'sizeRootDir', {
      get: function() {
        if (this._m_sizeRootDir !== undefined)
          return this._m_sizeRootDir;
        this._m_sizeRootDir = (this.lsPerRootDir * this.bpb.bytesPerLs);
        return this._m_sizeRootDir;
      }
    });

    /**
     * Basic BIOS parameter block, present in all versions of FAT
     */

    /**
     * FAT12/16-specific extended BIOS parameter block
     */

    /**
     * FAT32-specific extended BIOS parameter block
     */

    return BootSector;
  })();

  var BiosParamBlock = Vfat.BiosParamBlock = (function() {
    function BiosParamBlock(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    BiosParamBlock.prototype._read = function() {
      this.bytesPerLs = this._io.readU2le();
      this.lsPerClus = this._io.readU1();
      this.numReservedLs = this._io.readU2le();
      this.numFats = this._io.readU1();
      this.maxRootDirRec = this._io.readU2le();
      this.totalLs2 = this._io.readU2le();
      this.mediaCode = this._io.readU1();
      this.lsPerFat = this._io.readU2le();
      this.psPerTrack = this._io.readU2le();
      this.numHeads = this._io.readU2le();
      this.numHiddenSectors = this._io.readU4le();
      this.totalLs4 = this._io.readU4le();
    }

    /**
     * Bytes per logical sector
     */

    /**
     * Logical sectors per cluster
     */

    /**
     * Count of reserved logical sectors. The number of logical
     * sectors before the first FAT in the file system image.
     */

    /**
     * Number of File Allocation Tables
     */

    /**
     * Maximum number of FAT12 or FAT16 root directory entries. 0
     * for FAT32, where the root directory is stored in ordinary
     * data clusters.
     */

    /**
     * Total logical sectors (if zero, use total_ls_4)
     */

    /**
     * Media descriptor
     */

    /**
     * Logical sectors per File Allocation Table for
     * FAT12/FAT16. FAT32 sets this to 0 and uses the 32-bit value
     * at offset 0x024 instead.
     */

    /**
     * Physical sectors per track for disks with INT 13h CHS
     * geometry, e.g., 15 for a "1.20 MB" (1200 KB) floppy. A zero
     * entry indicates that this entry is reserved, but not used.
     */

    /**
     * Number of heads for disks with INT 13h CHS geometry,[9]
     * e.g., 2 for a double sided floppy.
     */

    /**
     * Number of hidden sectors preceding the partition that
     * contains this FAT volume. This field should always be zero
     * on media that are not partitioned. This DOS 3.0 entry is
     * incompatible with a similar entry at offset 0x01C in BPBs
     * since DOS 3.31.  It must not be used if the logical sectors
     * entry at offset 0x013 is zero.
     */

    /**
     * Total logical sectors including hidden sectors. This DOS 3.2
     * entry is incompatible with a similar entry at offset 0x020
     * in BPBs since DOS 3.31. It must not be used if the logical
     * sectors entry at offset 0x013 is zero.
     */

    return BiosParamBlock;
  })();

  var RootDirectoryRec = Vfat.RootDirectoryRec = (function() {
    function RootDirectoryRec(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    RootDirectoryRec.prototype._read = function() {
      this.fileName = this._io.readBytes(11);
      this._raw_attrs = this._io.readBytes(1);
      var _io__raw_attrs = new KaitaiStream(this._raw_attrs);
      this.attrs = new AttrFlags(_io__raw_attrs, this, this._root);
      this.reserved = this._io.readBytes(10);
      this._raw_lastWriteTime = this._io.readBytes(4);
      var _io__raw_lastWriteTime = new KaitaiStream(this._raw_lastWriteTime);
      this.lastWriteTime = new DosDatetime(_io__raw_lastWriteTime, this, null);
      this.startClus = this._io.readU2le();
      this.fileSize = this._io.readU4le();
    }

    var AttrFlags = RootDirectoryRec.AttrFlags = (function() {
      function AttrFlags(_io, _parent, _root) {
        this._io = _io;
        this._parent = _parent;
        this._root = _root || this;

        this._read();
      }
      AttrFlags.prototype._read = function() {
        this.readOnly = this._io.readBitsIntLe(1) != 0;
        this.hidden = this._io.readBitsIntLe(1) != 0;
        this.system = this._io.readBitsIntLe(1) != 0;
        this.volumeId = this._io.readBitsIntLe(1) != 0;
        this.isDirectory = this._io.readBitsIntLe(1) != 0;
        this.archive = this._io.readBitsIntLe(1) != 0;
        this.reserved = this._io.readBitsIntLe(2);
      }
      Object.defineProperty(AttrFlags.prototype, 'longName', {
        get: function() {
          if (this._m_longName !== undefined)
            return this._m_longName;
          this._m_longName =  ((this.readOnly) && (this.hidden) && (this.system) && (this.volumeId)) ;
          return this._m_longName;
        }
      });

      return AttrFlags;
    })();

    return RootDirectoryRec;
  })();

  var RootDirectory = Vfat.RootDirectory = (function() {
    function RootDirectory(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    RootDirectory.prototype._read = function() {
      this.records = new Array(this._root.bootSector.bpb.maxRootDirRec);
      for (var i = 0; i < this._root.bootSector.bpb.maxRootDirRec; i++) {
        this.records[i] = new RootDirectoryRec(this._io, this, this._root);
      }
    }

    return RootDirectory;
  })();

  /**
   * Extended BIOS Parameter Block (DOS 4.0+, OS/2 1.0+). Used only
   * for FAT12 and FAT16.
   */

  var ExtBiosParamBlockFat16 = Vfat.ExtBiosParamBlockFat16 = (function() {
    function ExtBiosParamBlockFat16(_io, _parent, _root) {
      this._io = _io;
      this._parent = _parent;
      this._root = _root || this;

      this._read();
    }
    ExtBiosParamBlockFat16.prototype._read = function() {
      this.physDriveNum = this._io.readU1();
      this.reserved1 = this._io.readU1();
      this.extBootSign = this._io.readU1();
      this.volumeId = this._io.readBytes(4);
      this.partitionVolumeLabel = KaitaiStream.bytesToStr(KaitaiStream.bytesStripRight(this._io.readBytes(11), 32), "ASCII");
      this.fsTypeStr = KaitaiStream.bytesToStr(KaitaiStream.bytesStripRight(this._io.readBytes(8), 32), "ASCII");
    }

    /**
     * Physical drive number (0x00 for (first) removable media,
     * 0x80 for (first) fixed disk as per INT 13h).
     */

    /**
     * Should be 0x29 to indicate that an EBPB with the following 3
     * entries exists.
     */

    /**
     * Volume ID (serial number).
     * 
     * Typically the serial number "xxxx-xxxx" is created by a
     * 16-bit addition of both DX values returned by INT 21h/AH=2Ah
     * (get system date) and INT 21h/AH=2Ch (get system time) for
     * the high word and another 16-bit addition of both CX values
     * for the low word of the serial number. Alternatively, some
     * DR-DOS disk utilities provide a /# option to generate a
     * human-readable time stamp "mmdd-hhmm" build from BCD-encoded
     * 8-bit values for the month, day, hour and minute instead of
     * a serial number.
     */

    return ExtBiosParamBlockFat16;
  })();
  Object.defineProperty(Vfat.prototype, 'fats', {
    get: function() {
      if (this._m_fats !== undefined)
        return this._m_fats;
      var _pos = this._io.pos;
      this._io.seek(this.bootSector.posFats);
      this._m_fats = new Array(this.bootSector.bpb.numFats);
      for (var i = 0; i < this.bootSector.bpb.numFats; i++) {
        this._m_fats[i] = this._io.readBytes(this.bootSector.sizeFat);
      }
      this._io.seek(_pos);
      return this._m_fats;
    }
  });
  Object.defineProperty(Vfat.prototype, 'rootDir', {
    get: function() {
      if (this._m_rootDir !== undefined)
        return this._m_rootDir;
      var _pos = this._io.pos;
      this._io.seek(this.bootSector.posRootDir);
      this._raw__m_rootDir = this._io.readBytes(this.bootSector.sizeRootDir);
      var _io__raw__m_rootDir = new KaitaiStream(this._raw__m_rootDir);
      this._m_rootDir = new RootDirectory(_io__raw__m_rootDir, this, this._root);
      this._io.seek(_pos);
      return this._m_rootDir;
    }
  });

  return Vfat;
})();
return Vfat;
}));