ruby_marshal: JavaScript parsing library

Ruby's Marshal module allows serialization and deserialization of many standard and arbitrary Ruby objects in a compact binary format. It is relatively fast, available in stdlibs standard and allows conservation of language-specific properties (such as symbols or encoding-aware strings).

Feature-wise, it is comparable to other language-specific implementations, such as:

From internal perspective, serialized stream consists of a simple magic header and a record.

KS implementation details

License: CC0-1.0

This page hosts a formal specification of ruby_marshal 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 RubyMarshal(new KaitaiStream(arrayBuffer));

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

data.version // => get version

JavaScript source code to parse ruby_marshal

RubyMarshal.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'], factory);
  } else if (typeof module === 'object' && module.exports) {
    module.exports = factory(require('kaitai-struct/KaitaiStream'));
  } else {
    root.RubyMarshal = factory(root.KaitaiStream);
  }
}(this, function (KaitaiStream) {
/**
 * Ruby's Marshal module allows serialization and deserialization of
 * many standard and arbitrary Ruby objects in a compact binary
 * format. It is relatively fast, available in stdlibs standard and
 * allows conservation of language-specific properties (such as symbols
 * or encoding-aware strings).
 * 
 * Feature-wise, it is comparable to other language-specific
 * implementations, such as:
 * 
 * * Java's
 *   [Serializable](https://docs.oracle.com/javase/8/docs/api/java/io/Serializable.html)
 * * .NET
 *   [BinaryFormatter](https://docs.microsoft.com/en-us/dotnet/api/system.runtime.serialization.formatters.binary.binaryformatter)
 * * Python's
 *   [marshal](https://docs.python.org/3/library/marshal.html),
 *   [pickle](https://docs.python.org/3/library/pickle.html) and
 *   [shelve](https://docs.python.org/3/library/shelve.html)
 * 
 * From internal perspective, serialized stream consists of a simple
 * magic header and a record.
 * @see {@link https://docs.ruby-lang.org/en/2.4.0/marshal_rdoc.html#label-Stream+Format|Source}
 */

var RubyMarshal = (function() {
  RubyMarshal.Codes = Object.freeze({
    RUBY_STRING: 34,
    CONST_NIL: 48,
    RUBY_SYMBOL: 58,
    RUBY_SYMBOL_LINK: 59,
    RUBY_OBJECT_LINK: 64,
    CONST_FALSE: 70,
    INSTANCE_VAR: 73,
    RUBY_STRUCT: 83,
    CONST_TRUE: 84,
    RUBY_ARRAY: 91,
    PACKED_INT: 105,
    BIGNUM: 108,
    RUBY_HASH: 123,

    34: "RUBY_STRING",
    48: "CONST_NIL",
    58: "RUBY_SYMBOL",
    59: "RUBY_SYMBOL_LINK",
    64: "RUBY_OBJECT_LINK",
    70: "CONST_FALSE",
    73: "INSTANCE_VAR",
    83: "RUBY_STRUCT",
    84: "CONST_TRUE",
    91: "RUBY_ARRAY",
    105: "PACKED_INT",
    108: "BIGNUM",
    123: "RUBY_HASH",
  });

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

    this._read();
  }
  RubyMarshal.prototype._read = function() {
    this.version = this._io.readBytes(2);
    if (!((KaitaiStream.byteArrayCompare(this.version, [4, 8]) == 0))) {
      throw new KaitaiStream.ValidationNotEqualError([4, 8], this.version, this._io, "/seq/0");
    }
    this.records = new Record(this._io, this, this._root);
  }

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

      this._read();
    }
    RubyArray.prototype._read = function() {
      this.numElements = new PackedInt(this._io, this, this._root);
      this.elements = new Array(this.numElements.value);
      for (var i = 0; i < this.numElements.value; i++) {
        this.elements[i] = new Record(this._io, this, this._root);
      }
    }

    return RubyArray;
  })();

  /**
   * @see {@link https://docs.ruby-lang.org/en/2.4.0/marshal_rdoc.html#label-Bignum|Source}
   */

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

      this._read();
    }
    Bignum.prototype._read = function() {
      this.sign = this._io.readU1();
      this.lenDiv2 = new PackedInt(this._io, this, this._root);
      this.body = this._io.readBytes((this.lenDiv2.value * 2));
    }

    /**
     * A single byte containing `+` for a positive value or `-` for a negative value.
     */

    /**
     * Length of bignum body, divided by 2.
     */

    /**
     * Bytes that represent the number, see ruby-lang.org docs for reconstruction algorithm.
     */

    return Bignum;
  })();

  /**
   * @see {@link https://docs.ruby-lang.org/en/2.4.0/marshal_rdoc.html#label-Struct|Source}
   */

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

      this._read();
    }
    RubyStruct.prototype._read = function() {
      this.name = new Record(this._io, this, this._root);
      this.numMembers = new PackedInt(this._io, this, this._root);
      this.members = new Array(this.numMembers.value);
      for (var i = 0; i < this.numMembers.value; i++) {
        this.members[i] = new Pair(this._io, this, this._root);
      }
    }

    /**
     * Symbol containing the name of the struct.
     */

    /**
     * Number of members in a struct
     */

    return RubyStruct;
  })();

  /**
   * @see {@link https://docs.ruby-lang.org/en/2.4.0/marshal_rdoc.html#label-Symbols+and+Byte+Sequence|Source}
   */

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

      this._read();
    }
    RubySymbol.prototype._read = function() {
      this.len = new PackedInt(this._io, this, this._root);
      this.name = KaitaiStream.bytesToStr(this._io.readBytes(this.len.value), "UTF-8");
    }

    return RubySymbol;
  })();

  /**
   * Ruby uses sophisticated system to pack integers: first `code`
   * byte either determines packing scheme or carries encoded
   * immediate value (thus allowing smaller values from -123 to 122
   * (inclusive) to take only one byte. There are 11 encoding schemes
   * in total:
   * 
   * * 0 is encoded specially (as 0)
   * * 1..122 are encoded as immediate value with a shift
   * * 123..255 are encoded with code of 0x01 and 1 extra byte
   * * 0x100..0xffff are encoded with code of 0x02 and 2 extra bytes
   * * 0x10000..0xffffff are encoded with code of 0x03 and 3 extra
   *   bytes
   * * 0x1000000..0xffffffff are encoded with code of 0x04 and 4
   *   extra bytes
   * * -123..-1 are encoded as immediate value with another shift
   * * -256..-124 are encoded with code of 0xff and 1 extra byte
   * * -0x10000..-257 are encoded with code of 0xfe and 2 extra bytes
   * * -0x1000000..0x10001 are encoded with code of 0xfd and 3 extra
   *    bytes
   * * -0x40000000..-0x1000001 are encoded with code of 0xfc and 4
   *    extra bytes
   * 
   * Values beyond that are serialized as bignum (even if they
   * technically might be not Bignum class in Ruby implementation,
   * i.e. if they fit into 64 bits on a 64-bit platform).
   * @see {@link https://docs.ruby-lang.org/en/2.4.0/marshal_rdoc.html#label-Fixnum+and+long|Source}
   */

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

      this._read();
    }
    PackedInt.prototype._read = function() {
      this.code = this._io.readU1();
      switch (this.code) {
      case 4:
        this.encoded = this._io.readU4le();
        break;
      case 1:
        this.encoded = this._io.readU1();
        break;
      case 252:
        this.encoded = this._io.readU4le();
        break;
      case 253:
        this.encoded = this._io.readU2le();
        break;
      case 3:
        this.encoded = this._io.readU2le();
        break;
      case 2:
        this.encoded = this._io.readU2le();
        break;
      case 255:
        this.encoded = this._io.readU1();
        break;
      case 254:
        this.encoded = this._io.readU2le();
        break;
      }
      switch (this.code) {
      case 3:
        this.encoded2 = this._io.readU1();
        break;
      case 253:
        this.encoded2 = this._io.readU1();
        break;
      }
    }
    Object.defineProperty(PackedInt.prototype, 'isImmediate', {
      get: function() {
        if (this._m_isImmediate !== undefined)
          return this._m_isImmediate;
        this._m_isImmediate =  ((this.code > 4) && (this.code < 252)) ;
        return this._m_isImmediate;
      }
    });
    Object.defineProperty(PackedInt.prototype, 'value', {
      get: function() {
        if (this._m_value !== undefined)
          return this._m_value;
        this._m_value = (this.isImmediate ? (this.code < 128 ? (this.code - 5) : (4 - (~(this.code) & 127))) : (this.code == 0 ? 0 : (this.code == 255 ? (this.encoded - 256) : (this.code == 254 ? (this.encoded - 65536) : (this.code == 253 ? (((this.encoded2 << 16) | this.encoded) - 16777216) : (this.code == 3 ? ((this.encoded2 << 16) | this.encoded) : this.encoded))))));
        return this._m_value;
      }
    });

    /**
     * One extra byte for 3-byte integers (0x03 and 0xfd), as
     * there is no standard `u3` type in KS.
     */

    return PackedInt;
  })();

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

      this._read();
    }
    Pair.prototype._read = function() {
      this.key = new Record(this._io, this, this._root);
      this.value = new Record(this._io, this, this._root);
    }

    return Pair;
  })();

  /**
   * @see {@link https://docs.ruby-lang.org/en/2.4.0/marshal_rdoc.html#label-Instance+Variables|Source}
   */

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

      this._read();
    }
    InstanceVar.prototype._read = function() {
      this.obj = new Record(this._io, this, this._root);
      this.numVars = new PackedInt(this._io, this, this._root);
      this.vars = new Array(this.numVars.value);
      for (var i = 0; i < this.numVars.value; i++) {
        this.vars[i] = new Pair(this._io, this, this._root);
      }
    }

    return InstanceVar;
  })();

  /**
   * Each record starts with a single byte that determines its type
   * (`code`) and contents. If necessary, additional info as parsed
   * as `body`, to be determined by `code`.
   */

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

      this._read();
    }
    Record.prototype._read = function() {
      this.code = this._io.readU1();
      switch (this.code) {
      case RubyMarshal.Codes.PACKED_INT:
        this.body = new PackedInt(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.BIGNUM:
        this.body = new Bignum(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.RUBY_ARRAY:
        this.body = new RubyArray(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.RUBY_SYMBOL_LINK:
        this.body = new PackedInt(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.RUBY_STRUCT:
        this.body = new RubyStruct(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.RUBY_STRING:
        this.body = new RubyString(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.INSTANCE_VAR:
        this.body = new InstanceVar(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.RUBY_HASH:
        this.body = new RubyHash(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.RUBY_SYMBOL:
        this.body = new RubySymbol(this._io, this, this._root);
        break;
      case RubyMarshal.Codes.RUBY_OBJECT_LINK:
        this.body = new PackedInt(this._io, this, this._root);
        break;
      }
    }

    return Record;
  })();

  /**
   * @see {@link https://docs.ruby-lang.org/en/2.4.0/marshal_rdoc.html#label-Hash+and+Hash+with+Default+Value|Source}
   */

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

      this._read();
    }
    RubyHash.prototype._read = function() {
      this.numPairs = new PackedInt(this._io, this, this._root);
      this.pairs = new Array(this.numPairs.value);
      for (var i = 0; i < this.numPairs.value; i++) {
        this.pairs[i] = new Pair(this._io, this, this._root);
      }
    }

    return RubyHash;
  })();

  /**
   * @see {@link https://docs.ruby-lang.org/en/2.4.0/marshal_rdoc.html#label-String|Source}
   */

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

      this._read();
    }
    RubyString.prototype._read = function() {
      this.len = new PackedInt(this._io, this, this._root);
      this.body = this._io.readBytes(this.len.value);
    }

    return RubyString;
  })();

  return RubyMarshal;
})();
return RubyMarshal;
}));