Subj : Re: object serialization
To   : netscape.public.mozilla.jseng
From : Jens Thiele <karme@unforgettable.com>
Date : Fri Mar 26 2004 01:12 am

a first hack to get serialization working in "pure" javascript
- intended for "pure" javascript objects)
- keeping the prototype (__proto__ field) right
- keep graph relationships
the hash function is shit - is there any way to get a hashvalue for
an object (perhaps based on its pointer/reference)?

karme


// a first object serializer hack
// based on code from Daniel Fournier  ( thanks!)

// todo this is shit
function hashfunc(obj,key,depth) {
  /*  if (!key) key='';
  if (!depth) depth=0;
  var i,t;
  for (i in obj) {
    key+=i;
    t=typeof(obj[i]);
    key+=t.substring(0,1);
    if (t == 'string') key+=obj[i].substring(0,3);
    if (t == 'number') key+=obj[i];
    else if ((depth<3)&&(t == 'object')) key+=hashfunc(obj[i],key,depth+1);
    if (key.length>60) return key;
  }
  return key;*/
  return obj.toSource();
}

function emptyproto(p) {
  for (a in p) return false;
  return true;
}

function Serializer() {};

// enter new scope
Serializer.prototype._push=function(v){
  this.scope.push(v);
  this.fqscope+=v;
}
// leave scope
Serializer.prototype._pop=function(){
  this.scope.pop();
  var r='';
  for (var i=0;i<this.scope.length;++i) {
    r+=this.scope[i];
  }
  this.fqscope=r;
}

// this object has been serialized
Serializer.prototype._serialized=function(obj){
  var key=hashfunc(obj);
  var slot=this._hash[key];
  if (!slot) slot=this._hash[key]=[];
  slot.push({o:obj,s:this.fqscope});
}
// is this object already serialized?
Serializer.prototype._getSerialized=function(obj){
  var key=hashfunc(obj);
  var slot=this._hash[key];
  if (!slot) return false;
  for (var i=0;i<slot.length;++i) {
    if (slot[i].o==obj) {
      return slot[i].s;
    }
  }
  return false;
}

Serializer.prototype.serialize=function(object, id){
  if (!object) throw "object required";
  if (!id) throw "id required";
  this.scope=[];
  this.fqscope='';
  this._push(id);
  this.append="";
  this._hash=[];
  var res=id + "=" + this._serialize(object)+";\n"+this.append;

  // debug hashfunc
  /*  var key,slot,c,ctotal=0;
  for (key in this._hash) {
    c=-1;
    for (slot in this._hash[key]) c++;
    ctotal+=c;
    print ("key: "+key+" collisions:"+c);
  }
  print ("total collisions:"+ctotal);
  */
  return res;
}

Serializer.prototype._serialize=function(object){
  var ot=typeof(object);
  if (ot == 'string') {
    this._pop();
    return "'" + object + "'";
  }
  if (ot == 'function') {
    this._serialized(object);
    this._pop();
    return object.toString();
  }
  if (ot != 'object') {
    // numbers, booleans
    this._pop();
    return object;
  }

  // i don't need to serialize dates
  // if (object instanceof Date) {
  //     this._serialized(object);
  //     this._pop();
  //     return object.toSource();
  //     }

  this._serialized(object);

  var closeSymbol, objectString = '', stored = '';
  if (object instanceof Array) {
    // array
    closeSymbol = ']';
    objectString += '[';
    var c=0;
    for (var k in object) {
      if ((stored=this._getSerialized(object[k])))
	this.append+=this.fqscope+"["+k+"]="+stored+";\n";
      else{
	if (c>0) objectString+=',';
	c++;
	this._push("["+k+"]");
	objectString += this._serialize(object[k]);
      }
    }
  } else {
    // object
    closeSymbol = '}';
    objectString += '{';
    var c=0;
    for (var k in object) {
      // test if this member comes from our prototype
      if (object.__proto__[k]!=object[k]) {
	if ((stored=this._getSerialized(object[k])))
	  this.append+=this.fqscope+"."+k+"="+stored+";\n";
	else{
	  if (c>0) objectString+=',';
	  c++;
	  this._push("."+k);
	  objectString += k + ':' + this._serialize(object[k]);
	}
      }
    }
    // serialize prototype
    if ((object.__proto__)&&(!emptyproto(object.__proto__))) {
      if ((stored=this._getSerialized(object.__proto__)))
	this.append+=this.fqscope+".__proto__="+stored+";\n";
      else{
	if (c>0) objectString+=',';
	c++;
	this._push(".__proto__");
	objectString += "__proto__" + ':' + this._serialize(object.__proto__);
      }
    }
  }
  objectString += closeSymbol;
  this._pop();
  return objectString;
}

// graph test
foo={a:4};
graph={x:foo, y:foo};
eval(new Serializer().serialize(graph, 'graph2'));
graph2.x.a=77;
// should print 77
print((graph2.y.a==77) ? "Test passed" : "Test failed");

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