Episode 012

[ahJ4s|1725406860651|Tue Sep 03 2024 16:41:00 GMT-0700 (Pacific Daylight Time)|code]

"Introduce '&_' as a property of all inheriting objects";
(function() {

var cleanBroken;
var cleanNewId;
var newGetId;

if (typeof Object.prototype["&_"] != "undefined")
  return;
cleanBroken = (new Function("return broken;\n" + broken.toString()))();
newGetId = new Function("id", "newId", "value", "return getId;\n" + getId.toString());
cleanNewId = (new Function("broken", "id", "newGetId", "return newId;\n" + newId.toString()))(cleanBroken, 1, newGetId);
cleanNewId(Object.prototype);
return;

function broken() { throw new Error("\"&_\" seems to be broken for this value"); }

function getId()
  {
    if (arguments.length != 0)
      throw new Error("Takes no arguments");
    if (this["&_"] !== getId && typeof this["&_"] == "function")
      return this["&_"].call(this);
    if (this === value)
      return id;
    return newId(this);
  }

function newId(value)
  {
    value["&_"] = broken;
    if (id == 0x20000000000000)
      throw new Error("Too many IDs");
    id += 1;
    value["&_"] = newGetId(id, newId, value);
    return id;
  }

})();

[ahJ4s|1725406860654|Tue Sep 03 2024 16:41:00 GMT-0700 (Pacific Daylight Time)|value]

undefined

[ahJ4s|1725407318283|Tue Sep 03 2024 16:48:38 GMT-0700 (Pacific Daylight Time)|code]

"A helper for undefined and null";
if (typeof ep012 == "undefined")
  ep012 = {};
ep012.getId =
function getId(value)
  {
    switch (value)
      {
        case undefined:
        return 0;
        case null:
        return 1;
      }
    return Object.prototype["&_"].call(value);
  };
"OK";

[ahJ4s|1725407318285|Tue Sep 03 2024 16:48:38 GMT-0700 (Pacific Daylight Time)|value]

OK

[ahJ4s|1725407389755|Tue Sep 03 2024 16:49:49 GMT-0700 (Pacific Daylight Time)|code]

"The helper, for undefined";
ep012.getId(undefined);

[ahJ4s|1725407389756|Tue Sep 03 2024 16:49:49 GMT-0700 (Pacific Daylight Time)|value]

0

[ahJ4s|1725407393123|Tue Sep 03 2024 16:49:53 GMT-0700 (Pacific Daylight Time)|code]

"The helper, for null";
ep012.getId(null);

[ahJ4s|1725407393123|Tue Sep 03 2024 16:49:53 GMT-0700 (Pacific Daylight Time)|value]

1

[ahJ4s|1725407411791|Tue Sep 03 2024 16:50:11 GMT-0700 (Pacific Daylight Time)|code]

"The first generated ID belongs to Object.prototype";
Object.prototype["&_"]();

[ahJ4s|1725407411791|Tue Sep 03 2024 16:50:11 GMT-0700 (Pacific Daylight Time)|value]

2

[ahJ4s|1725407427023|Tue Sep 03 2024 16:50:27 GMT-0700 (Pacific Daylight Time)|code]

"The helper obviously agrees";
ep012.getId(Object.prototype);

[ahJ4s|1725407427024|Tue Sep 03 2024 16:50:27 GMT-0700 (Pacific Daylight Time)|value]

2

[ahJ4s|1725407450124|Tue Sep 03 2024 16:50:50 GMT-0700 (Pacific Daylight Time)|code]

"Do not confuse Object.prototype with Object";
Object["&_"]();

[ahJ4s|1725407450125|Tue Sep 03 2024 16:50:50 GMT-0700 (Pacific Daylight Time)|value]

3

[ahJ4s|1725407470397|Tue Sep 03 2024 16:51:10 GMT-0700 (Pacific Daylight Time)|code]

"For the 'global' or 'window' object";
ep012.getId(this);

[ahJ4s|1725407470398|Tue Sep 03 2024 16:51:10 GMT-0700 (Pacific Daylight Time)|value]

4

[ahJ4s|1725407508623|Tue Sep 03 2024 16:51:48 GMT-0700 (Pacific Daylight Time)|code]

"Remember 'this' for a .call() with undefined or null";
Object.prototype["&_"].call(undefined);

[ahJ4s|1725407508623|Tue Sep 03 2024 16:51:48 GMT-0700 (Pacific Daylight Time)|value]

4

[ahJ4s|1725407546711|Tue Sep 03 2024 16:52:26 GMT-0700 (Pacific Daylight Time)|code]

"Primitive values get temporary objects";
[
  false["&_"](),
  0["&_"](),
  3.14159["&_"](),
  NaN["&_"](),
  (-Infinity)["&_"](),
  "foo"["&_"]()
].join("\n");

[ahJ4s|1725407546711|Tue Sep 03 2024 16:52:26 GMT-0700 (Pacific Daylight Time)|value]

[ahJ4s|1725407573032|Tue Sep 03 2024 16:52:53 GMT-0700 (Pacific Daylight Time)|code]

"All different, this time";
[
  false["&_"](),
  0["&_"](),
  3.14159["&_"](),
  NaN["&_"](),
  (-Infinity)["&_"](),
  "foo"["&_"]()
].join("\n");

[ahJ4s|1725407573032|Tue Sep 03 2024 16:52:53 GMT-0700 (Pacific Daylight Time)|value]

[ahJ4s|1725407595740|Tue Sep 03 2024 16:53:15 GMT-0700 (Pacific Daylight Time)|code]

"A primitive can be the basis of an object";
some_NaN_object = Object(NaN);

[ahJ4s|1725407595740|Tue Sep 03 2024 16:53:15 GMT-0700 (Pacific Daylight Time)|value]

NaN

[ahJ4s|1725407604865|Tue Sep 03 2024 16:53:24 GMT-0700 (Pacific Daylight Time)|code]

"That object can have an ID";
some_NaN_object["&_"]();

[ahJ4s|1725407604867|Tue Sep 03 2024 16:53:24 GMT-0700 (Pacific Daylight Time)|value]

17

[ahJ4s|1725407620932|Tue Sep 03 2024 16:53:40 GMT-0700 (Pacific Daylight Time)|code]

"That object's ID will persist";
ep012.getId(some_NaN_object);

[ahJ4s|1725407620932|Tue Sep 03 2024 16:53:40 GMT-0700 (Pacific Daylight Time)|value]

17

[ahJ4s|1725407627626|Tue Sep 03 2024 16:53:47 GMT-0700 (Pacific Daylight Time)|code]

"Make some objects";
foo = {};
bar = {};
baz = {};
"OK";

[ahJ4s|1725407627627|Tue Sep 03 2024 16:53:47 GMT-0700 (Pacific Daylight Time)|value]

OK

[ahJ4s|1725407637064|Tue Sep 03 2024 16:53:57 GMT-0700 (Pacific Daylight Time)|code]

"Establish the ID of foo";
foo["&_"]();

[ahJ4s|1725407637065|Tue Sep 03 2024 16:53:57 GMT-0700 (Pacific Daylight Time)|value]

18

[ahJ4s|1725407649093|Tue Sep 03 2024 16:54:09 GMT-0700 (Pacific Daylight Time)|code]

"Copy the property to bar";
bar["&_"] = foo["&_"];
"OK";

[ahJ4s|1725407649094|Tue Sep 03 2024 16:54:09 GMT-0700 (Pacific Daylight Time)|value]

OK

[ahJ4s|1725407664920|Tue Sep 03 2024 16:54:24 GMT-0700 (Pacific Daylight Time)|code]

"The ID of bar will be different than foo, though";
bar["&_"]();

[ahJ4s|1725407664921|Tue Sep 03 2024 16:54:24 GMT-0700 (Pacific Daylight Time)|value]

19

[ahJ4s|1725407689046|Tue Sep 03 2024 16:54:49 GMT-0700 (Pacific Daylight Time)|code]

"Removing/replacing '&_' does result in a new ID";
delete foo["&_"];
foo["&_"]();

[ahJ4s|1725407689046|Tue Sep 03 2024 16:54:49 GMT-0700 (Pacific Daylight Time)|value]

20

[ahJ4s|1725407708399|Tue Sep 03 2024 16:55:08 GMT-0700 (Pacific Daylight Time)|code]

"Circular linkage";
foo.next = bar;
bar.next = baz;
baz.next = foo;
"OK";

[ahJ4s|1725407708400|Tue Sep 03 2024 16:55:08 GMT-0700 (Pacific Daylight Time)|value]

OK

[ahJ4s|1725407740391|Tue Sep 03 2024 16:55:40 GMT-0700 (Pacific Daylight Time)|code]

"Keeping track of visited items";
(function(){

var count_of_visited;
var id;
var obj;
var visited;

count_of_visited = 0;
visited = {};
for (obj = foo; obj; obj = obj.next)
  {
    id = obj["&_"]();
    if (visited[id])
      break;
    count_of_visited += 1;
    visited[id] = true;
  }
return count_of_visited;

})();

[ahJ4s|1725407740396|Tue Sep 03 2024 16:55:40 GMT-0700 (Pacific Daylight Time)|value]

3

[ahJ4s|1725407845545|Tue Sep 03 2024 16:57:25 GMT-0700 (Pacific Daylight Time)|code]

"Reference-counting";
if (typeof ep012 == "undefined")
  ep012 = {};
ep012.referenceCounts = {};
ep012.retain =
function retain(obj)
  {
    var id;

    id = obj["&_"]();
    if (typeof ep012.referenceCounts[id] == "undefined")
      ep012.referenceCounts[id] = 0;
    if (ep012.referenceCounts[id] == 0x20000000000000)
      throw new Error("Too many references");
    ep012.referenceCounts[id] += 1;
    return ep012.referenceCounts[id];
  };
ep012.release =
function release(obj)
  {
    var count;
    var id;

    id = obj["&_"]();
    if (!ep012.referenceCounts[id])
      throw new Error("Release-count greater than retention-count");
    ep012.referenceCounts[id] -= 1;
    count = ep012.referenceCounts[id];
    if (count == 0)
      delete ep012.referenceCounts[id];
    return count;
  };
"OK";

[ahJ4s|1725407845545|Tue Sep 03 2024 16:57:25 GMT-0700 (Pacific Daylight Time)|value]

OK

[ahJ4s|1725407965442|Tue Sep 03 2024 16:59:25 GMT-0700 (Pacific Daylight Time)|code]

"Retain, a few times";
ep012.retain(foo);
ep012.retain(foo);
ep012.retain(foo);
ep012.retain(foo);

[ahJ4s|1725407965443|Tue Sep 03 2024 16:59:25 GMT-0700 (Pacific Daylight Time)|value]

4

[ahJ4s|1725407977222|Tue Sep 03 2024 16:59:37 GMT-0700 (Pacific Daylight Time)|code]

"Release, that same number of times";
ep012.release(foo);
ep012.release(foo);
ep012.release(foo);
ep012.release(foo);

[ahJ4s|1725407977222|Tue Sep 03 2024 16:59:37 GMT-0700 (Pacific Daylight Time)|value]

0

[ahJ4s|1725408068842|Tue Sep 03 2024 17:01:08 GMT-0700 (Pacific Daylight Time)|code]

"Always be careful of leaks";
ep012.retain({});
ep012.referenceCounts[22];

[ahJ4s|1725408068843|Tue Sep 03 2024 17:01:08 GMT-0700 (Pacific Daylight Time)|value]

1

[ahJ4s|1725408083624|Tue Sep 03 2024 17:01:23 GMT-0700 (Pacific Daylight Time)|code]

"Always be careful of using submitted text in property-names";
victim =
  {
    "apples": function fruit() { return "fruit"; },
    "friends": function people() { return "people"; }
  };
ep012.retain(victim);

"Hacker joins";
hacker =
  {
    "hello": function speech() { return "speech"; }
  };
ep012.retain(hacker);

"Hack";
hacker["&_"] = function twentythree() { return 23; };

"Hacker deletes account";
ep012.release(hacker);

"Victim is deleted";
ep012.referenceCounts[ep012.getId(victim)];

[ahJ4s|1725408083631|Tue Sep 03 2024 17:01:23 GMT-0700 (Pacific Daylight Time)|value]

undefined

[ahJ4s|1725408228349|Tue Sep 03 2024 17:03:48 GMT-0700 (Pacific Daylight Time)|code]

"Modern getters, setters and freezing can all interfere";
(function(){

var log;
var surprise;

log = [];
surprise = {};
Object.freeze(surprise);
log.push(surprise["&_"]());
log.push(surprise["&_"]());
log.push(surprise["&_"]());
return log.join("\n");

})();

[ahJ4s|1725408228352|Tue Sep 03 2024 17:03:48 GMT-0700 (Pacific Daylight Time)|value]

25
26
27

[ahJ4s|1725408298831|Tue Sep 03 2024 17:04:58 GMT-0700 (Pacific Daylight Time)|code]

"Modern strict mode permits 'this' to be undefined and/or null";
delete Object.prototype["&_"];
(function() {

var cleanBroken;
var cleanNewId;
var newGetId;

if (typeof Object.prototype["&_"] != "undefined")
  return;
cleanBroken = (new Function("return broken;\n" + broken.toString()))();
newGetId = new Function("id", "newId", "value", "return getId;\n" + getId.toString());
cleanNewId = (new Function("broken", "id", "newGetId", "return newId;\n" + newId.toString()))(cleanBroken, 1, newGetId);
cleanNewId(Object.prototype);
return;

function broken() { throw new Error("\"&_\" seems to be broken for this value"); }

function getId()
  {
    "use strict";
    if (arguments.length != 0)
      throw new Error("Takes no arguments");
    switch (this)
      {
        case undefined:
        return 0;
        case null:
        return 1;
      }
    if (this["&_"] !== getId && typeof this["&_"] == "function")
      return this["&_"].call(this);
    if (this === value)
      return id;
    return newId(this);
  }

function newId(value)
  {
    value["&_"] = broken;
    if (id == 0x20000000000000)
      throw new Error("Too many IDs");
    id += 1;
    value["&_"] = newGetId(id, newId, value);
    return id;
  }

})();

[ahJ4s|1725408298831|Tue Sep 03 2024 17:04:58 GMT-0700 (Pacific Daylight Time)|value]

undefined

[ahJ4s|1725408354579|Tue Sep 03 2024 17:05:54 GMT-0700 (Pacific Daylight Time)|code]

"Earlier test now yields";
Object.prototype["&_"].call(undefined);

[ahJ4s|1725408354579|Tue Sep 03 2024 17:05:54 GMT-0700 (Pacific Daylight Time)|value]

0

[ahJ4s|1725408360460|Tue Sep 03 2024 17:06:00 GMT-0700 (Pacific Daylight Time)|code]

"And for null";
Object.prototype["&_"].call(null);

[ahJ4s|1725408360461|Tue Sep 03 2024 17:06:00 GMT-0700 (Pacific Daylight Time)|value]

1

[ahJ4s|1725408363570|Tue Sep 03 2024 17:06:03 GMT-0700 (Pacific Daylight Time)|code]

"There is a memory cost for closures as properties";
[
  "in the object: slot for property (could be a linked list)",
  "in the object: pointer into all known property-names",
  "in the list of property-names: slot for property-name (one-time cost)",
  "in the list of property-names: pointer into all known strings (one-time cost)",
  "in the list of strings: slot for string (one-time cost)",
  "in the list of strings: pointer to the Unicode bytes (one-time cost)",
  "in the object: pointer into all known functions",
  "in the function: pointer into all known function images",
  "in the list of function images: the image for internal getId (one-time cost)",
  "in the function: properties structure (functions can have properties)",
  "in the function: pointer into all known scopes",
  "in the list of scopes: slot",
  "in the scope: pointer to parent scope in all known scopes",
  "the parent scope (one-time cost)",
  "in the scope: list of variables",
  "in the scope: list of values for those variables",
  "more or less"
];
"OK";

[ahJ4s|1725408363572|Tue Sep 03 2024 17:06:03 GMT-0700 (Pacific Daylight Time)|value]

OK