The Tor Browser: addon-sdk/source/lib/method/core.js@ac0c01689b40 (annotated)

addon-sdk/source/lib/method/core.js@ac0c01689b40 (annotated)

addon-sdk/source/lib/method/core.js

Thu, 15 Jan 2015 15:59:08 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 15 Jan 2015 15:59:08 +0100
branch: TOR_BUG_9701
changeset 10: ac0c01689b40
permissions: -rw-r--r--

Implement a real Private Browsing Mode condition by changing the API/ABI;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 "use strict";
 var defineProperty = Object.defineProperty || function(object, name, property) {
   object[name] = property.value
   return object
 }
 // Shortcut for `Object.prototype.toString` for faster access.
 var typefy = Object.prototype.toString
 // Map to for jumping from typeof(value) to associated type prefix used
 // as a hash in the map of builtin implementations.
 var types = { "function": "Object", "object": "Object" }
 // Array is used to save method implementations for the host objects in order
 // to avoid extending them with non-primitive values that could cause leaks.
 var host = []
 // Hash map is used to save method implementations for builtin types in order
 // to avoid extending their prototypes. This also allows to share method
 // implementations for types across diff contexts / frames / compartments.
 var builtin = {}
 function Primitive() {}
 function ObjectType() {}
 ObjectType.prototype = new Primitive()
 function ErrorType() {}
 ErrorType.prototype = new ObjectType()
 var Default = builtin.Default = Primitive.prototype
 var Null = builtin.Null = new Primitive()
 var Void = builtin.Void = new Primitive()
 builtin.String = new Primitive()
 builtin.Number = new Primitive()
 builtin.Boolean = new Primitive()
 builtin.Object = ObjectType.prototype
 builtin.Error = ErrorType.prototype
 builtin.EvalError = new ErrorType()
 builtin.InternalError = new ErrorType()
 builtin.RangeError = new ErrorType()
 builtin.ReferenceError = new ErrorType()
 builtin.StopIteration = new ErrorType()
 builtin.SyntaxError = new ErrorType()
 builtin.TypeError = new ErrorType()
 builtin.URIError = new ErrorType()
 function Method(hint) {
   /**
   Private Method is a callable private name that dispatches on the first
   arguments same named Method:
       method(object, ...rest) => object[method](...rest)
   Optionally hint string may be provided that will be used in generated names
   to ease debugging.
   ## Example
       var foo = Method()
       // Implementation for any types
       foo.define(function(value, arg1, arg2) {
         // ...
       })
       // Implementation for a specific type
       foo.define(BarType, function(bar, arg1, arg2) {
         // ...
       })
   **/
   // Create an internal unique name if `hint` is provided it is used to
   // prefix name to ease debugging.
   var name = (hint || "") + "#" + Math.random().toString(32).substr(2)
   function dispatch(value) {
     // Method dispatches on type of the first argument.
     // If first argument is `null` or `void` associated implementation is
     // looked up in the `builtin` hash where implementations for built-ins
     // are stored.
     var type = null
     var method = value === null ? Null[name] :
                  value === void(0) ? Void[name] :
                  // Otherwise attempt to use method with a generated private
                  // `name` that is supposedly in the prototype chain of the
                  // `target`.
                  value[name] ||
                  // Otherwise assume it's one of the built-in type instances,
                  // in which case implementation is stored in a `builtin` hash.
                  // Attempt to find a implementation for the given built-in
                  // via constructor name and method name.
                  ((type = builtin[(value.constructor || "").name]) &&
                   type[name]) ||
                  // Otherwise assume it's a host object. For host objects
                  // actual method implementations are stored in the `host`
                  // array and only index for the implementation is stored
                  // in the host object's prototype chain. This avoids memory
                  // leaks that otherwise could happen when saving JS objects
                  // on host object.
                  host[value["!" + name] || void(0)] ||
                  // Otherwise attempt to lookup implementation for builtins by
                  // a type of the value. This basically makes sure that all
                  // non primitive values will delegate to an `Object`.
                  ((type = builtin[types[typeof(value)]]) && type[name])
     // If method implementation for the type is still not found then
     // just fallback for default implementation.
     method = method || Default[name]
     // If implementation is still not found (which also means there is no
     // default) just throw an error with a descriptive message.
     if (!method) throw TypeError("Type does not implements method: " + name)
     // If implementation was found then just delegate.
     return method.apply(method, arguments)
   }
   // Make `toString` of the dispatch return a private name, this enables
   // method definition without sugar:
   //
   //    var method = Method()
   //    object[method] = function() { /***/ }
   dispatch.toString = function toString() { return name }
   // Copy utility methods for convenient API.
   dispatch.implement = implementMethod
   dispatch.define = defineMethod
   return dispatch
 }
 // Create method shortcuts form functions.
 var defineMethod = function defineMethod(Type, lambda) {
   return define(this, Type, lambda)
 }
 var implementMethod = function implementMethod(object, lambda) {
   return implement(this, object, lambda)
 }
 // Define `implement` and `define` polymorphic methods to allow definitions
 // and implementations through them.
 var implement = Method("implement")
 var define = Method("define")
 function _implement(method, object, lambda) {
   /**
   Implements `Method` for the given `object` with a provided `implementation`.
   Calling `Method` with `object` as a first argument will dispatch on provided
   implementation.
   **/
   return defineProperty(object, method.toString(), {
     enumerable: false,
     configurable: false,
     writable: false,
     value: lambda
   })
 }
 function _define(method, Type, lambda) {
   /**
   Defines `Method` for the given `Type` with a provided `implementation`.
   Calling `Method` with a first argument of this `Type` will dispatch on
   provided `implementation`. If `Type` is a `Method` default implementation
   is defined. If `Type` is a `null` or `undefined` `Method` is implemented
   for that value type.
   **/
   // Attempt to guess a type via `Object.prototype.toString.call` hack.
   var type = Type && typefy.call(Type.prototype)
   // If only two arguments are passed then `Type` is actually an implementation
   // for a default type.
   if (!lambda) Default[method] = Type
   // If `Type` is `null` or `void` store implementation accordingly.
   else if (Type === null) Null[method] = lambda
   else if (Type === void(0)) Void[method] = lambda
   // If `type` hack indicates built-in type and type has a name us it to
   // store a implementation into associated hash. If hash for this type does
   // not exists yet create one.
   else if (type !== "[object Object]" && Type.name) {
     var Bulitin = builtin[Type.name] || (builtin[Type.name] = new ObjectType())
     Bulitin[method] = lambda
   }
   // If `type` hack indicates an object, that may be either object or any
   // JS defined "Class". If name of the constructor is `Object`, assume it's
   // built-in `Object` and store implementation accordingly.
   else if (Type.name === "Object")
     builtin.Object[method] = lambda
   // Host objects are pain!!! Every browser does some crazy stuff for them
   // So far all browser seem to not implement `call` method for host object
   // constructors. If that is a case here, assume it's a host object and
   // store implementation in a `host` array and store `index` in the array
   // in a `Type.prototype` itself. This avoids memory leaks that could be
   // caused by storing JS objects on a host objects.
   else if (Type.call === void(0)) {
     var index = host.indexOf(lambda)
     if (index < 0) index = host.push(lambda) - 1
     // Prefix private name with `!` so it can be dispatched from the method
     // without type checks.
     implement("!" + method, Type.prototype, index)
   }
   // If Got that far `Type` is user defined JS `Class`. Define private name
   // as hidden property on it's prototype.
   else
     implement(method, Type.prototype, lambda)
 }
 // And provided implementations for a polymorphic equivalents.
 _define(define, _define)
 _define(implement, _implement)
 // Define exports on `Method` as it's only thing being exported.
 Method.implement = implement
 Method.define = define
 Method.Method = Method
 Method.method = Method
 Method.builtin = builtin
 Method.host = host
 module.exports = Method