dom/bindings/SimpleGlobalObject.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /**
   8  * A simplere nsIGlobalObject implementation that can be used to set up a new
   9  * global without anything interesting in it other than the JS builtins.  This
  10  * is safe to use on both mainthread and worker threads.
  11  */
  12
  13 #ifndef mozilla_dom_SimpleGlobalObject_h__
  14 #define mozilla_dom_SimpleGlobalObject_h__
  15
  16 #include "nsContentUtils.h"
  17 #include "nsIGlobalObject.h"
  18 #include "nsWrapperCache.h"
  19 #include "js/TypeDecls.h"
  20 #include "js/Value.h"
  21 #include "nsISupportsImpl.h"
  22 #include "nsCycleCollectionParticipant.h"
  23
  24 namespace mozilla::dom {
  25
  26 class SimpleGlobalObject : public nsIGlobalObject, public nsWrapperCache {
  27  public:
  28   enum class GlobalType {
  29     BindingDetail,  // Should only be used by DOM bindings code.
  30     WorkerDebuggerSandbox,
  31     NotSimpleGlobal  // Sentinel to be used by BasicGlobalType.
  32   };
  33
  34   // Create a new JS global object that can be used to do some work.  This
  35   // global will NOT have any DOM APIs exposed in it, will not be visible to the
  36   // debugger, and will not have a useful concept of principals, so don't try to
  37   // use it with any DOM objects.  Apart from that, running code with
  38   // side-effects is safe in this global.  Importantly, when you are first
  39   // handed this global it's guaranteed to have pristine built-ins.  The
  40   // corresponding nsIGlobalObject* for this global object will be a
  41   // SimpleGlobalObject of the type provided; JS::GetPrivate on the returned
  42   // JSObject* will return the SimpleGlobalObject*.
  43   //
  44   // If the provided prototype value is undefined, it is ignored.  If it's an
  45   // object or null, it's set as the prototype of the created global.  If it's
  46   // anything else, this function returns null.
  47   //
  48   // Note that creating new globals is not cheap and should not be done
  49   // gratuitously.  Please think carefully before you use this function.
  50   static JSObject* Create(GlobalType globalType, JS::Handle<JS::Value> proto =
  51                                                      JS::UndefinedHandleValue);
  52
  53   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
  54   NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(SimpleGlobalObject)
  55
  56   // Gets the GlobalType of this SimpleGlobalObject.
  57   GlobalType Type() const { return mType; }
  58
  59   // Gets the GlobalType of the SimpleGlobalObject for the given JSObject*, if
  60   // the given JSObject* is the global corresponding to a SimpleGlobalObject.
  61   // Oherwise, returns GlobalType::NotSimpleGlobal.
  62   static GlobalType SimpleGlobalType(JSObject* obj);
  63
  64   JSObject* GetGlobalJSObject() override { return GetWrapper(); }
  65   JSObject* GetGlobalJSObjectPreserveColor() const override {
  66     return GetWrapperPreserveColor();
  67   }
  68
  69   OriginTrials Trials() const override { return {}; }
  70
  71   JSObject* WrapObject(JSContext* cx,
  72                        JS::Handle<JSObject*> aGivenProto) override {
  73     MOZ_CRASH("SimpleGlobalObject doesn't use DOM bindings!");
  74   }
  75
  76   bool ShouldResistFingerprinting(RFPTarget aTarget) const override {
  77     return nsContentUtils::ShouldResistFingerprinting(
  78         "Presently we don't have enough context to make an informed decision"
  79         "on JS Sandboxes. See 1782853",
  80         aTarget);
  81   }
  82
  83  private:
  84   SimpleGlobalObject(JSObject* global, GlobalType type) : mType(type) {
  85     SetWrapper(global);
  86   }
  87
  88   virtual ~SimpleGlobalObject() { MOZ_ASSERT(!GetWrapperMaybeDead()); }
  89
  90   const GlobalType mType;
  91 };
  92
  93 }  // namespace mozilla::dom
  94
  95 #endif /* mozilla_dom_SimpleGlobalObject_h__ */