import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

dom/bindings/DOMJSClass.h

@@ -0,0 +1,467 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_DOMJSClass_h
+#define mozilla_dom_DOMJSClass_h
+
+#include "jsfriendapi.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/Likely.h"
+
+#include "mozilla/dom/PrototypeList.h" // auto-generated
+
+#include "mozilla/dom/JSSlots.h"
+
+class nsCycleCollectionParticipant;
+
+// All DOM globals must have a slot at DOM_PROTOTYPE_SLOT.
+#define DOM_PROTOTYPE_SLOT JSCLASS_GLOBAL_SLOT_COUNT
+
+// Keep this count up to date with any extra global slots added above.
+#define DOM_GLOBAL_SLOTS 1
+
+// We use these flag bits for the new bindings.
+#define JSCLASS_DOM_GLOBAL JSCLASS_USERBIT1
+#define JSCLASS_IS_DOMIFACEANDPROTOJSCLASS JSCLASS_USERBIT2
+
+namespace mozilla {
+namespace dom {
+
+/**
+ * Returns true if code running in the given JSContext is allowed to access
+ * [SecureContext] API on the given JSObject.
+ *
+ * [SecureContext] API exposure is restricted to use by code in a Secure
+ * Contexts:
+ *
+ *   https://w3c.github.io/webappsec-secure-contexts/
+ *
+ * Since we want [SecureContext] exposure to depend on the privileges of the
+ * running code (rather than the privileges of an object's creator), this
+ * function checks to see whether the given JSContext's Compartment is flagged
+ * as a Secure Context.  That allows us to make sure that system principal code
+ * (which is marked as a Secure Context) can access Secure Context API on an
+ * object in a different compartment, regardless of whether the other
+ * compartment is a Secure Context or not.
+ *
+ * Checking the JSContext's Compartment doesn't work for expanded principal
+ * globals accessing a Secure Context web page though (e.g. those used by frame
+ * scripts).  To handle that we fall back to checking whether the JSObject came
+ * from a Secure Context.
+ *
+ * Note: We'd prefer this function to live in BindingUtils.h, but we need to
+ * call it in this header, and BindingUtils.h includes us (i.e. we'd have a
+ * circular dependency between headers if it lived there).
+ */
+inline bool
+IsSecureContextOrObjectIsFromSecureContext(JSContext* aCx, JSObject* aObj)
+{
+  return JS::CompartmentCreationOptionsRef(js::GetContextCompartment(aCx)).secureContext() ||
+         JS::CompartmentCreationOptionsRef(js::GetObjectCompartment(aObj)).secureContext();
+}
+
+typedef bool
+(* ResolveOwnProperty)(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                       JS::Handle<JSObject*> obj, JS::Handle<jsid> id,
+                       JS::MutableHandle<JS::PropertyDescriptor> desc);
+
+typedef bool
+(* EnumerateOwnProperties)(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                           JS::Handle<JSObject*> obj,
+                           JS::AutoIdVector& props);
+
+typedef bool
+(* DeleteNamedProperty)(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                        JS::Handle<JSObject*> obj, JS::Handle<jsid> id,
+                        JS::ObjectOpResult& opresult);
+
+// Returns true if the given global is of a type whose bit is set in
+// aNonExposedGlobals.
+bool
+IsNonExposedGlobal(JSContext* aCx, JSObject* aGlobal,
+                   uint32_t aNonExposedGlobals);
+
+struct ConstantSpec
+{
+  const char* name;
+  JS::Value value;
+};
+
+typedef bool (*PropertyEnabled)(JSContext* cx, JSObject* global);
+
+namespace GlobalNames {
+// The names of our possible globals.  These are the names of the actual
+// interfaces, not of the global names used to refer to them in IDL [Exposed]
+// annotations.
+static const uint32_t Window = 1u << 0;
+static const uint32_t BackstagePass = 1u << 1;
+static const uint32_t DedicatedWorkerGlobalScope = 1u << 2;
+static const uint32_t SharedWorkerGlobalScope = 1u << 3;
+static const uint32_t ServiceWorkerGlobalScope = 1u << 4;
+static const uint32_t WorkerDebuggerGlobalScope = 1u << 5;
+static const uint32_t WorkletGlobalScope = 1u << 6;
+} // namespace GlobalNames
+
+struct PrefableDisablers {
+  inline bool isEnabled(JSContext* cx, JS::Handle<JSObject*> obj) const {
+    // Reading "enabled" on a worker thread is technically undefined behavior,
+    // because it's written only on main threads, with no barriers of any sort.
+    // So we want to avoid doing that.  But we don't particularly want to make
+    // expensive NS_IsMainThread calls here.
+    //
+    // The good news is that "enabled" is only written for things that have a
+    // Pref annotation, and such things can never be exposed on non-Window
+    // globals; our IDL parser enforces that.  So as long as we check our
+    // exposure set before checking "enabled" we will be ok.
+    if (nonExposedGlobals &&
+        IsNonExposedGlobal(cx, js::GetGlobalForObjectCrossCompartment(obj),
+                           nonExposedGlobals)) {
+      return false;
+    }
+    if (!enabled) {
+      return false;
+    }
+    if (secureContext && !IsSecureContextOrObjectIsFromSecureContext(cx, obj)) {
+      return false;
+    }
+    if (enabledFunc &&
+        !enabledFunc(cx, js::GetGlobalForObjectCrossCompartment(obj))) {
+      return false;
+    }
+    return true;
+  }
+
+  // A boolean indicating whether this set of specs is enabled. Not const
+  // because it will change at runtime if the corresponding pref is changed.
+  bool enabled;
+
+  // A boolean indicating whether a Secure Context is required.
+  const bool secureContext;
+
+  // Bitmask of global names that we should not be exposed in.
+  const uint16_t nonExposedGlobals;
+
+  // A function pointer to a function that can say the property is disabled
+  // even if "enabled" is set to true.  If the pointer is null the value of
+  // "enabled" is used as-is.
+  const PropertyEnabled enabledFunc;
+};
+
+template<typename T>
+struct Prefable {
+  inline bool isEnabled(JSContext* cx, JS::Handle<JSObject*> obj) const {
+    if (MOZ_LIKELY(!disablers)) {
+      return true;
+    }
+    return disablers->isEnabled(cx, obj);
+  }
+
+  // Things that can disable this set of specs. |nullptr| means "cannot be
+  // disabled".
+  PrefableDisablers* const disablers;
+
+  // Array of specs, terminated in whatever way is customary for T.
+  // Null to indicate a end-of-array for Prefable, when such an
+  // indicator is needed.
+  const T* const specs;
+};
+
+// Conceptually, NativeProperties has seven (Prefable<T>*, jsid*, T*) trios
+// (where T is one of JSFunctionSpec, JSPropertySpec, or ConstantSpec), one for
+// each of: static methods and attributes, methods and attributes, unforgeable
+// methods and attributes, and constants.
+//
+// That's 21 pointers, but in most instances most of the trios are all null,
+// and there are many instances. To save space we use a variable-length type,
+// NativePropertiesN<N>, to hold the data and getters to access it. It has N
+// actual trios (stored in trios[]), plus four bits for each of the 7 possible
+// trios: 1 bit that states if that trio is present, and 3 that state that
+// trio's offset (if present) in trios[].
+//
+// All trio accesses should be done via the getters, which contain assertions
+// that check we don't overrun the end of the struct. (The trio data members are
+// public only so they can be statically initialized.) These assertions should
+// never fail so long as (a) accesses to the variable-length part are guarded by
+// appropriate Has*() calls, and (b) all instances are well-formed, i.e. the
+// value of N matches the number of mHas* members that are true.
+//
+// Finally, we define a typedef of NativePropertiesN<7>, NativeProperties, which
+// we use as a "base" type used to refer to all instances of NativePropertiesN.
+// (7 is used because that's the maximum valid parameter, though any other
+// value 1..6 could also be used.) This is reasonable because of the
+// aforementioned assertions in the getters. Upcast() is used to convert
+// specific instances to this "base" type.
+//
+template <int N>
+struct NativePropertiesN {
+  // Trio structs are stored in the trios[] array, and each element in the
+  // array could require a different T. Therefore, we can't use the correct
+  // type for mPrefables and mSpecs. Instead we use void* and cast to the
+  // correct type in the getters.
+  struct Trio {
+    const /*Prefable<const T>*/ void* const mPrefables;
+    const jsid* const mIds;
+    const /*T*/ void* const mSpecs;
+  };
+
+  const int32_t iteratorAliasMethodIndex;
+
+  constexpr const NativePropertiesN<7>* Upcast() const {
+    return reinterpret_cast<const NativePropertiesN<7>*>(this);
+  }
+
+#define DO(SpecT, FieldName) \
+public: \
+  /* The bitfields indicating the trio's presence and (if present) offset. */ \
+  const uint32_t mHas##FieldName##s:1; \
+  const uint32_t m##FieldName##sOffset:3; \
+private: \
+  const Trio* FieldName##sTrio() const { \
+    MOZ_ASSERT(Has##FieldName##s()); \
+    return &trios[m##FieldName##sOffset]; \
+  } \
+public: \
+  bool Has##FieldName##s() const { \
+    return mHas##FieldName##s; \
+  } \
+  const Prefable<const SpecT>* FieldName##s() const { \
+    return static_cast<const Prefable<const SpecT>*> \
+                      (FieldName##sTrio()->mPrefables); \
+  } \
+  const jsid* FieldName##Ids() const { \
+    return FieldName##sTrio()->mIds; \
+  } \
+  const SpecT* FieldName##Specs() const { \
+    return static_cast<const SpecT*>(FieldName##sTrio()->mSpecs); \
+  }
+
+  DO(JSFunctionSpec, StaticMethod)
+  DO(JSPropertySpec, StaticAttribute)
+  DO(JSFunctionSpec, Method)
+  DO(JSPropertySpec, Attribute)
+  DO(JSFunctionSpec, UnforgeableMethod)
+  DO(JSPropertySpec, UnforgeableAttribute)
+  DO(ConstantSpec,   Constant)
+
+#undef DO
+
+  const Trio trios[N];
+};
+
+// Ensure the struct has the expected size. The 8 is for the
+// iteratorAliasMethodIndex plus the bitfields; the rest is for trios[].
+static_assert(sizeof(NativePropertiesN<1>) == 8 +  3*sizeof(void*), "1 size");
+static_assert(sizeof(NativePropertiesN<2>) == 8 +  6*sizeof(void*), "2 size");
+static_assert(sizeof(NativePropertiesN<3>) == 8 +  9*sizeof(void*), "3 size");
+static_assert(sizeof(NativePropertiesN<4>) == 8 + 12*sizeof(void*), "4 size");
+static_assert(sizeof(NativePropertiesN<5>) == 8 + 15*sizeof(void*), "5 size");
+static_assert(sizeof(NativePropertiesN<6>) == 8 + 18*sizeof(void*), "6 size");
+static_assert(sizeof(NativePropertiesN<7>) == 8 + 21*sizeof(void*), "7 size");
+
+// The "base" type.
+typedef NativePropertiesN<7> NativeProperties;
+
+struct NativePropertiesHolder
+{
+  const NativeProperties* regular;
+  const NativeProperties* chromeOnly;
+};
+
+// Helper structure for Xrays for DOM binding objects. The same instance is used
+// for instances, interface objects and interface prototype objects of a
+// specific interface.
+struct NativePropertyHooks
+{
+  // The hook to call for resolving indexed or named properties. May be null if
+  // there can't be any.
+  ResolveOwnProperty mResolveOwnProperty;
+  // The hook to call for enumerating indexed or named properties. May be null
+  // if there can't be any.
+  EnumerateOwnProperties mEnumerateOwnProperties;
+  // The hook to call to delete a named property.  May be null if there are no
+  // named properties or no named property deleter.  On success (true return)
+  // the "found" argument will be set to true if there was in fact such a named
+  // property and false otherwise.  If it's set to false, the caller is expected
+  // to proceed with whatever deletion behavior it would have if there were no
+  // named properties involved at all (i.e. if the hook were null).  If it's set
+  // to true, it will indicate via opresult whether the delete actually
+  // succeeded.
+  DeleteNamedProperty mDeleteNamedProperty;
+
+  // The property arrays for this interface.
+  NativePropertiesHolder mNativeProperties;
+
+  // This will be set to the ID of the interface prototype object for the
+  // interface, if it has one. If it doesn't have one it will be set to
+  // prototypes::id::_ID_Count.
+  prototypes::ID mPrototypeID;
+
+  // This will be set to the ID of the interface object for the interface, if it
+  // has one. If it doesn't have one it will be set to
+  // constructors::id::_ID_Count.
+  constructors::ID mConstructorID;
+
+  // The NativePropertyHooks instance for the parent interface (for
+  // ShimInterfaceInfo).
+  const NativePropertyHooks* mProtoHooks;
+
+  // The JSClass to use for expandos on our Xrays.  Can be null, in which case
+  // Xrays will use a default class of their choice.
+  const JSClass* mXrayExpandoClass;
+};
+
+enum DOMObjectType : uint8_t {
+  eInstance,
+  eGlobalInstance,
+  eInterface,
+  eInterfacePrototype,
+  eGlobalInterfacePrototype,
+  eNamedPropertiesObject
+};
+
+inline
+bool
+IsInstance(DOMObjectType type)
+{
+  return type == eInstance || type == eGlobalInstance;
+}
+
+inline
+bool
+IsInterfacePrototype(DOMObjectType type)
+{
+  return type == eInterfacePrototype || type == eGlobalInterfacePrototype;
+}
+
+typedef JSObject* (*AssociatedGlobalGetter)(JSContext* aCx,
+                                            JS::Handle<JSObject*> aObj);
+
+typedef JSObject* (*ProtoGetter)(JSContext* aCx);
+
+/**
+ * Returns a handle to the relevant WebIDL prototype object for the current
+ * compartment global (which may be a handle to null on out of memory).  Once
+ * allocated, the prototype object is guaranteed to exist as long as the global
+ * does, since the global traces its array of WebIDL prototypes and
+ * constructors.
+ */
+typedef JS::Handle<JSObject*> (*ProtoHandleGetter)(JSContext* aCx);
+
+// Special JSClass for reflected DOM objects.
+struct DOMJSClass
+{
+  // It would be nice to just inherit from JSClass, but that precludes pure
+  // compile-time initialization of the form |DOMJSClass = {...};|, since C++
+  // only allows brace initialization for aggregate/POD types.
+  const js::Class mBase;
+
+  // A list of interfaces that this object implements, in order of decreasing
+  // derivedness.
+  const prototypes::ID mInterfaceChain[MAX_PROTOTYPE_CHAIN_LENGTH];
+
+  // We store the DOM object in reserved slot with index DOM_OBJECT_SLOT or in
+  // the proxy private if we use a proxy object.
+  // Sometimes it's an nsISupports and sometimes it's not; this class tells
+  // us which it is.
+  const bool mDOMObjectIsISupports;
+
+  const NativePropertyHooks* mNativeHooks;
+
+  // A callback to find the associated global for our C++ object.  Note that
+  // this is used in cases when that global is _changing_, so it will not match
+  // the global of the JSObject* passed in to this function!
+  AssociatedGlobalGetter mGetAssociatedGlobal;
+  ProtoHandleGetter mGetProto;
+
+  // This stores the CC participant for the native, null if this class does not
+  // implement cycle collection or if it inherits from nsISupports (we can get
+  // the CC participant by QI'ing in that case).
+  nsCycleCollectionParticipant* mParticipant;
+
+  static const DOMJSClass* FromJSClass(const JSClass* base) {
+    MOZ_ASSERT(base->flags & JSCLASS_IS_DOMJSCLASS);
+    return reinterpret_cast<const DOMJSClass*>(base);
+  }
+
+  static const DOMJSClass* FromJSClass(const js::Class* base) {
+    return FromJSClass(Jsvalify(base));
+  }
+
+  const JSClass* ToJSClass() const { return Jsvalify(&mBase); }
+};
+
+// Special JSClass for DOM interface and interface prototype objects.
+struct DOMIfaceAndProtoJSClass
+{
+  // It would be nice to just inherit from js::Class, but that precludes pure
+  // compile-time initialization of the form
+  // |DOMJSInterfaceAndPrototypeClass = {...};|, since C++ only allows brace
+  // initialization for aggregate/POD types.
+  const js::Class mBase;
+
+  // Either eInterface, eInterfacePrototype, eGlobalInterfacePrototype or
+  // eNamedPropertiesObject.
+  DOMObjectType mType; // uint8_t
+
+  // Boolean indicating whether this object wants a @@hasInstance property
+  // pointing to InterfaceHasInstance defined on it.  Only ever true for the
+  // eInterface case.
+  bool wantsInterfaceHasInstance;
+
+  const prototypes::ID mPrototypeID; // uint16_t
+  const uint32_t mDepth;
+
+  const NativePropertyHooks* mNativeHooks;
+
+  // The value to return for toString() on this interface or interface prototype
+  // object.
+  const char* mToString;
+
+  ProtoGetter mGetParentProto;
+
+  static const DOMIfaceAndProtoJSClass* FromJSClass(const JSClass* base) {
+    MOZ_ASSERT(base->flags & JSCLASS_IS_DOMIFACEANDPROTOJSCLASS);
+    return reinterpret_cast<const DOMIfaceAndProtoJSClass*>(base);
+  }
+  static const DOMIfaceAndProtoJSClass* FromJSClass(const js::Class* base) {
+    return FromJSClass(Jsvalify(base));
+  }
+
+  const JSClass* ToJSClass() const { return Jsvalify(&mBase); }
+};
+
+class ProtoAndIfaceCache;
+
+inline bool
+DOMGlobalHasProtoAndIFaceCache(JSObject* global)
+{
+  MOZ_ASSERT(js::GetObjectClass(global)->flags & JSCLASS_DOM_GLOBAL);
+  // This can be undefined if we GC while creating the global
+  return !js::GetReservedSlot(global, DOM_PROTOTYPE_SLOT).isUndefined();
+}
+
+inline bool
+HasProtoAndIfaceCache(JSObject* global)
+{
+  if (!(js::GetObjectClass(global)->flags & JSCLASS_DOM_GLOBAL)) {
+    return false;
+  }
+  return DOMGlobalHasProtoAndIFaceCache(global);
+}
+
+inline ProtoAndIfaceCache*
+GetProtoAndIfaceCache(JSObject* global)
+{
+  MOZ_ASSERT(js::GetObjectClass(global)->flags & JSCLASS_DOM_GLOBAL);
+  return static_cast<ProtoAndIfaceCache*>(
+    js::GetReservedSlot(global, DOM_PROTOTYPE_SLOT).toPrivate());
+}
+
+} // namespace dom
+} // namespace mozilla
+
+#endif /* mozilla_dom_DOMJSClass_h */