gecko-dev/dom/bindings/BindingUtils.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
/* vim: set ts=2 sw=2 et tw=79: */
/* 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/. */

#include <stdarg.h>

#include "BindingUtils.h"

#include "AccessCheck.h"
#include "WrapperFactory.h"
#include "xpcprivate.h"
#include "nsContentUtils.h"
#include "XPCQuickStubs.h"
#include "nsIXPConnect.h"

namespace mozilla {
namespace dom {

JSErrorFormatString ErrorFormatString[] = {
#define MSG_DEF(_name, _argc, _str) \
  { _str, _argc, JSEXN_TYPEERR },
#include "mozilla/dom/Errors.msg"
#undef MSG_DEF
};

const JSErrorFormatString*
GetErrorMessage(void* aUserRef, const char* aLocale,
                const unsigned aErrorNumber)
{
  MOZ_ASSERT(aErrorNumber < ArrayLength(ErrorFormatString));
  return &ErrorFormatString[aErrorNumber];
}

bool
ThrowErrorMessage(JSContext* aCx, const ErrNum aErrorNumber, ...)
{
  va_list ap;
  va_start(ap, aErrorNumber);
  JS_ReportErrorNumberVA(aCx, GetErrorMessage, NULL,
                         static_cast<const unsigned>(aErrorNumber), ap);
  va_end(ap);
  return false;
}

bool
DefineConstants(JSContext* cx, JSObject* obj, ConstantSpec* cs)
{
  for (; cs->name; ++cs) {
    JSBool ok =
      JS_DefineProperty(cx, obj, cs->name, cs->value, NULL, NULL,
                        JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT);
    if (!ok) {
      return false;
    }
  }
  return true;
}

static inline bool
Define(JSContext* cx, JSObject* obj, JSFunctionSpec* spec) {
  return JS_DefineFunctions(cx, obj, spec);
}
static inline bool
Define(JSContext* cx, JSObject* obj, JSPropertySpec* spec) {
  return JS_DefineProperties(cx, obj, spec);
}
static inline bool
Define(JSContext* cx, JSObject* obj, ConstantSpec* spec) {
  return DefineConstants(cx, obj, spec);
}

template<typename T>
bool
DefinePrefable(JSContext* cx, JSObject* obj, Prefable<T>* props)
{
  MOZ_ASSERT(props);
  MOZ_ASSERT(props->specs);
  do {
    // Define if enabled
    if (props->enabled) {
      if (!Define(cx, obj, props->specs)) {
        return false;
      }
    }
  } while ((++props)->specs);
  return true;
}

bool
DefineUnforgeableAttributes(JSContext* cx, JSObject* obj,
                            Prefable<JSPropertySpec>* props)
{
  return DefinePrefable(cx, obj, props);
}


// We should use JSFunction objects for interface objects, but we need a custom
// hasInstance hook because we have new interface objects on prototype chains of
// old (XPConnect-based) bindings. Because Function.prototype.toString throws if
// passed a non-Function object we also need to provide our own toString method
// for interface objects.

enum {
  TOSTRING_CLASS_RESERVED_SLOT = 0,
  TOSTRING_NAME_RESERVED_SLOT = 1
};

JSBool
InterfaceObjectToString(JSContext* cx, unsigned argc, JS::Value *vp)
{
  JSObject* callee = JSVAL_TO_OBJECT(JS_CALLEE(cx, vp));

  JSObject* obj = JS_THIS_OBJECT(cx, vp);
  if (!obj) {
    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_CANT_CONVERT_TO,
                         "null", "object");
    return false;
  }

  jsval v = js::GetFunctionNativeReserved(callee, TOSTRING_CLASS_RESERVED_SLOT);
  JSClass* clasp = static_cast<JSClass*>(JSVAL_TO_PRIVATE(v));

  v = js::GetFunctionNativeReserved(callee, TOSTRING_NAME_RESERVED_SLOT);
  JSString* jsname = static_cast<JSString*>(JSVAL_TO_STRING(v));
  size_t length;
  const jschar* name = JS_GetInternedStringCharsAndLength(jsname, &length);

  if (js::GetObjectJSClass(obj) != clasp) {
    JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_INCOMPATIBLE_PROTO,
                         NS_ConvertUTF16toUTF8(name).get(), "toString",
                         "object");
    return false;
  }

  nsString str;
  str.AppendLiteral("function ");
  str.Append(name, length);
  str.AppendLiteral("() {");
  str.Append('\n');
  str.AppendLiteral("    [native code]");
  str.Append('\n');
  str.AppendLiteral("}");

  return xpc::NonVoidStringToJsval(cx, str, vp);
}

JSBool
Constructor(JSContext* cx, unsigned argc, JS::Value* vp)
{
  JSObject* callee = JSVAL_TO_OBJECT(JS_CALLEE(cx, vp));
  const JS::Value& v =
    js::GetFunctionNativeReserved(callee,
                                  CONSTRUCTOR_NATIVE_HOLDER_RESERVED_SLOT);
  JSNativeHolder* nativeHolder = static_cast<JSNativeHolder*>(v.toPrivate());
  return (nativeHolder->mNative)(cx, argc, vp);
}

static JSObject*
CreateInterfaceObject(JSContext* cx, JSObject* global,
                      JSClass* constructorClass,
                      JSNativeHolder* constructorNative,
                      unsigned ctorNargs,
                      JSObject* proto,
                      const NativeProperties* properties,
                      const NativeProperties* chromeOnlyProperties,
                      const char* name)
{
  JSObject* constructor;
  if (constructorClass) {
    JSObject* functionProto = JS_GetFunctionPrototype(cx, global);
    if (!functionProto) {
      return NULL;
    }
    constructor = JS_NewObject(cx, constructorClass, functionProto, global);
  } else {
    MOZ_ASSERT(constructorNative);
    JSFunction* fun = js::NewFunctionWithReserved(cx, Constructor, ctorNargs,
                                                  JSFUN_CONSTRUCTOR, global,
                                                  name);
    if (!fun) {
      return NULL;
    }
    constructor = JS_GetFunctionObject(fun);
    js::SetFunctionNativeReserved(constructor,
                                  CONSTRUCTOR_NATIVE_HOLDER_RESERVED_SLOT,
                                  js::PrivateValue(constructorNative));
  }
  if (!constructor) {
    return NULL;
  }

  if (constructorClass) {
    JSFunction* toString = js::DefineFunctionWithReserved(cx, constructor,
                                                          "toString",
                                                          InterfaceObjectToString,
                                                          0, 0);
    if (!toString) {
      return NULL;
    }

    JSObject* toStringObj = JS_GetFunctionObject(toString);
    js::SetFunctionNativeReserved(toStringObj, TOSTRING_CLASS_RESERVED_SLOT,
                                  PRIVATE_TO_JSVAL(constructorClass));

    JSString *str = ::JS_InternString(cx, name);
    if (!str) {
      return NULL;
    }
    js::SetFunctionNativeReserved(toStringObj, TOSTRING_NAME_RESERVED_SLOT,
                                  STRING_TO_JSVAL(str));
  }

  if (properties) {
    if (properties->staticMethods &&
        !DefinePrefable(cx, constructor, properties->staticMethods)) {
      return nullptr;
    }

    if (properties->constants &&
        !DefinePrefable(cx, constructor, properties->constants)) {
      return nullptr;
    }
  }

  if (chromeOnlyProperties) {
    if (chromeOnlyProperties->staticMethods &&
        !DefinePrefable(cx, constructor, chromeOnlyProperties->staticMethods)) {
      return nullptr;
    }

    if (chromeOnlyProperties->constants &&
        !DefinePrefable(cx, constructor, chromeOnlyProperties->constants)) {
      return nullptr;
    }
  }

  if (proto && !JS_LinkConstructorAndPrototype(cx, constructor, proto)) {
    return NULL;
  }

  JSBool alreadyDefined;
  if (!JS_AlreadyHasOwnProperty(cx, global, name, &alreadyDefined)) {
    return NULL;
  }

  // This is Enumerable: False per spec.
  if (!alreadyDefined &&
      !JS_DefineProperty(cx, global, name, OBJECT_TO_JSVAL(constructor), NULL,
                         NULL, 0)) {
    return NULL;
  }

  return constructor;
}

static JSObject*
CreateInterfacePrototypeObject(JSContext* cx, JSObject* global,
                               JSObject* parentProto, JSClass* protoClass,
                               const NativeProperties* properties,
                               const NativeProperties* chromeOnlyProperties)
{
  JSObject* ourProto = JS_NewObjectWithUniqueType(cx, protoClass, parentProto,
                                                  global);
  if (!ourProto) {
    return NULL;
  }

  if (properties) {
    if (properties->methods &&
        !DefinePrefable(cx, ourProto, properties->methods)) {
      return nullptr;
    }

    if (properties->attributes &&
        !DefinePrefable(cx, ourProto, properties->attributes)) {
      return nullptr;
    }

    if (properties->constants &&
        !DefinePrefable(cx, ourProto, properties->constants)) {
      return nullptr;
    }
  }

  if (chromeOnlyProperties) {
    if (chromeOnlyProperties->methods &&
        !DefinePrefable(cx, ourProto, chromeOnlyProperties->methods)) {
      return nullptr;
    }

    if (chromeOnlyProperties->attributes &&
        !DefinePrefable(cx, ourProto, chromeOnlyProperties->attributes)) {
      return nullptr;
    }

    if (chromeOnlyProperties->constants &&
        !DefinePrefable(cx, ourProto, chromeOnlyProperties->constants)) {
      return nullptr;
    }
  }

  return ourProto;
}

void
CreateInterfaceObjects(JSContext* cx, JSObject* global, JSObject* protoProto,
                       JSClass* protoClass, JSObject** protoCache,
                       JSClass* constructorClass, JSNativeHolder* constructor,
                       unsigned ctorNargs, JSObject** constructorCache,
                       const DOMClass* domClass,
                       const NativeProperties* properties,
                       const NativeProperties* chromeOnlyProperties,
                       const char* name)
{
  MOZ_ASSERT(protoClass || constructorClass || constructor,
             "Need at least one class or a constructor!");
  MOZ_ASSERT(!((properties &&
                (properties->methods || properties->attributes)) ||
               (chromeOnlyProperties &&
                (chromeOnlyProperties->methods ||
                 chromeOnlyProperties->attributes))) || protoClass,
             "Methods or properties but no protoClass!");
  MOZ_ASSERT(!((properties && properties->staticMethods) ||
               (chromeOnlyProperties && chromeOnlyProperties->staticMethods)) ||
             constructorClass || constructor,
             "Static methods but no constructorClass or constructor!");
  MOZ_ASSERT(bool(name) == bool(constructorClass || constructor),
             "Must have name precisely when we have an interface object");
  MOZ_ASSERT(!constructorClass || !constructor);
  MOZ_ASSERT(!protoClass == !protoCache,
             "If, and only if, there is an interface prototype object we need "
             "to cache it");
  MOZ_ASSERT(!(constructorClass || constructor) == !constructorCache,
             "If, and only if, there is an interface object we need to cache "
             "it");

  JSObject* proto;
  if (protoClass) {
    proto = CreateInterfacePrototypeObject(cx, global, protoProto, protoClass,
                                           properties, chromeOnlyProperties);
    if (!proto) {
      return;
    }

    js::SetReservedSlot(proto, DOM_PROTO_INSTANCE_CLASS_SLOT,
                        JS::PrivateValue(const_cast<DOMClass*>(domClass)));

    *protoCache = proto;
  }
  else {
    proto = NULL;
  }

  JSObject* interface;
  if (constructorClass || constructor) {
    interface = CreateInterfaceObject(cx, global, constructorClass, constructor,
                                      ctorNargs, proto, properties,
                                      chromeOnlyProperties, name);
    if (!interface) {
      if (protoCache) {
        // If we fail we need to make sure to clear the value of protoCache we
        // set above.
        *protoCache = nullptr;
      }
      return;
    }
    *constructorCache = interface;
  }
}

static bool
NativeInterface2JSObjectAndThrowIfFailed(XPCLazyCallContext& aLccx,
                                         JSContext* aCx,
                                         JS::Value* aRetval,
                                         xpcObjectHelper& aHelper,
                                         const nsIID* aIID,
                                         bool aAllowNativeWrapper)
{
  nsresult rv;
  if (!XPCConvert::NativeInterface2JSObject(aLccx, aRetval, NULL, aHelper, aIID,
                                            NULL, aAllowNativeWrapper, &rv)) {
    // I can't tell if NativeInterface2JSObject throws JS exceptions
    // or not.  This is a sloppy stab at the right semantics; the
    // method really ought to be fixed to behave consistently.
    if (!JS_IsExceptionPending(aCx)) {
      Throw<true>(aCx, NS_FAILED(rv) ? rv : NS_ERROR_UNEXPECTED);
    }
    return false;
  }
  return true;
}

bool
DoHandleNewBindingWrappingFailure(JSContext* cx, JSObject* scope,
                                  nsISupports* value, JS::Value* vp)
{
  if (JS_IsExceptionPending(cx)) {
    return false;
  }

  XPCLazyCallContext lccx(JS_CALLER, cx, scope);

  if (value) {
    xpcObjectHelper helper(value);
    return NativeInterface2JSObjectAndThrowIfFailed(lccx, cx, vp, helper, NULL,
                                                    true);
  }

  return Throw<true>(cx, NS_ERROR_XPC_BAD_CONVERT_JS);
}

// Can only be called with the immediate prototype of the instance object. Can
// only be called on the prototype of an object known to be a DOM instance.
JSBool
InstanceClassHasProtoAtDepth(JSHandleObject protoObject, uint32_t protoID,
                             uint32_t depth)
{
  const DOMClass* domClass = static_cast<DOMClass*>(
    js::GetReservedSlot(protoObject, DOM_PROTO_INSTANCE_CLASS_SLOT).toPrivate());
  return (uint32_t)domClass->mInterfaceChain[depth] == protoID;
}

// Only set allowNativeWrapper to false if you really know you need it, if in
// doubt use true. Setting it to false disables security wrappers.
bool
XPCOMObjectToJsval(JSContext* cx, JSObject* scope, xpcObjectHelper &helper,
                   const nsIID* iid, bool allowNativeWrapper, JS::Value* rval)
{
  XPCLazyCallContext lccx(JS_CALLER, cx, scope);

  if (!NativeInterface2JSObjectAndThrowIfFailed(lccx, cx, rval, helper, iid,
                                                allowNativeWrapper)) {
    return false;
  }

#ifdef DEBUG
  JSObject* jsobj = JSVAL_TO_OBJECT(*rval);
  if (jsobj && !js::GetObjectParent(jsobj))
    NS_ASSERTION(js::GetObjectClass(jsobj)->flags & JSCLASS_IS_GLOBAL,
                 "Why did we recreate this wrapper?");
#endif

  return true;
}

JSBool
QueryInterface(JSContext* cx, unsigned argc, JS::Value* vp)
{
  JS::Value thisv = JS_THIS(cx, vp);
  if (thisv == JSVAL_NULL)
    return false;

  // Get the object. It might be a security wrapper, in which case we do a checked
  // unwrap.
  JSObject* origObj = JSVAL_TO_OBJECT(thisv);
  JSObject* obj = js::UnwrapObjectChecked(cx, origObj);
  if (!obj)
      return false;

  nsISupports* native;
  if (!UnwrapDOMObjectToISupports(obj, native)) {
    return Throw<true>(cx, NS_ERROR_FAILURE);
  }

  if (argc < 1) {
    return Throw<true>(cx, NS_ERROR_XPC_NOT_ENOUGH_ARGS);
  }

  JS::Value* argv = JS_ARGV(cx, vp);
  if (!argv[0].isObject()) {
    return Throw<true>(cx, NS_ERROR_XPC_BAD_CONVERT_JS);
  }

  nsIJSIID* iid;
  xpc_qsSelfRef iidRef;
  if (NS_FAILED(xpc_qsUnwrapArg<nsIJSIID>(cx, argv[0], &iid, &iidRef.ptr,
                                          &argv[0]))) {
    return Throw<true>(cx, NS_ERROR_XPC_BAD_CONVERT_JS);
  }
  MOZ_ASSERT(iid);

  if (iid->GetID()->Equals(NS_GET_IID(nsIClassInfo))) {
    nsresult rv;
    nsCOMPtr<nsIClassInfo> ci = do_QueryInterface(native, &rv);
    if (NS_FAILED(rv)) {
      return Throw<true>(cx, rv);
    }

    return WrapObject(cx, origObj, ci, &NS_GET_IID(nsIClassInfo), vp);
  }

  // Lie, otherwise we need to check classinfo or QI
  *vp = thisv;
  return true;
}

JSBool
ThrowingConstructor(JSContext* cx, unsigned argc, JS::Value* vp)
{
  return ThrowErrorMessage(cx, MSG_ILLEGAL_CONSTRUCTOR);
}

inline const NativePropertyHooks*
GetNativePropertyHooks(JSContext *cx, JSObject *obj, DOMObjectType& type)
{
  const DOMClass* domClass;
  if (GetDOMClass(obj, domClass) != eNonDOMObject) {
    type = eInstance;
    return domClass->mNativeHooks;
  }

  if (JS_ObjectIsFunction(cx, obj)) {
    MOZ_ASSERT(JS_IsNativeFunction(obj, Constructor));
    type = eInterface;
    const JS::Value& v =
      js::GetFunctionNativeReserved(obj,
                                    CONSTRUCTOR_NATIVE_HOLDER_RESERVED_SLOT);
    JSNativeHolder* nativeHolder = static_cast<JSNativeHolder*>(v.toPrivate());
    return nativeHolder->mPropertyHooks;
  }

  MOZ_ASSERT(IsDOMIfaceAndProtoClass(js::GetObjectClass(obj)));
  const DOMIfaceAndProtoJSClass* ifaceAndProtoJSClass =
    DOMIfaceAndProtoJSClass::FromJSClass(js::GetObjectClass(obj));
  type = ifaceAndProtoJSClass->mType;
  return ifaceAndProtoJSClass->mNativeHooks;
}

bool
XrayResolveOwnProperty(JSContext* cx, JSObject* wrapper, JSObject* obj, jsid id,
                       bool set, JSPropertyDescriptor* desc)
{
  DOMObjectType type;
  const NativePropertyHooks *nativePropertyHooks =
    GetNativePropertyHooks(cx, obj, type);

  return type != eInstance || !nativePropertyHooks->mResolveOwnProperty ||
         nativePropertyHooks->mResolveOwnProperty(cx, wrapper, obj, id, set,
                                                  desc);
}

static bool
XrayResolveAttribute(JSContext* cx, JSObject* wrapper, jsid id,
                     Prefable<JSPropertySpec>* attributes, jsid* attributeIds,
                     JSPropertySpec* attributeSpecs, JSPropertyDescriptor* desc)
{
  for (; attributes->specs; ++attributes) {
    if (attributes->enabled) {
      // Set i to be the index into our full list of ids/specs that we're
      // looking at now.
      size_t i = attributes->specs - attributeSpecs;
      for ( ; attributeIds[i] != JSID_VOID; ++i) {
        if (id == attributeIds[i]) {
          JSPropertySpec& attrSpec = attributeSpecs[i];
          // Because of centralization, we need to make sure we fault in the
          // JitInfos as well. At present, until the JSAPI changes, the easiest
          // way to do this is wrap them up as functions ourselves.
          desc->attrs = attrSpec.flags & ~JSPROP_NATIVE_ACCESSORS;
          // They all have getters, so we can just make it.
          JSObject *global = JS_GetGlobalForObject(cx, wrapper);
          JSFunction *fun = JS_NewFunction(cx, (JSNative)attrSpec.getter.op,
                                           0, 0, global, nullptr);
          if (!fun)
            return false;
          SET_JITINFO(fun, attrSpec.getter.info);
          JSObject *funobj = JS_GetFunctionObject(fun);
          desc->getter = js::CastAsJSPropertyOp(funobj);
          desc->attrs |= JSPROP_GETTER;
          if (attrSpec.setter.op) {
            // We have a setter! Make it.
            fun = JS_NewFunction(cx, (JSNative)attrSpec.setter.op, 1, 0,
                                 global, nullptr);
            if (!fun)
              return false;
            SET_JITINFO(fun, attrSpec.setter.info);
            funobj = JS_GetFunctionObject(fun);
            desc->setter = js::CastAsJSStrictPropertyOp(funobj);
            desc->attrs |= JSPROP_SETTER;
          } else {
            desc->setter = nullptr;
          }
          desc->obj = wrapper;
          return true;
        }
      }
    }
  }
  return true;
}

static bool
XrayResolveProperty(JSContext* cx, JSObject* wrapper, jsid id,
                    JSPropertyDescriptor* desc, DOMObjectType type,
                    const NativeProperties* nativeProperties)
{
  Prefable<JSFunctionSpec>* methods;
  jsid* methodIds;
  JSFunctionSpec* methodsSpecs;
  if (type == eInterface) {
    methods = nativeProperties->staticMethods;
    methodIds = nativeProperties->staticMethodIds;
    methodsSpecs = nativeProperties->staticMethodsSpecs;
  } else {
    methods = nativeProperties->methods;
    methodIds = nativeProperties->methodIds;
    methodsSpecs = nativeProperties->methodsSpecs;
  }
  if (methods) {
    Prefable<JSFunctionSpec>* method;
    for (method = methods; method->specs; ++method) {
      if (method->enabled) {
        // Set i to be the index into our full list of ids/specs that we're
        // looking at now.
        size_t i = method->specs - methodsSpecs;
        for ( ; methodIds[i] != JSID_VOID; ++i) {
          if (id == methodIds[i]) {
            JSFunctionSpec& methodSpec = methodsSpecs[i];
            JSFunction *fun = JS_NewFunctionById(cx, methodSpec.call.op,
                                                 methodSpec.nargs, 0,
                                                 wrapper, id);
            if (!fun) {
              return false;
            }
            SET_JITINFO(fun, methodSpec.call.info);
            JSObject *funobj = JS_GetFunctionObject(fun);
            desc->value.setObject(*funobj);
            desc->attrs = methodSpec.flags;
            desc->obj = wrapper;
            desc->setter = nullptr;
            desc->getter = nullptr;
           return true;
          }
        }
      }
    }
  }

  if (type != eInterface) {
    if (nativeProperties->attributes) {
      if (!XrayResolveAttribute(cx, wrapper, id,
                                nativeProperties->attributes,
                                nativeProperties->attributeIds,
                                nativeProperties->attributeSpecs, desc)) {
        return false;
      }
      if (desc->obj) {
        return true;
      }
    }
    if (nativeProperties->unforgeableAttributes) {
      if (!XrayResolveAttribute(cx, wrapper, id,
                                nativeProperties->unforgeableAttributes,
                                nativeProperties->unforgeableAttributeIds,
                                nativeProperties->unforgeableAttributeSpecs,
                                desc)) {
        return false;
      }
      if (desc->obj) {
        return true;
      }
    }
  }

  if (nativeProperties->constants) {
    Prefable<ConstantSpec>* constant;
    for (constant = nativeProperties->constants; constant->specs; ++constant) {
      if (constant->enabled) {
        // Set i to be the index into our full list of ids/specs that we're
        // looking at now.
        size_t i = constant->specs - nativeProperties->constantSpecs;
        for ( ; nativeProperties->constantIds[i] != JSID_VOID; ++i) {
          if (id == nativeProperties->constantIds[i]) {
            desc->attrs = JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT;
            desc->obj = wrapper;
            desc->value = nativeProperties->constantSpecs[i].value;
            return true;
          }
        }
      }
    }
  }

  return true;
}

static bool
ResolvePrototypeOrConstructor(JSContext* cx, JSObject* wrapper, JSObject* obj,
                              size_t protoAndIfaceArrayIndex, unsigned attrs,
                              JSPropertyDescriptor* desc)
{
  JSObject* global = js::GetGlobalForObjectCrossCompartment(obj);
  {
    JSAutoCompartment ac(cx, global);
    JSObject** protoAndIfaceArray = GetProtoAndIfaceArray(global);
    JSObject* protoOrIface = protoAndIfaceArray[protoAndIfaceArrayIndex];
    if (!protoOrIface) {
      return false;
    }
    desc->obj = wrapper;
    desc->shortid = 0;
    desc->attrs = attrs;
    desc->getter = JS_PropertyStub;
    desc->setter = JS_StrictPropertyStub;
    desc->value = JS::ObjectValue(*protoOrIface);
  }
  return JS_WrapPropertyDescriptor(cx, desc);
}

bool
XrayResolveNativeProperty(JSContext* cx, JSObject* wrapper,
                          const NativePropertyHooks* nativePropertyHooks,
                          DOMObjectType type, JSObject* obj, jsid id,
                          JSPropertyDescriptor* desc)
{
  if (type == eInterface && IdEquals(id, "prototype")) {
    return nativePropertyHooks->mPrototypeID == prototypes::id::_ID_Count ||
           ResolvePrototypeOrConstructor(cx, wrapper, obj,
                                         nativePropertyHooks->mPrototypeID,
                                         JSPROP_PERMANENT | JSPROP_READONLY,
                                         desc);
  }

  if (type == eInterfacePrototype && IdEquals(id, "constructor")) {
    return nativePropertyHooks->mConstructorID == constructors::id::_ID_Count ||
           ResolvePrototypeOrConstructor(cx, wrapper, obj,
                                         nativePropertyHooks->mConstructorID,
                                         0, desc);
  }

  const NativePropertiesHolder& nativeProperties =
    nativePropertyHooks->mNativeProperties;

  if (nativeProperties.regular &&
      !XrayResolveProperty(cx, wrapper, id, desc, type,
                           nativeProperties.regular)) {
    return false;
  }

  if (!desc->obj &&
      nativeProperties.chromeOnly &&
      xpc::AccessCheck::isChrome(js::GetObjectCompartment(wrapper)) &&
      !XrayResolveProperty(cx, wrapper, id, desc, type,
                           nativeProperties.chromeOnly)) {
    return false;
  }

  return true;
}

bool
XrayResolveNativeProperty(JSContext* cx, JSObject* wrapper, JSObject* obj,
                          jsid id, JSPropertyDescriptor* desc)
{
  DOMObjectType type;
  const NativePropertyHooks* nativePropertyHooks =
    GetNativePropertyHooks(cx, obj, type);

  if (type == eInstance) {
    // Force the type to be eInterfacePrototype, since we need to walk the
    // prototype chain.
    type = eInterfacePrototype;
  }

  if (type == eInterfacePrototype) {
    do {
      if (!XrayResolveNativeProperty(cx, wrapper, nativePropertyHooks, type,
                                     obj, id, desc)) {
        return false;
      }

      if (desc->obj) {
        return true;
      }
    } while ((nativePropertyHooks = nativePropertyHooks->mProtoHooks));

    return true;
  }

  return XrayResolveNativeProperty(cx, wrapper, nativePropertyHooks, type, obj,
                                   id, desc);
}

bool
XrayEnumerateAttributes(Prefable<JSPropertySpec>* attributes,
                        jsid* attributeIds, JSPropertySpec* attributeSpecs,
                        JS::AutoIdVector& props)
{
  for (; attributes->specs; ++attributes) {
    if (attributes->enabled) {
      // Set i to be the index into our full list of ids/specs that we're
      // looking at now.
      size_t i = attributes->specs - attributeSpecs;
      for ( ; attributeIds[i] != JSID_VOID; ++i) {
        if ((attributeSpecs[i].flags & JSPROP_ENUMERATE) &&
            !props.append(attributeIds[i])) {
          return false;
        }
      }
    }
  }
  return true;
}

bool
XrayEnumerateProperties(JS::AutoIdVector& props, DOMObjectType type,
                        const NativeProperties* nativeProperties)
{
  Prefable<JSFunctionSpec>* methods;
  jsid* methodIds;
  JSFunctionSpec* methodsSpecs;
  if (type == eInterface) {
    methods = nativeProperties->staticMethods;
    methodIds = nativeProperties->staticMethodIds;
    methodsSpecs = nativeProperties->staticMethodsSpecs;
  } else {
    methods = nativeProperties->methods;
    methodIds = nativeProperties->methodIds;
    methodsSpecs = nativeProperties->methodsSpecs;
  }
  if (methods) {
    Prefable<JSFunctionSpec>* method;
    for (method = methods; method->specs; ++method) {
      if (method->enabled) {
        // Set i to be the index into our full list of ids/specs that we're
        // looking at now.
        size_t i = method->specs - methodsSpecs;
        for ( ; methodIds[i] != JSID_VOID; ++i) {
          if ((methodsSpecs[i].flags & JSPROP_ENUMERATE) &&
              !props.append(methodIds[i])) {
            return false;
          }
        }
      }
    }
  }

  if (type != eInterface) {
    if (nativeProperties->attributes &&
        !XrayEnumerateAttributes(nativeProperties->attributes,
                                 nativeProperties->attributeIds,
                                 nativeProperties->attributeSpecs, props)) {
      return false;
    }
    if (nativeProperties->unforgeableAttributes &&
        !XrayEnumerateAttributes(nativeProperties->unforgeableAttributes,
                                 nativeProperties->unforgeableAttributeIds,
                                 nativeProperties->unforgeableAttributeSpecs,
                                 props)) {
      return false;
    }
  }

  if (nativeProperties->constants) {
    Prefable<ConstantSpec>* constant;
    for (constant = nativeProperties->constants; constant->specs; ++constant) {
      if (constant->enabled) {
        // Set i to be the index into our full list of ids/specs that we're
        // looking at now.
        size_t i = constant->specs - nativeProperties->constantSpecs;
        for ( ; nativeProperties->constantIds[i] != JSID_VOID; ++i) {
          if (!props.append(nativeProperties->constantIds[i])) {
            return false;
          }
        }
      }
    }
  }

  return true;
}

bool
XrayEnumerateNativeProperties(JSContext* cx, JSObject* wrapper,
                              const NativePropertyHooks* nativePropertyHooks,
                              DOMObjectType type, JSObject* obj,
                              JS::AutoIdVector& props)
{
  if (type == eInterface &&
      nativePropertyHooks->mPrototypeID != prototypes::id::_ID_Count &&
      !AddStringToIDVector(cx, props, "prototype")) {
    return false;
  }

  if (type == eInterfacePrototype &&
      nativePropertyHooks->mConstructorID != constructors::id::_ID_Count &&
      !AddStringToIDVector(cx, props, "constructor")) {
    return false;
  }

  const NativePropertiesHolder& nativeProperties =
    nativePropertyHooks->mNativeProperties;

  if (nativeProperties.regular &&
      !XrayEnumerateProperties(props, type, nativeProperties.regular)) {
    return false;
  }

  if (nativeProperties.chromeOnly &&
      xpc::AccessCheck::isChrome(js::GetObjectCompartment(wrapper)) &&
      !XrayEnumerateProperties(props, type, nativeProperties.chromeOnly)) {
    return false;
  }

  return true;
}

bool
XrayEnumerateProperties(JSContext* cx, JSObject* wrapper, JSObject* obj,
                        bool ownOnly, JS::AutoIdVector& props)
{
  DOMObjectType type;
  const NativePropertyHooks* nativePropertyHooks =
    GetNativePropertyHooks(cx, obj, type);

  if (type == eInstance) {
    if (nativePropertyHooks->mEnumerateOwnProperties &&
        !nativePropertyHooks->mEnumerateOwnProperties(cx, wrapper, obj,
                                                      props)) {
      return false;
    }

    if (ownOnly) {
      return true;
    }

    // Force the type to be eInterfacePrototype, since we need to walk the
    // prototype chain.
    type = eInterfacePrototype;
  }

  if (type == eInterfacePrototype) {
    do {
      if (!XrayEnumerateNativeProperties(cx, wrapper, nativePropertyHooks, type,
                                         obj, props)) {
        return false;
      }
    } while ((nativePropertyHooks = nativePropertyHooks->mProtoHooks));

    return true;
  }

  return XrayEnumerateNativeProperties(cx, wrapper, nativePropertyHooks, type,
                                       obj, props);
}

NativePropertyHooks sWorkerNativePropertyHooks = {
  nullptr,
  nullptr,
  {
    nullptr,
    nullptr
  },
  prototypes::id::_ID_Count,
  constructors::id::_ID_Count,
  nullptr
};

bool
GetPropertyOnPrototype(JSContext* cx, JSObject* proxy, jsid id, bool* found,
                       JS::Value* vp)
{
  JSObject* proto;
  if (!js::GetObjectProto(cx, proxy, &proto)) {
    return false;
  }
  if (!proto) {
    *found = false;
    return true;
  }

  JSBool hasProp;
  if (!JS_HasPropertyById(cx, proto, id, &hasProp)) {
    return false;
  }

  *found = hasProp;
  if (!hasProp || !vp) {
    return true;
  }

  return JS_ForwardGetPropertyTo(cx, proto, id, proxy, vp);
}

bool
HasPropertyOnPrototype(JSContext* cx, JSObject* proxy, DOMProxyHandler* handler,
                       jsid id)
{
  Maybe<JSAutoCompartment> ac;
  if (xpc::WrapperFactory::IsXrayWrapper(proxy)) {
    proxy = js::UnwrapObject(proxy);
    ac.construct(cx, proxy);
  }
  MOZ_ASSERT(js::IsProxy(proxy) && js::GetProxyHandler(proxy) == handler);

  bool found;
  // We ignore an error from GetPropertyOnPrototype.
  return !GetPropertyOnPrototype(cx, proxy, id, &found, NULL) || found;
}

bool
WrapCallbackInterface(JSContext *cx, JSObject *scope, nsISupports* callback,
                      JS::Value* vp)
{
  nsCOMPtr<nsIXPConnectWrappedJS> wrappedJS = do_QueryInterface(callback);
  MOZ_ASSERT(wrappedJS, "How can we not have an XPCWrappedJS here?");
  JSObject* obj;
  DebugOnly<nsresult> rv = wrappedJS->GetJSObject(&obj);
  MOZ_ASSERT(NS_SUCCEEDED(rv) && obj, "What are we wrapping?");
  *vp = JS::ObjectValue(*obj);
  return JS_WrapValue(cx, vp);
}

JSObject*
GetXrayExpandoChain(JSObject* obj)
{
  js::Class* clasp = js::GetObjectClass(obj);
  JS::Value v;
  if (IsDOMClass(clasp) || IsDOMIfaceAndProtoClass(clasp)) {
    v = js::GetReservedSlot(obj, DOM_XRAY_EXPANDO_SLOT);
  } else if (js::IsObjectProxyClass(clasp) || js::IsFunctionProxyClass(clasp)) {
    MOZ_ASSERT(js::GetProxyHandler(obj)->family() == ProxyFamily());
    v = js::GetProxyExtra(obj, JSPROXYSLOT_XRAY_EXPANDO);
  } else {
    MOZ_ASSERT(JS_IsNativeFunction(obj, Constructor));
    v = js::GetFunctionNativeReserved(obj, CONSTRUCTOR_XRAY_EXPANDO_SLOT);
  }
  return v.isUndefined() ? nullptr : &v.toObject();
}

void
SetXrayExpandoChain(JSObject* obj, JSObject* chain)
{
  JS::Value v = chain ? JS::ObjectValue(*chain) : JSVAL_VOID;
  js::Class* clasp = js::GetObjectClass(obj);
  if (IsDOMClass(clasp) || IsDOMIfaceAndProtoClass(clasp)) {
    js::SetReservedSlot(obj, DOM_XRAY_EXPANDO_SLOT, v);
  } else if (js::IsObjectProxyClass(clasp) || js::IsFunctionProxyClass(clasp)) {
    MOZ_ASSERT(js::GetProxyHandler(obj)->family() == ProxyFamily());
    js::SetProxyExtra(obj, JSPROXYSLOT_XRAY_EXPANDO, v);
  } else {
    MOZ_ASSERT(JS_IsNativeFunction(obj, Constructor));
    js::SetFunctionNativeReserved(obj, CONSTRUCTOR_XRAY_EXPANDO_SLOT, v);
  }
}

JSContext*
MainThreadDictionaryBase::ParseJSON(const nsAString& aJSON,
                                    mozilla::Maybe<JSAutoRequest>& aAr,
                                    mozilla::Maybe<JSAutoCompartment>& aAc,
                                    JS::Value& aVal)
{
  JSContext* cx = nsContentUtils::ThreadJSContextStack()->GetSafeJSContext();
  NS_ENSURE_TRUE(cx, nullptr);
  JSObject* global = JS_GetGlobalObject(cx);
  aAr.construct(cx);
  aAc.construct(cx, global);
  if (aJSON.IsEmpty()) {
    return cx;
  }
  if (!JS_ParseJSON(cx,
                    static_cast<const jschar*>(PromiseFlatString(aJSON).get()),
                    aJSON.Length(), &aVal)) {
    return nullptr;
  }
  return cx;
}

static JSString*
ConcatJSString(JSContext* cx, const char* pre, JSString* str, const char* post)
{
  if (!str) {
    return nullptr;
  }

  JSString* preString = JS_NewStringCopyN(cx, pre, strlen(pre));
  JSString* postString = JS_NewStringCopyN(cx, post, strlen(post));
  if (!preString || !postString) {
    return nullptr;
  }

  str = JS_ConcatStrings(cx, preString, str);
  if (!str) {
    return nullptr;
  }

  return JS_ConcatStrings(cx, str, postString);
}

bool
NativeToString(JSContext* cx, JSObject* wrapper, JSObject* obj, const char* pre,
               const char* post, JS::Value* v)
{
  JSPropertyDescriptor toStringDesc;
  toStringDesc.obj = nullptr;
  toStringDesc.attrs = 0;
  toStringDesc.shortid = 0;
  toStringDesc.getter = nullptr;
  toStringDesc.setter = nullptr;
  toStringDesc.value = JS::UndefinedValue();
  if (!XrayResolveNativeProperty(cx, wrapper, obj,
                                 nsXPConnect::GetRuntimeInstance()->GetStringID(XPCJSRuntime::IDX_TO_STRING),
                                 &toStringDesc)) {
    return false;
  }

  JSString* str;
  {
    JSAutoCompartment ac(cx, obj);
    if (toStringDesc.obj) {
      JS::Value toString = toStringDesc.value;
      if (!JS_WrapValue(cx, &toString)) {
        return false;
      }
      MOZ_ASSERT(JS_ObjectIsCallable(cx, &toString.toObject()));
      JS::Value toStringResult;
      if (JS_CallFunctionValue(cx, obj, toString, 0, nullptr,
                               &toStringResult)) {
        str = toStringResult.toString();
      } else {
        str = nullptr;
      }
    } else {
      if (IsDOMProxy(obj)) {
        str = js::GetProxyHandler(obj)->obj_toString(cx, obj);
      } else if (IsDOMClass(JS_GetClass(obj)) ||
                 IsDOMIfaceAndProtoClass(JS_GetClass(obj))) {
        str = ConcatJSString(cx, "[object ",
                             JS_NewStringCopyZ(cx, JS_GetClass(obj)->name),
                                               "]");
      } else if (JS_IsNativeFunction(obj, Constructor)) {
        str = JS_DecompileFunction(cx, JS_GetObjectFunction(obj), 0);
      }
      str = ConcatJSString(cx, pre, str, post);
    }
  }

  if (!str) {
    return false;
  }

  v->setString(str);
  return JS_WrapValue(cx, v);
}

} // namespace dom
} // namespace mozilla