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 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-

  * vim: set ts=8 sts=4 et sw=4 tw=99:

  * 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/. */

 /* JavaScript iterators. */

 #include "jsiter.h"

 #include "mozilla/ArrayUtils.h"

 #include "mozilla/MemoryReporting.h"

 #include "mozilla/PodOperations.h"

 #include "jsarray.h"

 #include "jsatom.h"

 #include "jscntxt.h"

 #include "jsgc.h"

 #include "jsobj.h"

 #include "jsopcode.h"

 #include "jsproxy.h"

 #include "jsscript.h"

 #include "jstypes.h"

 #include "jsutil.h"

 #include "ds/Sort.h"

 #include "gc/Marking.h"

 #include "vm/GeneratorObject.h"

 #include "vm/GlobalObject.h"

 #include "vm/Interpreter.h"

 #include "vm/Shape.h"

 #include "vm/StopIterationObject.h"

 #include "jsinferinlines.h"

 #include "jsobjinlines.h"

 #include "jsscriptinlines.h"

 #include "vm/Stack-inl.h"

 #include "vm/String-inl.h"

 using namespace js;

 using namespace js::gc;

 using JS::ForOfIterator;

 using mozilla::ArrayLength;

 #ifdef JS_MORE_DETERMINISTIC

 using mozilla::PodCopy;

 #endif

 using mozilla::PodZero;

 typedef Rooted<PropertyIteratorObject*> RootedPropertyIteratorObject;

 static const gc::AllocKind ITERATOR_FINALIZE_KIND = gc::FINALIZE_OBJECT2_BACKGROUND;

 void

 NativeIterator::mark(JSTracer *trc)

 {

     for (HeapPtr<JSFlatString> *str = begin(); str < end(); str++)

         MarkString(trc, str, "prop");

     if (obj)

         MarkObject(trc, &obj, "obj");

     // The SuppressDeletedPropertyHelper loop can GC, so make sure that if the

     // GC removes any elements from the list, it won't remove this one.

     if (iterObj_)

         MarkObjectUnbarriered(trc, &iterObj_, "iterObj");

 }

 struct IdHashPolicy {

     typedef jsid Lookup;

     static HashNumber hash(jsid id) {

         return JSID_BITS(id);

     }

     static bool match(jsid id1, jsid id2) {

         return id1 == id2;

     }

 };

 typedef HashSet<jsid, IdHashPolicy> IdSet;

 static inline bool

 NewKeyValuePair(JSContext *cx, jsid id, const Value &val, MutableHandleValue rval)

 {

     JS::AutoValueArray<2> vec(cx);

     vec[0].set(IdToValue(id));

     vec[1].set(val);

     JSObject *aobj = NewDenseCopiedArray(cx, 2, vec.begin());

     if (!aobj)

         return false;

     rval.setObject(*aobj);

     return true;

 }

 static inline bool

 Enumerate(JSContext *cx, HandleObject pobj, jsid id,

           bool enumerable, unsigned flags, IdSet& ht, AutoIdVector *props)

 {

     /*

      * We implement __proto__ using a property on |Object.prototype|, but

      * because __proto__ is highly deserving of removal, we don't want it to

      * show up in property enumeration, even if only for |Object.prototype|

      * (think introspection by Prototype-like frameworks that add methods to

      * the built-in prototypes).  So exclude __proto__ if the object where the

      * property was found has no [[Prototype]] and might be |Object.prototype|.

      */

     if (MOZ_UNLIKELY(!pobj->getTaggedProto().isObject() && JSID_IS_ATOM(id, cx->names().proto)))

         return true;

     if (!(flags & JSITER_OWNONLY) || pobj->is<ProxyObject>() || pobj->getOps()->enumerate) {

         /* If we've already seen this, we definitely won't add it. */

         IdSet::AddPtr p = ht.lookupForAdd(id);

         if (MOZ_UNLIKELY(!!p))

             return true;

         /*

          * It's not necessary to add properties to the hash table at the end of

          * the prototype chain, but custom enumeration behaviors might return

          * duplicated properties, so always add in such cases.

          */

         if ((pobj->is<ProxyObject>() || pobj->getProto() || pobj->getOps()->enumerate) && !ht.add(p, id))

             return false;

     }

     if (enumerable || (flags & JSITER_HIDDEN))

         return props->append(id);

     return true;

 }

 static bool

 EnumerateNativeProperties(JSContext *cx, HandleObject pobj, unsigned flags, IdSet &ht,

                           AutoIdVector *props)

 {

     /* Collect any dense elements from this object. */

     size_t initlen = pobj->getDenseInitializedLength();

     const Value *vp = pobj->getDenseElements();

     for (size_t i = 0; i < initlen; ++i, ++vp) {

         if (!vp->isMagic(JS_ELEMENTS_HOLE)) {

             /* Dense arrays never get so large that i would not fit into an integer id. */

             if (!Enumerate(cx, pobj, INT_TO_JSID(i), /* enumerable = */ true, flags, ht, props))

                 return false;

         }

     }

     /* Collect any typed array elements from this object. */

     if (pobj->is<TypedArrayObject>()) {

         size_t len = pobj->as<TypedArrayObject>().length();

         for (size_t i = 0; i < len; i++) {

             if (!Enumerate(cx, pobj, INT_TO_JSID(i), /* enumerable = */ true, flags, ht, props))

                 return false;

         }

     }

     size_t initialLength = props->length();

     /* Collect all unique properties from this object's scope. */

     Shape::Range<NoGC> r(pobj->lastProperty());

     for (; !r.empty(); r.popFront()) {

         Shape &shape = r.front();

         if (!Enumerate(cx, pobj, shape.propid(), shape.enumerable(), flags, ht, props))

             return false;

     }

     ::Reverse(props->begin() + initialLength, props->end());

     return true;

 }

 #ifdef JS_MORE_DETERMINISTIC

 struct SortComparatorIds

 {

     JSContext   *const cx;

     SortComparatorIds(JSContext *cx)

       : cx(cx) {}

     bool operator()(jsid a, jsid b, bool *lessOrEqualp)

     {

         /* Pick an arbitrary total order on jsids that is stable across executions. */

         RootedString astr(cx, IdToString(cx, a));

 	if (!astr)

 	    return false;

         RootedString bstr(cx, IdToString(cx, b));

         if (!bstr)

             return false;

         int32_t result;

         if (!CompareStrings(cx, astr, bstr, &result))

             return false;

         *lessOrEqualp = (result <= 0);

         return true;

     }

 };

 #endif /* JS_MORE_DETERMINISTIC */

 static bool

 Snapshot(JSContext *cx, JSObject *pobj_, unsigned flags, AutoIdVector *props)

 {

     IdSet ht(cx);

     if (!ht.init(32))

         return false;

     RootedObject pobj(cx, pobj_);

     do {

         const Class *clasp = pobj->getClass();

         if (pobj->isNative() &&

             !pobj->getOps()->enumerate &&

             !(clasp->flags & JSCLASS_NEW_ENUMERATE)) {

             if (!clasp->enumerate(cx, pobj))

                 return false;

             if (!EnumerateNativeProperties(cx, pobj, flags, ht, props))

                 return false;

         } else {

             if (pobj->is<ProxyObject>()) {

                 AutoIdVector proxyProps(cx);

                 if (flags & JSITER_OWNONLY) {

                     if (flags & JSITER_HIDDEN) {

                         if (!Proxy::getOwnPropertyNames(cx, pobj, proxyProps))

                             return false;

                     } else {

                         if (!Proxy::keys(cx, pobj, proxyProps))

                             return false;

                     }

                 } else {

                     if (!Proxy::enumerate(cx, pobj, proxyProps))

                         return false;

                 }

                 for (size_t n = 0, len = proxyProps.length(); n < len; n++) {

                     if (!Enumerate(cx, pobj, proxyProps[n], true, flags, ht, props))

                         return false;

                 }

                 /* Proxy objects enumerate the prototype on their own, so we are done here. */

                 break;

             }

             RootedValue state(cx);

             RootedId id(cx);

             JSIterateOp op = (flags & JSITER_HIDDEN) ? JSENUMERATE_INIT_ALL : JSENUMERATE_INIT;

             if (!JSObject::enumerate(cx, pobj, op, &state, &id))

                 return false;

             if (state.isMagic(JS_NATIVE_ENUMERATE)) {

                 if (!EnumerateNativeProperties(cx, pobj, flags, ht, props))

                     return false;

             } else {

                 while (true) {

                     RootedId id(cx);

                     if (!JSObject::enumerate(cx, pobj, JSENUMERATE_NEXT, &state, &id))

                         return false;

                     if (state.isNull())

                         break;

                     if (!Enumerate(cx, pobj, id, true, flags, ht, props))

                         return false;

                 }

             }

         }

         if (flags & JSITER_OWNONLY)

             break;

     } while ((pobj = pobj->getProto()) != nullptr);

 #ifdef JS_MORE_DETERMINISTIC

     /*

      * In some cases the enumeration order for an object depends on the

      * execution mode (interpreter vs. JIT), especially for native objects

      * with a class enumerate hook (where resolving a property changes the

      * resulting enumeration order). These aren't really bugs, but the

      * differences can change the generated output and confuse correctness

      * fuzzers, so we sort the ids if such a fuzzer is running.

      *

      * We don't do this in the general case because (a) doing so is slow,

      * and (b) it also breaks the web, which expects enumeration order to

      * follow the order in which properties are added, in certain cases.

      * Since ECMA does not specify an enumeration order for objects, both

      * behaviors are technically correct to do.

      */

     jsid *ids = props->begin();

     size_t n = props->length();

     AutoIdVector tmp(cx);

     if (!tmp.resize(n))

         return false;

     PodCopy(tmp.begin(), ids, n);

     if (!MergeSort(ids, n, tmp.begin(), SortComparatorIds(cx)))

         return false;

 #endif /* JS_MORE_DETERMINISTIC */

     return true;

 }

 bool

 js::VectorToIdArray(JSContext *cx, AutoIdVector &props, JSIdArray **idap)

 {

     JS_STATIC_ASSERT(sizeof(JSIdArray) > sizeof(jsid));

     size_t len = props.length();

     size_t idsz = len * sizeof(jsid);

     size_t sz = (sizeof(JSIdArray) - sizeof(jsid)) + idsz;

     JSIdArray *ida = static_cast<JSIdArray *>(cx->malloc_(sz));

     if (!ida)

         return false;

     ida->length = static_cast<int>(len);

     jsid *v = props.begin();

     for (int i = 0; i < ida->length; i++)

         ida->vector[i].init(v[i]);

     *idap = ida;

     return true;

 }

 JS_FRIEND_API(bool)

 js::GetPropertyNames(JSContext *cx, JSObject *obj, unsigned flags, AutoIdVector *props)

 {

     return Snapshot(cx, obj, flags & (JSITER_OWNONLY | JSITER_HIDDEN), props);

 }

 size_t sCustomIteratorCount = 0;

 static inline bool

 GetCustomIterator(JSContext *cx, HandleObject obj, unsigned flags, MutableHandleValue vp)

 {

     JS_CHECK_RECURSION(cx, return false);

     /* Check whether we have a valid __iterator__ method. */

     HandlePropertyName name = cx->names().iteratorIntrinsic;

     if (!JSObject::getProperty(cx, obj, obj, name, vp))

         return false;

     /* If there is no custom __iterator__ method, we are done here. */

     if (!vp.isObject()) {

         vp.setUndefined();

         return true;

     }

     if (!cx->runningWithTrustedPrincipals())

         ++sCustomIteratorCount;

     /* Otherwise call it and return that object. */

     Value arg = BooleanValue((flags & JSITER_FOREACH) == 0);

     if (!Invoke(cx, ObjectValue(*obj), vp, 1, &arg, vp))

         return false;

     if (vp.isPrimitive()) {

         /*

          * We are always coming from js::ValueToIterator, and we are no longer on

          * trace, so the object we are iterating over is on top of the stack (-1).

          */

         JSAutoByteString bytes;

         if (!AtomToPrintableString(cx, name, &bytes))

             return false;

         RootedValue val(cx, ObjectValue(*obj));

         js_ReportValueError2(cx, JSMSG_BAD_TRAP_RETURN_VALUE,

                              -1, val, js::NullPtr(), bytes.ptr());

         return false;

     }

     return true;

 }

 template <typename T>

 static inline bool

 Compare(T *a, T *b, size_t c)

 {

     size_t n = (c + size_t(7)) / size_t(8);

     switch (c % 8) {

       case 0: do { if (*a++ != *b++) return false;

       case 7:      if (*a++ != *b++) return false;

       case 6:      if (*a++ != *b++) return false;

       case 5:      if (*a++ != *b++) return false;

       case 4:      if (*a++ != *b++) return false;

       case 3:      if (*a++ != *b++) return false;

       case 2:      if (*a++ != *b++) return false;

       case 1:      if (*a++ != *b++) return false;

               } while (--n > 0);

     }

     return true;

 }

 static inline PropertyIteratorObject *

 NewPropertyIteratorObject(JSContext *cx, unsigned flags)

 {

     if (flags & JSITER_ENUMERATE) {

         RootedTypeObject type(cx, cx->getNewType(&PropertyIteratorObject::class_, nullptr));

         if (!type)

             return nullptr;

         JSObject *metadata = nullptr;

         if (!NewObjectMetadata(cx, &metadata))

             return nullptr;

         const Class *clasp = &PropertyIteratorObject::class_;

         RootedShape shape(cx, EmptyShape::getInitialShape(cx, clasp, nullptr, nullptr, metadata,

                                                           ITERATOR_FINALIZE_KIND));

         if (!shape)

             return nullptr;

         JSObject *obj = JSObject::create(cx, ITERATOR_FINALIZE_KIND,

                                          GetInitialHeap(GenericObject, clasp), shape, type);

         if (!obj)

             return nullptr;

         JS_ASSERT(obj->numFixedSlots() == JSObject::ITER_CLASS_NFIXED_SLOTS);

         return &obj->as<PropertyIteratorObject>();

     }

     JSObject *obj = NewBuiltinClassInstance(cx, &PropertyIteratorObject::class_);

     if (!obj)

         return nullptr;

     return &obj->as<PropertyIteratorObject>();

 }

 NativeIterator *

 NativeIterator::allocateIterator(JSContext *cx, uint32_t slength, const AutoIdVector &props)

 {

     size_t plength = props.length();

     NativeIterator *ni = (NativeIterator *)

         cx->malloc_(sizeof(NativeIterator)

                     + plength * sizeof(JSString *)

                     + slength * sizeof(Shape *));

     if (!ni)

         return nullptr;

     AutoValueVector strings(cx);

     ni->props_array = ni->props_cursor = (HeapPtr<JSFlatString> *) (ni + 1);

     ni->props_end = ni->props_array + plength;

     if (plength) {

         for (size_t i = 0; i < plength; i++) {

             JSFlatString *str = IdToString(cx, props[i]);

             if (!str || !strings.append(StringValue(str)))

                 return nullptr;

             ni->props_array[i].init(str);

         }

     }

     ni->next_ = nullptr;

     ni->prev_ = nullptr;

     return ni;

 }

 NativeIterator *

 NativeIterator::allocateSentinel(JSContext *cx)

 {

     NativeIterator *ni = (NativeIterator *)js_malloc(sizeof(NativeIterator));

     if (!ni)

         return nullptr;

     PodZero(ni);

     ni->next_ = ni;

     ni->prev_ = ni;

     return ni;

 }

 inline void

 NativeIterator::init(JSObject *obj, JSObject *iterObj, unsigned flags, uint32_t slength, uint32_t key)

 {

     this->obj.init(obj);

     this->iterObj_ = iterObj;

     this->flags = flags;

     this->shapes_array = (Shape **) this->props_end;

     this->shapes_length = slength;

     this->shapes_key = key;

 }

 static inline void

 RegisterEnumerator(JSContext *cx, PropertyIteratorObject *iterobj, NativeIterator *ni)

 {

     /* Register non-escaping native enumerators (for-in) with the current context. */

     if (ni->flags & JSITER_ENUMERATE) {

         ni->link(cx->compartment()->enumerators);

         JS_ASSERT(!(ni->flags & JSITER_ACTIVE));

         ni->flags |= JSITER_ACTIVE;

     }

 }

 static inline bool

 VectorToKeyIterator(JSContext *cx, HandleObject obj, unsigned flags, AutoIdVector &keys,

                     uint32_t slength, uint32_t key, MutableHandleValue vp)

 {

     JS_ASSERT(!(flags & JSITER_FOREACH));

     if (obj) {

         if (obj->hasSingletonType() && !obj->setIteratedSingleton(cx))

             return false;

         types::MarkTypeObjectFlags(cx, obj, types::OBJECT_FLAG_ITERATED);

     }

     Rooted<PropertyIteratorObject *> iterobj(cx, NewPropertyIteratorObject(cx, flags));

     if (!iterobj)

         return false;

     NativeIterator *ni = NativeIterator::allocateIterator(cx, slength, keys);

     if (!ni)

         return false;

     ni->init(obj, iterobj, flags, slength, key);

     if (slength) {

         /*

          * Fill in the shape array from scratch.  We can't use the array that was

          * computed for the cache lookup earlier, as constructing iterobj could

          * have triggered a shape-regenerating GC.  Don't bother with regenerating

          * the shape key; if such a GC *does* occur, we can only get hits through

          * the one-slot lastNativeIterator cache.

          */

         JSObject *pobj = obj;

         size_t ind = 0;

         do {

             ni->shapes_array[ind++] = pobj->lastProperty();

             pobj = pobj->getProto();

         } while (pobj);

         JS_ASSERT(ind == slength);

     }

     iterobj->setNativeIterator(ni);

     vp.setObject(*iterobj);

     RegisterEnumerator(cx, iterobj, ni);

     return true;

 }

 bool

 js::VectorToKeyIterator(JSContext *cx, HandleObject obj, unsigned flags, AutoIdVector &props,

                         MutableHandleValue vp)

 {

     return VectorToKeyIterator(cx, obj, flags, props, 0, 0, vp);

 }

 bool

 js::VectorToValueIterator(JSContext *cx, HandleObject obj, unsigned flags, AutoIdVector &keys,

                           MutableHandleValue vp)

 {

     JS_ASSERT(flags & JSITER_FOREACH);

     if (obj) {

         if (obj->hasSingletonType() && !obj->setIteratedSingleton(cx))

             return false;

         types::MarkTypeObjectFlags(cx, obj, types::OBJECT_FLAG_ITERATED);

     }

     Rooted<PropertyIteratorObject*> iterobj(cx, NewPropertyIteratorObject(cx, flags));

     if (!iterobj)

         return false;

     NativeIterator *ni = NativeIterator::allocateIterator(cx, 0, keys);

     if (!ni)

         return false;

     ni->init(obj, iterobj, flags, 0, 0);

     iterobj->setNativeIterator(ni);

     vp.setObject(*iterobj);

     RegisterEnumerator(cx, iterobj, ni);

     return true;

 }

 bool

 js::EnumeratedIdVectorToIterator(JSContext *cx, HandleObject obj, unsigned flags,

                                  AutoIdVector &props, MutableHandleValue vp)

 {

     if (!(flags & JSITER_FOREACH))

         return VectorToKeyIterator(cx, obj, flags, props, vp);

     return VectorToValueIterator(cx, obj, flags, props, vp);

 }

 static inline void

 UpdateNativeIterator(NativeIterator *ni, JSObject *obj)

 {

     // Update the object for which the native iterator is associated, so

     // SuppressDeletedPropertyHelper will recognize the iterator as a match.

     ni->obj = obj;

 }

 bool

 js::GetIterator(JSContext *cx, HandleObject obj, unsigned flags, MutableHandleValue vp)

 {

     Vector<Shape *, 8> shapes(cx);

     uint32_t key = 0;

     bool keysOnly = (flags == JSITER_ENUMERATE);

     if (obj) {

         if (JSIteratorOp op = obj->getClass()->ext.iteratorObject) {

             JSObject *iterobj = op(cx, obj, !(flags & JSITER_FOREACH));

             if (!iterobj)

                 return false;

             vp.setObject(*iterobj);

             return true;

         }

         if (keysOnly) {

             /*

              * Check to see if this is the same as the most recent object which

              * was iterated over.  We don't explicitly check for shapeless

              * objects here, as they are not inserted into the cache and

              * will result in a miss.

              */

             PropertyIteratorObject *last = cx->runtime()->nativeIterCache.last;

             if (last) {

                 NativeIterator *lastni = last->getNativeIterator();

                 if (!(lastni->flags & (JSITER_ACTIVE|JSITER_UNREUSABLE)) &&

                     obj->isNative() &&

                     obj->hasEmptyElements() &&

                     obj->lastProperty() == lastni->shapes_array[0])

                 {

                     JSObject *proto = obj->getProto();

                     if (proto->isNative() &&

                         proto->hasEmptyElements() &&

                         proto->lastProperty() == lastni->shapes_array[1] &&

                         !proto->getProto())

                     {

                         vp.setObject(*last);

                         UpdateNativeIterator(lastni, obj);

                         RegisterEnumerator(cx, last, lastni);

                         return true;

                     }

                 }

             }

             /*

              * The iterator object for JSITER_ENUMERATE never escapes, so we

              * don't care for the proper parent/proto to be set. This also

              * allows us to re-use a previous iterator object that is not

              * currently active.

              */

             {

                 JSObject *pobj = obj;

                 do {

                     if (!pobj->isNative() ||

                         !pobj->hasEmptyElements() ||

                         pobj->is<TypedArrayObject>() ||

                         pobj->hasUncacheableProto() ||

                         pobj->getOps()->enumerate ||

                         pobj->getClass()->enumerate != JS_EnumerateStub ||

                         pobj->nativeContainsPure(cx->names().iteratorIntrinsic))

                     {

                         shapes.clear();

                         goto miss;

                     }

                     Shape *shape = pobj->lastProperty();

                     key = (key + (key << 16)) ^ (uintptr_t(shape) >> 3);

                     if (!shapes.append(shape))

                         return false;

                     pobj = pobj->getProto();

                 } while (pobj);

             }

             PropertyIteratorObject *iterobj = cx->runtime()->nativeIterCache.get(key);

             if (iterobj) {

                 NativeIterator *ni = iterobj->getNativeIterator();

                 if (!(ni->flags & (JSITER_ACTIVE|JSITER_UNREUSABLE)) &&

                     ni->shapes_key == key &&

                     ni->shapes_length == shapes.length() &&

                     Compare(ni->shapes_array, shapes.begin(), ni->shapes_length)) {

                     vp.setObject(*iterobj);

                     UpdateNativeIterator(ni, obj);

                     RegisterEnumerator(cx, iterobj, ni);

                     if (shapes.length() == 2)

                         cx->runtime()->nativeIterCache.last = iterobj;

                     return true;

                 }

             }

         }

       miss:

         if (obj->is<ProxyObject>())

             return Proxy::iterate(cx, obj, flags, vp);

         if (!GetCustomIterator(cx, obj, flags, vp))

             return false;

         if (!vp.isUndefined())

             return true;

     }

     /* NB: for (var p in null) succeeds by iterating over no properties. */

     AutoIdVector keys(cx);

     if (flags & JSITER_FOREACH) {

         if (MOZ_LIKELY(obj != nullptr) && !Snapshot(cx, obj, flags, &keys))

             return false;

         JS_ASSERT(shapes.empty());

         if (!VectorToValueIterator(cx, obj, flags, keys, vp))

             return false;

     } else {

         if (MOZ_LIKELY(obj != nullptr) && !Snapshot(cx, obj, flags, &keys))

             return false;

         if (!VectorToKeyIterator(cx, obj, flags, keys, shapes.length(), key, vp))

             return false;

     }

     PropertyIteratorObject *iterobj = &vp.toObject().as<PropertyIteratorObject>();

     /* Cache the iterator object if possible. */

     if (shapes.length())

         cx->runtime()->nativeIterCache.set(key, iterobj);

     if (shapes.length() == 2)

         cx->runtime()->nativeIterCache.last = iterobj;

     return true;

 }

 JSObject *

 js::GetIteratorObject(JSContext *cx, HandleObject obj, uint32_t flags)

 {

     RootedValue value(cx);

     if (!GetIterator(cx, obj, flags, &value))

         return nullptr;

     return &value.toObject();

 }

 JSObject *

 js::CreateItrResultObject(JSContext *cx, HandleValue value, bool done)

 {

     // FIXME: We can cache the iterator result object shape somewhere.

     AssertHeapIsIdle(cx);

     RootedObject proto(cx, cx->global()->getOrCreateObjectPrototype(cx));

     if (!proto)

         return nullptr;

     RootedObject obj(cx, NewObjectWithGivenProto(cx, &JSObject::class_, proto, cx->global()));

     if (!obj)

         return nullptr;

     if (!JSObject::defineProperty(cx, obj, cx->names().value, value))

         return nullptr;

     RootedValue doneBool(cx, BooleanValue(done));

     if (!JSObject::defineProperty(cx, obj, cx->names().done, doneBool))

         return nullptr;

     return obj;

 }

 bool

 js_ThrowStopIteration(JSContext *cx)

 {

     JS_ASSERT(!JS_IsExceptionPending(cx));

     // StopIteration isn't a constructor, but it's stored in GlobalObject

     // as one, out of laziness. Hence the GetBuiltinConstructor call here.

     RootedObject ctor(cx);

     if (GetBuiltinConstructor(cx, JSProto_StopIteration, &ctor))

         cx->setPendingException(ObjectValue(*ctor));

     return false;

 }

 /*** Iterator objects ****************************************************************************/

 bool

 js::IteratorConstructor(JSContext *cx, unsigned argc, Value *vp)

 {

     CallArgs args = CallArgsFromVp(argc, vp);

     if (args.length() == 0) {

         js_ReportMissingArg(cx, args.calleev(), 0);

         return false;

     }

     bool keyonly = false;

     if (args.length() >= 2)

         keyonly = ToBoolean(args[1]);

     unsigned flags = JSITER_OWNONLY | (keyonly ? 0 : (JSITER_FOREACH | JSITER_KEYVALUE));

     if (!ValueToIterator(cx, flags, args[0]))

         return false;

     args.rval().set(args[0]);

     return true;

 }

 MOZ_ALWAYS_INLINE bool

 IsIterator(HandleValue v)

 {

     return v.isObject() && v.toObject().hasClass(&PropertyIteratorObject::class_);

 }

 MOZ_ALWAYS_INLINE bool

 iterator_next_impl(JSContext *cx, CallArgs args)

 {

     JS_ASSERT(IsIterator(args.thisv()));

     RootedObject thisObj(cx, &args.thisv().toObject());

     if (!js_IteratorMore(cx, thisObj, args.rval()))

         return false;

     if (!args.rval().toBoolean()) {

         js_ThrowStopIteration(cx);

         return false;

     }

     return js_IteratorNext(cx, thisObj, args.rval());

 }

 static bool

 iterator_next(JSContext *cx, unsigned argc, Value *vp)

 {

     CallArgs args = CallArgsFromVp(argc, vp);

     return CallNonGenericMethod<IsIterator, iterator_next_impl>(cx, args);

 }

 static const JSFunctionSpec iterator_methods[] = {

     JS_SELF_HOSTED_FN("@@iterator", "LegacyIteratorShim", 0, 0),

     JS_FN("next",      iterator_next,       0, 0),

     JS_FS_END

 };

 static JSObject *

 iterator_iteratorObject(JSContext *cx, HandleObject obj, bool keysonly)

 {

     return obj;

 }

 size_t

 PropertyIteratorObject::sizeOfMisc(mozilla::MallocSizeOf mallocSizeOf) const

 {

     return mallocSizeOf(getPrivate());

 }

 void

 PropertyIteratorObject::trace(JSTracer *trc, JSObject *obj)

 {

     if (NativeIterator *ni = obj->as<PropertyIteratorObject>().getNativeIterator())

         ni->mark(trc);

 }

 void

 PropertyIteratorObject::finalize(FreeOp *fop, JSObject *obj)

 {

     if (NativeIterator *ni = obj->as<PropertyIteratorObject>().getNativeIterator())

         fop->free_(ni);

 }

 const Class PropertyIteratorObject::class_ = {

     "Iterator",

     JSCLASS_IMPLEMENTS_BARRIERS |

     JSCLASS_HAS_CACHED_PROTO(JSProto_Iterator) |

     JSCLASS_HAS_PRIVATE |

     JSCLASS_BACKGROUND_FINALIZE,

     JS_PropertyStub,         /* addProperty */

     JS_DeletePropertyStub,   /* delProperty */

     JS_PropertyStub,         /* getProperty */

     JS_StrictPropertyStub,   /* setProperty */

     JS_EnumerateStub,

     JS_ResolveStub,

     JS_ConvertStub,

     finalize,

     nullptr,                 /* call        */

     nullptr,                 /* hasInstance */

     nullptr,                 /* construct   */

     trace,

     JS_NULL_CLASS_SPEC,

     {

         nullptr,             /* outerObject    */

         nullptr,             /* innerObject    */

         iterator_iteratorObject,

     }

 };

 enum {

     ArrayIteratorSlotIteratedObject,

     ArrayIteratorSlotNextIndex,

     ArrayIteratorSlotItemKind,

     ArrayIteratorSlotCount

 };

 const Class ArrayIteratorObject::class_ = {

     "Array Iterator",

     JSCLASS_IMPLEMENTS_BARRIERS |

     JSCLASS_HAS_RESERVED_SLOTS(ArrayIteratorSlotCount),

     JS_PropertyStub,         /* addProperty */

     JS_DeletePropertyStub,   /* delProperty */

     JS_PropertyStub,         /* getProperty */

     JS_StrictPropertyStub,   /* setProperty */

     JS_EnumerateStub,

     JS_ResolveStub,

     JS_ConvertStub,

     nullptr                  /* finalize    */

 };

 static const JSFunctionSpec array_iterator_methods[] = {

     JS_SELF_HOSTED_FN("@@iterator", "ArrayIteratorIdentity", 0, 0),

     JS_SELF_HOSTED_FN("next", "ArrayIteratorNext", 0, 0),

     JS_FS_END

 };

 static const Class StringIteratorPrototypeClass = {

     "String Iterator",

     JSCLASS_IMPLEMENTS_BARRIERS,

     JS_PropertyStub,         /* addProperty */

     JS_DeletePropertyStub,   /* delProperty */

     JS_PropertyStub,         /* getProperty */

     JS_StrictPropertyStub,   /* setProperty */

     JS_EnumerateStub,

     JS_ResolveStub,

     JS_ConvertStub,

     nullptr                  /* finalize    */

 };

 enum {

     StringIteratorSlotIteratedObject,

     StringIteratorSlotNextIndex,

     StringIteratorSlotCount

 };

 const Class StringIteratorObject::class_ = {

     "String Iterator",

     JSCLASS_IMPLEMENTS_BARRIERS |

     JSCLASS_HAS_RESERVED_SLOTS(StringIteratorSlotCount),

     JS_PropertyStub,         /* addProperty */

     JS_DeletePropertyStub,   /* delProperty */

     JS_PropertyStub,         /* getProperty */

     JS_StrictPropertyStub,   /* setProperty */

     JS_EnumerateStub,

     JS_ResolveStub,

     JS_ConvertStub,

     nullptr                  /* finalize    */

 };

 static const JSFunctionSpec string_iterator_methods[] = {

     JS_SELF_HOSTED_FN("@@iterator", "StringIteratorIdentity", 0, 0),

     JS_SELF_HOSTED_FN("next", "StringIteratorNext", 0, 0),

     JS_FS_END

 };

 static bool

 CloseLegacyGenerator(JSContext *cx, HandleObject genobj);

 bool

 js::ValueToIterator(JSContext *cx, unsigned flags, MutableHandleValue vp)

 {

     /* JSITER_KEYVALUE must always come with JSITER_FOREACH */

     JS_ASSERT_IF(flags & JSITER_KEYVALUE, flags & JSITER_FOREACH);

     /*

      * Make sure the more/next state machine doesn't get stuck. A value might

      * be left in iterValue when a trace is left due to an interrupt after

      * JSOP_MOREITER but before the value is picked up by FOR*.

      */

     cx->iterValue.setMagic(JS_NO_ITER_VALUE);

     RootedObject obj(cx);

     if (vp.isObject()) {

         /* Common case. */

         obj = &vp.toObject();

     } else {

         /*

          * Enumerating over null and undefined gives an empty enumerator, so

          * that |for (var p in <null or undefined>) <loop>;| never executes

          * <loop>, per ES5 12.6.4.

          */

         if (!(flags & JSITER_ENUMERATE) || !vp.isNullOrUndefined()) {

             obj = ToObject(cx, vp);

             if (!obj)

                 return false;

         }

     }

     return GetIterator(cx, obj, flags, vp);

 }

 bool

 js::CloseIterator(JSContext *cx, HandleObject obj)

 {

     cx->iterValue.setMagic(JS_NO_ITER_VALUE);

     if (obj->is<PropertyIteratorObject>()) {

         /* Remove enumerators from the active list, which is a stack. */

         NativeIterator *ni = obj->as<PropertyIteratorObject>().getNativeIterator();

         if (ni->flags & JSITER_ENUMERATE) {

             ni->unlink();

             JS_ASSERT(ni->flags & JSITER_ACTIVE);

             ni->flags &= ~JSITER_ACTIVE;

             /*

              * Reset the enumerator; it may still be in the cached iterators

              * for this thread, and can be reused.

              */

             ni->props_cursor = ni->props_array;

         }

     } else if (obj->is<LegacyGeneratorObject>()) {

         return CloseLegacyGenerator(cx, obj);

     }

     return true;

 }

 bool

 js::UnwindIteratorForException(JSContext *cx, HandleObject obj)

 {

     RootedValue v(cx);

     bool getOk = cx->getPendingException(&v);

     cx->clearPendingException();

     if (!CloseIterator(cx, obj))

         return false;

     if (!getOk)

         return false;

     cx->setPendingException(v);

     return true;

 }

 void

 js::UnwindIteratorForUncatchableException(JSContext *cx, JSObject *obj)

 {

     if (obj->is<PropertyIteratorObject>()) {

         NativeIterator *ni = obj->as<PropertyIteratorObject>().getNativeIterator();

         if (ni->flags & JSITER_ENUMERATE)

             ni->unlink();

     }

 }

 /*

  * Suppress enumeration of deleted properties. This function must be called

  * when a property is deleted and there might be active enumerators.

  *

  * We maintain a list of active non-escaping for-in enumerators. To suppress

  * a property, we check whether each active enumerator contains the (obj, id)

  * pair and has not yet enumerated |id|. If so, and |id| is the next property,

  * we simply advance the cursor. Otherwise, we delete |id| from the list.

  *

  * We do not suppress enumeration of a property deleted along an object's

  * prototype chain. Only direct deletions on the object are handled.

  *

  * This function can suppress multiple properties at once. The |predicate|

  * argument is an object which can be called on an id and returns true or

  * false. It also must have a method |matchesAtMostOne| which allows us to

  * stop searching after the first deletion if true.

  */

 template<typename StringPredicate>

 static bool

 SuppressDeletedPropertyHelper(JSContext *cx, HandleObject obj, StringPredicate predicate)

 {

     NativeIterator *enumeratorList = cx->compartment()->enumerators;

     NativeIterator *ni = enumeratorList->next();

     while (ni != enumeratorList) {

       again:

         /* This only works for identified suppressed keys, not values. */

         if (ni->isKeyIter() && ni->obj == obj && ni->props_cursor < ni->props_end) {

             /* Check whether id is still to come. */

             HeapPtr<JSFlatString> *props_cursor = ni->current();

             HeapPtr<JSFlatString> *props_end = ni->end();

             for (HeapPtr<JSFlatString> *idp = props_cursor; idp < props_end; ++idp) {

                 if (predicate(*idp)) {

                     /*

                      * Check whether another property along the prototype chain

                      * became visible as a result of this deletion.

                      */

                     RootedObject proto(cx);

                     if (!JSObject::getProto(cx, obj, &proto))

                         return false;

                     if (proto) {

                         RootedObject obj2(cx);

                         RootedShape prop(cx);

                         RootedId id(cx);

                         RootedValue idv(cx, StringValue(*idp));

                         if (!ValueToId<CanGC>(cx, idv, &id))

                             return false;

                         if (!JSObject::lookupGeneric(cx, proto, id, &obj2, &prop))

                             return false;

                         if (prop) {

                             unsigned attrs;

                             if (obj2->isNative())

                                 attrs = GetShapeAttributes(obj2, prop);

                             else if (!JSObject::getGenericAttributes(cx, obj2, id, &attrs))

                                 return false;

                             if (attrs & JSPROP_ENUMERATE)

                                 continue;

                         }

                     }

                     /*

                      * If lookupProperty or getAttributes above removed a property from

                      * ni, start over.

                      */

                     if (props_end != ni->props_end || props_cursor != ni->props_cursor)

                         goto again;

                     /*

                      * No property along the prototype chain stepped in to take the

                      * property's place, so go ahead and delete id from the list.

                      * If it is the next property to be enumerated, just skip it.

                      */

                     if (idp == props_cursor) {

                         ni->incCursor();

                     } else {

                         for (HeapPtr<JSFlatString> *p = idp; p + 1 != props_end; p++)

                             *p = *(p + 1);

                         ni->props_end = ni->end() - 1;

                         /*

                          * This invokes the pre barrier on this element, since

                          * it's no longer going to be marked, and ensures that

                          * any existing remembered set entry will be dropped.

                          */

                         *ni->props_end = nullptr;

                     }

                     /* Don't reuse modified native iterators. */

                     ni->flags |= JSITER_UNREUSABLE;

                     if (predicate.matchesAtMostOne())

                         break;

                 }

             }

         }

         ni = ni->next();

     }

     return true;

 }

 namespace {

 class SingleStringPredicate {

     Handle<JSFlatString*> str;

 public:

     SingleStringPredicate(Handle<JSFlatString*> str) : str(str) {}

     bool operator()(JSFlatString *str) { return EqualStrings(str, this->str); }

     bool matchesAtMostOne() { return true; }

 };

 } /* anonymous namespace */

 bool

 js_SuppressDeletedProperty(JSContext *cx, HandleObject obj, jsid id)

 {

     Rooted<JSFlatString*> str(cx, IdToString(cx, id));

     if (!str)

         return false;

     return SuppressDeletedPropertyHelper(cx, obj, SingleStringPredicate(str));

 }

 bool

 js_SuppressDeletedElement(JSContext *cx, HandleObject obj, uint32_t index)

 {

     RootedId id(cx);

     if (!IndexToId(cx, index, &id))

         return false;

     return js_SuppressDeletedProperty(cx, obj, id);

 }

 namespace {

 class IndexRangePredicate {

     uint32_t begin, end;

   public:

     IndexRangePredicate(uint32_t begin, uint32_t end) : begin(begin), end(end) {}

     bool operator()(JSFlatString *str) {

         uint32_t index;

         return str->isIndex(&index) && begin <= index && index < end;

     }

     bool matchesAtMostOne() { return false; }

 };

 } /* anonymous namespace */

 bool

 js_SuppressDeletedElements(JSContext *cx, HandleObject obj, uint32_t begin, uint32_t end)

 {

     return SuppressDeletedPropertyHelper(cx, obj, IndexRangePredicate(begin, end));

 }

 bool

 js_IteratorMore(JSContext *cx, HandleObject iterobj, MutableHandleValue rval)

 {

     /* Fast path for native iterators */

     NativeIterator *ni = nullptr;

     if (iterobj->is<PropertyIteratorObject>()) {

         /* Key iterators are handled by fast-paths. */

         ni = iterobj->as<PropertyIteratorObject>().getNativeIterator();

         bool more = ni->props_cursor < ni->props_end;

         if (ni->isKeyIter() || !more) {

             rval.setBoolean(more);

             return true;

         }

     }

     /* We might still have a pending value. */

     if (!cx->iterValue.isMagic(JS_NO_ITER_VALUE)) {

         rval.setBoolean(true);

         return true;

     }

     /* We're reentering below and can call anything. */

     JS_CHECK_RECURSION(cx, return false);

     /* Fetch and cache the next value from the iterator. */

     if (ni) {

         JS_ASSERT(!ni->isKeyIter());

         RootedId id(cx);

         RootedValue current(cx, StringValue(*ni->current()));

         if (!ValueToId<CanGC>(cx, current, &id))

             return false;

         ni->incCursor();

         RootedObject obj(cx, ni->obj);

         if (!JSObject::getGeneric(cx, obj, obj, id, rval))

             return false;

         if ((ni->flags & JSITER_KEYVALUE) && !NewKeyValuePair(cx, id, rval, rval))

             return false;

     } else {

         /* Call the iterator object's .next method. */

         if (!JSObject::getProperty(cx, iterobj, iterobj, cx->names().next, rval))

             return false;

         if (!Invoke(cx, ObjectValue(*iterobj), rval, 0, nullptr, rval)) {

             /* Check for StopIteration. */

             if (!cx->isExceptionPending())

                 return false;

             RootedValue exception(cx);

             if (!cx->getPendingException(&exception))

                 return false;

             if (!JS_IsStopIteration(exception))

                 return false;

             cx->clearPendingException();

             cx->iterValue.setMagic(JS_NO_ITER_VALUE);

             rval.setBoolean(false);

             return true;

         }

     }

     /* Cache the value returned by iterobj.next() so js_IteratorNext() can find it. */

     JS_ASSERT(!rval.isMagic(JS_NO_ITER_VALUE));

     cx->iterValue = rval;

     rval.setBoolean(true);

     return true;

 }

 bool

 js_IteratorNext(JSContext *cx, HandleObject iterobj, MutableHandleValue rval)

 {

     /* Fast path for native iterators */

     if (iterobj->is<PropertyIteratorObject>()) {

         /*

          * Implement next directly as all the methods of the native iterator are

          * read-only and permanent.

          */

         NativeIterator *ni = iterobj->as<PropertyIteratorObject>().getNativeIterator();

         if (ni->isKeyIter()) {

             JS_ASSERT(ni->props_cursor < ni->props_end);

             rval.setString(*ni->current());

             ni->incCursor();

             return true;

         }

     }

     JS_ASSERT(!cx->iterValue.isMagic(JS_NO_ITER_VALUE));

     rval.set(cx->iterValue);

     cx->iterValue.setMagic(JS_NO_ITER_VALUE);

     return true;

 }

 static bool

 stopiter_hasInstance(JSContext *cx, HandleObject obj, MutableHandleValue v, bool *bp)

 {

     *bp = JS_IsStopIteration(v);

     return true;

 }

 const Class StopIterationObject::class_ = {

     "StopIteration",

     JSCLASS_HAS_CACHED_PROTO(JSProto_StopIteration),

     JS_PropertyStub,         /* addProperty */

     JS_DeletePropertyStub,   /* delProperty */

     JS_PropertyStub,         /* getProperty */

     JS_StrictPropertyStub,   /* setProperty */

     JS_EnumerateStub,

     JS_ResolveStub,

     JS_ConvertStub,

     nullptr,                 /* finalize    */

     nullptr,                 /* call        */

     stopiter_hasInstance,

     nullptr                  /* construct   */

 };

 bool

 ForOfIterator::init(HandleValue iterable, NonIterableBehavior nonIterableBehavior)

 {

     JSContext *cx = cx_;

     RootedObject iterableObj(cx, ToObject(cx, iterable));

     if (!iterableObj)

         return false;

     JS_ASSERT(index == NOT_ARRAY);

     // Check the PIC first for a match.

     if (iterableObj->is<ArrayObject>()) {

         ForOfPIC::Chain *stubChain = ForOfPIC::getOrCreate(cx);

         if (!stubChain)

             return false;

         bool optimized;

         if (!stubChain->tryOptimizeArray(cx, iterableObj, &optimized))

             return false;

         if (optimized) {

             // Got optimized stub.  Array is optimizable.

             index = 0;

             iterator = iterableObj;

             return true;

         }

     }

     JS_ASSERT(index == NOT_ARRAY);

     // The iterator is the result of calling obj[@@iterator]().

     InvokeArgs args(cx);

     if (!args.init(0))

         return false;

     args.setThis(ObjectValue(*iterableObj));

     RootedValue callee(cx);

     if (!JSObject::getProperty(cx, iterableObj, iterableObj, cx->names().std_iterator, &callee))

         return false;

     // Throw if obj[@@iterator] isn't callable if we were asked to do so.

     // js::Invoke is about to check for this kind of error anyway, but it would

     // throw an inscrutable error message about |method| rather than this nice

     // one about |obj|.

     if (!callee.isObject() || !callee.toObject().isCallable()) {

         if (nonIterableBehavior == AllowNonIterable)

             return true;

         char *bytes = DecompileValueGenerator(cx, JSDVG_SEARCH_STACK, iterable, NullPtr());

         if (!bytes)

             return false;

         JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_NOT_ITERABLE, bytes);

         js_free(bytes);

         return false;

     }

     args.setCallee(callee);

     if (!Invoke(cx, args))

         return false;

     iterator = ToObject(cx, args.rval());

     if (!iterator)

         return false;

     return true;

 }

 inline bool

 ForOfIterator::nextFromOptimizedArray(MutableHandleValue vp, bool *done)

 {

     JS_ASSERT(index != NOT_ARRAY);

     if (!CheckForInterrupt(cx_))

         return false;

     JS_ASSERT(iterator->isNative());

     JS_ASSERT(iterator->is<ArrayObject>());

     if (index >= iterator->as<ArrayObject>().length()) {

         vp.setUndefined();

         *done = true;

         return true;

     }

     *done = false;

     // Try to get array element via direct access.

     if (index < iterator->getDenseInitializedLength()) {

         vp.set(iterator->getDenseElement(index));

         if (!vp.isMagic(JS_ELEMENTS_HOLE)) {

             ++index;

             return true;

         }

     }

     return JSObject::getElement(cx_, iterator, iterator, index++, vp);

 }

 bool

 ForOfIterator::next(MutableHandleValue vp, bool *done)

 {

     JS_ASSERT(iterator);

     if (index != NOT_ARRAY) {

         ForOfPIC::Chain *stubChain = ForOfPIC::getOrCreate(cx_);

         if (!stubChain)

             return false;

         if (stubChain->isArrayNextStillSane())

             return nextFromOptimizedArray(vp, done);

         // ArrayIterator.prototype.next changed, materialize a proper

         // ArrayIterator instance and fall through to slowpath case.

         if (!materializeArrayIterator())

             return false;

     }

     RootedValue method(cx_);

     if (!JSObject::getProperty(cx_, iterator, iterator, cx_->names().next, &method))

         return false;

     InvokeArgs args(cx_);

     if (!args.init(1))

         return false;

     args.setCallee(method);

     args.setThis(ObjectValue(*iterator));

     args[0].setUndefined();

     if (!Invoke(cx_, args))

         return false;

     RootedObject resultObj(cx_, ToObject(cx_, args.rval()));

     if (!resultObj)

         return false;

     RootedValue doneVal(cx_);

     if (!JSObject::getProperty(cx_, resultObj, resultObj, cx_->names().done, &doneVal))

         return false;

     *done = ToBoolean(doneVal);

     if (*done) {

         vp.setUndefined();

         return true;

     }

     return JSObject::getProperty(cx_, resultObj, resultObj, cx_->names().value, vp);

 }

 bool

 ForOfIterator::materializeArrayIterator()

 {

     JS_ASSERT(index != NOT_ARRAY);

     const char *nameString = "ArrayValuesAt";

     RootedAtom name(cx_, Atomize(cx_, nameString, strlen(nameString)));

     if (!name)

         return false;

     RootedValue val(cx_);

     if (!cx_->global()->getSelfHostedFunction(cx_, name, name, 1, &val))

         return false;

     InvokeArgs args(cx_);

     if (!args.init(1))

         return false;

     args.setCallee(val);

     args.setThis(ObjectValue(*iterator));

     args[0].set(Int32Value(index));

     if (!Invoke(cx_, args))

         return false;

     index = NOT_ARRAY;

     // Result of call to ArrayValuesAt must be an object.

     iterator = &args.rval().toObject();

     return true;

 }

 /*** Generators **********************************************************************************/

 template<typename T>

 static void

 FinalizeGenerator(FreeOp *fop, JSObject *obj)

 {

     JS_ASSERT(obj->is<T>());

     JSGenerator *gen = obj->as<T>().getGenerator();

     JS_ASSERT(gen);

     // gen is open when a script has not called its close method while

     // explicitly manipulating it.

     JS_ASSERT(gen->state == JSGEN_NEWBORN ||

               gen->state == JSGEN_CLOSED ||

               gen->state == JSGEN_OPEN);

     // If gen->state is JSGEN_CLOSED, gen->fp may be nullptr.

     if (gen->fp)

         JS_POISON(gen->fp, JS_SWEPT_FRAME_PATTERN, sizeof(InterpreterFrame));

     JS_POISON(gen, JS_SWEPT_FRAME_PATTERN, sizeof(JSGenerator));

     fop->free_(gen);

 }

 static void

 MarkGeneratorFrame(JSTracer *trc, JSGenerator *gen)

 {

     MarkValueRange(trc,

                    HeapValueify(gen->fp->generatorArgsSnapshotBegin()),

                    HeapValueify(gen->fp->generatorArgsSnapshotEnd()),

                    "Generator Floating Args");

     gen->fp->mark(trc);

     MarkValueRange(trc,

                    HeapValueify(gen->fp->generatorSlotsSnapshotBegin()),

                    HeapValueify(gen->regs.sp),

                    "Generator Floating Stack");

 }

 static void

 GeneratorWriteBarrierPre(JSContext *cx, JSGenerator *gen)

 {

     JS::Zone *zone = cx->zone();

     if (zone->needsBarrier())

         MarkGeneratorFrame(zone->barrierTracer(), gen);

 }

 static void

 GeneratorWriteBarrierPost(JSContext *cx, JSGenerator *gen)

 {

 #ifdef JSGC_GENERATIONAL

     cx->runtime()->gcStoreBuffer.putWholeCell(gen->obj);

 #endif

 }

 /*

  * Only mark generator frames/slots when the generator is not active on the

  * stack or closed. Barriers when copying onto the stack or closing preserve

  * gc invariants.

  */

 static bool

 GeneratorHasMarkableFrame(JSGenerator *gen)

 {

     return gen->state == JSGEN_NEWBORN || gen->state == JSGEN_OPEN;

 }

 /*

  * When a generator is closed, the GC things reachable from the contained frame

  * and slots become unreachable and thus require a write barrier.

  */

 static void

 SetGeneratorClosed(JSContext *cx, JSGenerator *gen)

 {

     JS_ASSERT(gen->state != JSGEN_CLOSED);

     if (GeneratorHasMarkableFrame(gen))

         GeneratorWriteBarrierPre(cx, gen);

     gen->state = JSGEN_CLOSED;

 #ifdef DEBUG

     MakeRangeGCSafe(gen->fp->generatorArgsSnapshotBegin(),

                     gen->fp->generatorArgsSnapshotEnd());

     MakeRangeGCSafe(gen->fp->generatorSlotsSnapshotBegin(),

                     gen->regs.sp);

     PodZero(&gen->regs, 1);

     gen->fp = nullptr;

 #endif

 }

 template<typename T>

 static void

 TraceGenerator(JSTracer *trc, JSObject *obj)

 {

     JS_ASSERT(obj->is<T>());

     JSGenerator *gen = obj->as<T>().getGenerator();

     JS_ASSERT(gen);

     if (GeneratorHasMarkableFrame(gen))

         MarkGeneratorFrame(trc, gen);

 }

 GeneratorState::GeneratorState(JSContext *cx, JSGenerator *gen, JSGeneratorState futureState)

   : RunState(cx, Generator, gen->fp->script()),

     cx_(cx),

     gen_(gen),

     futureState_(futureState),

     entered_(false)

 { }

 GeneratorState::~GeneratorState()

 {

     gen_->fp->setSuspended();

     if (entered_)

         cx_->leaveGenerator(gen_);

 }

 InterpreterFrame *

 GeneratorState::pushInterpreterFrame(JSContext *cx)

 {

     /*

      * Write barrier is needed since the generator stack can be updated,

      * and it's not barriered in any other way. We need to do it before

      * gen->state changes, which can cause us to trace the generator

      * differently.

      *

      * We could optimize this by setting a bit on the generator to signify

      * that it has been marked. If this bit has already been set, there is no

      * need to mark again. The bit would have to be reset before the next GC,

      * or else some kind of epoch scheme would have to be used.

      */

     GeneratorWriteBarrierPre(cx, gen_);

     gen_->state = futureState_;

     gen_->fp->clearSuspended();

     cx->enterGenerator(gen_);   /* OOM check above. */

     entered_ = true;

     return gen_->fp;

 }

 const Class LegacyGeneratorObject::class_ = {

     "Generator",

     JSCLASS_HAS_PRIVATE | JSCLASS_IMPLEMENTS_BARRIERS,

     JS_PropertyStub,         /* addProperty */

     JS_DeletePropertyStub,   /* delProperty */

     JS_PropertyStub,         /* getProperty */

     JS_StrictPropertyStub,   /* setProperty */

     JS_EnumerateStub,

     JS_ResolveStub,

     JS_ConvertStub,

     FinalizeGenerator<LegacyGeneratorObject>,

     nullptr,                 /* call        */

     nullptr,                 /* hasInstance */

     nullptr,                 /* construct   */

     TraceGenerator<LegacyGeneratorObject>,

     JS_NULL_CLASS_SPEC,

     {

         nullptr,             /* outerObject    */

         nullptr,             /* innerObject    */

         iterator_iteratorObject,

     }

 };

 const Class StarGeneratorObject::class_ = {

     "Generator",

     JSCLASS_HAS_PRIVATE | JSCLASS_IMPLEMENTS_BARRIERS,

     JS_PropertyStub,         /* addProperty */

     JS_DeletePropertyStub,   /* delProperty */

     JS_PropertyStub,         /* getProperty */

     JS_StrictPropertyStub,   /* setProperty */

     JS_EnumerateStub,

     JS_ResolveStub,

     JS_ConvertStub,

     FinalizeGenerator<StarGeneratorObject>,

     nullptr,                 /* call        */

     nullptr,                 /* hasInstance */

     nullptr,                 /* construct   */

     TraceGenerator<StarGeneratorObject>,

     JS_NULL_CLASS_SPEC,

     {

         nullptr,             /* outerObject    */

         nullptr,             /* innerObject    */

         iterator_iteratorObject,

     }

 };

 /*

  * Called from the JSOP_GENERATOR case in the interpreter, with fp referring

  * to the frame by which the generator function was activated.  Create a new

  * JSGenerator object, which contains its own InterpreterFrame that we populate

  * from *fp.  We know that upon return, the JSOP_GENERATOR opcode will return

  * from the activation in fp, so we can steal away fp->callobj and fp->argsobj

  * if they are non-null.

  */

 JSObject *

 js_NewGenerator(JSContext *cx, const InterpreterRegs &stackRegs)

 {

     JS_ASSERT(stackRegs.stackDepth() == 0);

     InterpreterFrame *stackfp = stackRegs.fp();

     JS_ASSERT(stackfp->script()->isGenerator());

     Rooted<GlobalObject*> global(cx, &stackfp->global());

     RootedObject obj(cx);

     if (stackfp->script()->isStarGenerator()) {

         RootedValue pval(cx);

         RootedObject fun(cx, stackfp->fun());

         // FIXME: This would be faster if we could avoid doing a lookup to get

         // the prototype for the instance.  Bug 906600.

         if (!JSObject::getProperty(cx, fun, fun, cx->names().prototype, &pval))

             return nullptr;

         JSObject *proto = pval.isObject() ? &pval.toObject() : nullptr;

         if (!proto) {

             proto = GlobalObject::getOrCreateStarGeneratorObjectPrototype(cx, global);

             if (!proto)

                 return nullptr;

         }

         obj = NewObjectWithGivenProto(cx, &StarGeneratorObject::class_, proto, global);

     } else {

         JS_ASSERT(stackfp->script()->isLegacyGenerator());

         JSObject *proto = GlobalObject::getOrCreateLegacyGeneratorObjectPrototype(cx, global);

         if (!proto)

             return nullptr;

         obj = NewObjectWithGivenProto(cx, &LegacyGeneratorObject::class_, proto, global);

     }

     if (!obj)

         return nullptr;

     /* Load and compute stack slot counts. */

     Value *stackvp = stackfp->generatorArgsSnapshotBegin();

     unsigned vplen = stackfp->generatorArgsSnapshotEnd() - stackvp;

     /* Compute JSGenerator size. */

     unsigned nbytes = sizeof(JSGenerator) +

                    (-1 + /* one Value included in JSGenerator */

                     vplen +

                     VALUES_PER_STACK_FRAME +

                     stackfp->script()->nslots()) * sizeof(HeapValue);

     JS_ASSERT(nbytes % sizeof(Value) == 0);

     JS_STATIC_ASSERT(sizeof(InterpreterFrame) % sizeof(HeapValue) == 0);

     JSGenerator *gen = (JSGenerator *) cx->calloc_(nbytes);

     if (!gen)

         return nullptr;

     /* Cut up floatingStack space. */

     HeapValue *genvp = gen->stackSnapshot;

     SetValueRangeToUndefined((Value *)genvp, vplen);

     InterpreterFrame *genfp = reinterpret_cast<InterpreterFrame *>(genvp + vplen);

     /* Initialize JSGenerator. */

     gen->obj.init(obj);

     gen->state = JSGEN_NEWBORN;

     gen->fp = genfp;

     gen->prevGenerator = nullptr;

     /* Copy from the stack to the generator's floating frame. */

     gen->regs.rebaseFromTo(stackRegs, *genfp);

     genfp->copyFrameAndValues<InterpreterFrame::DoPostBarrier>(cx, (Value *)genvp, stackfp,

                                                          stackvp, stackRegs.sp);

     genfp->setSuspended();

     obj->setPrivate(gen);

     return obj;

 }

 static void

 SetGeneratorClosed(JSContext *cx, JSGenerator *gen);

 typedef enum JSGeneratorOp {

     JSGENOP_NEXT,

     JSGENOP_SEND,

     JSGENOP_THROW,

     JSGENOP_CLOSE

 } JSGeneratorOp;

 /*

  * Start newborn or restart yielding generator and perform the requested

  * operation inside its frame.

  */

 static bool

 SendToGenerator(JSContext *cx, JSGeneratorOp op, HandleObject obj,

                 JSGenerator *gen, HandleValue arg, GeneratorKind generatorKind,

                 MutableHandleValue rval)

 {

     JS_ASSERT(generatorKind == LegacyGenerator || generatorKind == StarGenerator);

     if (gen->state == JSGEN_RUNNING || gen->state == JSGEN_CLOSING) {

         JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_NESTING_GENERATOR);

         return false;

     }

     JSGeneratorState futureState;

     JS_ASSERT(gen->state == JSGEN_NEWBORN || gen->state == JSGEN_OPEN);

     switch (op) {

       case JSGENOP_NEXT:

       case JSGENOP_SEND:

         if (gen->state == JSGEN_OPEN) {

             /*

              * Store the argument to send as the result of the yield

              * expression. The generator stack is not barriered, so we need

              * write barriers here.

              */

             HeapValue::writeBarrierPre(gen->regs.sp[-1]);

             gen->regs.sp[-1] = arg;

             HeapValue::writeBarrierPost(cx->runtime(), gen->regs.sp[-1], &gen->regs.sp[-1]);

         }

         futureState = JSGEN_RUNNING;

         break;

       case JSGENOP_THROW:

         cx->setPendingException(arg);

         futureState = JSGEN_RUNNING;

         break;

       default:

         JS_ASSERT(op == JSGENOP_CLOSE);

         JS_ASSERT(generatorKind == LegacyGenerator);

         cx->setPendingException(MagicValue(JS_GENERATOR_CLOSING));

         futureState = JSGEN_CLOSING;

         break;

     }

     bool ok;

     {

         GeneratorState state(cx, gen, futureState);

         ok = RunScript(cx, state);

         if (!ok && gen->state == JSGEN_CLOSED)

             return false;

     }

     if (gen->fp->isYielding()) {

         /*

          * Yield is ordinarily infallible, but ok can be false here if a

          * Debugger.Frame.onPop hook fails.

          */

         JS_ASSERT(gen->state == JSGEN_RUNNING);

         JS_ASSERT(op != JSGENOP_CLOSE);

         gen->fp->clearYielding();

         gen->state = JSGEN_OPEN;

         GeneratorWriteBarrierPost(cx, gen);

         rval.set(gen->fp->returnValue());

         return ok;

     }

     if (ok) {

         if (generatorKind == StarGenerator) {

             // Star generators return a {value:FOO, done:true} object.

             rval.set(gen->fp->returnValue());

         } else {

             JS_ASSERT(generatorKind == LegacyGenerator);

             // Otherwise we discard the return value and throw a StopIteration

             // if needed.

             rval.setUndefined();

             if (op != JSGENOP_CLOSE)

                 ok = js_ThrowStopIteration(cx);

         }

     }

     SetGeneratorClosed(cx, gen);

     return ok;

 }

 MOZ_ALWAYS_INLINE bool

 star_generator_next(JSContext *cx, CallArgs args)

 {

     RootedObject thisObj(cx, &args.thisv().toObject());

     JSGenerator *gen = thisObj->as<StarGeneratorObject>().getGenerator();

     if (gen->state == JSGEN_CLOSED) {

         RootedObject obj(cx, CreateItrResultObject(cx, JS::UndefinedHandleValue, true));

         if (!obj)

             return false;

         args.rval().setObject(*obj);

         return true;

     }

     if (gen->state == JSGEN_NEWBORN && args.hasDefined(0)) {

         RootedValue val(cx, args[0]);

         js_ReportValueError(cx, JSMSG_BAD_GENERATOR_SEND,

                             JSDVG_SEARCH_STACK, val, js::NullPtr());

         return false;

     }

     return SendToGenerator(cx, JSGENOP_SEND, thisObj, gen, args.get(0), StarGenerator,

                            args.rval());

 }

 MOZ_ALWAYS_INLINE bool

 star_generator_throw(JSContext *cx, CallArgs args)

 {

     RootedObject thisObj(cx, &args.thisv().toObject());

     JSGenerator *gen = thisObj->as<StarGeneratorObject>().getGenerator();

     if (gen->state == JSGEN_CLOSED) {

         cx->setPendingException(args.get(0));

         return false;

     }

     return SendToGenerator(cx, JSGENOP_THROW, thisObj, gen, args.get(0), StarGenerator,

                            args.rval());

 }

 MOZ_ALWAYS_INLINE bool

 legacy_generator_next(JSContext *cx, CallArgs args)

 {

     RootedObject thisObj(cx, &args.thisv().toObject());

     JSGenerator *gen = thisObj->as<LegacyGeneratorObject>().getGenerator();

     if (gen->state == JSGEN_CLOSED)

         return js_ThrowStopIteration(cx);

     if (gen->state == JSGEN_NEWBORN && args.hasDefined(0)) {

         RootedValue val(cx, args[0]);

         js_ReportValueError(cx, JSMSG_BAD_GENERATOR_SEND,

                             JSDVG_SEARCH_STACK, val, js::NullPtr());

         return false;

     }

     return SendToGenerator(cx, JSGENOP_SEND, thisObj, gen, args.get(0), LegacyGenerator,

                            args.rval());

 }

 MOZ_ALWAYS_INLINE bool

 legacy_generator_throw(JSContext *cx, CallArgs args)

 {

     RootedObject thisObj(cx, &args.thisv().toObject());

     JSGenerator *gen = thisObj->as<LegacyGeneratorObject>().getGenerator();

     if (gen->state == JSGEN_CLOSED) {

         cx->setPendingException(args.length() >= 1 ? args[0] : UndefinedValue());

         return false;

     }

     return SendToGenerator(cx, JSGENOP_THROW, thisObj, gen, args.get(0), LegacyGenerator,

                            args.rval());

 }

 static bool

 CloseLegacyGenerator(JSContext *cx, HandleObject obj, MutableHandleValue rval)

 {

     JS_ASSERT(obj->is<LegacyGeneratorObject>());

     JSGenerator *gen = obj->as<LegacyGeneratorObject>().getGenerator();

     if (gen->state == JSGEN_CLOSED) {

         rval.setUndefined();

         return true;

     }

     if (gen->state == JSGEN_NEWBORN) {

         SetGeneratorClosed(cx, gen);

         rval.setUndefined();

         return true;

     }

     return SendToGenerator(cx, JSGENOP_CLOSE, obj, gen, JS::UndefinedHandleValue, LegacyGenerator,

                            rval);

 }

 static bool

 CloseLegacyGenerator(JSContext *cx, HandleObject obj)

 {

     RootedValue rval(cx);

     return CloseLegacyGenerator(cx, obj, &rval);

 }

 MOZ_ALWAYS_INLINE bool

 legacy_generator_close(JSContext *cx, CallArgs args)

 {

     RootedObject thisObj(cx, &args.thisv().toObject());

     return CloseLegacyGenerator(cx, thisObj, args.rval());

 }

 template<typename T>

 MOZ_ALWAYS_INLINE bool

 IsObjectOfType(HandleValue v)

 {

     return v.isObject() && v.toObject().is<T>();

 }

 template<typename T, NativeImpl Impl>

 static bool

 NativeMethod(JSContext *cx, unsigned argc, Value *vp)

 {

     CallArgs args = CallArgsFromVp(argc, vp);

     return CallNonGenericMethod<IsObjectOfType<T>, Impl>(cx, args);

 }

 #define JSPROP_ROPERM   (JSPROP_READONLY | JSPROP_PERMANENT)

 #define JS_METHOD(name, T, impl, len, attrs) JS_FN(name, (NativeMethod<T,impl>), len, attrs)

 static const JSFunctionSpec star_generator_methods[] = {

     JS_SELF_HOSTED_FN("@@iterator", "IteratorIdentity", 0, 0),

     JS_METHOD("next", StarGeneratorObject, star_generator_next, 1, 0),

     JS_METHOD("throw", StarGeneratorObject, star_generator_throw, 1, 0),

     JS_FS_END

 };

 static const JSFunctionSpec legacy_generator_methods[] = {

     JS_SELF_HOSTED_FN("@@iterator", "LegacyGeneratorIteratorShim", 0, 0),

     // "send" is an alias for "next".

     JS_METHOD("next", LegacyGeneratorObject, legacy_generator_next, 1, JSPROP_ROPERM),

     JS_METHOD("send", LegacyGeneratorObject, legacy_generator_next, 1, JSPROP_ROPERM),

     JS_METHOD("throw", LegacyGeneratorObject, legacy_generator_throw, 1, JSPROP_ROPERM),

     JS_METHOD("close", LegacyGeneratorObject, legacy_generator_close, 0, JSPROP_ROPERM),

     JS_FS_END

 };

 static JSObject*

 NewSingletonObjectWithObjectPrototype(JSContext *cx, Handle<GlobalObject *> global)

 {

     JSObject *proto = global->getOrCreateObjectPrototype(cx);

     if (!proto)

         return nullptr;

     return NewObjectWithGivenProto(cx, &JSObject::class_, proto, global, SingletonObject);

 }

 static JSObject*

 NewSingletonObjectWithFunctionPrototype(JSContext *cx, Handle<GlobalObject *> global)

 {

     JSObject *proto = global->getOrCreateFunctionPrototype(cx);

     if (!proto)

         return nullptr;

     return NewObjectWithGivenProto(cx, &JSObject::class_, proto, global, SingletonObject);

 }

 /* static */ bool

 GlobalObject::initIteratorClasses(JSContext *cx, Handle<GlobalObject *> global)

 {

     RootedObject iteratorProto(cx);

     Value iteratorProtoVal = global->getPrototype(JSProto_Iterator);

     if (iteratorProtoVal.isObject()) {

         iteratorProto = &iteratorProtoVal.toObject();

     } else {

         iteratorProto = global->createBlankPrototype(cx, &PropertyIteratorObject::class_);

         if (!iteratorProto)

             return false;

         AutoIdVector blank(cx);

         NativeIterator *ni = NativeIterator::allocateIterator(cx, 0, blank);

         if (!ni)

             return false;

         ni->init(nullptr, nullptr, 0 /* flags */, 0, 0);

         iteratorProto->as<PropertyIteratorObject>().setNativeIterator(ni);

         Rooted<JSFunction*> ctor(cx);

         ctor = global->createConstructor(cx, IteratorConstructor, cx->names().Iterator, 2);

         if (!ctor)

             return false;

         if (!LinkConstructorAndPrototype(cx, ctor, iteratorProto))

             return false;

         if (!DefinePropertiesAndBrand(cx, iteratorProto, nullptr, iterator_methods))

             return false;

         if (!GlobalObject::initBuiltinConstructor(cx, global, JSProto_Iterator,

                                                   ctor, iteratorProto))

         {

             return false;

         }

     }

     RootedObject proto(cx);

     if (global->getSlot(ARRAY_ITERATOR_PROTO).isUndefined()) {

         const Class *cls = &ArrayIteratorObject::class_;

         proto = global->createBlankPrototypeInheriting(cx, cls, *iteratorProto);

         if (!proto || !DefinePropertiesAndBrand(cx, proto, nullptr, array_iterator_methods))

             return false;

         global->setReservedSlot(ARRAY_ITERATOR_PROTO, ObjectValue(*proto));

     }

     if (global->getSlot(STRING_ITERATOR_PROTO).isUndefined()) {

         const Class *cls = &StringIteratorPrototypeClass;

         proto = global->createBlankPrototype(cx, cls);

         if (!proto || !DefinePropertiesAndBrand(cx, proto, nullptr, string_iterator_methods))

             return false;

         global->setReservedSlot(STRING_ITERATOR_PROTO, ObjectValue(*proto));

     }

     if (global->getSlot(LEGACY_GENERATOR_OBJECT_PROTO).isUndefined()) {

         proto = NewSingletonObjectWithObjectPrototype(cx, global);

         if (!proto || !DefinePropertiesAndBrand(cx, proto, nullptr, legacy_generator_methods))

             return false;

         global->setReservedSlot(LEGACY_GENERATOR_OBJECT_PROTO, ObjectValue(*proto));

     }

     if (global->getSlot(STAR_GENERATOR_OBJECT_PROTO).isUndefined()) {

         RootedObject genObjectProto(cx, NewSingletonObjectWithObjectPrototype(cx, global));

         if (!genObjectProto)

             return false;

         if (!DefinePropertiesAndBrand(cx, genObjectProto, nullptr, star_generator_methods))

             return false;

         RootedObject genFunctionProto(cx, NewSingletonObjectWithFunctionPrototype(cx, global));

         if (!genFunctionProto)

             return false;

         if (!LinkConstructorAndPrototype(cx, genFunctionProto, genObjectProto))

             return false;

         RootedValue function(cx, global->getConstructor(JSProto_Function));

         if (!function.toObjectOrNull())

             return false;

         RootedAtom name(cx, cx->names().GeneratorFunction);

         RootedObject genFunction(cx, NewFunctionWithProto(cx, NullPtr(), Generator, 1,

                                                           JSFunction::NATIVE_CTOR, global, name,

                                                           &function.toObject()));

         if (!genFunction)

             return false;

         if (!LinkConstructorAndPrototype(cx, genFunction, genFunctionProto))

             return false;

         global->setSlot(STAR_GENERATOR_OBJECT_PROTO, ObjectValue(*genObjectProto));

         global->setConstructor(JSProto_GeneratorFunction, ObjectValue(*genFunction));

         global->setPrototype(JSProto_GeneratorFunction, ObjectValue(*genFunctionProto));

     }

     if (global->getPrototype(JSProto_StopIteration).isUndefined()) {

         proto = global->createBlankPrototype(cx, &StopIterationObject::class_);

         if (!proto || !JSObject::freeze(cx, proto))

             return false;

         // This should use a non-JSProtoKey'd slot, but this is easier for now.

         if (!GlobalObject::initBuiltinConstructor(cx, global, JSProto_StopIteration, proto, proto))

             return false;

         global->setConstructor(JSProto_StopIteration, ObjectValue(*proto));

     }

     return true;

 }

 JSObject *

 js_InitIteratorClasses(JSContext *cx, HandleObject obj)

 {

     Rooted<GlobalObject*> global(cx, &obj->as<GlobalObject>());

     if (!GlobalObject::initIteratorClasses(cx, global))

         return nullptr;

     return global->getIteratorPrototype();

 }