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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/*
* JS object implementation.
*/
#include "vm/PlainObject-inl.h"
#include "mozilla/Assertions.h" // MOZ_ASSERT
#include "jspubtd.h" // JSProto_Object
#include "ds/IdValuePair.h" // js::IdValuePair
#include "gc/AllocKind.h" // js::gc::AllocKind
#include "vm/JSContext.h" // JSContext
#include "vm/JSFunction.h" // JSFunction
#include "vm/JSObject.h" // JSObject, js::GetPrototypeFromConstructor
#include "vm/TaggedProto.h" // js::TaggedProto
#include "vm/JSFunction-inl.h"
#include "vm/JSObject-inl.h" // js::NewObjectWithGroup, js::NewObjectGCKind
using namespace js;
using JS::Handle;
using JS::Rooted;
static MOZ_ALWAYS_INLINE SharedShape* GetPlainObjectShapeWithProto(
JSContext* cx, JSObject* proto, gc::AllocKind kind) {
MOZ_ASSERT(JSCLASS_RESERVED_SLOTS(&PlainObject::class_) == 0,
"all slots can be used for properties");
uint32_t nfixed = GetGCKindSlots(kind);
return SharedShape::getInitialShape(cx, &PlainObject::class_, cx->realm(),
TaggedProto(proto), nfixed);
}
SharedShape* js::ThisShapeForFunction(JSContext* cx, Handle<JSFunction*> callee,
Handle<JSObject*> newTarget) {
MOZ_ASSERT(cx->realm() == callee->realm());
MOZ_ASSERT(!callee->constructorNeedsUninitializedThis());
Rooted<JSObject*> proto(cx);
if (!GetPrototypeFromConstructor(cx, newTarget, JSProto_Object, &proto)) {
return nullptr;
}
js::gc::AllocKind allocKind = NewObjectGCKind();
if (!JSFunction::getAllocKindForThis(cx, callee, allocKind)) {
return nullptr;
}
SharedShape* res;
if (proto && proto != cx->global()->maybeGetPrototype(JSProto_Object)) {
res = GetPlainObjectShapeWithProto(cx, proto, allocKind);
} else {
res = GlobalObject::getPlainObjectShapeWithDefaultProto(cx, allocKind);
}
MOZ_ASSERT_IF(res, res->realm() == callee->realm());
return res;
}
#ifdef DEBUG
void PlainObject::assertHasNoNonWritableOrAccessorPropExclProto() const {
// Check the most recent MaxCount properties to not slow down debug builds too
// much.
static constexpr size_t MaxCount = 8;
size_t count = 0;
PropertyName* protoName = runtimeFromMainThread()->commonNames->proto_;
for (ShapePropertyIter<NoGC> iter(shape()); !iter.done(); iter++) {
// __proto__ is always allowed.
if (iter->key().isAtom(protoName)) {
continue;
}
MOZ_ASSERT(iter->isDataProperty());
MOZ_ASSERT(iter->writable());
count++;
if (count > MaxCount) {
return;
}
}
}
#endif
// static
PlainObject* PlainObject::createWithTemplateFromDifferentRealm(
JSContext* cx, Handle<PlainObject*> templateObject) {
MOZ_ASSERT(cx->realm() != templateObject->realm(),
"Use createWithTemplate() for same-realm objects");
// Currently only implemented for null-proto.
MOZ_ASSERT(templateObject->staticPrototype() == nullptr);
// The object mustn't be in dictionary mode.
MOZ_ASSERT(!templateObject->shape()->isDictionary());
TaggedProto proto = TaggedProto(nullptr);
SharedShape* templateShape = templateObject->sharedShape();
Rooted<SharedPropMap*> map(cx, templateShape->propMap());
Rooted<SharedShape*> shape(
cx, SharedShape::getInitialOrPropMapShape(
cx, &PlainObject::class_, cx->realm(), proto,
templateShape->numFixedSlots(), map,
templateShape->propMapLength(), templateShape->objectFlags()));
if (!shape) {
return nullptr;
}
return createWithShape(cx, shape);
}
// static
SharedShape* GlobalObject::createPlainObjectShapeWithDefaultProto(
JSContext* cx, gc::AllocKind kind) {
PlainObjectSlotsKind slotsKind = PlainObjectSlotsKindFromAllocKind(kind);
GCPtr<SharedShape*>& shapeRef =
cx->global()->data().plainObjectShapesWithDefaultProto[slotsKind];
MOZ_ASSERT(!shapeRef);
JSObject* proto = &cx->global()->getObjectPrototype();
SharedShape* shape = GetPlainObjectShapeWithProto(cx, proto, kind);
if (!shape) {
return nullptr;
}
shapeRef.init(shape);
return shape;
}
PlainObject* js::NewPlainObject(JSContext* cx, NewObjectKind newKind) {
constexpr gc::AllocKind allocKind = gc::AllocKind::OBJECT0;
MOZ_ASSERT(gc::GetGCObjectKind(&PlainObject::class_) == allocKind);
Rooted<SharedShape*> shape(
cx, GlobalObject::getPlainObjectShapeWithDefaultProto(cx, allocKind));
if (!shape) {
return nullptr;
}
return PlainObject::createWithShape(cx, shape, allocKind, newKind);
}
PlainObject* js::NewPlainObjectWithAllocKind(JSContext* cx,
gc::AllocKind allocKind,
NewObjectKind newKind) {
Rooted<SharedShape*> shape(
cx, GlobalObject::getPlainObjectShapeWithDefaultProto(cx, allocKind));
if (!shape) {
return nullptr;
}
return PlainObject::createWithShape(cx, shape, allocKind, newKind);
}
PlainObject* js::NewPlainObjectWithProto(JSContext* cx, HandleObject proto,
NewObjectKind newKind) {
// Use a faster path if |proto| is %Object.prototype% (the common case).
if (proto && proto == cx->global()->maybeGetPrototype(JSProto_Object)) {
return NewPlainObject(cx, newKind);
}
constexpr gc::AllocKind allocKind = gc::AllocKind::OBJECT0;
MOZ_ASSERT(gc::GetGCObjectKind(&PlainObject::class_) == allocKind);
Rooted<SharedShape*> shape(
cx, GetPlainObjectShapeWithProto(cx, proto, allocKind));
if (!shape) {
return nullptr;
}
return PlainObject::createWithShape(cx, shape, allocKind, newKind);
}
PlainObject* js::NewPlainObjectWithProtoAndAllocKind(JSContext* cx,
HandleObject proto,
gc::AllocKind allocKind,
NewObjectKind newKind) {
// Use a faster path if |proto| is %Object.prototype% (the common case).
if (proto && proto == cx->global()->maybeGetPrototype(JSProto_Object)) {
return NewPlainObjectWithAllocKind(cx, allocKind, newKind);
}
Rooted<SharedShape*> shape(
cx, GetPlainObjectShapeWithProto(cx, proto, allocKind));
if (!shape) {
return nullptr;
}
return PlainObject::createWithShape(cx, shape, allocKind, newKind);
}
void js::NewPlainObjectWithPropsCache::add(SharedShape* shape) {
MOZ_ASSERT(shape);
MOZ_ASSERT(shape->slotSpan() > 0);
for (size_t i = NumEntries - 1; i > 0; i--) {
entries_[i] = entries_[i - 1];
}
entries_[0] = shape;
}
static bool ShapeMatches(Handle<IdValueVector> properties, SharedShape* shape) {
if (shape->slotSpan() != properties.length()) {
return false;
}
SharedShapePropertyIter<NoGC> iter(shape);
for (size_t i = properties.length(); i > 0; i--) {
MOZ_ASSERT(iter->isDataProperty());
MOZ_ASSERT(iter->flags() == PropertyFlags::defaultDataPropFlags);
if (properties[i - 1].get().id != iter->key()) {
return false;
}
iter++;
}
MOZ_ASSERT(iter.done());
return true;
}
SharedShape* js::NewPlainObjectWithPropsCache::lookup(
Handle<IdValueVector> properties) const {
for (size_t i = 0; i < NumEntries; i++) {
SharedShape* shape = entries_[i];
if (shape && ShapeMatches(properties, shape)) {
return shape;
}
}
return nullptr;
}
enum class KeysKind { UniqueNames, Unknown };
template <KeysKind Kind>
static PlainObject* NewPlainObjectWithProperties(
JSContext* cx, Handle<IdValueVector> properties, NewObjectKind newKind) {
auto& cache = cx->realm()->newPlainObjectWithPropsCache;
// If we recently created an object with these properties, we can use that
// Shape directly.
if (SharedShape* shape = cache.lookup(properties)) {
Rooted<SharedShape*> shapeRoot(cx, shape);
PlainObject* obj = PlainObject::createWithShape(cx, shapeRoot, newKind);
if (!obj) {
return nullptr;
}
MOZ_ASSERT(obj->slotSpan() == properties.length());
for (size_t i = 0; i < properties.length(); i++) {
obj->initSlot(i, properties[i].get().value);
}
return obj;
}
gc::AllocKind allocKind = gc::GetGCObjectKind(properties.length());
Rooted<PlainObject*> obj(cx,
NewPlainObjectWithAllocKind(cx, allocKind, newKind));
if (!obj) {
return nullptr;
}
if (properties.empty()) {
return obj;
}
Rooted<PropertyKey> key(cx);
Rooted<Value> value(cx);
bool canCache = true;
for (const auto& prop : properties) {
key = prop.id;
value = prop.value;
// Integer keys may need to be stored in dense elements. This is uncommon so
// just fall back to NativeDefineDataProperty.
if constexpr (Kind == KeysKind::Unknown) {
if (MOZ_UNLIKELY(key.isInt())) {
canCache = false;
if (!NativeDefineDataProperty(cx, obj, key, value, JSPROP_ENUMERATE)) {
return nullptr;
}
continue;
}
}
MOZ_ASSERT(key.isAtom() || key.isSymbol());
// Check for duplicate keys. In this case we must overwrite the earlier
// property value.
if constexpr (Kind == KeysKind::UniqueNames) {
MOZ_ASSERT(!obj->containsPure(key));
} else {
mozilla::Maybe<PropertyInfo> prop = obj->lookup(cx, key);
if (MOZ_UNLIKELY(prop)) {
canCache = false;
MOZ_ASSERT(prop->isDataProperty());
obj->setSlot(prop->slot(), value);
continue;
}
}
if (!AddDataPropertyToPlainObject(cx, obj, key, value)) {
return nullptr;
}
}
if (canCache && !obj->inDictionaryMode()) {
MOZ_ASSERT(obj->getDenseInitializedLength() == 0);
MOZ_ASSERT(obj->slotSpan() == properties.length());
cache.add(obj->sharedShape());
}
return obj;
}
PlainObject* js::NewPlainObjectWithUniqueNames(JSContext* cx,
Handle<IdValueVector> properties,
NewObjectKind newKind) {
return NewPlainObjectWithProperties<KeysKind::UniqueNames>(cx, properties,
newKind);
}
PlainObject* js::NewPlainObjectWithMaybeDuplicateKeys(
JSContext* cx, Handle<IdValueVector> properties, NewObjectKind newKind) {
return NewPlainObjectWithProperties<KeysKind::Unknown>(cx, properties,
newKind);
}