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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
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef vm_PropertyInfo_h
#define vm_PropertyInfo_h
#include "mozilla/Assertions.h"
#include <limits>
#include <stdint.h>
#include "jstypes.h"
#include "NamespaceImports.h"
#include "js/GCVector.h"
#include "js/PropertyDescriptor.h"
#include "util/EnumFlags.h"
namespace js {
/* Limit on the number of slotful properties in an object. */
static constexpr uint32_t SHAPE_INVALID_SLOT = Bit(24) - 1;
static constexpr uint32_t SHAPE_MAXIMUM_SLOT = Bit(24) - 2;
// Flags associated with each property stored in the shape tree.
enum class PropertyFlag : uint8_t {
// Property attributes. See also JS::PropertyAttribute.
Configurable = 1 << 0,
Enumerable = 1 << 1,
Writable = 1 << 2,
// Whether this is an accessor property. Accessor properties have a slot that
// stores a GetterSetter instance.
AccessorProperty = 1 << 3,
// If set, this is a custom data property. The property is exposed as a data
// property to JS code and PropertyDescriptor, but instead of an object slot
// it uses custom get/set logic.
//
// This is used to implement the special array.length and ArgumentsObject
// properties.
//
// This flag is deprecated (we don't want to add more uses).
CustomDataProperty = 1 << 4,
};
class PropertyFlags : public EnumFlags<PropertyFlag> {
using Base = EnumFlags<PropertyFlag>;
using Base::Base;
public:
static const PropertyFlags defaultDataPropFlags;
static PropertyFlags fromRaw(uint8_t flags) { return PropertyFlags(flags); }
bool configurable() const { return hasFlag(PropertyFlag::Configurable); }
bool enumerable() const { return hasFlag(PropertyFlag::Enumerable); }
bool writable() const {
MOZ_ASSERT(isDataDescriptor());
return hasFlag(PropertyFlag::Writable);
}
// Note: this returns true only for plain data properties with a slot. Returns
// false for custom data properties. See CustomDataProperty flag.
bool isDataProperty() const {
return !isAccessorProperty() && !isCustomDataProperty();
}
bool isAccessorProperty() const {
return hasFlag(PropertyFlag::AccessorProperty);
}
bool isCustomDataProperty() const {
return hasFlag(PropertyFlag::CustomDataProperty);
}
// Note: unlike isDataProperty, this returns true also for custom data
// properties.
bool isDataDescriptor() const { return !isAccessorProperty(); }
};
constexpr PropertyFlags PropertyFlags::defaultDataPropFlags = {
PropertyFlag::Configurable, PropertyFlag::Enumerable,
PropertyFlag::Writable};
// PropertyInfo contains information (PropertyFlags, slot number) for a
// property stored in the Shape tree. Property lookups on NativeObjects return a
// PropertyInfo.
//
// There's also a CompactPropertyInfo type that's used by CompactPropMap to
// store small slot numbers (CompactPropertyInfo is two bytes instead of four).
template <typename T>
class PropertyInfoBase {
static_assert(std::is_same_v<T, uint32_t> || std::is_same_v<T, uint16_t>);
static constexpr uint32_t FlagsMask = 0xff;
static constexpr uint32_t SlotShift = 8;
T slotAndFlags_ = 0;
static_assert(SHAPE_INVALID_SLOT <= (UINT32_MAX >> SlotShift),
"SHAPE_INVALID_SLOT must fit in slotAndFlags_");
static_assert(SHAPE_MAXIMUM_SLOT <= (UINT32_MAX >> SlotShift),
"SHAPE_MAXIMUM_SLOT must fit in slotAndFlags_");
// Constructor is private, code should prefer Maybe<PropertyInfo>. This
// constructor is only used for the propInfos array in property maps
// (CompactPropMap and LinkedPropMap are friend classes for this reason).
PropertyInfoBase() = default;
template <typename U>
friend class PropertyInfoBase;
friend class CompactPropMap;
friend class LinkedPropMap;
public:
static constexpr size_t MaxSlotNumber =
std::numeric_limits<T>::max() >> SlotShift;
PropertyInfoBase(PropertyFlags flags, uint32_t slot)
: slotAndFlags_((slot << SlotShift) | flags.toRaw()) {
MOZ_ASSERT(maybeSlot() == slot);
MOZ_ASSERT(this->flags() == flags);
}
template <typename U>
explicit PropertyInfoBase(PropertyInfoBase<U> other)
: slotAndFlags_(other.slotAndFlags_) {
// Assert assigning PropertyInfo to CompactPropertyInfo doesn't lose
// information.
MOZ_ASSERT(slotAndFlags_ == other.slotAndFlags_);
}
bool isDataProperty() const { return flags().isDataProperty(); }
bool isCustomDataProperty() const { return flags().isCustomDataProperty(); }
bool isAccessorProperty() const { return flags().isAccessorProperty(); }
bool isDataDescriptor() const { return flags().isDataDescriptor(); }
bool hasSlot() const { return !isCustomDataProperty(); }
uint32_t slot() const {
MOZ_ASSERT(hasSlot());
MOZ_ASSERT(maybeSlot() < SHAPE_INVALID_SLOT);
return maybeSlot();
}
uint32_t maybeSlot() const { return slotAndFlags_ >> SlotShift; }
PropertyFlags flags() const {
return PropertyFlags::fromRaw(slotAndFlags_ & FlagsMask);
}
bool writable() const { return flags().writable(); }
bool configurable() const { return flags().configurable(); }
bool enumerable() const { return flags().enumerable(); }
JS::PropertyAttributes propAttributes() const {
JS::PropertyAttributes attrs{};
if (configurable()) {
attrs += JS::PropertyAttribute::Configurable;
}
if (enumerable()) {
attrs += JS::PropertyAttribute::Enumerable;
}
if (isDataDescriptor() && writable()) {
attrs += JS::PropertyAttribute::Writable;
}
return attrs;
}
T toRaw() const { return slotAndFlags_; }
bool operator==(const PropertyInfoBase<T>& other) const {
return slotAndFlags_ == other.slotAndFlags_;
}
bool operator!=(const PropertyInfoBase<T>& other) const {
return !operator==(other);
}
};
using PropertyInfo = PropertyInfoBase<uint32_t>;
using CompactPropertyInfo = PropertyInfoBase<uint16_t>;
static_assert(sizeof(PropertyInfo) == sizeof(uint32_t));
static_assert(sizeof(CompactPropertyInfo) == sizeof(uint16_t));
class PropertyInfoWithKey : public PropertyInfo {
PropertyKey key_;
public:
PropertyInfoWithKey(PropertyFlags flags, uint32_t slot, PropertyKey key)
: PropertyInfo(flags, slot), key_(key) {}
PropertyInfoWithKey(PropertyInfo prop, PropertyKey key)
: PropertyInfo(prop), key_(key) {}
PropertyKey key() const { return key_; }
void trace(JSTracer* trc) {
TraceRoot(trc, &key_, "PropertyInfoWithKey-key");
}
};
template <class Wrapper>
class WrappedPtrOperations<PropertyInfoWithKey, Wrapper> {
const PropertyInfoWithKey& value() const {
return static_cast<const Wrapper*>(this)->get();
}
public:
bool isDataProperty() const { return value().isDataProperty(); }
uint32_t slot() const { return value().slot(); }
PropertyKey key() const { return value().key(); }
PropertyFlags flags() const { return value().flags(); }
};
using PropertyInfoWithKeyVector = GCVector<PropertyInfoWithKey, 8>;
} // namespace js
#endif /* vm_PropertyInfo_h */
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