1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
|
/* -*- 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, 16>;
} // namespace js
#endif /* vm_PropertyInfo_h */
|
