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
|
// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_PROTOTYPE_H_
#define V8_PROTOTYPE_H_
#include "src/isolate.h"
#include "src/objects.h"
namespace v8 {
namespace internal {
/**
* A class to uniformly access the prototype of any Object and walk its
* prototype chain.
*
* The PrototypeIterator can either start at the prototype (default), or
* include the receiver itself. If a PrototypeIterator is constructed for a
* Map, it will always start at the prototype.
*
* The PrototypeIterator can either run to the null_value(), the first
* non-hidden prototype, or a given object.
*/
class PrototypeIterator {
public:
enum WhereToEnd { END_AT_NULL, END_AT_NON_HIDDEN };
PrototypeIterator(Isolate* isolate, Handle<JSReceiver> receiver,
WhereToStart where_to_start = kStartAtPrototype,
WhereToEnd where_to_end = END_AT_NULL)
: isolate_(isolate),
object_(nullptr),
handle_(receiver),
where_to_end_(where_to_end),
is_at_end_(false),
seen_proxies_(0) {
CHECK(!handle_.is_null());
if (where_to_start == kStartAtPrototype) Advance();
}
PrototypeIterator(Isolate* isolate, JSReceiver* receiver,
WhereToStart where_to_start = kStartAtPrototype,
WhereToEnd where_to_end = END_AT_NULL)
: isolate_(isolate),
object_(receiver),
where_to_end_(where_to_end),
is_at_end_(false),
seen_proxies_(0) {
if (where_to_start == kStartAtPrototype) Advance();
}
explicit PrototypeIterator(Map* receiver_map,
WhereToEnd where_to_end = END_AT_NULL)
: isolate_(receiver_map->GetIsolate()),
object_(receiver_map->GetPrototypeChainRootMap(isolate_)->prototype()),
where_to_end_(where_to_end),
is_at_end_(object_->IsNull(isolate_)),
seen_proxies_(0) {
if (!is_at_end_ && where_to_end_ == END_AT_NON_HIDDEN) {
DCHECK(object_->IsJSReceiver());
Map* map = JSReceiver::cast(object_)->map();
is_at_end_ = !map->has_hidden_prototype();
}
}
explicit PrototypeIterator(Handle<Map> receiver_map,
WhereToEnd where_to_end = END_AT_NULL)
: isolate_(receiver_map->GetIsolate()),
object_(nullptr),
handle_(receiver_map->GetPrototypeChainRootMap(isolate_)->prototype(),
isolate_),
where_to_end_(where_to_end),
is_at_end_(handle_->IsNull(isolate_)),
seen_proxies_(0) {
if (!is_at_end_ && where_to_end_ == END_AT_NON_HIDDEN) {
DCHECK(handle_->IsJSReceiver());
Map* map = JSReceiver::cast(*handle_)->map();
is_at_end_ = !map->has_hidden_prototype();
}
}
~PrototypeIterator() {}
bool HasAccess() const {
// We can only perform access check in the handlified version of the
// PrototypeIterator.
DCHECK(!handle_.is_null());
if (handle_->IsAccessCheckNeeded()) {
return isolate_->MayAccess(handle(isolate_->context()),
Handle<JSObject>::cast(handle_));
}
return true;
}
template <typename T = Object>
T* GetCurrent() const {
DCHECK(handle_.is_null());
return T::cast(object_);
}
template <typename T = Object>
static Handle<T> GetCurrent(const PrototypeIterator& iterator) {
DCHECK(!iterator.handle_.is_null());
DCHECK_NULL(iterator.object_);
return Handle<T>::cast(iterator.handle_);
}
void Advance() {
if (handle_.is_null() && object_->IsJSProxy()) {
is_at_end_ = true;
object_ = isolate_->heap()->null_value();
return;
} else if (!handle_.is_null() && handle_->IsJSProxy()) {
is_at_end_ = true;
handle_ = isolate_->factory()->null_value();
return;
}
AdvanceIgnoringProxies();
}
void AdvanceIgnoringProxies() {
Object* object = handle_.is_null() ? object_ : *handle_;
Map* map = HeapObject::cast(object)->map();
Object* prototype = map->prototype();
is_at_end_ = where_to_end_ == END_AT_NON_HIDDEN
? !map->has_hidden_prototype()
: prototype->IsNull(isolate_);
if (handle_.is_null()) {
object_ = prototype;
} else {
handle_ = handle(prototype, isolate_);
}
}
// Returns false iff a call to JSProxy::GetPrototype throws.
// TODO(neis): This should probably replace Advance().
V8_WARN_UNUSED_RESULT bool AdvanceFollowingProxies() {
DCHECK(!(handle_.is_null() && object_->IsJSProxy()));
if (!HasAccess()) {
// Abort the lookup if we do not have access to the current object.
handle_ = isolate_->factory()->null_value();
is_at_end_ = true;
return true;
}
return AdvanceFollowingProxiesIgnoringAccessChecks();
}
V8_WARN_UNUSED_RESULT bool AdvanceFollowingProxiesIgnoringAccessChecks() {
if (handle_.is_null() || !handle_->IsJSProxy()) {
AdvanceIgnoringProxies();
return true;
}
// Due to possible __proto__ recursion limit the number of Proxies
// we visit to an arbitrarily chosen large number.
seen_proxies_++;
if (seen_proxies_ > JSProxy::kMaxIterationLimit) {
isolate_->StackOverflow();
return false;
}
MaybeHandle<Object> proto =
JSProxy::GetPrototype(Handle<JSProxy>::cast(handle_));
if (!proto.ToHandle(&handle_)) return false;
is_at_end_ =
where_to_end_ == END_AT_NON_HIDDEN || handle_->IsNull(isolate_);
return true;
}
bool IsAtEnd() const { return is_at_end_; }
Isolate* isolate() const { return isolate_; }
private:
Isolate* isolate_;
Object* object_;
Handle<Object> handle_;
WhereToEnd where_to_end_;
bool is_at_end_;
int seen_proxies_;
DISALLOW_COPY_AND_ASSIGN(PrototypeIterator);
};
} // namespace internal
} // namespace v8
#endif // V8_PROTOTYPE_H_
|
