forked from nodejs/node
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathpersistent.h
More file actions
377 lines (327 loc) · 13.6 KB
/
persistent.h
File metadata and controls
377 lines (327 loc) · 13.6 KB
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
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
// Copyright 2020 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 INCLUDE_CPPGC_PERSISTENT_H_
#define INCLUDE_CPPGC_PERSISTENT_H_
#include <type_traits>
#include "cppgc/internal/persistent-node.h"
#include "cppgc/internal/pointer-policies.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/source-location.h"
#include "cppgc/type-traits.h"
#include "cppgc/visitor.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
namespace internal {
// PersistentBase always refers to the object as const object and defers to
// BasicPersistent on casting to the right type as needed.
class PersistentBase {
protected:
PersistentBase() = default;
explicit PersistentBase(const void* raw) : raw_(raw) {}
const void* GetValue() const { return raw_; }
void SetValue(const void* value) { raw_ = value; }
PersistentNode* GetNode() const { return node_; }
void SetNode(PersistentNode* node) { node_ = node; }
// Performs a shallow clear which assumes that internal persistent nodes are
// destroyed elsewhere.
void ClearFromGC() const {
raw_ = nullptr;
node_ = nullptr;
}
protected:
mutable const void* raw_ = nullptr;
mutable PersistentNode* node_ = nullptr;
friend class PersistentRegionBase;
};
// The basic class from which all Persistent classes are generated.
template <typename T, typename WeaknessPolicy, typename LocationPolicy,
typename CheckingPolicy>
class BasicPersistent final : public PersistentBase,
public LocationPolicy,
private WeaknessPolicy,
private CheckingPolicy {
public:
using typename WeaknessPolicy::IsStrongPersistent;
using PointeeType = T;
// Null-state/sentinel constructors.
BasicPersistent( // NOLINT
const SourceLocation& loc = SourceLocation::Current())
: LocationPolicy(loc) {}
BasicPersistent(std::nullptr_t, // NOLINT
const SourceLocation& loc = SourceLocation::Current())
: LocationPolicy(loc) {}
BasicPersistent( // NOLINT
SentinelPointer s, const SourceLocation& loc = SourceLocation::Current())
: PersistentBase(s), LocationPolicy(loc) {}
// Raw value constructors.
BasicPersistent(T* raw, // NOLINT
const SourceLocation& loc = SourceLocation::Current())
: PersistentBase(raw), LocationPolicy(loc) {
if (!IsValid()) return;
SetNode(WeaknessPolicy::GetPersistentRegion(GetValue())
.AllocateNode(this, &TraceAsRoot));
this->CheckPointer(Get());
}
BasicPersistent(T& raw, // NOLINT
const SourceLocation& loc = SourceLocation::Current())
: BasicPersistent(&raw, loc) {}
// Copy ctor.
BasicPersistent(const BasicPersistent& other,
const SourceLocation& loc = SourceLocation::Current())
: BasicPersistent(other.Get(), loc) {}
// Heterogeneous ctor.
template <typename U, typename OtherWeaknessPolicy,
typename OtherLocationPolicy, typename OtherCheckingPolicy,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
// NOLINTNEXTLINE
BasicPersistent(
const BasicPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>& other,
const SourceLocation& loc = SourceLocation::Current())
: BasicPersistent(other.Get(), loc) {}
// Move ctor. The heterogeneous move ctor is not supported since e.g.
// persistent can't reuse persistent node from weak persistent.
BasicPersistent(
BasicPersistent&& other,
const SourceLocation& loc = SourceLocation::Current()) noexcept
: PersistentBase(std::move(other)), LocationPolicy(std::move(other)) {
if (!IsValid()) return;
GetNode()->UpdateOwner(this);
other.SetValue(nullptr);
other.SetNode(nullptr);
this->CheckPointer(Get());
}
// Constructor from member.
template <typename U, typename MemberBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
// NOLINTNEXTLINE
BasicPersistent(const internal::BasicMember<
U, MemberBarrierPolicy, MemberWeaknessTag,
MemberCheckingPolicy, MemberStorageType>& member,
const SourceLocation& loc = SourceLocation::Current())
: BasicPersistent(member.Get(), loc) {}
~BasicPersistent() { Clear(); }
// Copy assignment.
BasicPersistent& operator=(const BasicPersistent& other) {
return operator=(other.Get());
}
template <typename U, typename OtherWeaknessPolicy,
typename OtherLocationPolicy, typename OtherCheckingPolicy,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicPersistent& operator=(
const BasicPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>& other) {
return operator=(other.Get());
}
// Move assignment.
BasicPersistent& operator=(BasicPersistent&& other) noexcept {
if (this == &other) return *this;
Clear();
PersistentBase::operator=(std::move(other));
LocationPolicy::operator=(std::move(other));
if (!IsValid()) return *this;
GetNode()->UpdateOwner(this);
other.SetValue(nullptr);
other.SetNode(nullptr);
this->CheckPointer(Get());
return *this;
}
// Assignment from member.
template <typename U, typename MemberBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType,
typename = std::enable_if_t<std::is_base_of<T, U>::value>>
BasicPersistent& operator=(
const internal::BasicMember<U, MemberBarrierPolicy, MemberWeaknessTag,
MemberCheckingPolicy, MemberStorageType>&
member) {
return operator=(member.Get());
}
BasicPersistent& operator=(T* other) {
Assign(other);
return *this;
}
BasicPersistent& operator=(std::nullptr_t) {
Clear();
return *this;
}
BasicPersistent& operator=(SentinelPointer s) {
Assign(s);
return *this;
}
explicit operator bool() const { return Get(); }
// Historically we allow implicit conversions to T*.
// NOLINTNEXTLINE
operator T*() const { return Get(); }
T* operator->() const { return Get(); }
T& operator*() const { return *Get(); }
// CFI cast exemption to allow passing SentinelPointer through T* and support
// heterogeneous assignments between different Member and Persistent handles
// based on their actual types.
V8_CLANG_NO_SANITIZE("cfi-unrelated-cast") T* Get() const {
// The const_cast below removes the constness from PersistentBase storage.
// The following static_cast re-adds any constness if specified through the
// user-visible template parameter T.
return static_cast<T*>(const_cast<void*>(GetValue()));
}
void Clear() {
// Simplified version of `Assign()` to allow calling without a complete type
// `T`.
if (IsValid()) {
WeaknessPolicy::GetPersistentRegion(GetValue()).FreeNode(GetNode());
SetNode(nullptr);
}
SetValue(nullptr);
}
T* Release() {
T* result = Get();
Clear();
return result;
}
template <typename U, typename OtherWeaknessPolicy = WeaknessPolicy,
typename OtherLocationPolicy = LocationPolicy,
typename OtherCheckingPolicy = CheckingPolicy>
BasicPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>
To() const {
return BasicPersistent<U, OtherWeaknessPolicy, OtherLocationPolicy,
OtherCheckingPolicy>(static_cast<U*>(Get()));
}
private:
static void TraceAsRoot(RootVisitor& root_visitor, const void* ptr) {
root_visitor.Trace(*static_cast<const BasicPersistent*>(ptr));
}
bool IsValid() const {
// Ideally, handling kSentinelPointer would be done by the embedder. On the
// other hand, having Persistent aware of it is beneficial since no node
// gets wasted.
return GetValue() != nullptr && GetValue() != kSentinelPointer;
}
void Assign(T* ptr) {
if (IsValid()) {
if (ptr && ptr != kSentinelPointer) {
// Simply assign the pointer reusing the existing node.
SetValue(ptr);
this->CheckPointer(ptr);
return;
}
WeaknessPolicy::GetPersistentRegion(GetValue()).FreeNode(GetNode());
SetNode(nullptr);
}
SetValue(ptr);
if (!IsValid()) return;
SetNode(WeaknessPolicy::GetPersistentRegion(GetValue())
.AllocateNode(this, &TraceAsRoot));
this->CheckPointer(Get());
}
void ClearFromGC() const {
if (IsValid()) {
WeaknessPolicy::GetPersistentRegion(GetValue()).FreeNode(GetNode());
PersistentBase::ClearFromGC();
}
}
// Set Get() for details.
V8_CLANG_NO_SANITIZE("cfi-unrelated-cast")
T* GetFromGC() const {
return static_cast<T*>(const_cast<void*>(GetValue()));
}
friend class internal::RootVisitor;
};
template <typename T1, typename WeaknessPolicy1, typename LocationPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessPolicy2,
typename LocationPolicy2, typename CheckingPolicy2>
bool operator==(const BasicPersistent<T1, WeaknessPolicy1, LocationPolicy1,
CheckingPolicy1>& p1,
const BasicPersistent<T2, WeaknessPolicy2, LocationPolicy2,
CheckingPolicy2>& p2) {
return p1.Get() == p2.Get();
}
template <typename T1, typename WeaknessPolicy1, typename LocationPolicy1,
typename CheckingPolicy1, typename T2, typename WeaknessPolicy2,
typename LocationPolicy2, typename CheckingPolicy2>
bool operator!=(const BasicPersistent<T1, WeaknessPolicy1, LocationPolicy1,
CheckingPolicy1>& p1,
const BasicPersistent<T2, WeaknessPolicy2, LocationPolicy2,
CheckingPolicy2>& p2) {
return !(p1 == p2);
}
template <typename T1, typename PersistentWeaknessPolicy,
typename PersistentLocationPolicy, typename PersistentCheckingPolicy,
typename T2, typename MemberWriteBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType>
bool operator==(
const BasicPersistent<T1, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
p,
const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
MemberCheckingPolicy, MemberStorageType>& m) {
return p.Get() == m.Get();
}
template <typename T1, typename PersistentWeaknessPolicy,
typename PersistentLocationPolicy, typename PersistentCheckingPolicy,
typename T2, typename MemberWriteBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType>
bool operator!=(
const BasicPersistent<T1, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
p,
const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
MemberCheckingPolicy, MemberStorageType>& m) {
return !(p == m);
}
template <typename T1, typename MemberWriteBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType, typename T2,
typename PersistentWeaknessPolicy, typename PersistentLocationPolicy,
typename PersistentCheckingPolicy>
bool operator==(
const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
MemberCheckingPolicy, MemberStorageType>& m,
const BasicPersistent<T1, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
p) {
return m.Get() == p.Get();
}
template <typename T1, typename MemberWriteBarrierPolicy,
typename MemberWeaknessTag, typename MemberCheckingPolicy,
typename MemberStorageType, typename T2,
typename PersistentWeaknessPolicy, typename PersistentLocationPolicy,
typename PersistentCheckingPolicy>
bool operator!=(
const BasicMember<T2, MemberWeaknessTag, MemberWriteBarrierPolicy,
MemberCheckingPolicy, MemberStorageType>& m,
const BasicPersistent<T1, PersistentWeaknessPolicy,
PersistentLocationPolicy, PersistentCheckingPolicy>&
p) {
return !(m == p);
}
template <typename T, typename LocationPolicy, typename CheckingPolicy>
struct IsWeak<BasicPersistent<T, internal::WeakPersistentPolicy, LocationPolicy,
CheckingPolicy>> : std::true_type {};
} // namespace internal
/**
* Persistent is a way to create a strong pointer from an off-heap object to
* another on-heap object. As long as the Persistent handle is alive the GC will
* keep the object pointed to alive. The Persistent handle is always a GC root
* from the point of view of the GC. Persistent must be constructed and
* destructed in the same thread.
*/
template <typename T>
using Persistent =
internal::BasicPersistent<T, internal::StrongPersistentPolicy>;
/**
* WeakPersistent is a way to create a weak pointer from an off-heap object to
* an on-heap object. The pointer is automatically cleared when the pointee gets
* collected. WeakPersistent must be constructed and destructed in the same
* thread.
*/
template <typename T>
using WeakPersistent =
internal::BasicPersistent<T, internal::WeakPersistentPolicy>;
} // namespace cppgc
#endif // INCLUDE_CPPGC_PERSISTENT_H_