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
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
// Copyright 2019-2021 the Deno authors. All rights reserved. MIT license.
use crate::function::FunctionCallbackInfo;
use crate::handle::FinalizerCallback;
use crate::handle::FinalizerMap;
use crate::isolate_create_params::raw;
use crate::isolate_create_params::CreateParams;
use crate::promise::PromiseRejectMessage;
use crate::scope::data::ScopeData;
use crate::snapshot::SnapshotCreator;
use crate::support::Allocated;
use crate::support::MapFnFrom;
use crate::support::MapFnTo;
use crate::support::Opaque;
use crate::support::ToCFn;
use crate::support::UnitType;
use crate::wasm::trampoline;
use crate::wasm::WasmStreaming;
use crate::Array;
use crate::CallbackScope;
use crate::Context;
use crate::Data;
use crate::ExternalReferences;
use crate::FixedArray;
use crate::Function;
use crate::FunctionCodeHandling;
use crate::HandleScope;
use crate::Local;
use crate::Message;
use crate::Module;
use crate::Object;
use crate::Promise;
use crate::PromiseResolver;
use crate::StartupData;
use crate::String;
use crate::Value;

use std::any::Any;
use std::any::TypeId;
use std::collections::HashMap;
use std::ffi::c_void;
use std::fmt::{self, Debug, Formatter};
use std::hash::BuildHasher;
use std::hash::Hasher;
use std::mem::align_of;
use std::mem::forget;
use std::mem::needs_drop;
use std::mem::size_of;
use std::mem::MaybeUninit;
use std::ops::Deref;
use std::ops::DerefMut;
use std::os::raw::c_char;
use std::ptr;
use std::ptr::drop_in_place;
use std::ptr::null_mut;
use std::ptr::NonNull;
use std::sync::Arc;
use std::sync::Mutex;

/// Policy for running microtasks:
///   - explicit: microtasks are invoked with the
///               Isolate::PerformMicrotaskCheckpoint() method;
///   - auto: microtasks are invoked when the script call depth decrements
///           to zero.
#[derive(Debug, Clone, Copy, PartialEq)]
#[repr(C)]
pub enum MicrotasksPolicy {
  Explicit = 0,
  // Scoped = 1 (RAII) is omitted for now, doesn't quite map to idiomatic Rust.
  Auto = 2,
}

/// PromiseHook with type Init is called when a new promise is
/// created. When a new promise is created as part of the chain in the
/// case of Promise.then or in the intermediate promises created by
/// Promise.{race, all}/AsyncFunctionAwait, we pass the parent promise
/// otherwise we pass undefined.
///
/// PromiseHook with type Resolve is called at the beginning of
/// resolve or reject function defined by CreateResolvingFunctions.
///
/// PromiseHook with type Before is called at the beginning of the
/// PromiseReactionJob.
///
/// PromiseHook with type After is called right at the end of the
/// PromiseReactionJob.
#[derive(Debug, Clone, Copy, PartialEq)]
#[repr(C)]
pub enum PromiseHookType {
  Init,
  Resolve,
  Before,
  After,
}

pub type MessageCallback = extern "C" fn(Local<Message>, Local<Value>);

pub type PromiseHook =
  extern "C" fn(PromiseHookType, Local<Promise>, Local<Value>);

pub type PromiseRejectCallback = extern "C" fn(PromiseRejectMessage);

#[derive(Debug, Clone, Copy, PartialEq)]
#[repr(C)]
pub enum WasmAsyncSuccess {
  Success,
  Fail,
}
pub type WasmAsyncResolvePromiseCallback = extern "C" fn(
  *mut Isolate,
  Local<Context>,
  Local<PromiseResolver>,
  Local<Value>,
  WasmAsyncSuccess,
);

/// HostInitializeImportMetaObjectCallback is called the first time import.meta
/// is accessed for a module. Subsequent access will reuse the same value.
///
/// The method combines two implementation-defined abstract operations into one:
/// HostGetImportMetaProperties and HostFinalizeImportMeta.
///
/// The embedder should use v8::Object::CreateDataProperty to add properties on
/// the meta object.
pub type HostInitializeImportMetaObjectCallback =
  extern "C" fn(Local<Context>, Local<Module>, Local<Object>);

/// HostImportModuleDynamicallyCallback is called when we require the embedder
/// to load a module. This is used as part of the dynamic import syntax.
///
/// The referrer contains metadata about the script/module that calls import.
///
/// The specifier is the name of the module that should be imported.
///
/// The import_assertions are import assertions for this request in the form:
/// [key1, value1, key2, value2, ...] where the keys and values are of type
/// v8::String. Note, unlike the FixedArray passed to ResolveModuleCallback and
/// returned from ModuleRequest::GetImportAssertions(), this array does not
/// contain the source Locations of the assertions.
///
/// The embedder must compile, instantiate, evaluate the Module, and obtain its
/// namespace object.
///
/// The Promise returned from this function is forwarded to userland JavaScript.
/// The embedder must resolve this promise with the module namespace object. In
/// case of an exception, the embedder must reject this promise with the
/// exception. If the promise creation itself fails (e.g. due to stack
/// overflow), the embedder must propagate that exception by returning an empty
/// MaybeLocal.
///
/// # Example
///
/// ```
/// fn host_import_module_dynamically_callback_example<'s>(
///   scope: &mut v8::HandleScope<'s>,
///   host_defined_options: v8::Local<'s, v8::Data>,
///   resource_name: v8::Local<'s, v8::Value>,
///   specifier: v8::Local<'s, v8::String>,
///   import_assertions: v8::Local<'s, v8::FixedArray>,
/// ) -> Option<v8::Local<'s, v8::Promise>> {
///   todo!()
/// }
/// ```
pub trait HostImportModuleDynamicallyCallback:
  UnitType
  + for<'s> FnOnce(
    &mut HandleScope<'s>,
    Local<'s, Data>,
    Local<'s, Value>,
    Local<'s, String>,
    Local<'s, FixedArray>,
  ) -> Option<Local<'s, Promise>>
{
  fn to_c_fn(self) -> RawHostImportModuleDynamicallyCallback;
}

#[cfg(target_family = "unix")]
pub(crate) type RawHostImportModuleDynamicallyCallback =
  for<'s> extern "C" fn(
    Local<'s, Context>,
    Local<'s, Data>,
    Local<'s, Value>,
    Local<'s, String>,
    Local<'s, FixedArray>,
  ) -> *mut Promise;

#[cfg(all(target_family = "windows", target_arch = "x86_64"))]
pub type RawHostImportModuleDynamicallyCallback =
  for<'s> extern "C" fn(
    *mut *mut Promise,
    Local<'s, Context>,
    Local<'s, Data>,
    Local<'s, Value>,
    Local<'s, String>,
    Local<'s, FixedArray>,
  ) -> *mut *mut Promise;

impl<F> HostImportModuleDynamicallyCallback for F
where
  F: UnitType
    + for<'s> FnOnce(
      &mut HandleScope<'s>,
      Local<'s, Data>,
      Local<'s, Value>,
      Local<'s, String>,
      Local<'s, FixedArray>,
    ) -> Option<Local<'s, Promise>>,
{
  #[inline(always)]
  fn to_c_fn(self) -> RawHostImportModuleDynamicallyCallback {
    #[inline(always)]
    fn scope_adapter<'s, F: HostImportModuleDynamicallyCallback>(
      context: Local<'s, Context>,
      host_defined_options: Local<'s, Data>,
      resource_name: Local<'s, Value>,
      specifier: Local<'s, String>,
      import_assertions: Local<'s, FixedArray>,
    ) -> Option<Local<'s, Promise>> {
      let scope = &mut unsafe { CallbackScope::new(context) };
      (F::get())(
        scope,
        host_defined_options,
        resource_name,
        specifier,
        import_assertions,
      )
    }

    #[cfg(target_family = "unix")]
    #[inline(always)]
    extern "C" fn abi_adapter<'s, F: HostImportModuleDynamicallyCallback>(
      context: Local<'s, Context>,
      host_defined_options: Local<'s, Data>,
      resource_name: Local<'s, Value>,
      specifier: Local<'s, String>,
      import_assertions: Local<'s, FixedArray>,
    ) -> *mut Promise {
      scope_adapter::<F>(
        context,
        host_defined_options,
        resource_name,
        specifier,
        import_assertions,
      )
      .map(|return_value| return_value.as_non_null().as_ptr())
      .unwrap_or_else(null_mut)
    }

    #[cfg(all(target_family = "windows", target_arch = "x86_64"))]
    #[inline(always)]
    extern "C" fn abi_adapter<'s, F: HostImportModuleDynamicallyCallback>(
      return_value: *mut *mut Promise,
      context: Local<'s, Context>,
      host_defined_options: Local<'s, Data>,
      resource_name: Local<'s, Value>,
      specifier: Local<'s, String>,
      import_assertions: Local<'s, FixedArray>,
    ) -> *mut *mut Promise {
      unsafe {
        std::ptr::write(
          return_value,
          scope_adapter::<F>(
            context,
            host_defined_options,
            resource_name,
            specifier,
            import_assertions,
          )
          .map(|return_value| return_value.as_non_null().as_ptr())
          .unwrap_or_else(null_mut),
        );
        return_value
      }
    }

    abi_adapter::<F>
  }
}

/// `HostCreateShadowRealmContextCallback` is called each time a `ShadowRealm`
/// is being constructed. You can use [`HandleScope::get_current_context`] to
/// get the [`Context`] in which the constructor is being run.
///
/// The method combines [`Context`] creation and the implementation-defined
/// abstract operation `HostInitializeShadowRealm` into one.
///
/// The embedder should use [`Context::new`] to create a new context. If the
/// creation fails, the embedder must propagate that exception by returning
/// [`None`].
pub type HostCreateShadowRealmContextCallback =
  for<'s> fn(scope: &mut HandleScope<'s>) -> Option<Local<'s, Context>>;

pub type InterruptCallback =
  extern "C" fn(isolate: &mut Isolate, data: *mut c_void);

pub type NearHeapLimitCallback = extern "C" fn(
  data: *mut c_void,
  current_heap_limit: usize,
  initial_heap_limit: usize,
) -> usize;

#[repr(C)]
pub struct OomDetails {
  pub is_heap_oom: bool,
  pub detail: *const c_char,
}

pub type OomErrorCallback =
  extern "C" fn(location: *const c_char, details: &OomDetails);

/// Collection of V8 heap information.
///
/// Instances of this class can be passed to v8::Isolate::GetHeapStatistics to
/// get heap statistics from V8.
// Must be >= sizeof(v8::HeapStatistics), see v8__HeapStatistics__CONSTRUCT().
#[repr(C)]
#[derive(Debug)]
pub struct HeapStatistics([usize; 16]);

// Windows x64 ABI: MaybeLocal<Value> returned on the stack.
#[cfg(target_os = "windows")]
pub type PrepareStackTraceCallback<'s> = extern "C" fn(
  *mut *const Value,
  Local<'s, Context>,
  Local<'s, Value>,
  Local<'s, Array>,
) -> *mut *const Value;

// System V ABI: MaybeLocal<Value> returned in a register.
// System V i386 ABI: Local<Value> returned in hidden pointer (struct).
#[cfg(not(target_os = "windows"))]
#[repr(C)]
pub struct PrepareStackTraceCallbackRet(*const Value);

#[cfg(not(target_os = "windows"))]
pub type PrepareStackTraceCallback<'s> =
  extern "C" fn(
    Local<'s, Context>,
    Local<'s, Value>,
    Local<'s, Array>,
  ) -> PrepareStackTraceCallbackRet;

extern "C" {
  static v8__internal__Internals__kIsolateEmbedderDataOffset: usize;

  fn v8__Isolate__New(params: *const raw::CreateParams) -> *mut Isolate;
  fn v8__Isolate__Dispose(this: *mut Isolate);
  fn v8__Isolate__GetNumberOfDataSlots(this: *const Isolate) -> u32;
  fn v8__Isolate__Enter(this: *mut Isolate);
  fn v8__Isolate__Exit(this: *mut Isolate);
  fn v8__Isolate__ClearKeptObjects(isolate: *mut Isolate);
  fn v8__Isolate__LowMemoryNotification(isolate: *mut Isolate);
  fn v8__Isolate__GetHeapStatistics(this: *mut Isolate, s: *mut HeapStatistics);
  fn v8__Isolate__SetCaptureStackTraceForUncaughtExceptions(
    this: *mut Isolate,
    caputre: bool,
    frame_limit: i32,
  );
  fn v8__Isolate__AddMessageListener(
    isolate: *mut Isolate,
    callback: MessageCallback,
  ) -> bool;
  fn v8__Isolate__AddNearHeapLimitCallback(
    isolate: *mut Isolate,
    callback: NearHeapLimitCallback,
    data: *mut c_void,
  );
  fn v8__Isolate__RemoveNearHeapLimitCallback(
    isolate: *mut Isolate,
    callback: NearHeapLimitCallback,
    heap_limit: usize,
  );
  fn v8__Isolate__SetOOMErrorHandler(
    isolate: *mut Isolate,
    callback: OomErrorCallback,
  );
  fn v8__Isolate__AdjustAmountOfExternalAllocatedMemory(
    isolate: *mut Isolate,
    change_in_bytes: i64,
  ) -> i64;
  fn v8__Isolate__SetPrepareStackTraceCallback(
    isolate: *mut Isolate,
    callback: PrepareStackTraceCallback,
  );
  fn v8__Isolate__SetPromiseHook(isolate: *mut Isolate, hook: PromiseHook);
  fn v8__Isolate__SetPromiseRejectCallback(
    isolate: *mut Isolate,
    callback: PromiseRejectCallback,
  );
  fn v8__Isolate__SetWasmAsyncResolvePromiseCallback(
    isolate: *mut Isolate,
    callback: WasmAsyncResolvePromiseCallback,
  );
  fn v8__Isolate__SetHostInitializeImportMetaObjectCallback(
    isolate: *mut Isolate,
    callback: HostInitializeImportMetaObjectCallback,
  );
  fn v8__Isolate__SetHostImportModuleDynamicallyCallback(
    isolate: *mut Isolate,
    callback: RawHostImportModuleDynamicallyCallback,
  );
  #[cfg(not(target_os = "windows"))]
  fn v8__Isolate__SetHostCreateShadowRealmContextCallback(
    isolate: *mut Isolate,
    callback: extern "C" fn(initiator_context: Local<Context>) -> *mut Context,
  );
  #[cfg(target_os = "windows")]
  fn v8__Isolate__SetHostCreateShadowRealmContextCallback(
    isolate: *mut Isolate,
    callback: extern "C" fn(
      rv: *mut *mut Context,
      initiator_context: Local<Context>,
    ) -> *mut *mut Context,
  );
  fn v8__Isolate__RequestInterrupt(
    isolate: *const Isolate,
    callback: InterruptCallback,
    data: *mut c_void,
  );
  fn v8__Isolate__TerminateExecution(isolate: *const Isolate);
  fn v8__Isolate__IsExecutionTerminating(isolate: *const Isolate) -> bool;
  fn v8__Isolate__CancelTerminateExecution(isolate: *const Isolate);
  fn v8__Isolate__GetMicrotasksPolicy(
    isolate: *const Isolate,
  ) -> MicrotasksPolicy;
  fn v8__Isolate__SetMicrotasksPolicy(
    isolate: *mut Isolate,
    policy: MicrotasksPolicy,
  );
  fn v8__Isolate__PerformMicrotaskCheckpoint(isolate: *mut Isolate);
  fn v8__Isolate__EnqueueMicrotask(
    isolate: *mut Isolate,
    function: *const Function,
  );
  fn v8__Isolate__SetAllowAtomicsWait(isolate: *mut Isolate, allow: bool);
  fn v8__Isolate__SetWasmStreamingCallback(
    isolate: *mut Isolate,
    callback: extern "C" fn(*const FunctionCallbackInfo),
  );
  fn v8__Isolate__HasPendingBackgroundTasks(isolate: *const Isolate) -> bool;

  fn v8__HeapProfiler__TakeHeapSnapshot(
    isolate: *mut Isolate,
    callback: extern "C" fn(*mut c_void, *const u8, usize) -> bool,
    arg: *mut c_void,
  );

  fn v8__HeapStatistics__CONSTRUCT(s: *mut MaybeUninit<HeapStatistics>);
  fn v8__HeapStatistics__total_heap_size(s: *const HeapStatistics) -> usize;
  fn v8__HeapStatistics__total_heap_size_executable(
    s: *const HeapStatistics,
  ) -> usize;
  fn v8__HeapStatistics__total_physical_size(s: *const HeapStatistics)
    -> usize;
  fn v8__HeapStatistics__total_available_size(
    s: *const HeapStatistics,
  ) -> usize;
  fn v8__HeapStatistics__total_global_handles_size(
    s: *const HeapStatistics,
  ) -> usize;
  fn v8__HeapStatistics__used_global_handles_size(
    s: *const HeapStatistics,
  ) -> usize;
  fn v8__HeapStatistics__used_heap_size(s: *const HeapStatistics) -> usize;
  fn v8__HeapStatistics__heap_size_limit(s: *const HeapStatistics) -> usize;
  fn v8__HeapStatistics__malloced_memory(s: *const HeapStatistics) -> usize;
  fn v8__HeapStatistics__external_memory(s: *const HeapStatistics) -> usize;
  fn v8__HeapStatistics__peak_malloced_memory(
    s: *const HeapStatistics,
  ) -> usize;
  fn v8__HeapStatistics__number_of_native_contexts(
    s: *const HeapStatistics,
  ) -> usize;
  fn v8__HeapStatistics__number_of_detached_contexts(
    s: *const HeapStatistics,
  ) -> usize;
  fn v8__HeapStatistics__does_zap_garbage(s: *const HeapStatistics) -> usize;
}

/// Isolate represents an isolated instance of the V8 engine.  V8 isolates have
/// completely separate states.  Objects from one isolate must not be used in
/// other isolates.  The embedder can create multiple isolates and use them in
/// parallel in multiple threads.  An isolate can be entered by at most one
/// thread at any given time.  The Locker/Unlocker API must be used to
/// synchronize.
///
/// rusty_v8 note: Unlike in the C++ API, the Isolate is entered when it is
/// constructed and exited when dropped.
#[repr(C)]
#[derive(Debug)]
pub struct Isolate(Opaque);

impl Isolate {
  // Total number of isolate data slots provided by V8.
  const EMBEDDER_DATA_SLOT_COUNT: u32 = 4;

  // Byte offset inside `Isolate` where the isolate data slots are stored. This
  // should be the same as the value of `kIsolateEmbedderDataOffset` which is
  // defined in `v8-internal.h`.
  const EMBEDDER_DATA_OFFSET: usize = size_of::<[*const (); 23]>();

  // Isolate data slots used internally by rusty_v8.
  const ANNEX_SLOT: u32 = 0;
  const CURRENT_SCOPE_DATA_SLOT: u32 = 1;
  const INTERNAL_DATA_SLOT_COUNT: u32 = 2;

  #[inline(always)]
  fn assert_embedder_data_slot_count_and_offset_correct(&self) {
    assert_eq!(
      unsafe { v8__Isolate__GetNumberOfDataSlots(self) },
      Self::EMBEDDER_DATA_SLOT_COUNT
    );
    assert_eq!(
      unsafe { v8__internal__Internals__kIsolateEmbedderDataOffset },
      Self::EMBEDDER_DATA_OFFSET
    );
  }

  /// Creates a new isolate.  Does not change the currently entered
  /// isolate.
  ///
  /// When an isolate is no longer used its resources should be freed
  /// by calling V8::dispose().  Using the delete operator is not allowed.
  ///
  /// V8::initialize() must have run prior to this.
  #[allow(clippy::new_ret_no_self)]
  pub fn new(params: CreateParams) -> OwnedIsolate {
    crate::V8::assert_initialized();
    let (raw_create_params, create_param_allocations) = params.finalize();
    let cxx_isolate = unsafe { v8__Isolate__New(&raw_create_params) };
    let mut owned_isolate = OwnedIsolate::new(cxx_isolate);
    owned_isolate.assert_embedder_data_slot_count_and_offset_correct();
    ScopeData::new_root(&mut owned_isolate);
    owned_isolate.create_annex(create_param_allocations);
    unsafe {
      owned_isolate.enter();
    }
    owned_isolate
  }

  #[allow(clippy::new_ret_no_self)]
  pub fn snapshot_creator(
    external_references: Option<&'static ExternalReferences>,
  ) -> OwnedIsolate {
    SnapshotCreator::new(external_references)
  }

  #[allow(clippy::new_ret_no_self)]
  pub fn snapshot_creator_from_existing_snapshot(
    existing_snapshot_blob: impl Allocated<[u8]>,
    external_references: Option<&'static ExternalReferences>,
  ) -> OwnedIsolate {
    SnapshotCreator::from_existing_snapshot(
      existing_snapshot_blob,
      external_references,
    )
  }

  /// Initial configuration parameters for a new Isolate.
  #[inline(always)]
  pub fn create_params() -> CreateParams {
    CreateParams::default()
  }

  #[inline(always)]
  pub fn thread_safe_handle(&self) -> IsolateHandle {
    IsolateHandle::new(self)
  }

  /// See [`IsolateHandle::terminate_execution`]
  #[inline(always)]
  pub fn terminate_execution(&self) -> bool {
    self.thread_safe_handle().terminate_execution()
  }

  /// See [`IsolateHandle::cancel_terminate_execution`]
  #[inline(always)]
  pub fn cancel_terminate_execution(&self) -> bool {
    self.thread_safe_handle().cancel_terminate_execution()
  }

  /// See [`IsolateHandle::is_execution_terminating`]
  #[inline(always)]
  pub fn is_execution_terminating(&self) -> bool {
    self.thread_safe_handle().is_execution_terminating()
  }

  pub(crate) fn create_annex(
    &mut self,
    create_param_allocations: Box<dyn Any>,
  ) {
    let annex_arc = Arc::new(IsolateAnnex::new(self, create_param_allocations));
    let annex_ptr = Arc::into_raw(annex_arc);
    assert!(self.get_data_internal(Self::ANNEX_SLOT).is_null());
    self.set_data_internal(Self::ANNEX_SLOT, annex_ptr as *mut _);
  }

  #[inline(always)]
  fn get_annex(&self) -> &IsolateAnnex {
    let annex_ptr =
      self.get_data_internal(Self::ANNEX_SLOT) as *const IsolateAnnex;
    assert!(!annex_ptr.is_null());
    unsafe { &*annex_ptr }
  }

  #[inline(always)]
  fn get_annex_mut(&mut self) -> &mut IsolateAnnex {
    let annex_ptr =
      self.get_data_internal(Self::ANNEX_SLOT) as *mut IsolateAnnex;
    assert!(!annex_ptr.is_null());
    unsafe { &mut *annex_ptr }
  }

  pub(crate) fn set_snapshot_creator(
    &mut self,
    snapshot_creator: SnapshotCreator,
  ) {
    let prev = self
      .get_annex_mut()
      .maybe_snapshot_creator
      .replace(snapshot_creator);
    assert!(prev.is_none());
  }

  pub(crate) fn get_finalizer_map(&self) -> &FinalizerMap {
    &self.get_annex().finalizer_map
  }

  pub(crate) fn get_finalizer_map_mut(&mut self) -> &mut FinalizerMap {
    &mut self.get_annex_mut().finalizer_map
  }

  fn get_annex_arc(&self) -> Arc<IsolateAnnex> {
    let annex_ptr = self.get_annex();
    let annex_arc = unsafe { Arc::from_raw(annex_ptr) };
    let _ = Arc::into_raw(annex_arc.clone());
    annex_arc
  }

  /// Retrieve embedder-specific data from the isolate.
  /// Returns NULL if SetData has never been called for the given `slot`.
  pub fn get_data(&self, slot: u32) -> *mut c_void {
    self.get_data_internal(Self::INTERNAL_DATA_SLOT_COUNT + slot)
  }

  /// Associate embedder-specific data with the isolate. `slot` has to be
  /// between 0 and `Isolate::get_number_of_data_slots()`.
  #[inline(always)]
  pub fn set_data(&mut self, slot: u32, data: *mut c_void) {
    self.set_data_internal(Self::INTERNAL_DATA_SLOT_COUNT + slot, data)
  }

  /// Returns the maximum number of available embedder data slots. Valid slots
  /// are in the range of `0 <= n < Isolate::get_number_of_data_slots()`.
  pub fn get_number_of_data_slots(&self) -> u32 {
    Self::EMBEDDER_DATA_SLOT_COUNT - Self::INTERNAL_DATA_SLOT_COUNT
  }

  #[inline(always)]
  pub(crate) fn get_data_internal(&self, slot: u32) -> *mut c_void {
    let slots = unsafe {
      let p = self as *const Self as *const u8;
      let p = p.add(Self::EMBEDDER_DATA_OFFSET);
      let p = p as *const [*mut c_void; Self::EMBEDDER_DATA_SLOT_COUNT as _];
      &*p
    };
    slots[slot as usize]
  }

  #[inline(always)]
  pub(crate) fn set_data_internal(&mut self, slot: u32, data: *mut c_void) {
    let slots = unsafe {
      let p = self as *mut Self as *mut u8;
      let p = p.add(Self::EMBEDDER_DATA_OFFSET);
      let p = p as *mut [*mut c_void; Self::EMBEDDER_DATA_SLOT_COUNT as _];
      &mut *p
    };
    slots[slot as usize] = data;
  }

  /// Returns a pointer to the `ScopeData` struct for the current scope.
  #[inline(always)]
  pub(crate) fn get_current_scope_data(&self) -> Option<NonNull<ScopeData>> {
    let scope_data_ptr = self.get_data_internal(Self::CURRENT_SCOPE_DATA_SLOT);
    NonNull::new(scope_data_ptr).map(NonNull::cast)
  }

  /// Updates the slot that stores a `ScopeData` pointer for the current scope.
  #[inline(always)]
  pub(crate) fn set_current_scope_data(
    &mut self,
    scope_data: Option<NonNull<ScopeData>>,
  ) {
    let scope_data_ptr = scope_data
      .map(NonNull::cast)
      .map(NonNull::as_ptr)
      .unwrap_or_else(null_mut);
    self.set_data_internal(Self::CURRENT_SCOPE_DATA_SLOT, scope_data_ptr);
  }

  /// Get a reference to embedder data added with `set_slot()`.
  #[inline(always)]
  pub fn get_slot<T: 'static>(&self) -> Option<&T> {
    self
      .get_annex()
      .slots
      .get(&TypeId::of::<T>())
      .map(|slot| unsafe { slot.borrow::<T>() })
  }

  /// Get a mutable reference to embedder data added with `set_slot()`.
  #[inline(always)]
  pub fn get_slot_mut<T: 'static>(&mut self) -> Option<&mut T> {
    self
      .get_annex_mut()
      .slots
      .get_mut(&TypeId::of::<T>())
      .map(|slot| unsafe { slot.borrow_mut::<T>() })
  }

  /// Use with Isolate::get_slot and Isolate::get_slot_mut to associate state
  /// with an Isolate.
  ///
  /// This method gives ownership of value to the Isolate. Exactly one object of
  /// each type can be associated with an Isolate. If called more than once with
  /// an object of the same type, the earlier version will be dropped and
  /// replaced.
  ///
  /// Returns true if value was set without replacing an existing value.
  ///
  /// The value will be dropped when the isolate is dropped.
  #[inline(always)]
  pub fn set_slot<T: 'static>(&mut self, value: T) -> bool {
    self
      .get_annex_mut()
      .slots
      .insert(TypeId::of::<T>(), RawSlot::new(value))
      .is_none()
  }

  /// Removes the embedder data added with `set_slot()` and returns it if it exists.
  #[inline(always)]
  pub fn remove_slot<T: 'static>(&mut self) -> Option<T> {
    self
      .get_annex_mut()
      .slots
      .remove(&TypeId::of::<T>())
      .map(|slot| unsafe { slot.into_inner::<T>() })
  }

  /// Sets this isolate as the entered one for the current thread.
  /// Saves the previously entered one (if any), so that it can be
  /// restored when exiting.  Re-entering an isolate is allowed.
  ///
  /// rusty_v8 note: Unlike in the C++ API, the isolate is entered when it is
  /// constructed and exited when dropped.
  #[inline(always)]
  pub unsafe fn enter(&mut self) {
    v8__Isolate__Enter(self)
  }

  /// Exits this isolate by restoring the previously entered one in the
  /// current thread.  The isolate may still stay the same, if it was
  /// entered more than once.
  ///
  /// Requires: self == Isolate::GetCurrent().
  ///
  /// rusty_v8 note: Unlike in the C++ API, the isolate is entered when it is
  /// constructed and exited when dropped.
  #[inline(always)]
  pub unsafe fn exit(&mut self) {
    v8__Isolate__Exit(self)
  }

  /// Clears the set of objects held strongly by the heap. This set of
  /// objects are originally built when a WeakRef is created or
  /// successfully dereferenced.
  ///
  /// This is invoked automatically after microtasks are run. See
  /// MicrotasksPolicy for when microtasks are run.
  ///
  /// This needs to be manually invoked only if the embedder is manually
  /// running microtasks via a custom MicrotaskQueue class's PerformCheckpoint.
  /// In that case, it is the embedder's responsibility to make this call at a
  /// time which does not interrupt synchronous ECMAScript code execution.
  #[inline(always)]
  pub fn clear_kept_objects(&mut self) {
    unsafe { v8__Isolate__ClearKeptObjects(self) }
  }

  /// Optional notification that the system is running low on memory.
  /// V8 uses these notifications to attempt to free memory.
  #[inline(always)]
  pub fn low_memory_notification(&mut self) {
    unsafe { v8__Isolate__LowMemoryNotification(self) }
  }

  /// Get statistics about the heap memory usage.
  #[inline(always)]
  pub fn get_heap_statistics(&mut self, s: &mut HeapStatistics) {
    unsafe { v8__Isolate__GetHeapStatistics(self, s) }
  }

  /// Tells V8 to capture current stack trace when uncaught exception occurs
  /// and report it to the message listeners. The option is off by default.
  #[inline(always)]
  pub fn set_capture_stack_trace_for_uncaught_exceptions(
    &mut self,
    capture: bool,
    frame_limit: i32,
  ) {
    unsafe {
      v8__Isolate__SetCaptureStackTraceForUncaughtExceptions(
        self,
        capture,
        frame_limit,
      )
    }
  }

  /// Adds a message listener (errors only).
  ///
  /// The same message listener can be added more than once and in that
  /// case it will be called more than once for each message.
  ///
  /// The exception object will be passed to the callback.
  #[inline(always)]
  pub fn add_message_listener(&mut self, callback: MessageCallback) -> bool {
    unsafe { v8__Isolate__AddMessageListener(self, callback) }
  }

  /// This specifies the callback called when the stack property of Error
  /// is accessed.
  ///
  /// PrepareStackTraceCallback is called when the stack property of an error is
  /// first accessed. The return value will be used as the stack value. If this
  /// callback is registed, the |Error.prepareStackTrace| API will be disabled.
  /// |sites| is an array of call sites, specified in
  /// https://v8.dev/docs/stack-trace-api
  #[inline(always)]
  pub fn set_prepare_stack_trace_callback<'s>(
    &mut self,
    callback: impl MapFnTo<PrepareStackTraceCallback<'s>>,
  ) {
    // Note: the C++ API returns a MaybeLocal but V8 asserts at runtime when
    // it's empty. That is, you can't return None and that's why the Rust API
    // expects Local<Value> instead of Option<Local<Value>>.
    unsafe {
      v8__Isolate__SetPrepareStackTraceCallback(self, callback.map_fn_to())
    };
  }

  /// Set the PromiseHook callback for various promise lifecycle
  /// events.
  #[inline(always)]
  pub fn set_promise_hook(&mut self, hook: PromiseHook) {
    unsafe { v8__Isolate__SetPromiseHook(self, hook) }
  }

  /// Set callback to notify about promise reject with no handler, or
  /// revocation of such a previous notification once the handler is added.
  #[inline(always)]
  pub fn set_promise_reject_callback(
    &mut self,
    callback: PromiseRejectCallback,
  ) {
    unsafe { v8__Isolate__SetPromiseRejectCallback(self, callback) }
  }

  #[inline(always)]
  pub fn set_wasm_async_resolve_promise_callback(
    &mut self,
    callback: WasmAsyncResolvePromiseCallback,
  ) {
    unsafe { v8__Isolate__SetWasmAsyncResolvePromiseCallback(self, callback) }
  }

  #[inline(always)]
  /// This specifies the callback called by the upcoming importa.meta
  /// language feature to retrieve host-defined meta data for a module.
  pub fn set_host_initialize_import_meta_object_callback(
    &mut self,
    callback: HostInitializeImportMetaObjectCallback,
  ) {
    unsafe {
      v8__Isolate__SetHostInitializeImportMetaObjectCallback(self, callback)
    }
  }

  /// This specifies the callback called by the upcoming dynamic
  /// import() language feature to load modules.
  #[inline(always)]
  pub fn set_host_import_module_dynamically_callback(
    &mut self,
    callback: impl HostImportModuleDynamicallyCallback,
  ) {
    unsafe {
      v8__Isolate__SetHostImportModuleDynamicallyCallback(
        self,
        callback.to_c_fn(),
      )
    }
  }

  /// This specifies the callback called by the upcoming `ShadowRealm`
  /// construction language feature to retrieve host created globals.
  pub fn set_host_create_shadow_realm_context_callback(
    &mut self,
    callback: HostCreateShadowRealmContextCallback,
  ) {
    #[inline]
    extern "C" fn rust_shadow_realm_callback(
      initiator_context: Local<Context>,
    ) -> *mut Context {
      let mut scope = unsafe { CallbackScope::new(initiator_context) };
      let callback = scope
        .get_slot::<HostCreateShadowRealmContextCallback>()
        .unwrap();
      let context = callback(&mut scope);
      context
        .map(|l| l.as_non_null().as_ptr())
        .unwrap_or_else(null_mut)
    }

    // Windows x64 ABI: MaybeLocal<Context> must be returned on the stack.
    #[cfg(target_os = "windows")]
    extern "C" fn rust_shadow_realm_callback_windows(
      rv: *mut *mut Context,
      initiator_context: Local<Context>,
    ) -> *mut *mut Context {
      let ret = rust_shadow_realm_callback(initiator_context);
      unsafe {
        rv.write(ret);
      }
      rv
    }

    let slot_didnt_exist_before = self.set_slot(callback);
    if slot_didnt_exist_before {
      unsafe {
        #[cfg(target_os = "windows")]
        v8__Isolate__SetHostCreateShadowRealmContextCallback(
          self,
          rust_shadow_realm_callback_windows,
        );
        #[cfg(not(target_os = "windows"))]
        v8__Isolate__SetHostCreateShadowRealmContextCallback(
          self,
          rust_shadow_realm_callback,
        );
      }
    }
  }

  /// Add a callback to invoke in case the heap size is close to the heap limit.
  /// If multiple callbacks are added, only the most recently added callback is
  /// invoked.
  #[allow(clippy::not_unsafe_ptr_arg_deref)] // False positive.
  #[inline(always)]
  pub fn add_near_heap_limit_callback(
    &mut self,
    callback: NearHeapLimitCallback,
    data: *mut c_void,
  ) {
    unsafe { v8__Isolate__AddNearHeapLimitCallback(self, callback, data) };
  }

  /// Remove the given callback and restore the heap limit to the given limit.
  /// If the given limit is zero, then it is ignored. If the current heap size
  /// is greater than the given limit, then the heap limit is restored to the
  /// minimal limit that is possible for the current heap size.
  #[inline(always)]
  pub fn remove_near_heap_limit_callback(
    &mut self,
    callback: NearHeapLimitCallback,
    heap_limit: usize,
  ) {
    unsafe {
      v8__Isolate__RemoveNearHeapLimitCallback(self, callback, heap_limit)
    };
  }

  /// Adjusts the amount of registered external memory. Used to give V8 an
  /// indication of the amount of externally allocated memory that is kept
  /// alive by JavaScript objects. V8 uses this to decide when to perform
  /// global garbage collections. Registering externally allocated memory
  /// will trigger global garbage collections more often than it would
  /// otherwise in an attempt to garbage collect the JavaScript objects
  /// that keep the externally allocated memory alive.
  #[inline(always)]
  pub fn adjust_amount_of_external_allocated_memory(
    &mut self,
    change_in_bytes: i64,
  ) -> i64 {
    unsafe {
      v8__Isolate__AdjustAmountOfExternalAllocatedMemory(self, change_in_bytes)
    }
  }

  #[inline(always)]
  pub fn set_oom_error_handler(&mut self, callback: OomErrorCallback) {
    unsafe { v8__Isolate__SetOOMErrorHandler(self, callback) };
  }

  /// Returns the policy controlling how Microtasks are invoked.
  #[inline(always)]
  pub fn get_microtasks_policy(&self) -> MicrotasksPolicy {
    unsafe { v8__Isolate__GetMicrotasksPolicy(self) }
  }

  /// Returns the policy controlling how Microtasks are invoked.
  #[inline(always)]
  pub fn set_microtasks_policy(&mut self, policy: MicrotasksPolicy) {
    unsafe { v8__Isolate__SetMicrotasksPolicy(self, policy) }
  }

  /// Runs the default MicrotaskQueue until it gets empty and perform other
  /// microtask checkpoint steps, such as calling ClearKeptObjects. Asserts that
  /// the MicrotasksPolicy is not kScoped. Any exceptions thrown by microtask
  /// callbacks are swallowed.
  #[inline(always)]
  pub fn perform_microtask_checkpoint(&mut self) {
    unsafe { v8__Isolate__PerformMicrotaskCheckpoint(self) }
  }

  /// An alias for PerformMicrotaskCheckpoint.
  #[deprecated(note = "Use Isolate::perform_microtask_checkpoint() instead")]
  pub fn run_microtasks(&mut self) {
    self.perform_microtask_checkpoint()
  }

  /// Enqueues the callback to the default MicrotaskQueue
  #[inline(always)]
  pub fn enqueue_microtask(&mut self, microtask: Local<Function>) {
    unsafe { v8__Isolate__EnqueueMicrotask(self, &*microtask) }
  }

  /// Set whether calling Atomics.wait (a function that may block) is allowed in
  /// this isolate. This can also be configured via
  /// CreateParams::allow_atomics_wait.
  #[inline(always)]
  pub fn set_allow_atomics_wait(&mut self, allow: bool) {
    unsafe { v8__Isolate__SetAllowAtomicsWait(self, allow) }
  }

  /// Embedder injection point for `WebAssembly.compileStreaming(source)`.
  /// The expectation is that the embedder sets it at most once.
  ///
  /// The callback receives the source argument (string, Promise, etc.)
  /// and an instance of [WasmStreaming]. The [WasmStreaming] instance
  /// can outlive the callback and is used to feed data chunks to V8
  /// asynchronously.
  #[inline(always)]
  pub fn set_wasm_streaming_callback<F>(&mut self, _: F)
  where
    F: UnitType + Fn(&mut HandleScope, Local<Value>, WasmStreaming),
  {
    unsafe { v8__Isolate__SetWasmStreamingCallback(self, trampoline::<F>()) }
  }

  /// Returns true if there is ongoing background work within V8 that will
  /// eventually post a foreground task, like asynchronous WebAssembly
  /// compilation.
  #[inline(always)]
  pub fn has_pending_background_tasks(&self) -> bool {
    unsafe { v8__Isolate__HasPendingBackgroundTasks(self) }
  }

  unsafe fn clear_scope_and_annex(&mut self) {
    // Drop the scope stack.
    ScopeData::drop_root(self);

    // If there are finalizers left to call, we trigger GC to try and call as
    // many of them as possible.
    if !self.get_annex().finalizer_map.is_empty() {
      // A low memory notification triggers a synchronous GC, which means
      // finalizers will be called during the course of the call, rather than at
      // some later point.
      self.low_memory_notification();
    }

    // Set the `isolate` pointer inside the annex struct to null, so any
    // IsolateHandle that outlives the isolate will know that it can't call
    // methods on the isolate.
    let annex = self.get_annex_mut();
    {
      let _lock = annex.isolate_mutex.lock().unwrap();
      annex.isolate = null_mut();
    }

    // Clear slots and drop owned objects that were taken out of `CreateParams`.
    annex.create_param_allocations = Box::new(());
    annex.slots.clear();

    // Run through any remaining guaranteed finalizers.
    for finalizer in annex.finalizer_map.drain() {
      if let FinalizerCallback::Guaranteed(callback) = finalizer {
        callback();
      }
    }

    // Subtract one from the Arc<IsolateAnnex> reference count.
    Arc::from_raw(annex);
    self.set_data(0, null_mut());
  }

  /// Disposes the isolate.  The isolate must not be entered by any
  /// thread to be disposable.
  unsafe fn dispose(&mut self) {
    // No test case in rusty_v8 show this, but there have been situations in
    // deno where dropping Annex before the states causes a segfault.
    v8__Isolate__Dispose(self)
  }

  /// Take a heap snapshot. The callback is invoked one or more times
  /// with byte slices containing the snapshot serialized as JSON.
  /// It's the callback's responsibility to reassemble them into
  /// a single document, e.g., by writing them to a file.
  /// Note that Chrome DevTools refuses to load snapshots without
  /// a .heapsnapshot suffix.
  pub fn take_heap_snapshot<F>(&mut self, mut callback: F)
  where
    F: FnMut(&[u8]) -> bool,
  {
    extern "C" fn trampoline<F>(
      arg: *mut c_void,
      data: *const u8,
      size: usize,
    ) -> bool
    where
      F: FnMut(&[u8]) -> bool,
    {
      let p = arg as *mut F;
      let callback = unsafe { &mut *p };
      let slice = unsafe { std::slice::from_raw_parts(data, size) };
      callback(slice)
    }

    let arg = &mut callback as *mut F as *mut c_void;
    unsafe { v8__HeapProfiler__TakeHeapSnapshot(self, trampoline::<F>, arg) }
  }

  /// Set the default context to be included in the snapshot blob.
  /// The snapshot will not contain the global proxy, and we expect one or a
  /// global object template to create one, to be provided upon deserialization.
  ///
  /// # Panics
  ///
  /// Panics if the isolate was not created using [`Isolate::snapshot_creator`]
  #[inline(always)]
  pub fn set_default_context(&mut self, context: Local<Context>) {
    let snapshot_creator = self
      .get_annex_mut()
      .maybe_snapshot_creator
      .as_mut()
      .unwrap();
    snapshot_creator.set_default_context(context);
  }

  /// Add additional context to be included in the snapshot blob.
  /// The snapshot will include the global proxy.
  ///
  /// Returns the index of the context in the snapshot blob.
  ///
  /// # Panics
  ///
  /// Panics if the isolate was not created using [`Isolate::snapshot_creator`]
  #[inline(always)]
  pub fn add_context(&mut self, context: Local<Context>) -> usize {
    let snapshot_creator = self
      .get_annex_mut()
      .maybe_snapshot_creator
      .as_mut()
      .unwrap();
    snapshot_creator.add_context(context)
  }

  /// Attach arbitrary `v8::Data` to the isolate snapshot, which can be
  /// retrieved via `HandleScope::get_context_data_from_snapshot_once()` after
  /// deserialization. This data does not survive when a new snapshot is created
  /// from an existing snapshot.
  ///
  /// # Panics
  ///
  /// Panics if the isolate was not created using [`Isolate::snapshot_creator`]
  #[inline(always)]
  pub fn add_isolate_data<T>(&mut self, data: Local<T>) -> usize
  where
    for<'l> Local<'l, T>: Into<Local<'l, Data>>,
  {
    let snapshot_creator = self
      .get_annex_mut()
      .maybe_snapshot_creator
      .as_mut()
      .unwrap();
    snapshot_creator.add_isolate_data(data)
  }

  /// Attach arbitrary `v8::Data` to the context snapshot, which can be
  /// retrieved via `HandleScope::get_context_data_from_snapshot_once()` after
  /// deserialization. This data does not survive when a new snapshot is
  /// created from an existing snapshot.
  ///
  /// # Panics
  ///
  /// Panics if the isolate was not created using [`Isolate::snapshot_creator`]
  #[inline(always)]
  pub fn add_context_data<T>(
    &mut self,
    context: Local<Context>,
    data: Local<T>,
  ) -> usize
  where
    for<'l> Local<'l, T>: Into<Local<'l, Data>>,
  {
    let snapshot_creator = self
      .get_annex_mut()
      .maybe_snapshot_creator
      .as_mut()
      .unwrap();
    snapshot_creator.add_context_data(context, data)
  }
}

pub(crate) struct IsolateAnnex {
  create_param_allocations: Box<dyn Any>,
  slots: HashMap<TypeId, RawSlot, BuildTypeIdHasher>,
  finalizer_map: FinalizerMap,
  maybe_snapshot_creator: Option<SnapshotCreator>,
  // The `isolate` and `isolate_mutex` fields are there so an `IsolateHandle`
  // (which may outlive the isolate itself) can determine whether the isolate
  // is still alive, and if so, get a reference to it. Safety rules:
  // - The 'main thread' must lock the mutex and reset `isolate` to null just
  //   before the isolate is disposed.
  // - Any other thread must lock the mutex while it's reading/using the
  //   `isolate` pointer.
  isolate: *mut Isolate,
  isolate_mutex: Mutex<()>,
}

impl IsolateAnnex {
  fn new(
    isolate: &mut Isolate,
    create_param_allocations: Box<dyn Any>,
  ) -> Self {
    Self {
      create_param_allocations,
      slots: HashMap::default(),
      finalizer_map: FinalizerMap::default(),
      maybe_snapshot_creator: None,
      isolate,
      isolate_mutex: Mutex::new(()),
    }
  }
}

impl Debug for IsolateAnnex {
  fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
    f.debug_struct("IsolateAnnex")
      .field("isolate", &self.isolate)
      .field("isolate_mutex", &self.isolate_mutex)
      .finish()
  }
}

/// IsolateHandle is a thread-safe reference to an Isolate. It's main use is to
/// terminate execution of a running isolate from another thread.
///
/// It is created with Isolate::thread_safe_handle().
///
/// IsolateHandle is Cloneable, Send, and Sync.
#[derive(Clone, Debug)]
pub struct IsolateHandle(Arc<IsolateAnnex>);

unsafe impl Send for IsolateHandle {}
unsafe impl Sync for IsolateHandle {}

impl IsolateHandle {
  // This function is marked unsafe because it must be called only with either
  // IsolateAnnex::mutex locked, or from the main thread associated with the V8
  // isolate.
  pub(crate) unsafe fn get_isolate_ptr(&self) -> *mut Isolate {
    self.0.isolate
  }

  #[inline(always)]
  fn new(isolate: &Isolate) -> Self {
    Self(isolate.get_annex_arc())
  }

  /// Forcefully terminate the current thread of JavaScript execution
  /// in the given isolate.
  ///
  /// This method can be used by any thread even if that thread has not
  /// acquired the V8 lock with a Locker object.
  ///
  /// Returns false if Isolate was already destroyed.
  #[inline(always)]
  pub fn terminate_execution(&self) -> bool {
    let _lock = self.0.isolate_mutex.lock().unwrap();
    if self.0.isolate.is_null() {
      false
    } else {
      unsafe { v8__Isolate__TerminateExecution(self.0.isolate) };
      true
    }
  }

  /// Resume execution capability in the given isolate, whose execution
  /// was previously forcefully terminated using TerminateExecution().
  ///
  /// When execution is forcefully terminated using TerminateExecution(),
  /// the isolate can not resume execution until all JavaScript frames
  /// have propagated the uncatchable exception which is generated.  This
  /// method allows the program embedding the engine to handle the
  /// termination event and resume execution capability, even if
  /// JavaScript frames remain on the stack.
  ///
  /// This method can be used by any thread even if that thread has not
  /// acquired the V8 lock with a Locker object.
  ///
  /// Returns false if Isolate was already destroyed.
  #[inline(always)]
  pub fn cancel_terminate_execution(&self) -> bool {
    let _lock = self.0.isolate_mutex.lock().unwrap();
    if self.0.isolate.is_null() {
      false
    } else {
      unsafe { v8__Isolate__CancelTerminateExecution(self.0.isolate) };
      true
    }
  }

  /// Is V8 terminating JavaScript execution.
  ///
  /// Returns true if JavaScript execution is currently terminating
  /// because of a call to TerminateExecution.  In that case there are
  /// still JavaScript frames on the stack and the termination
  /// exception is still active.
  ///
  /// Returns false if Isolate was already destroyed.
  #[inline(always)]
  pub fn is_execution_terminating(&self) -> bool {
    let _lock = self.0.isolate_mutex.lock().unwrap();
    if self.0.isolate.is_null() {
      false
    } else {
      unsafe { v8__Isolate__IsExecutionTerminating(self.0.isolate) }
    }
  }

  /// Request V8 to interrupt long running JavaScript code and invoke
  /// the given |callback| passing the given |data| to it. After |callback|
  /// returns control will be returned to the JavaScript code.
  /// There may be a number of interrupt requests in flight.
  /// Can be called from another thread without acquiring a |Locker|.
  /// Registered |callback| must not reenter interrupted Isolate.
  ///
  /// Returns false if Isolate was already destroyed.
  // Clippy warns that this method is dereferencing a raw pointer, but it is
  // not: https://github.com/rust-lang/rust-clippy/issues/3045
  #[allow(clippy::not_unsafe_ptr_arg_deref)]
  #[inline(always)]
  pub fn request_interrupt(
    &self,
    callback: InterruptCallback,
    data: *mut c_void,
  ) -> bool {
    let _lock = self.0.isolate_mutex.lock().unwrap();
    if self.0.isolate.is_null() {
      false
    } else {
      unsafe { v8__Isolate__RequestInterrupt(self.0.isolate, callback, data) };
      true
    }
  }
}

/// Same as Isolate but gets disposed when it goes out of scope.
#[derive(Debug)]
pub struct OwnedIsolate {
  cxx_isolate: NonNull<Isolate>,
}

impl OwnedIsolate {
  pub(crate) fn new(cxx_isolate: *mut Isolate) -> Self {
    let cxx_isolate = NonNull::new(cxx_isolate).unwrap();
    Self { cxx_isolate }
  }
}

impl Drop for OwnedIsolate {
  fn drop(&mut self) {
    unsafe {
      let snapshot_creator = self.get_annex_mut().maybe_snapshot_creator.take();
      assert!(
        snapshot_creator.is_none(),
        "If isolate was created using v8::Isolate::snapshot_creator, you should use v8::OwnedIsolate::create_blob before dropping an isolate."
      );
      self.exit();
      self.cxx_isolate.as_mut().clear_scope_and_annex();
      self.cxx_isolate.as_mut().dispose();
    }
  }
}

impl Deref for OwnedIsolate {
  type Target = Isolate;
  fn deref(&self) -> &Self::Target {
    unsafe { self.cxx_isolate.as_ref() }
  }
}

impl DerefMut for OwnedIsolate {
  fn deref_mut(&mut self) -> &mut Self::Target {
    unsafe { self.cxx_isolate.as_mut() }
  }
}

impl AsMut<Isolate> for OwnedIsolate {
  fn as_mut(&mut self) -> &mut Isolate {
    self
  }
}

impl AsMut<Isolate> for Isolate {
  fn as_mut(&mut self) -> &mut Isolate {
    self
  }
}

impl OwnedIsolate {
  /// Creates a snapshot data blob.
  /// This must not be called from within a handle scope.
  ///
  /// # Panics
  ///
  /// Panics if the isolate was not created using [`Isolate::snapshot_creator`]
  #[inline(always)]
  pub fn create_blob(
    mut self,
    function_code_handling: FunctionCodeHandling,
  ) -> Option<StartupData> {
    let mut snapshot_creator =
      self.get_annex_mut().maybe_snapshot_creator.take().unwrap();
    unsafe { self.cxx_isolate.as_mut().clear_scope_and_annex() };
    // The isolate is owned by the snapshot creator; we need to forget it
    // here as the snapshot creator will drop it when running the destructor.
    std::mem::forget(self);
    snapshot_creator.create_blob(function_code_handling)
  }
}

impl HeapStatistics {
  #[inline(always)]
  pub fn total_heap_size(&self) -> usize {
    unsafe { v8__HeapStatistics__total_heap_size(self) }
  }

  #[inline(always)]
  pub fn total_heap_size_executable(&self) -> usize {
    unsafe { v8__HeapStatistics__total_heap_size_executable(self) }
  }

  #[inline(always)]
  pub fn total_physical_size(&self) -> usize {
    unsafe { v8__HeapStatistics__total_physical_size(self) }
  }

  #[inline(always)]
  pub fn total_available_size(&self) -> usize {
    unsafe { v8__HeapStatistics__total_available_size(self) }
  }

  #[inline(always)]
  pub fn total_global_handles_size(&self) -> usize {
    unsafe { v8__HeapStatistics__total_global_handles_size(self) }
  }

  #[inline(always)]
  pub fn used_global_handles_size(&self) -> usize {
    unsafe { v8__HeapStatistics__used_global_handles_size(self) }
  }

  #[inline(always)]
  pub fn used_heap_size(&self) -> usize {
    unsafe { v8__HeapStatistics__used_heap_size(self) }
  }

  #[inline(always)]
  pub fn heap_size_limit(&self) -> usize {
    unsafe { v8__HeapStatistics__heap_size_limit(self) }
  }

  #[inline(always)]
  pub fn malloced_memory(&self) -> usize {
    unsafe { v8__HeapStatistics__malloced_memory(self) }
  }

  #[inline(always)]
  pub fn external_memory(&self) -> usize {
    unsafe { v8__HeapStatistics__external_memory(self) }
  }

  #[inline(always)]
  pub fn peak_malloced_memory(&self) -> usize {
    unsafe { v8__HeapStatistics__peak_malloced_memory(self) }
  }

  #[inline(always)]
  pub fn number_of_native_contexts(&self) -> usize {
    unsafe { v8__HeapStatistics__number_of_native_contexts(self) }
  }

  #[inline(always)]
  pub fn number_of_detached_contexts(&self) -> usize {
    unsafe { v8__HeapStatistics__number_of_detached_contexts(self) }
  }

  /// Returns a 0/1 boolean, which signifies whether the V8 overwrite heap
  /// garbage with a bit pattern.
  #[inline(always)]
  pub fn does_zap_garbage(&self) -> usize {
    unsafe { v8__HeapStatistics__does_zap_garbage(self) }
  }
}

impl Default for HeapStatistics {
  fn default() -> Self {
    let mut s = MaybeUninit::<Self>::uninit();
    unsafe {
      v8__HeapStatistics__CONSTRUCT(&mut s);
      s.assume_init()
    }
  }
}

impl<'s, F> MapFnFrom<F> for PrepareStackTraceCallback<'s>
where
  F: UnitType
    + Fn(
      &mut HandleScope<'s>,
      Local<'s, Value>,
      Local<'s, Array>,
    ) -> Local<'s, Value>,
{
  // Windows x64 ABI: MaybeLocal<Value> returned on the stack.
  #[cfg(target_os = "windows")]
  fn mapping() -> Self {
    let f = |ret_ptr, context, error, sites| {
      let mut scope: CallbackScope = unsafe { CallbackScope::new(context) };
      let r = (F::get())(&mut scope, error, sites);
      unsafe { std::ptr::write(ret_ptr, &*r as *const _) };
      ret_ptr
    };
    f.to_c_fn()
  }

  // System V ABI
  #[cfg(not(target_os = "windows"))]
  fn mapping() -> Self {
    let f = |context, error, sites| {
      let mut scope: CallbackScope = unsafe { CallbackScope::new(context) };
      let r = (F::get())(&mut scope, error, sites);
      PrepareStackTraceCallbackRet(&*r as *const _)
    };
    f.to_c_fn()
  }
}

/// A special hasher that is optimized for hashing `std::any::TypeId` values.
/// `TypeId` values are actually 64-bit values which themselves come out of some
/// hash function, so it's unnecessary to shuffle their bits any further.
#[derive(Clone, Default)]
pub(crate) struct TypeIdHasher {
  state: Option<u64>,
}

impl Hasher for TypeIdHasher {
  fn write(&mut self, _bytes: &[u8]) {
    panic!("TypeIdHasher::write() called unexpectedly");
  }

  #[inline]
  fn write_u64(&mut self, value: u64) {
    let prev_state = self.state.replace(value);
    debug_assert_eq!(prev_state, None);
  }

  #[inline]
  fn finish(&self) -> u64 {
    self.state.unwrap()
  }
}

/// Factory for instances of `TypeIdHasher`. This is the type that one would
/// pass to the constructor of some map/set type in order to make it use
/// `TypeIdHasher` instead of the default hasher implementation.
#[derive(Copy, Clone, Default)]
pub(crate) struct BuildTypeIdHasher;

impl BuildHasher for BuildTypeIdHasher {
  type Hasher = TypeIdHasher;

  #[inline]
  fn build_hasher(&self) -> Self::Hasher {
    Default::default()
  }
}

const _: () = {
  assert!(size_of::<TypeId>() == size_of::<u64>());
  assert!(align_of::<TypeId>() == align_of::<u64>());
};

pub(crate) struct RawSlot {
  data: RawSlotData,
  dtor: Option<RawSlotDtor>,
}

type RawSlotData = MaybeUninit<usize>;
type RawSlotDtor = unsafe fn(&mut RawSlotData) -> ();

impl RawSlot {
  #[inline]
  pub fn new<T: 'static>(value: T) -> Self {
    if Self::needs_box::<T>() {
      Self::new_internal(Box::new(value))
    } else {
      Self::new_internal(value)
    }
  }

  // SAFETY: a valid value of type `T` must haven been stored in the slot
  // earlier. There is no verification that the type param provided by the
  // caller is correct.
  #[inline]
  pub unsafe fn borrow<T: 'static>(&self) -> &T {
    if Self::needs_box::<T>() {
      &*(self.data.as_ptr() as *const Box<T>)
    } else {
      &*(self.data.as_ptr() as *const T)
    }
  }

  // Safety: see [`RawSlot::borrow`].
  #[inline]
  pub unsafe fn borrow_mut<T: 'static>(&mut self) -> &mut T {
    if Self::needs_box::<T>() {
      &mut *(self.data.as_mut_ptr() as *mut Box<T>)
    } else {
      &mut *(self.data.as_mut_ptr() as *mut T)
    }
  }

  // Safety: see [`RawSlot::borrow`].
  #[inline]
  pub unsafe fn into_inner<T: 'static>(self) -> T {
    let value = if Self::needs_box::<T>() {
      *std::ptr::read(self.data.as_ptr() as *mut Box<T>)
    } else {
      std::ptr::read(self.data.as_ptr() as *mut T)
    };
    forget(self);
    value
  }

  const fn needs_box<T: 'static>() -> bool {
    size_of::<T>() > size_of::<RawSlotData>()
      || align_of::<T>() > align_of::<RawSlotData>()
  }

  #[inline]
  fn new_internal<B: 'static>(value: B) -> Self {
    assert!(!Self::needs_box::<B>());
    let mut self_ = Self {
      data: RawSlotData::zeroed(),
      dtor: None,
    };
    unsafe {
      ptr::write(self_.data.as_mut_ptr() as *mut B, value);
    }
    if needs_drop::<B>() {
      self_.dtor.replace(Self::drop_internal::<B>);
    };
    self_
  }

  // SAFETY: a valid value of type `T` or `Box<T>` must be stored in the slot.
  unsafe fn drop_internal<B: 'static>(data: &mut RawSlotData) {
    assert!(!Self::needs_box::<B>());
    drop_in_place(data.as_mut_ptr() as *mut B);
  }
}

impl Drop for RawSlot {
  fn drop(&mut self) {
    if let Some(dtor) = self.dtor {
      unsafe { dtor(&mut self.data) };
    }
  }
}