summaryrefslogtreecommitdiffstats
path: root/widget/android/jni/Refs.h
blob: 29812fe6a55c837a3cfbf6a114f8b17e8f8a8f02 (plain)
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
/* -*- 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 mozilla_jni_Refs_h__
#define mozilla_jni_Refs_h__

#include <jni.h>

#include <utility>

#include "mozilla/fallible.h"
#include "mozilla/jni/Utils.h"
#include "mozilla/jni/TypeAdapter.h"
#include "nsError.h"  // for nsresult
#include "nsString.h"
#include "nsTArray.h"

namespace mozilla {
namespace jni {

// Wrapped object reference (e.g. jobject, jclass, etc...)
template <class Cls, typename JNIType>
class Ref;
// Represents a calling context for JNI methods.
template <class Cls, typename JNIType>
class Context;
// Wrapped local reference that inherits from Ref.
template <class Cls>
class LocalRef;
// Wrapped global reference that inherits from Ref.
template <class Cls>
class GlobalRef;
// Wrapped weak reference that inherits from Ref.
template <class Cls>
class WeakRef;
// Wrapped dangling reference that's owned by someone else.
template <class Cls>
class DependentRef;

// Class to hold the native types of a method's arguments.
// For example, if a method has signature (ILjava/lang/String;)V,
// its arguments class would be jni::Args<int32_t, jni::String::Param>
template <typename...>
struct Args {};

class Object;

// Base class for Ref and its specializations.
template <class Cls, typename Type>
class Ref {
  template <class C, typename T>
  friend class Ref;

  using Self = Ref<Cls, Type>;
  using bool_type = void (Self::*)() const;
  void non_null_reference() const {}

  // A Cls-derivative that allows copying
  // (e.g. when acting as a return value).
  struct CopyableCtx : public Context<Cls, Type> {
    CopyableCtx(JNIEnv* env, Type instance)
        : Context<Cls, Type>(env, instance) {}

    CopyableCtx(const CopyableCtx& cls)
        : Context<Cls, Type>(cls.Env(), cls.Get()) {}
  };

  // Private copy constructor so that there's no danger of assigning a
  // temporary LocalRef/GlobalRef to a Ref, and potentially use the Ref
  // after the source had been freed.
  Ref(const Ref&) = default;

 protected:
  static JNIEnv* FindEnv() {
    return Cls::callingThread == CallingThread::GECKO ? GetGeckoThreadEnv()
                                                      : GetEnvForThread();
  }

  Type mInstance;

  // Protected jobject constructor because outside code should be using
  // Ref::From. Using Ref::From makes it very easy to see which code is using
  // raw JNI types for future refactoring.
  explicit Ref(Type instance) : mInstance(instance) {}

 public:
  using JNIType = Type;

  class AutoLock {
    friend class Ref<Cls, Type>;

    JNIEnv* const mEnv;
    Type mInstance;

    explicit AutoLock(Type aInstance)
        : mEnv(FindEnv()), mInstance(mEnv->NewLocalRef(aInstance)) {
      mEnv->MonitorEnter(mInstance);
      MOZ_CATCH_JNI_EXCEPTION(mEnv);
    }

   public:
    AutoLock(AutoLock&& aOther)
        : mEnv(aOther.mEnv), mInstance(aOther.mInstance) {
      aOther.mInstance = nullptr;
    }

    ~AutoLock() { Unlock(); }

    void Unlock() {
      if (mInstance) {
        mEnv->MonitorExit(mInstance);
        mEnv->DeleteLocalRef(mInstance);
        MOZ_CATCH_JNI_EXCEPTION(mEnv);
        mInstance = nullptr;
      }
    }
  };

  // Construct a Ref form a raw JNI reference.
  static Ref<Cls, Type> From(JNIType obj) { return Ref<Cls, Type>(obj); }

  // Construct a Ref form a generic object reference.
  static Ref<Cls, Type> From(const Ref<Object, jobject>& obj) {
    return Ref<Cls, Type>(JNIType(obj.Get()));
  }

  MOZ_IMPLICIT Ref(decltype(nullptr)) : mInstance(nullptr) {}

  // Get the raw JNI reference.
  JNIType Get() const { return mInstance; }

  template <class T>
  bool IsInstanceOf() const {
    return FindEnv()->IsInstanceOf(mInstance, typename T::Context().ClassRef());
  }

  template <class T>
  typename T::Ref Cast() const {
#ifdef MOZ_CHECK_JNI
    MOZ_RELEASE_ASSERT(FindEnv()->IsAssignableFrom(
        Context<Cls, Type>().ClassRef(), typename T::Context().ClassRef()));
#endif
    return T::Ref::From(*this);
  }

  AutoLock Lock() const { return AutoLock(mInstance); }

  bool operator==(const Ref& other) const {
    // Treat two references of the same object as being the same.
    return mInstance == other.mInstance ||
           JNI_FALSE != FindEnv()->IsSameObject(mInstance, other.mInstance);
  }

  bool operator!=(const Ref& other) const { return !operator==(other); }

  bool operator==(decltype(nullptr)) const { return !mInstance; }

  bool operator!=(decltype(nullptr)) const { return !!mInstance; }

  CopyableCtx operator->() const { return CopyableCtx(FindEnv(), mInstance); }

  CopyableCtx operator*() const { return operator->(); }

  // Any ref can be cast to an object ref.
  operator Ref<Object, jobject>() const {
    return Ref<Object, jobject>(mInstance);
  }

  // Null checking (e.g. !!ref) using the safe-bool idiom.
  operator bool_type() const {
    return mInstance ? &Self::non_null_reference : nullptr;
  }

  // We don't allow implicit conversion to jobject because that can lead
  // to easy mistakes such as assigning a temporary LocalRef to a jobject,
  // and using the jobject after the LocalRef has been freed.

  // We don't allow explicit conversion, to make outside code use Ref::Get.
  // Using Ref::Get makes it very easy to see which code is using raw JNI
  // types to make future refactoring easier.

  // operator JNIType() const = delete;
};

// Represents a calling context for JNI methods.
template <class Cls, typename Type>
class Context : public Ref<Cls, Type> {
  using Ref = jni::Ref<Cls, Type>;

  static jclass sClassRef;  // global reference

 protected:
  JNIEnv* const mEnv;

 public:
  Context() : Ref(nullptr), mEnv(Ref::FindEnv()) {}

  Context(JNIEnv* env, Type instance) : Ref(instance), mEnv(env) {}

  jclass ClassRef() const {
    if (!sClassRef) {
      const jclass cls = GetClassRef(mEnv, Cls::name);
      sClassRef = jclass(mEnv->NewGlobalRef(cls));
      mEnv->DeleteLocalRef(cls);
    }
    return sClassRef;
  }

  JNIEnv* Env() const { return mEnv; }

  template <class T>
  bool IsInstanceOf() const {
    return mEnv->IsInstanceOf(Ref::mInstance,
                              typename T::Context(mEnv, nullptr).ClassRef());
  }

  bool operator==(const Ref& other) const {
    // Treat two references of the same object as being the same.
    return Ref::mInstance == other.Get() ||
           JNI_FALSE != mEnv->IsSameObject(Ref::mInstance, other.Get());
  }

  bool operator!=(const Ref& other) const { return !operator==(other); }

  bool operator==(decltype(nullptr)) const { return !Ref::mInstance; }

  bool operator!=(decltype(nullptr)) const { return !!Ref::mInstance; }

  Cls operator->() const {
    MOZ_ASSERT(Ref::mInstance, "Null jobject");
    return Cls(*this);
  }

  const Context<Cls, Type>& operator*() const { return *this; }
};

template <class C, typename T>
jclass Context<C, T>::sClassRef;

template <class Cls, typename Type = jobject>
class ObjectBase {
 protected:
  const jni::Context<Cls, Type>& mCtx;

  jclass ClassRef() const { return mCtx.ClassRef(); }
  JNIEnv* Env() const { return mCtx.Env(); }
  Type Instance() const { return mCtx.Get(); }

 public:
  using Ref = jni::Ref<Cls, Type>;
  using Context = jni::Context<Cls, Type>;
  using LocalRef = jni::LocalRef<Cls>;
  using GlobalRef = jni::GlobalRef<Cls>;
  using WeakRef = jni::WeakRef<Cls>;
  using Param = const Ref&;

  static const CallingThread callingThread = CallingThread::ANY;
  static const char name[];

  explicit ObjectBase(const Context& ctx) : mCtx(ctx) {}

  Cls* operator->() { return static_cast<Cls*>(this); }
};

// Binding for a plain jobject.
class Object : public ObjectBase<Object, jobject> {
 public:
  explicit Object(const Context& ctx) : ObjectBase<Object, jobject>(ctx) {}
};

// Binding for a built-in object reference other than jobject.
template <typename T>
class TypedObject : public ObjectBase<TypedObject<T>, T> {
 public:
  explicit TypedObject(const Context<TypedObject<T>, T>& ctx)
      : ObjectBase<TypedObject<T>, T>(ctx) {}
};

// Binding for a boxed primitive object.
template <typename T>
class BoxedObject : public ObjectBase<BoxedObject<T>, jobject> {
 public:
  explicit BoxedObject(const Context<BoxedObject<T>, jobject>& ctx)
      : ObjectBase<BoxedObject<T>, jobject>(ctx) {}
};

template <>
const char ObjectBase<Object, jobject>::name[];
template <>
const char ObjectBase<TypedObject<jstring>, jstring>::name[];
template <>
const char ObjectBase<TypedObject<jclass>, jclass>::name[];
template <>
const char ObjectBase<TypedObject<jthrowable>, jthrowable>::name[];
template <>
const char ObjectBase<BoxedObject<jboolean>, jobject>::name[];
template <>
const char ObjectBase<BoxedObject<jbyte>, jobject>::name[];
template <>
const char ObjectBase<BoxedObject<jchar>, jobject>::name[];
template <>
const char ObjectBase<BoxedObject<jshort>, jobject>::name[];
template <>
const char ObjectBase<BoxedObject<jint>, jobject>::name[];
template <>
const char ObjectBase<BoxedObject<jlong>, jobject>::name[];
template <>
const char ObjectBase<BoxedObject<jfloat>, jobject>::name[];
template <>
const char ObjectBase<BoxedObject<jdouble>, jobject>::name[];
template <>
const char ObjectBase<TypedObject<jbooleanArray>, jbooleanArray>::name[];
template <>
const char ObjectBase<TypedObject<jbyteArray>, jbyteArray>::name[];
template <>
const char ObjectBase<TypedObject<jcharArray>, jcharArray>::name[];
template <>
const char ObjectBase<TypedObject<jshortArray>, jshortArray>::name[];
template <>
const char ObjectBase<TypedObject<jintArray>, jintArray>::name[];
template <>
const char ObjectBase<TypedObject<jlongArray>, jlongArray>::name[];
template <>
const char ObjectBase<TypedObject<jfloatArray>, jfloatArray>::name[];
template <>
const char ObjectBase<TypedObject<jdoubleArray>, jdoubleArray>::name[];
template <>
const char ObjectBase<TypedObject<jobjectArray>, jobjectArray>::name[];

// Define bindings for built-in types.
using String = TypedObject<jstring>;
using Class = TypedObject<jclass>;
using Throwable = TypedObject<jthrowable>;

using Boolean = BoxedObject<jboolean>;
using Byte = BoxedObject<jbyte>;
using Character = BoxedObject<jchar>;
using Short = BoxedObject<jshort>;
using Integer = BoxedObject<jint>;
using Long = BoxedObject<jlong>;
using Float = BoxedObject<jfloat>;
using Double = BoxedObject<jdouble>;

using BooleanArray = TypedObject<jbooleanArray>;
using ByteArray = TypedObject<jbyteArray>;
using CharArray = TypedObject<jcharArray>;
using ShortArray = TypedObject<jshortArray>;
using IntArray = TypedObject<jintArray>;
using LongArray = TypedObject<jlongArray>;
using FloatArray = TypedObject<jfloatArray>;
using DoubleArray = TypedObject<jdoubleArray>;
using ObjectArray = TypedObject<jobjectArray>;

namespace detail {

// See explanation in LocalRef.
template <class Cls>
struct GenericObject {
  using Type = Object;
};
template <>
struct GenericObject<Object> {
  struct Type {
    using Ref = jni::Ref<Type, jobject>;
    using Context = jni::Context<Type, jobject>;
  };
};
template <class Cls>
struct GenericLocalRef {
  template <class C>
  struct Type : jni::Object {};
};
template <>
struct GenericLocalRef<Object> {
  template <class C>
  using Type = jni::LocalRef<C>;
};

}  // namespace detail

template <class Cls>
class LocalRef : public Cls::Context {
  template <class C>
  friend class LocalRef;

  using Ctx = typename Cls::Context;
  using Ref = typename Cls::Ref;
  using JNIType = typename Ref::JNIType;

  // In order to be able to convert LocalRef<Object> to LocalRef<Cls>, we
  // need constructors and copy assignment operators that take in a
  // LocalRef<Object> argument. However, if Cls *is* Object, we would have
  // duplicated constructors and operators with LocalRef<Object> arguments. To
  // avoid this conflict, we use GenericObject, which is defined as Object for
  // LocalRef<non-Object> and defined as a dummy class for LocalRef<Object>.
  using GenericObject = typename detail::GenericObject<Cls>::Type;

  // Similarly, GenericLocalRef is useed to convert LocalRef<Cls> to,
  // LocalRef<Object>. It's defined as LocalRef<C> for Cls == Object,
  // and defined as a dummy template class for Cls != Object.
  template <class C>
  using GenericLocalRef =
      typename detail::GenericLocalRef<Cls>::template Type<C>;

  static JNIType NewLocalRef(JNIEnv* env, JNIType obj) {
    return JNIType(obj ? env->NewLocalRef(obj) : nullptr);
  }

  LocalRef(JNIEnv* env, JNIType instance) : Ctx(env, instance) {}

  LocalRef& swap(LocalRef& other) {
    auto instance = other.mInstance;
    other.mInstance = Ctx::mInstance;
    Ctx::mInstance = instance;
    return *this;
  }

 public:
  // Construct a LocalRef from a raw JNI local reference. Unlike Ref::From,
  // LocalRef::Adopt returns a LocalRef that will delete the local reference
  // when going out of scope.
  static LocalRef Adopt(JNIType instance) {
    return LocalRef(Ref::FindEnv(), instance);
  }

  static LocalRef Adopt(JNIEnv* env, JNIType instance) {
    return LocalRef(env, instance);
  }

  // Copy constructor.
  LocalRef(const LocalRef<Cls>& ref)
      : Ctx(ref.mEnv, NewLocalRef(ref.mEnv, ref.mInstance)) {}

  // Move constructor.
  LocalRef(LocalRef<Cls>&& ref) : Ctx(ref.mEnv, ref.mInstance) {
    ref.mInstance = nullptr;
  }

  explicit LocalRef(JNIEnv* env = Ref::FindEnv()) : Ctx(env, nullptr) {}

  // Construct a LocalRef from any Ref,
  // which means creating a new local reference.
  MOZ_IMPLICIT LocalRef(const Ref& ref) : Ctx(Ref::FindEnv(), nullptr) {
    Ctx::mInstance = NewLocalRef(Ctx::mEnv, ref.Get());
  }

  LocalRef(JNIEnv* env, const Ref& ref)
      : Ctx(env, NewLocalRef(env, ref.Get())) {}

  // Move a LocalRef<Object> into a LocalRef<Cls> without
  // creating/deleting local references.
  MOZ_IMPLICIT LocalRef(LocalRef<GenericObject>&& ref)
      : Ctx(ref.mEnv, JNIType(ref.mInstance)) {
    ref.mInstance = nullptr;
  }

  template <class C>
  MOZ_IMPLICIT LocalRef(GenericLocalRef<C>&& ref)
      : Ctx(ref.mEnv, ref.mInstance) {
    ref.mInstance = nullptr;
  }

  // Implicitly converts nullptr to LocalRef.
  MOZ_IMPLICIT LocalRef(decltype(nullptr)) : Ctx(Ref::FindEnv(), nullptr) {}

  ~LocalRef() {
    if (Ctx::mInstance) {
      Ctx::mEnv->DeleteLocalRef(Ctx::mInstance);
      Ctx::mInstance = nullptr;
    }
  }

  // Get the raw JNI reference that can be used as a return value.
  // Returns the same JNI type (jobject, jstring, etc.) as the underlying Ref.
  typename Ref::JNIType Forget() {
    const auto obj = Ctx::Get();
    Ctx::mInstance = nullptr;
    return obj;
  }

  LocalRef<Cls>& operator=(LocalRef<Cls> ref) & { return swap(ref); }

  LocalRef<Cls>& operator=(const Ref& ref) & {
    LocalRef<Cls> newRef(Ctx::mEnv, ref);
    return swap(newRef);
  }

  LocalRef<Cls>& operator=(LocalRef<GenericObject>&& ref) & {
    LocalRef<Cls> newRef(std::move(ref));
    return swap(newRef);
  }

  template <class C>
  LocalRef<Cls>& operator=(GenericLocalRef<C>&& ref) & {
    LocalRef<Cls> newRef(std::move(ref));
    return swap(newRef);
  }

  LocalRef<Cls>& operator=(decltype(nullptr)) & {
    LocalRef<Cls> newRef(Ctx::mEnv, nullptr);
    return swap(newRef);
  }
};

template <class Cls>
class GlobalRef : public Cls::Ref {
  using Ref = typename Cls::Ref;
  using JNIType = typename Ref::JNIType;

  static JNIType NewGlobalRef(JNIEnv* env, JNIType instance) {
    return JNIType(instance ? env->NewGlobalRef(instance) : nullptr);
  }

  GlobalRef& swap(GlobalRef& other) {
    auto instance = other.mInstance;
    other.mInstance = Ref::mInstance;
    Ref::mInstance = instance;
    return *this;
  }

 public:
  GlobalRef() : Ref(nullptr) {}

  // Copy constructor
  GlobalRef(const GlobalRef& ref)
      : Ref(NewGlobalRef(GetEnvForThread(), ref.mInstance)) {}

  // Move constructor
  GlobalRef(GlobalRef&& ref) : Ref(ref.mInstance) { ref.mInstance = nullptr; }

  MOZ_IMPLICIT GlobalRef(const Ref& ref)
      : Ref(NewGlobalRef(GetEnvForThread(), ref.Get())) {}

  GlobalRef(JNIEnv* env, const Ref& ref) : Ref(NewGlobalRef(env, ref.Get())) {}

  MOZ_IMPLICIT GlobalRef(const LocalRef<Cls>& ref)
      : Ref(NewGlobalRef(ref.Env(), ref.Get())) {}

  // Implicitly converts nullptr to GlobalRef.
  MOZ_IMPLICIT GlobalRef(decltype(nullptr)) : Ref(nullptr) {}

  ~GlobalRef() {
    if (Ref::mInstance) {
      Clear(GetEnvForThread());
    }
  }

  // Get the raw JNI reference that can be used as a return value.
  // Returns the same JNI type (jobject, jstring, etc.) as the underlying Ref.
  typename Ref::JNIType Forget() {
    const auto obj = Ref::Get();
    Ref::mInstance = nullptr;
    return obj;
  }

  void Clear(JNIEnv* env) {
    if (Ref::mInstance) {
      env->DeleteGlobalRef(Ref::mInstance);
      Ref::mInstance = nullptr;
    }
  }

  GlobalRef<Cls>& operator=(GlobalRef<Cls> ref) & { return swap(ref); }

  GlobalRef<Cls>& operator=(const Ref& ref) & {
    GlobalRef<Cls> newRef(ref);
    return swap(newRef);
  }

  GlobalRef<Cls>& operator=(const LocalRef<Cls>& ref) & {
    GlobalRef<Cls> newRef(ref);
    return swap(newRef);
  }

  GlobalRef<Cls>& operator=(decltype(nullptr)) & {
    GlobalRef<Cls> newRef(nullptr);
    return swap(newRef);
  }
};

template <class Cls>
class WeakRef : public Ref<Cls, jweak> {
  using Ref = Ref<Cls, jweak>;
  using JNIType = typename Ref::JNIType;

  static JNIType NewWeakRef(JNIEnv* env, JNIType instance) {
    return JNIType(instance ? env->NewWeakGlobalRef(instance) : nullptr);
  }

  WeakRef& swap(WeakRef& other) {
    auto instance = other.mInstance;
    other.mInstance = Ref::mInstance;
    Ref::mInstance = instance;
    return *this;
  }

 public:
  WeakRef() : Ref(nullptr) {}

  // Copy constructor
  WeakRef(const WeakRef& ref)
      : Ref(NewWeakRef(GetEnvForThread(), ref.mInstance)) {}

  // Move constructor
  WeakRef(WeakRef&& ref) : Ref(ref.mInstance) { ref.mInstance = nullptr; }

  MOZ_IMPLICIT WeakRef(const Ref& ref)
      : Ref(NewWeakRef(GetEnvForThread(), ref.Get())) {}

  WeakRef(JNIEnv* env, const Ref& ref) : Ref(NewWeakRef(env, ref.Get())) {}

  MOZ_IMPLICIT WeakRef(const LocalRef<Cls>& ref)
      : Ref(NewWeakRef(ref.Env(), ref.Get())) {}

  // Implicitly converts nullptr to WeakRef.
  MOZ_IMPLICIT WeakRef(decltype(nullptr)) : Ref(nullptr) {}

  ~WeakRef() {
    if (Ref::mInstance) {
      Clear(GetEnvForThread());
    }
  }

  // Get the raw JNI reference that can be used as a return value.
  // Returns the same JNI type (jobject, jstring, etc.) as the underlying Ref.
  typename Ref::JNIType Forget() {
    const auto obj = Ref::Get();
    Ref::mInstance = nullptr;
    return obj;
  }

  void Clear(JNIEnv* env) {
    if (Ref::mInstance) {
      env->DeleteWeakGlobalRef(Ref::mInstance);
      Ref::mInstance = nullptr;
    }
  }

  WeakRef<Cls>& operator=(WeakRef<Cls> ref) & { return swap(ref); }

  WeakRef<Cls>& operator=(const Ref& ref) & {
    WeakRef<Cls> newRef(ref);
    return swap(newRef);
  }

  WeakRef<Cls>& operator=(const LocalRef<Cls>& ref) & {
    WeakRef<Cls> newRef(ref);
    return swap(newRef);
  }

  WeakRef<Cls>& operator=(decltype(nullptr)) & {
    WeakRef<Cls> newRef(nullptr);
    return swap(newRef);
  }

  void operator->() const = delete;
  void operator*() const = delete;
};

template <class Cls>
class DependentRef : public Cls::Ref {
  using Ref = typename Cls::Ref;

 public:
  explicit DependentRef(typename Ref::JNIType instance) : Ref(instance) {}

  DependentRef(const DependentRef& ref) : Ref(ref.Get()) {}
};

class StringParam;

template <>
class TypedObject<jstring> : public ObjectBase<TypedObject<jstring>, jstring> {
  using Base = ObjectBase<TypedObject<jstring>, jstring>;

 public:
  using Param = const StringParam&;

  explicit TypedObject(const Context& ctx) : Base(ctx) {}

  size_t Length() const {
    const size_t ret = Base::Env()->GetStringLength(Base::Instance());
    MOZ_CATCH_JNI_EXCEPTION(Base::Env());
    return ret;
  }

  nsString ToString() const {
    const jchar* const str =
        Base::Env()->GetStringChars(Base::Instance(), nullptr);
    const jsize len = Base::Env()->GetStringLength(Base::Instance());

    nsString result(reinterpret_cast<const char16_t*>(str), len);
    Base::Env()->ReleaseStringChars(Base::Instance(), str);
    return result;
  }

  nsCString ToCString() const { return NS_ConvertUTF16toUTF8(ToString()); }

  // Convert jstring to a nsString.
  operator nsString() const { return ToString(); }

  // Convert jstring to a nsCString.
  operator nsCString() const { return ToCString(); }
};

// Define a custom parameter type for String,
// which accepts both String::Ref and nsAString/nsACString
class StringParam : public String::Ref {
  using Ref = String::Ref;

 private:
  // Not null if we should delete ref on destruction.
  JNIEnv* const mEnv;

  static jstring GetString(JNIEnv* env, const nsAString& str) {
    const jstring result = env->NewString(
        reinterpret_cast<const jchar*>(str.BeginReading()), str.Length());
    if (!result) {
      NS_ABORT_OOM(str.Length() * sizeof(char16_t));
    }
    MOZ_CATCH_JNI_EXCEPTION(env);
    return result;
  }

  static jstring GetString(JNIEnv* env, const nsAString& str,
                           const fallible_t&) {
    const jstring result = env->NewString(
        reinterpret_cast<const jchar*>(str.BeginReading()), str.Length());
    if (env->ExceptionCheck()) {
#ifdef MOZ_CHECK_JNI
      env->ExceptionDescribe();
#endif
      env->ExceptionClear();
    }
    return result;
  }

  static jstring GetString(JNIEnv* env, const nsACString& str,
                           const fallible_t& aFallible) {
    nsAutoString utf16;
    if (!CopyUTF8toUTF16(str, utf16, aFallible)) {
      return nullptr;
    }
    return GetString(env, utf16, aFallible);
  }

 public:
  MOZ_IMPLICIT StringParam(decltype(nullptr)) : Ref(nullptr), mEnv(nullptr) {}

  MOZ_IMPLICIT StringParam(const Ref& ref) : Ref(ref.Get()), mEnv(nullptr) {}

  MOZ_IMPLICIT StringParam(const nsAString& str, JNIEnv* env = Ref::FindEnv())
      : Ref(GetString(env, str)), mEnv(env) {}

  MOZ_IMPLICIT StringParam(const nsAString& str, JNIEnv* env,
                           const fallible_t& aFallible)
      : Ref(GetString(env, str, aFallible)), mEnv(env) {}

  MOZ_IMPLICIT StringParam(const nsLiteralString& str,
                           JNIEnv* env = Ref::FindEnv())
      : Ref(GetString(env, str)), mEnv(env) {}

  MOZ_IMPLICIT StringParam(const char16_t* str, JNIEnv* env = Ref::FindEnv())
      : Ref(GetString(env, nsDependentString(str))), mEnv(env) {}

  MOZ_IMPLICIT StringParam(const nsACString& str, JNIEnv* env = Ref::FindEnv())
      : Ref(GetString(env, NS_ConvertUTF8toUTF16(str))), mEnv(env) {}

  MOZ_IMPLICIT StringParam(const nsACString& str, JNIEnv* env,
                           const fallible_t& aFallible)
      : Ref(GetString(env, str, aFallible)), mEnv(env) {}

  MOZ_IMPLICIT StringParam(const nsLiteralCString& str,
                           JNIEnv* env = Ref::FindEnv())
      : Ref(GetString(env, NS_ConvertUTF8toUTF16(str))), mEnv(env) {}

  MOZ_IMPLICIT StringParam(const char* str, JNIEnv* env = Ref::FindEnv())
      : Ref(GetString(env, NS_ConvertUTF8toUTF16(str))), mEnv(env) {}

  StringParam(StringParam&& other) : Ref(other.Get()), mEnv(other.mEnv) {
    other.mInstance = nullptr;
  }

  ~StringParam() {
    if (mEnv && Get()) {
      mEnv->DeleteLocalRef(Get());
    }
  }

  operator String::LocalRef() const {
    // We can't return our existing ref because the returned
    // LocalRef could be freed first, so we need a new local ref.
    return String::LocalRef(mEnv ? mEnv : Ref::FindEnv(), *this);
  }
};

namespace detail {
template <typename T>
struct TypeAdapter;
}

// Ref specialization for arrays.
template <typename JNIType, class ElementType>
class ArrayRefBase : public ObjectBase<TypedObject<JNIType>, JNIType> {
 protected:
  using Base = ObjectBase<TypedObject<JNIType>, JNIType>;

 public:
  explicit ArrayRefBase(const Context<TypedObject<JNIType>, JNIType>& ctx)
      : Base(ctx) {}

  static typename Base::LocalRef New(const ElementType* data, size_t length) {
    using JNIElemType = typename detail::TypeAdapter<ElementType>::JNIType;
    static_assert(sizeof(ElementType) == sizeof(JNIElemType),
                  "Size of native type must match size of JNI type");
    JNIEnv* const jenv = mozilla::jni::GetEnvForThread();
    auto result = (jenv->*detail::TypeAdapter<ElementType>::NewArray)(length);
    MOZ_CATCH_JNI_EXCEPTION(jenv);
    (jenv->*detail::TypeAdapter<ElementType>::SetArray)(
        result, jsize(0), length, reinterpret_cast<const JNIElemType*>(data));
    MOZ_CATCH_JNI_EXCEPTION(jenv);
    return Base::LocalRef::Adopt(jenv, result);
  }

  static typename Base::LocalRef New(const ElementType* data, size_t length,
                                     const fallible_t&) {
    using JNIElemType = typename detail::TypeAdapter<ElementType>::JNIType;
    static_assert(sizeof(ElementType) == sizeof(JNIElemType),
                  "Size of native type must match size of JNI type");
    JNIEnv* const jenv = mozilla::jni::GetEnvForThread();
    auto result = (jenv->*detail::TypeAdapter<ElementType>::NewArray)(length);
    if (jenv->ExceptionCheck()) {
      if (!IsOOMException(jenv)) {
        // This exception isn't excepted due not to OOM. This is unrecoverable
        // error.
        MOZ_CATCH_JNI_EXCEPTION(jenv);
      }
#ifdef MOZ_CHECK_JNI
      jenv->ExceptionDescribe();
#endif
      jenv->ExceptionClear();
      return Base::LocalRef::Adopt(jenv, nullptr);
    }
    (jenv->*detail::TypeAdapter<ElementType>::SetArray)(
        result, jsize(0), length, reinterpret_cast<const JNIElemType*>(data));
    if (jenv->ExceptionCheck()) {
      if (!IsOOMException(jenv)) {
        // This exception isn't excepted due not to OOM. This is unrecoverable
        // error.
        MOZ_CATCH_JNI_EXCEPTION(jenv);
      }
#ifdef MOZ_CHECK_JNI
      jenv->ExceptionDescribe();
#endif
      jenv->ExceptionClear();
      jenv->DeleteLocalRef(result);
      return Base::LocalRef::Adopt(jenv, nullptr);
    }
    return Base::LocalRef::Adopt(jenv, result);
  }

  size_t Length() const {
    const size_t ret = Base::Env()->GetArrayLength(Base::Instance());
    MOZ_CATCH_JNI_EXCEPTION(Base::Env());
    return ret;
  }

  ElementType GetElement(size_t index) const {
    using JNIElemType = typename detail::TypeAdapter<ElementType>::JNIType;
    static_assert(sizeof(ElementType) == sizeof(JNIElemType),
                  "Size of native type must match size of JNI type");

    ElementType ret;
    (Base::Env()->*detail::TypeAdapter<ElementType>::GetArray)(
        Base::Instance(), jsize(index), 1,
        reinterpret_cast<JNIElemType*>(&ret));
    MOZ_CATCH_JNI_EXCEPTION(Base::Env());
    return ret;
  }

  nsTArray<ElementType> GetElements() const {
    using JNIElemType = typename detail::TypeAdapter<ElementType>::JNIType;
    static_assert(sizeof(ElementType) == sizeof(JNIElemType),
                  "Size of native type must match size of JNI type");

    const size_t len = size_t(Base::Env()->GetArrayLength(Base::Instance()));

    nsTArray<ElementType> array(len);
    array.SetLength(len);
    CopyTo(array.Elements(), len);
    return array;
  }

  // returns number of elements copied
  size_t CopyTo(ElementType* buffer, size_t size) const {
    using JNIElemType = typename detail::TypeAdapter<ElementType>::JNIType;
    static_assert(sizeof(ElementType) == sizeof(JNIElemType),
                  "Size of native type must match size of JNI type");

    const size_t len = size_t(Base::Env()->GetArrayLength(Base::Instance()));
    const size_t amountToCopy = (len > size ? size : len);
    (Base::Env()->*detail::TypeAdapter<ElementType>::GetArray)(
        Base::Instance(), 0, jsize(amountToCopy),
        reinterpret_cast<JNIElemType*>(buffer));
    return amountToCopy;
  }

  ElementType operator[](size_t index) const { return GetElement(index); }

  operator nsTArray<ElementType>() const { return GetElements(); }
};

#define DEFINE_PRIMITIVE_ARRAY_REF_HEADER(JNIType, ElementType)                \
  template <>                                                                  \
  class TypedObject<JNIType> : public ArrayRefBase<JNIType, ElementType> {     \
   public:                                                                     \
    explicit TypedObject(const Context& ctx)                                   \
        : ArrayRefBase<JNIType, ElementType>(ctx) {}                           \
    static typename Base::LocalRef From(const nsTArray<ElementType>& aArray) { \
      return New(aArray.Elements(), aArray.Length());                          \
    }

#define DEFINE_PRIMITIVE_ARRAY_REF_FOOTER }

#define DEFINE_PRIMITIVE_ARRAY_REF_FROM_IMPLICIT_CONVERSION(ElementType,     \
                                                            ConvertFromType) \
  static typename Base::LocalRef From(                                       \
      const nsTArray<ConvertFromType>& aArray) {                             \
    return New(reinterpret_cast<const ElementType*>(aArray.Elements()),      \
               aArray.Length());                                             \
  }

#define DEFINE_PRIMITIVE_ARRAY_REF(JNIType, ElementType)  \
  DEFINE_PRIMITIVE_ARRAY_REF_HEADER(JNIType, ElementType) \
  DEFINE_PRIMITIVE_ARRAY_REF_FOOTER

#define DEFINE_PRIMITIVE_ARRAY_REF_WITH_IMPLICIT_CONVERSION(           \
    JNIType, ElementType, ConvertFromType)                             \
  DEFINE_PRIMITIVE_ARRAY_REF_HEADER(JNIType, ElementType)              \
  DEFINE_PRIMITIVE_ARRAY_REF_FROM_IMPLICIT_CONVERSION(ElementType,     \
                                                      ConvertFromType) \
  DEFINE_PRIMITIVE_ARRAY_REF_FOOTER

DEFINE_PRIMITIVE_ARRAY_REF(jbooleanArray, bool);
DEFINE_PRIMITIVE_ARRAY_REF_WITH_IMPLICIT_CONVERSION(jbyteArray, int8_t,
                                                    uint8_t);
DEFINE_PRIMITIVE_ARRAY_REF(jcharArray, char16_t);
DEFINE_PRIMITIVE_ARRAY_REF_WITH_IMPLICIT_CONVERSION(jshortArray, int16_t,
                                                    uint16_t);
DEFINE_PRIMITIVE_ARRAY_REF_WITH_IMPLICIT_CONVERSION(jintArray, int32_t,
                                                    uint32_t);
DEFINE_PRIMITIVE_ARRAY_REF(jfloatArray, float);
DEFINE_PRIMITIVE_ARRAY_REF_WITH_IMPLICIT_CONVERSION(jlongArray, int64_t,
                                                    uint64_t);
DEFINE_PRIMITIVE_ARRAY_REF(jdoubleArray, double);

#undef DEFINE_PRIMITIVE_ARRAY_REF
#undef DEFINE_PRIMITIVE_ARRAY_REF_WITH_IMPLICIT_CONVERSION
#undef DEFINE_PRIMITIVE_ARRAY_HEADER
#undef DEFINE_PRIMITIVE_ARRAY_FROM_IMPLICIT_CONVERSION
#undef DEFINE_PRIMITIVE_ARRAY_FOOTER

class ByteBuffer : public ObjectBase<ByteBuffer, jobject> {
 public:
  explicit ByteBuffer(const Context& ctx)
      : ObjectBase<ByteBuffer, jobject>(ctx) {}

  static LocalRef New(void* data, size_t capacity) {
    JNIEnv* const env = GetEnvForThread();
    const auto ret =
        LocalRef::Adopt(env, env->NewDirectByteBuffer(data, jlong(capacity)));
    MOZ_CATCH_JNI_EXCEPTION(env);
    return ret;
  }

  static LocalRef New(void* data, size_t capacity, const fallible_t&) {
    JNIEnv* const env = GetEnvForThread();
    const jobject result = env->NewDirectByteBuffer(data, jlong(capacity));
    if (env->ExceptionCheck()) {
      if (!IsOOMException(env)) {
        // This exception isn't excepted due not to OOM. This is unrecoverable
        // error.
        MOZ_CATCH_JNI_EXCEPTION(env);
      }
#ifdef MOZ_CHECK_JNI
      env->ExceptionDescribe();
#endif
      env->ExceptionClear();
      return LocalRef::Adopt(env, nullptr);
    }
    return LocalRef::Adopt(env, result);
  }

  void* Address() {
    void* const ret = Env()->GetDirectBufferAddress(Instance());
    MOZ_CATCH_JNI_EXCEPTION(Env());
    return ret;
  }

  size_t Capacity() {
    const size_t ret = size_t(Env()->GetDirectBufferCapacity(Instance()));
    MOZ_CATCH_JNI_EXCEPTION(Env());
    return ret;
  }
};

template <>
const char ObjectBase<ByteBuffer, jobject>::name[];

template <>
class TypedObject<jobjectArray>
    : public ObjectBase<TypedObject<jobjectArray>, jobjectArray> {
  using Base = ObjectBase<TypedObject<jobjectArray>, jobjectArray>;

 public:
  template <class Cls = Object>
  static Base::LocalRef New(size_t length,
                            typename Cls::Param initialElement = nullptr) {
    JNIEnv* const env = GetEnvForThread();
    jobjectArray array = env->NewObjectArray(
        jsize(length), typename Cls::Context(env, nullptr).ClassRef(),
        initialElement.Get());
    MOZ_CATCH_JNI_EXCEPTION(env);
    return Base::LocalRef::Adopt(env, array);
  }

  explicit TypedObject(const Context& ctx) : Base(ctx) {}

  size_t Length() const {
    const size_t ret = Base::Env()->GetArrayLength(Base::Instance());
    MOZ_CATCH_JNI_EXCEPTION(Base::Env());
    return ret;
  }

  Object::LocalRef GetElement(size_t index) const {
    auto ret = Object::LocalRef::Adopt(
        Base::Env(),
        Base::Env()->GetObjectArrayElement(Base::Instance(), jsize(index)));
    MOZ_CATCH_JNI_EXCEPTION(Base::Env());
    return ret;
  }

  nsTArray<Object::LocalRef> GetElements() const {
    const jsize len = size_t(Base::Env()->GetArrayLength(Base::Instance()));

    nsTArray<Object::LocalRef> array((size_t(len)));
    for (jsize i = 0; i < len; i++) {
      array.AppendElement(Object::LocalRef::Adopt(
          Base::Env(),
          Base::Env()->GetObjectArrayElement(Base::Instance(), i)));
      MOZ_CATCH_JNI_EXCEPTION(Base::Env());
    }
    return array;
  }

  Object::LocalRef operator[](size_t index) const { return GetElement(index); }

  operator nsTArray<Object::LocalRef>() const { return GetElements(); }

  void SetElement(size_t index, Object::Param element) const {
    Base::Env()->SetObjectArrayElement(Base::Instance(), jsize(index),
                                       element.Get());
    MOZ_CATCH_JNI_EXCEPTION(Base::Env());
  }
};

// Support conversion from LocalRef<T>* to LocalRef<Object>*:
//   LocalRef<Foo> foo;
//   Foo::GetFoo(&foo); // error because parameter type is LocalRef<Object>*.
//   Foo::GetFoo(ReturnTo(&foo)); // OK because ReturnTo converts the argument.
template <class Cls>
class ReturnToLocal {
 private:
  LocalRef<Cls>* const localRef;
  LocalRef<Object> objRef;

 public:
  explicit ReturnToLocal(LocalRef<Cls>* ref) : localRef(ref) {}
  operator LocalRef<Object>*() { return &objRef; }

  ~ReturnToLocal() {
    if (objRef) {
      *localRef = std::move(objRef);
    }
  }
};

template <class Cls>
ReturnToLocal<Cls> ReturnTo(LocalRef<Cls>* ref) {
  return ReturnToLocal<Cls>(ref);
}

// Support conversion from GlobalRef<T>* to LocalRef<Object/T>*:
//   GlobalRef<Foo> foo;
//   Foo::GetFoo(&foo); // error because parameter type is LocalRef<Foo>*.
//   Foo::GetFoo(ReturnTo(&foo)); // OK because ReturnTo converts the argument.
template <class Cls>
class ReturnToGlobal {
 private:
  GlobalRef<Cls>* const globalRef;
  LocalRef<Object> objRef;
  LocalRef<Cls> clsRef;

 public:
  explicit ReturnToGlobal(GlobalRef<Cls>* ref) : globalRef(ref) {}
  operator LocalRef<Object>*() { return &objRef; }
  operator LocalRef<Cls>*() { return &clsRef; }

  ~ReturnToGlobal() {
    if (objRef) {
      *globalRef = (clsRef = std::move(objRef));
    } else if (clsRef) {
      *globalRef = clsRef;
    }
  }
};

template <class Cls>
ReturnToGlobal<Cls> ReturnTo(GlobalRef<Cls>* ref) {
  return ReturnToGlobal<Cls>(ref);
}

// Make a LocalRef<T> from any other Ref<T>
template <typename Cls, typename JNIType>
LocalRef<Cls> ToLocalRef(const Ref<Cls, JNIType>& aRef) {
  return LocalRef<Cls>(aRef);
}

}  // namespace jni
}  // namespace mozilla

#endif  // mozilla_jni_Refs_h__