summaryrefslogtreecommitdiffstats
path: root/js/xpconnect/src/XPCWrappedNativeInfo.cpp
blob: a93b006f0fd53055c9ac3bf2719995ba2fe31243 (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
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* 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/. */

/* Manage the shared info about interfaces for use by wrappedNatives. */

#include "xpcprivate.h"
#include "jswrapper.h"

#include "mozilla/MemoryReporting.h"
#include "mozilla/XPTInterfaceInfoManager.h"
#include "nsIScriptError.h"
#include "nsPrintfCString.h"

using namespace JS;
using namespace mozilla;

/***************************************************************************/

// XPCNativeMember

// static
bool
XPCNativeMember::GetCallInfo(JSObject* funobj,
                             RefPtr<XPCNativeInterface>* pInterface,
                             XPCNativeMember**    pMember)
{
    funobj = js::UncheckedUnwrap(funobj);
    Value memberVal =
        js::GetFunctionNativeReserved(funobj,
                                      XPC_FUNCTION_NATIVE_MEMBER_SLOT);

    *pMember = static_cast<XPCNativeMember*>(memberVal.toPrivate());
    *pInterface = (*pMember)->GetInterface();

    return true;
}

bool
XPCNativeMember::NewFunctionObject(XPCCallContext& ccx,
                                   XPCNativeInterface* iface, HandleObject parent,
                                   Value* pval)
{
    MOZ_ASSERT(!IsConstant(), "Only call this if you're sure this is not a constant!");

    return Resolve(ccx, iface, parent, pval);
}

bool
XPCNativeMember::Resolve(XPCCallContext& ccx, XPCNativeInterface* iface,
                         HandleObject parent, Value* vp)
{
    MOZ_ASSERT(iface == GetInterface());
    if (IsConstant()) {
        RootedValue resultVal(ccx);
        nsXPIDLCString name;
        if (NS_FAILED(iface->GetInterfaceInfo()->GetConstant(mIndex, &resultVal,
                                                             getter_Copies(name))))
            return false;

        *vp = resultVal;

        return true;
    }
    // else...

    // This is a method or attribute - we'll be needing a function object

    int argc;
    JSNative callback;

    if (IsMethod()) {
        const nsXPTMethodInfo* info;
        if (NS_FAILED(iface->GetInterfaceInfo()->GetMethodInfo(mIndex, &info)))
            return false;

        // Note: ASSUMES that retval is last arg.
        argc = (int) info->GetParamCount();
        if (argc && info->GetParam((uint8_t)(argc-1)).IsRetval())
            argc-- ;

        callback = XPC_WN_CallMethod;
    } else {
        argc = 0;
        callback = XPC_WN_GetterSetter;
    }

    JSFunction* fun = js::NewFunctionByIdWithReserved(ccx, callback, argc, 0, GetName());
    if (!fun)
        return false;

    JSObject* funobj = JS_GetFunctionObject(fun);
    if (!funobj)
        return false;

    js::SetFunctionNativeReserved(funobj, XPC_FUNCTION_NATIVE_MEMBER_SLOT,
                                  PrivateValue(this));
    js::SetFunctionNativeReserved(funobj, XPC_FUNCTION_PARENT_OBJECT_SLOT,
                                  ObjectValue(*parent));

    vp->setObject(*funobj);

    return true;
}

/***************************************************************************/
// XPCNativeInterface

XPCNativeInterface::~XPCNativeInterface()
{
    XPCJSContext::Get()->GetIID2NativeInterfaceMap()->Remove(this);
}

// static
already_AddRefed<XPCNativeInterface>
XPCNativeInterface::GetNewOrUsed(const nsIID* iid)
{
    RefPtr<XPCNativeInterface> iface;
    XPCJSContext* cx = XPCJSContext::Get();

    IID2NativeInterfaceMap* map = cx->GetIID2NativeInterfaceMap();
    if (!map)
        return nullptr;

    iface = map->Find(*iid);

    if (iface)
        return iface.forget();

    nsCOMPtr<nsIInterfaceInfo> info;
    XPTInterfaceInfoManager::GetSingleton()->GetInfoForIID(iid, getter_AddRefs(info));
    if (!info)
        return nullptr;

    iface = NewInstance(info);
    if (!iface)
        return nullptr;

    XPCNativeInterface* iface2 = map->Add(iface);
    if (!iface2) {
        NS_ERROR("failed to add our interface!");
        iface = nullptr;
    } else if (iface2 != iface) {
        iface = iface2;
    }

    return iface.forget();
}

// static
already_AddRefed<XPCNativeInterface>
XPCNativeInterface::GetNewOrUsed(nsIInterfaceInfo* info)
{
    RefPtr<XPCNativeInterface> iface;

    const nsIID* iid;
    if (NS_FAILED(info->GetIIDShared(&iid)) || !iid)
        return nullptr;

    XPCJSContext* cx = XPCJSContext::Get();

    IID2NativeInterfaceMap* map = cx->GetIID2NativeInterfaceMap();
    if (!map)
        return nullptr;

    iface = map->Find(*iid);

    if (iface)
        return iface.forget();

    iface = NewInstance(info);
    if (!iface)
        return nullptr;

    RefPtr<XPCNativeInterface> iface2 = map->Add(iface);
    if (!iface2) {
        NS_ERROR("failed to add our interface!");
        iface = nullptr;
    } else if (iface2 != iface) {
        iface = iface2;
    }

    return iface.forget();
}

// static
already_AddRefed<XPCNativeInterface>
XPCNativeInterface::GetNewOrUsed(const char* name)
{
    nsCOMPtr<nsIInterfaceInfo> info;
    XPTInterfaceInfoManager::GetSingleton()->GetInfoForName(name, getter_AddRefs(info));
    return info ? GetNewOrUsed(info) : nullptr;
}

// static
already_AddRefed<XPCNativeInterface>
XPCNativeInterface::GetISupports()
{
    // XXX We should optimize this to cache this common XPCNativeInterface.
    return GetNewOrUsed(&NS_GET_IID(nsISupports));
}

// static
already_AddRefed<XPCNativeInterface>
XPCNativeInterface::NewInstance(nsIInterfaceInfo* aInfo)
{
    AutoJSContext cx;
    static const uint16_t MAX_LOCAL_MEMBER_COUNT = 16;
    XPCNativeMember local_members[MAX_LOCAL_MEMBER_COUNT];
    RefPtr<XPCNativeInterface> obj;
    XPCNativeMember* members = nullptr;

    int i;
    bool failed = false;
    uint16_t constCount;
    uint16_t methodCount;
    uint16_t totalCount;
    uint16_t realTotalCount = 0;
    XPCNativeMember* cur;
    RootedString str(cx);
    RootedId interfaceName(cx);

    // XXX Investigate lazy init? This is a problem given the
    // 'placement new' scheme - we need to at least know how big to make
    // the object. We might do a scan of methods to determine needed size,
    // then make our object, but avoid init'ing *any* members until asked?
    // Find out how often we create these objects w/o really looking at
    // (or using) the members.

    bool canScript;
    if (NS_FAILED(aInfo->IsScriptable(&canScript)) || !canScript)
        return nullptr;

    bool mainProcessScriptableOnly;
    if (NS_FAILED(aInfo->IsMainProcessScriptableOnly(&mainProcessScriptableOnly)))
        return nullptr;
    if (mainProcessScriptableOnly && !XRE_IsParentProcess()) {
        nsCOMPtr<nsIConsoleService> console(do_GetService(NS_CONSOLESERVICE_CONTRACTID));
        if (console) {
            const char* intfNameChars;
            aInfo->GetNameShared(&intfNameChars);
            nsPrintfCString errorMsg("Use of %s in content process is deprecated.", intfNameChars);

            nsAutoString filename;
            uint32_t lineno = 0, column = 0;
            nsJSUtils::GetCallingLocation(cx, filename, &lineno, &column);
            nsCOMPtr<nsIScriptError> error(do_CreateInstance(NS_SCRIPTERROR_CONTRACTID));
            error->Init(NS_ConvertUTF8toUTF16(errorMsg),
                        filename, EmptyString(),
                        lineno, column, nsIScriptError::warningFlag, "chrome javascript");
            console->LogMessage(error);
        }
    }

    if (NS_FAILED(aInfo->GetMethodCount(&methodCount)) ||
        NS_FAILED(aInfo->GetConstantCount(&constCount)))
        return nullptr;

    // If the interface does not have nsISupports in its inheritance chain
    // then we know we can't reflect its methods. However, some interfaces that
    // are used just to reflect constants are declared this way. We need to
    // go ahead and build the thing. But, we'll ignore whatever methods it may
    // have.
    if (!nsXPConnect::IsISupportsDescendant(aInfo))
        methodCount = 0;

    totalCount = methodCount + constCount;

    if (totalCount > MAX_LOCAL_MEMBER_COUNT) {
        members = new XPCNativeMember[totalCount];
        if (!members)
            return nullptr;
    } else {
        members = local_members;
    }

    // NOTE: since getters and setters share a member, we might not use all
    // of the member objects.

    for (i = 0; i < methodCount; i++) {
        const nsXPTMethodInfo* info;
        if (NS_FAILED(aInfo->GetMethodInfo(i, &info))) {
            failed = true;
            break;
        }

        // don't reflect Addref or Release
        if (i == 1 || i == 2)
            continue;

        if (!XPCConvert::IsMethodReflectable(*info))
            continue;

        str = JS_AtomizeAndPinString(cx, info->GetName());
        if (!str) {
            NS_ERROR("bad method name");
            failed = true;
            break;
        }
        jsid name = INTERNED_STRING_TO_JSID(cx, str);

        if (info->IsSetter()) {
            MOZ_ASSERT(realTotalCount,"bad setter");
            // Note: ASSUMES Getter/Setter pairs are next to each other
            // This is a rule of the typelib spec.
            cur = &members[realTotalCount-1];
            MOZ_ASSERT(cur->GetName() == name,"bad setter");
            MOZ_ASSERT(cur->IsReadOnlyAttribute(),"bad setter");
            MOZ_ASSERT(cur->GetIndex() == i-1,"bad setter");
            cur->SetWritableAttribute();
        } else {
            // XXX need better way to find dups
            // MOZ_ASSERT(!LookupMemberByID(name),"duplicate method name");
            if (realTotalCount == XPCNativeMember::GetMaxIndexInInterface()) {
                NS_WARNING("Too many members in interface");
                failed = true;
                break;
            }
            cur = &members[realTotalCount];
            cur->SetName(name);
            if (info->IsGetter())
                cur->SetReadOnlyAttribute(i);
            else
                cur->SetMethod(i);
            cur->SetIndexInInterface(realTotalCount);
            ++realTotalCount;
        }
    }

    if (!failed) {
        for (i = 0; i < constCount; i++) {
            RootedValue constant(cx);
            nsXPIDLCString namestr;
            if (NS_FAILED(aInfo->GetConstant(i, &constant, getter_Copies(namestr)))) {
                failed = true;
                break;
            }

            str = JS_AtomizeAndPinString(cx, namestr);
            if (!str) {
                NS_ERROR("bad constant name");
                failed = true;
                break;
            }
            jsid name = INTERNED_STRING_TO_JSID(cx, str);

            // XXX need better way to find dups
            //MOZ_ASSERT(!LookupMemberByID(name),"duplicate method/constant name");
            if (realTotalCount == XPCNativeMember::GetMaxIndexInInterface()) {
                NS_WARNING("Too many members in interface");
                failed = true;
                break;
            }
            cur = &members[realTotalCount];
            cur->SetName(name);
            cur->SetConstant(i);
            cur->SetIndexInInterface(realTotalCount);
            ++realTotalCount;
        }
    }

    if (!failed) {
        const char* bytes;
        if (NS_FAILED(aInfo->GetNameShared(&bytes)) || !bytes ||
            nullptr == (str = JS_AtomizeAndPinString(cx, bytes))) {
            failed = true;
        }
        interfaceName = INTERNED_STRING_TO_JSID(cx, str);
    }

    if (!failed) {
        // Use placement new to create an object with the right amount of space
        // to hold the members array
        int size = sizeof(XPCNativeInterface);
        if (realTotalCount > 1)
            size += (realTotalCount - 1) * sizeof(XPCNativeMember);
        void* place = new char[size];
        if (place)
            obj = new(place) XPCNativeInterface(aInfo, interfaceName);

        if (obj) {
            obj->mMemberCount = realTotalCount;
            // copy valid members
            if (realTotalCount)
                memcpy(obj->mMembers, members,
                       realTotalCount * sizeof(XPCNativeMember));
        }
    }

    if (members && members != local_members)
        delete [] members;

    return obj.forget();
}

// static
void
XPCNativeInterface::DestroyInstance(XPCNativeInterface* inst)
{
    inst->~XPCNativeInterface();
    delete [] (char*) inst;
}

size_t
XPCNativeInterface::SizeOfIncludingThis(MallocSizeOf mallocSizeOf)
{
    return mallocSizeOf(this);
}

void
XPCNativeInterface::DebugDump(int16_t depth)
{
#ifdef DEBUG
    depth--;
    XPC_LOG_ALWAYS(("XPCNativeInterface @ %x", this));
        XPC_LOG_INDENT();
        XPC_LOG_ALWAYS(("name is %s", GetNameString()));
        XPC_LOG_ALWAYS(("mMemberCount is %d", mMemberCount));
        XPC_LOG_ALWAYS(("mInfo @ %x", mInfo.get()));
        XPC_LOG_OUTDENT();
#endif
}

/***************************************************************************/
// XPCNativeSetKey

static PLDHashNumber
HashPointer(const void* ptr)
{
    return NS_PTR_TO_UINT32(ptr) >> 2;
}

PLDHashNumber
XPCNativeSetKey::Hash() const
{
    PLDHashNumber h = 0;

    if (mBaseSet) {
        XPCNativeInterface** current = mBaseSet->GetInterfaceArray();
        uint16_t count = mBaseSet->GetInterfaceCount();
        for (uint16_t i = 0; i < count; i++) {
            h ^= HashPointer(*(current++));
        }
    } else {
        // A newly created set will contain nsISupports first...
        RefPtr<XPCNativeInterface> isupp = XPCNativeInterface::GetISupports();
        h ^= HashPointer(isupp);

        // ...but no more than once.
        if (isupp == mAddition)
            return h;
    }

    if (mAddition) {
        h ^= HashPointer(mAddition);
    }

    return h;
}

/***************************************************************************/
// XPCNativeSet

XPCNativeSet::~XPCNativeSet()
{
    // Remove |this| before we clear the interfaces to ensure that the
    // hashtable look up is correct.
    XPCJSContext::Get()->GetNativeSetMap()->Remove(this);

    for (int i = 0; i < mInterfaceCount; i++) {
        NS_RELEASE(mInterfaces[i]);
    }
}

// static
already_AddRefed<XPCNativeSet>
XPCNativeSet::GetNewOrUsed(const nsIID* iid)
{
    RefPtr<XPCNativeInterface> iface =
        XPCNativeInterface::GetNewOrUsed(iid);
    if (!iface)
        return nullptr;

    XPCNativeSetKey key(iface);

    XPCJSContext* xpccx = XPCJSContext::Get();
    NativeSetMap* map = xpccx->GetNativeSetMap();
    if (!map)
        return nullptr;

    RefPtr<XPCNativeSet> set = map->Find(&key);

    if (set)
        return set.forget();

    set = NewInstance({iface.forget()});
    if (!set)
        return nullptr;

    if (!map->AddNew(&key, set)) {
        NS_ERROR("failed to add our set!");
        set = nullptr;
    }

    return set.forget();
}

// static
already_AddRefed<XPCNativeSet>
XPCNativeSet::GetNewOrUsed(nsIClassInfo* classInfo)
{
    XPCJSContext* xpccx = XPCJSContext::Get();
    ClassInfo2NativeSetMap* map = xpccx->GetClassInfo2NativeSetMap();
    if (!map)
        return nullptr;

    RefPtr<XPCNativeSet> set = map->Find(classInfo);

    if (set)
        return set.forget();

    nsIID** iidArray = nullptr;
    uint32_t iidCount = 0;

    if (NS_FAILED(classInfo->GetInterfaces(&iidCount, &iidArray))) {
        // Note: I'm making it OK for this call to fail so that one can add
        // nsIClassInfo to classes implemented in script without requiring this
        // method to be implemented.

        // Make sure these are set correctly...
        iidArray = nullptr;
        iidCount = 0;
    }

    MOZ_ASSERT((iidCount && iidArray) || !(iidCount || iidArray), "GetInterfaces returned bad array");

    // !!! from here on we only exit through the 'out' label !!!

    if (iidCount) {
        nsTArray<RefPtr<XPCNativeInterface>> interfaceArray(iidCount);
        nsIID** currentIID = iidArray;

        for (uint32_t i = 0; i < iidCount; i++) {
            nsIID* iid = *(currentIID++);
            if (!iid) {
                NS_ERROR("Null found in classinfo interface list");
                continue;
            }

            RefPtr<XPCNativeInterface> iface =
                XPCNativeInterface::GetNewOrUsed(iid);

            if (!iface) {
                // XXX warn here
                continue;
            }

            interfaceArray.AppendElement(iface.forget());
        }

        if (interfaceArray.Length() > 0) {
            set = NewInstance(Move(interfaceArray));
            if (set) {
                NativeSetMap* map2 = xpccx->GetNativeSetMap();
                if (!map2)
                    goto out;

                XPCNativeSetKey key(set);

                XPCNativeSet* set2 = map2->Add(&key, set);
                if (!set2) {
                    NS_ERROR("failed to add our set!");
                    set = nullptr;
                    goto out;
                }
                // It is okay to find an existing entry here because
                // we did not look for one before we called Add().
                if (set2 != set) {
                    set = set2;
                }
            }
        } else
            set = GetNewOrUsed(&NS_GET_IID(nsISupports));
    } else
        set = GetNewOrUsed(&NS_GET_IID(nsISupports));

    if (set) {
#ifdef DEBUG
        XPCNativeSet* set2 =
#endif
          map->Add(classInfo, set);
        MOZ_ASSERT(set2, "failed to add our set!");
        MOZ_ASSERT(set2 == set, "hashtables inconsistent!");
    }

out:
    if (iidArray)
        NS_FREE_XPCOM_ALLOCATED_POINTER_ARRAY(iidCount, iidArray);

    return set.forget();
}

// static
void
XPCNativeSet::ClearCacheEntryForClassInfo(nsIClassInfo* classInfo)
{
    XPCJSContext* xpccx = nsXPConnect::GetContextInstance();
    ClassInfo2NativeSetMap* map = xpccx->GetClassInfo2NativeSetMap();
    if (map)
        map->Remove(classInfo);
}

// static
already_AddRefed<XPCNativeSet>
XPCNativeSet::GetNewOrUsed(XPCNativeSetKey* key)
{
    NativeSetMap* map = XPCJSContext::Get()->GetNativeSetMap();
    if (!map)
        return nullptr;

    RefPtr<XPCNativeSet> set = map->Find(key);

    if (set)
        return set.forget();

    if (key->GetBaseSet())
        set = NewInstanceMutate(key);
    else
        set = NewInstance({key->GetAddition()});

    if (!set)
        return nullptr;

    if (!map->AddNew(key, set)) {
        NS_ERROR("failed to add our set!");
        set = nullptr;
    }

    return set.forget();
}

// static
already_AddRefed<XPCNativeSet>
XPCNativeSet::GetNewOrUsed(XPCNativeSet* firstSet,
                           XPCNativeSet* secondSet,
                           bool preserveFirstSetOrder)
{
    // Figure out how many interfaces we'll need in the new set.
    uint32_t uniqueCount = firstSet->mInterfaceCount;
    for (uint32_t i = 0; i < secondSet->mInterfaceCount; ++i) {
        if (!firstSet->HasInterface(secondSet->mInterfaces[i]))
            uniqueCount++;
    }

    // If everything in secondSet was a duplicate, we can just use the first
    // set.
    if (uniqueCount == firstSet->mInterfaceCount)
        return RefPtr<XPCNativeSet>(firstSet).forget();

    // If the secondSet is just a superset of the first, we can use it provided
    // that the caller doesn't care about ordering.
    if (!preserveFirstSetOrder && uniqueCount == secondSet->mInterfaceCount)
        return RefPtr<XPCNativeSet>(secondSet).forget();

    // Ok, darn. Now we have to make a new set.
    //
    // It would be faster to just create the new set all at once, but that
    // would involve wrangling with some pretty hairy code - especially since
    // a lot of stuff assumes that sets are created by adding one interface to an
    // existing set. So let's just do the slow and easy thing and hope that the
    // above optimizations handle the common cases.
    RefPtr<XPCNativeSet> currentSet = firstSet;
    for (uint32_t i = 0; i < secondSet->mInterfaceCount; ++i) {
        XPCNativeInterface* iface = secondSet->mInterfaces[i];
        if (!currentSet->HasInterface(iface)) {
            // Create a new augmented set, inserting this interface at the end.
            XPCNativeSetKey key(currentSet, iface);
            currentSet = XPCNativeSet::GetNewOrUsed(&key);
            if (!currentSet)
                return nullptr;
        }
    }

    // We've got the union set. Hand it back to the caller.
    MOZ_ASSERT(currentSet->mInterfaceCount == uniqueCount);
    return currentSet.forget();
}

// static
already_AddRefed<XPCNativeSet>
XPCNativeSet::NewInstance(nsTArray<RefPtr<XPCNativeInterface>>&& array)
{
    if (array.Length() == 0)
        return nullptr;

    // We impose the invariant:
    // "All sets have exactly one nsISupports interface and it comes first."
    // This is the place where we impose that rule - even if given inputs
    // that don't exactly follow the rule.

    RefPtr<XPCNativeInterface> isup = XPCNativeInterface::GetISupports();
    uint16_t slots = array.Length() + 1;

    for (auto key = array.begin(); key != array.end(); key++) {
        if (*key == isup)
            slots--;
    }

    // Use placement new to create an object with the right amount of space
    // to hold the members array
    int size = sizeof(XPCNativeSet);
    if (slots > 1)
        size += (slots - 1) * sizeof(XPCNativeInterface*);
    void* place = new char[size];
    RefPtr<XPCNativeSet> obj = new(place) XPCNativeSet();

    // Stick the nsISupports in front and skip additional nsISupport(s)
    XPCNativeInterface** outp = (XPCNativeInterface**) &obj->mInterfaces;
    uint16_t memberCount = 1;   // for the one member in nsISupports

    NS_ADDREF(*(outp++) = isup);

    for (auto key = array.begin(); key != array.end(); key++) {
        RefPtr<XPCNativeInterface> cur = key->forget();
        if (isup == cur)
            continue;
        memberCount += cur->GetMemberCount();
        *(outp++) = cur.forget().take();
    }
    obj->mMemberCount = memberCount;
    obj->mInterfaceCount = slots;

    return obj.forget();
}

// static
already_AddRefed<XPCNativeSet>
XPCNativeSet::NewInstanceMutate(XPCNativeSetKey* key)
{
    XPCNativeSet* otherSet = key->GetBaseSet();
    XPCNativeInterface* newInterface = key->GetAddition();

    MOZ_ASSERT(otherSet);

    if (!newInterface)
        return nullptr;

    // Use placement new to create an object with the right amount of space
    // to hold the members array
    int size = sizeof(XPCNativeSet);
    size += otherSet->mInterfaceCount * sizeof(XPCNativeInterface*);
    void* place = new char[size];
    RefPtr<XPCNativeSet> obj = new(place) XPCNativeSet();

    obj->mMemberCount = otherSet->GetMemberCount() +
        newInterface->GetMemberCount();
    obj->mInterfaceCount = otherSet->mInterfaceCount + 1;

    XPCNativeInterface** src = otherSet->mInterfaces;
    XPCNativeInterface** dest = obj->mInterfaces;
    for (uint16_t i = 0; i < otherSet->mInterfaceCount; i++) {
        NS_ADDREF(*dest++ = *src++);
    }
    NS_ADDREF(*dest++ = newInterface);

    return obj.forget();
}

// static
void
XPCNativeSet::DestroyInstance(XPCNativeSet* inst)
{
    inst->~XPCNativeSet();
    delete [] (char*) inst;
}

size_t
XPCNativeSet::SizeOfIncludingThis(MallocSizeOf mallocSizeOf)
{
    return mallocSizeOf(this);
}

void
XPCNativeSet::DebugDump(int16_t depth)
{
#ifdef DEBUG
    depth--;
    XPC_LOG_ALWAYS(("XPCNativeSet @ %x", this));
        XPC_LOG_INDENT();

        XPC_LOG_ALWAYS(("mInterfaceCount of %d", mInterfaceCount));
        if (depth) {
            for (uint16_t i = 0; i < mInterfaceCount; i++)
                mInterfaces[i]->DebugDump(depth);
        }
        XPC_LOG_ALWAYS(("mMemberCount of %d", mMemberCount));
        XPC_LOG_OUTDENT();
#endif
}