js/src/gc/FinalizationObservers.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef gc_FinalizationObservers_h
   8 #define gc_FinalizationObservers_h
   9
  10 #include "gc/Barrier.h"
  11 #include "gc/WeakMap.h"
  12 #include "gc/ZoneAllocator.h"
  13 #include "js/GCHashTable.h"
  14 #include "js/GCVector.h"
  15
  16 namespace js {
  17
  18 class FinalizationRegistryObject;
  19 class FinalizationRecordObject;
  20 class WeakRefObject;
  21
  22 namespace gc {
  23
  24 // Per-zone data structures to support FinalizationRegistry and WeakRef.
  25 class FinalizationObservers {
  26   Zone* const zone;
  27
  28   // The set of all finalization registries in the associated zone. These are
  29   // direct pointers and are not wrapped.
  30   using RegistrySet =
  31       GCHashSet<HeapPtr<JSObject*>, StableCellHasher<HeapPtr<JSObject*>>,
  32                 ZoneAllocPolicy>;
  33   RegistrySet registries;
  34
  35   // A vector of FinalizationRecord objects, or CCWs to them.
  36   using RecordVector = GCVector<HeapPtr<JSObject*>, 1, ZoneAllocPolicy>;
  37
  38   // A map from finalization registry targets to a vector of finalization
  39   // records representing registries that the target is registered with and
  40   // their associated held values. The records may be in other zones and are
  41   // wrapped appropriately.
  42   using RecordMap =
  43       GCHashMap<HeapPtr<JSObject*>, RecordVector,
  44                 StableCellHasher<HeapPtr<JSObject*>>, ZoneAllocPolicy>;
  45   RecordMap recordMap;
  46
  47   // A weak map used as a set of cross-zone wrappers. This is used for both
  48   // finalization registries and weak refs. For the former it has wrappers to
  49   // finalization record objects and for the latter wrappers to weak refs.
  50   //
  51   // The weak map marking rules keep the wrappers alive while their targets are
  52   // alive and ensure that they are both swept in the same sweep group.
  53   using WrapperWeakSet = ObjectValueWeakMap;
  54   WrapperWeakSet crossZoneRecords;
  55
  56   // A map of weak ref targets to a vector of weak refs that are observing the
  57   // target. The weak refs may be in other zones and are wrapped appropriately.
  58   using WeakRefHeapPtrVector =
  59       GCVector<js::HeapPtr<JSObject*>, 1, js::ZoneAllocPolicy>;
  60   using WeakRefMap =
  61       GCHashMap<HeapPtr<JSObject*>, WeakRefHeapPtrVector,
  62                 StableCellHasher<HeapPtr<JSObject*>>, ZoneAllocPolicy>;
  63   WeakRefMap weakRefMap;
  64
  65   // A weak map used as a set of cross-zone weak refs wrappers.
  66   WrapperWeakSet crossZoneWeakRefs;
  67
  68  public:
  69   explicit FinalizationObservers(Zone* zone);
  70   ~FinalizationObservers();
  71
  72   // FinalizationRegistry support:
  73   bool addRegistry(Handle<FinalizationRegistryObject*> registry);
  74   bool addRecord(HandleObject target, HandleObject record);
  75   void clearRecords();
  76
  77   void updateForRemovedRecord(JSObject* wrapper,
  78                               FinalizationRecordObject* record);
  79
  80   // WeakRef support:
  81   bool addWeakRefTarget(HandleObject target, HandleObject weakRef);
  82
  83   void unregisterWeakRefWrapper(JSObject* wrapper, WeakRefObject* weakRef);
  84
  85   void traceRoots(JSTracer* trc);
  86   void traceWeakEdges(JSTracer* trc);
  87
  88 #ifdef DEBUG
  89   void checkTables() const;
  90 #endif
  91
  92  private:
  93   bool addCrossZoneWrapper(WrapperWeakSet& weakSet, JSObject* wrapper);
  94   void removeCrossZoneWrapper(WrapperWeakSet& weakSet, JSObject* wrapper);
  95
  96   void updateForRemovedWeakRef(JSObject* wrapper, WeakRefObject* weakRef);
  97
  98   void traceWeakFinalizationRegistryEdges(JSTracer* trc);
  99   void traceWeakWeakRefEdges(JSTracer* trc);
 100   void traceWeakWeakRefVector(JSTracer* trc, WeakRefHeapPtrVector& weakRefs,
 101                               JSObject* target);
 102
 103   static bool shouldRemoveRecord(FinalizationRecordObject* record);
 104 };
 105
 106 // Per-global data structures to support FinalizationRegistry.
 107 class FinalizationRegistryGlobalData {
 108   // Set of finalization records for finalization registries in this
 109   // realm. These are traced as part of the realm's global.
 110   using RecordSet =
 111       GCHashSet<HeapPtr<JSObject*>, StableCellHasher<HeapPtr<JSObject*>>,
 112                 ZoneAllocPolicy>;
 113   RecordSet recordSet;
 114
 115  public:
 116   explicit FinalizationRegistryGlobalData(Zone* zone);
 117
 118   bool addRecord(FinalizationRecordObject* record);
 119   void removeRecord(FinalizationRecordObject* record);
 120
 121   void trace(JSTracer* trc);
 122 };
 123
 124 }  // namespace gc
 125 }  // namespace js
 126
 127 #endif  // gc_FinalizationObservers_h