1 files changed, 140 insertions, 0 deletions
diff --git a/js/src/gc/FinalizationRegistry.cpp b/js/src/gc/FinalizationRegistry.cpp
new file mode 100644
index 0000000000..1d1575972f
--- /dev/null
+++ b/js/src/gc/FinalizationRegistry.cpp
@@ -0,0 +1,140 @@
+/* -*- 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/. */
+
+/*
+ * Finalization registry GC implementation.
+ */
+
+#include "builtin/FinalizationRegistryObject.h"
+#include "gc/GCRuntime.h"
+#include "gc/Zone.h"
+#include "vm/JSContext.h"
+
+#include "gc/PrivateIterators-inl.h"
+#include "vm/JSObject-inl.h"
+
+using namespace js;
+using namespace js::gc;
+
+bool GCRuntime::addFinalizationRegistry(JSContext* cx,
+                                        FinalizationRegistryObject* registry) {
+  if (!cx->zone()->finalizationRegistries().put(registry)) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+
+  return true;
+}
+
+bool GCRuntime::registerWithFinalizationRegistry(JSContext* cx,
+                                                 HandleObject target,
+                                                 HandleObject record) {
+  MOZ_ASSERT(!IsCrossCompartmentWrapper(target));
+  MOZ_ASSERT(
+      UncheckedUnwrapWithoutExpose(record)->is<FinalizationRecordObject>());
+  MOZ_ASSERT(target->compartment() == record->compartment());
+
+  auto& map = target->zone()->finalizationRecordMap();
+  auto ptr = map.lookupForAdd(target);
+  if (!ptr) {
+    if (!map.add(ptr, target, FinalizationRecordVector(target->zone()))) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+  }
+  if (!ptr->value().append(record)) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+  return true;
+}
+
+void GCRuntime::markFinalizationRegistryRoots(JSTracer* trc) {
+  // All finalization records stored in the zone maps are marked as roots.
+  // Records can be removed from these maps during sweeping in which case they
+  // die in the next collection.
+  for (GCZonesIter zone(this); !zone.done(); zone.next()) {
+    Zone::FinalizationRecordMap& map = zone->finalizationRecordMap();
+    for (Zone::FinalizationRecordMap::Enum e(map); !e.empty(); e.popFront()) {
+      e.front().value().trace(trc);
+    }
+  }
+}
+
+static FinalizationRecordObject* UnwrapFinalizationRecord(JSObject* obj) {
+  obj = UncheckedUnwrapWithoutExpose(obj);
+  if (!obj->is<FinalizationRecordObject>()) {
+    MOZ_ASSERT(JS_IsDeadWrapper(obj));
+    // CCWs between the compartments have been nuked. The
+    // FinalizationRegistry's callback doesn't run in this case.
+    return nullptr;
+  }
+  return &obj->as<FinalizationRecordObject>();
+}
+
+void GCRuntime::sweepFinalizationRegistries(Zone* zone) {
+  // Sweep finalization registry data and queue finalization records for cleanup
+  // for any entries whose target is dying and remove them from the map.
+
+  Zone::FinalizationRegistrySet& set = zone->finalizationRegistries();
+  for (Zone::FinalizationRegistrySet::Enum e(set); !e.empty(); e.popFront()) {
+    if (IsAboutToBeFinalized(&e.mutableFront())) {
+      e.front()->as<FinalizationRegistryObject>().queue()->setHasRegistry(
+          false);
+      e.removeFront();
+    } else {
+      e.front()->as<FinalizationRegistryObject>().sweep();
+    }
+  }
+
+  Zone::FinalizationRecordMap& map = zone->finalizationRecordMap();
+  for (Zone::FinalizationRecordMap::Enum e(map); !e.empty(); e.popFront()) {
+    FinalizationRecordVector& records = e.front().value();
+
+    // Update any pointers moved by the GC.
+    records.sweep();
+
+    // Sweep finalization records and remove records for:
+    records.eraseIf([](JSObject* obj) {
+      FinalizationRecordObject* record = UnwrapFinalizationRecord(obj);
+      return !record ||                        // Nuked CCW to record.
+             !record->isActive() ||            // Unregistered record.
+             !record->queue()->hasRegistry();  // Dead finalization registry.
+    });
+
+    // Queue finalization records for targets that are dying.
+    if (IsAboutToBeFinalized(&e.front().mutableKey())) {
+      for (JSObject* obj : records) {
+        FinalizationRecordObject* record = UnwrapFinalizationRecord(obj);
+        FinalizationQueueObject* queue = record->queue();
+        queue->queueRecordToBeCleanedUp(record);
+        queueFinalizationRegistryForCleanup(queue);
+      }
+      e.removeFront();
+    }
+  }
+}
+
+void GCRuntime::queueFinalizationRegistryForCleanup(
+    FinalizationQueueObject* queue) {
+  // Prod the embedding to call us back later to run the finalization callbacks,
+  // if necessary.
+
+  if (queue->isQueuedForCleanup()) {
+    return;
+  }
+
+  // Derive the incumbent global by unwrapping the incumbent global object and
+  // then getting its global.
+  JSObject* object = UncheckedUnwrapWithoutExpose(queue->incumbentObject());
+  MOZ_ASSERT(object);
+  GlobalObject* incumbentGlobal = &object->nonCCWGlobal();
+
+  callHostCleanupFinalizationRegistryCallback(queue->doCleanupFunction(),
+                                              incumbentGlobal);
+
+  queue->setQueuedForCleanup(true);
+}