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// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_OBJECTS_JS_WEAK_REFS_INL_H_
#define V8_OBJECTS_JS_WEAK_REFS_INL_H_
#include "src/objects/js-weak-refs.h"
#include "src/api/api-inl.h"
#include "src/heap/heap-write-barrier-inl.h"
#include "src/objects/smi-inl.h"
// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"
namespace v8 {
namespace internal {
TQ_OBJECT_CONSTRUCTORS_IMPL(WeakCell)
TQ_OBJECT_CONSTRUCTORS_IMPL(JSWeakRef)
OBJECT_CONSTRUCTORS_IMPL(JSFinalizationGroup, JSObject)
TQ_OBJECT_CONSTRUCTORS_IMPL(JSFinalizationGroupCleanupIterator)
ACCESSORS(JSFinalizationGroup, native_context, NativeContext,
kNativeContextOffset)
ACCESSORS(JSFinalizationGroup, cleanup, Object, kCleanupOffset)
ACCESSORS(JSFinalizationGroup, active_cells, HeapObject, kActiveCellsOffset)
ACCESSORS(JSFinalizationGroup, cleared_cells, HeapObject, kClearedCellsOffset)
ACCESSORS(JSFinalizationGroup, key_map, Object, kKeyMapOffset)
SMI_ACCESSORS(JSFinalizationGroup, flags, kFlagsOffset)
ACCESSORS(JSFinalizationGroup, next, Object, kNextOffset)
CAST_ACCESSOR(JSFinalizationGroup)
void JSFinalizationGroup::Register(
Handle<JSFinalizationGroup> finalization_group, Handle<JSReceiver> target,
Handle<Object> holdings, Handle<Object> key, Isolate* isolate) {
Handle<WeakCell> weak_cell = isolate->factory()->NewWeakCell();
weak_cell->set_finalization_group(*finalization_group);
weak_cell->set_target(*target);
weak_cell->set_holdings(*holdings);
weak_cell->set_prev(ReadOnlyRoots(isolate).undefined_value());
weak_cell->set_next(ReadOnlyRoots(isolate).undefined_value());
weak_cell->set_key(*key);
weak_cell->set_key_list_prev(ReadOnlyRoots(isolate).undefined_value());
weak_cell->set_key_list_next(ReadOnlyRoots(isolate).undefined_value());
// Add to active_cells.
weak_cell->set_next(finalization_group->active_cells());
if (finalization_group->active_cells().IsWeakCell()) {
WeakCell::cast(finalization_group->active_cells()).set_prev(*weak_cell);
}
finalization_group->set_active_cells(*weak_cell);
if (!key->IsUndefined(isolate)) {
Handle<ObjectHashTable> key_map;
if (finalization_group->key_map().IsUndefined(isolate)) {
key_map = ObjectHashTable::New(isolate, 1);
} else {
key_map =
handle(ObjectHashTable::cast(finalization_group->key_map()), isolate);
}
Object value = key_map->Lookup(key);
if (value.IsWeakCell()) {
WeakCell existing_weak_cell = WeakCell::cast(value);
existing_weak_cell.set_key_list_prev(*weak_cell);
weak_cell->set_key_list_next(existing_weak_cell);
} else {
DCHECK(value.IsTheHole(isolate));
}
key_map = ObjectHashTable::Put(key_map, key, weak_cell);
finalization_group->set_key_map(*key_map);
}
}
bool JSFinalizationGroup::Unregister(
Handle<JSFinalizationGroup> finalization_group,
Handle<JSReceiver> unregister_token, Isolate* isolate) {
// Iterate through the doubly linked list of WeakCells associated with the
// key. Each WeakCell will be in the "active_cells" or "cleared_cells" list of
// its FinalizationGroup; remove it from there.
if (!finalization_group->key_map().IsUndefined(isolate)) {
Handle<ObjectHashTable> key_map =
handle(ObjectHashTable::cast(finalization_group->key_map()), isolate);
Object value = key_map->Lookup(unregister_token);
HeapObject undefined = ReadOnlyRoots(isolate).undefined_value();
while (value.IsWeakCell()) {
WeakCell weak_cell = WeakCell::cast(value);
weak_cell.RemoveFromFinalizationGroupCells(isolate);
value = weak_cell.key_list_next();
weak_cell.set_key_list_prev(undefined);
weak_cell.set_key_list_next(undefined);
}
bool was_present;
key_map = ObjectHashTable::Remove(isolate, key_map, unregister_token,
&was_present);
finalization_group->set_key_map(*key_map);
return was_present;
}
return false;
}
bool JSFinalizationGroup::NeedsCleanup() const {
return cleared_cells().IsWeakCell();
}
bool JSFinalizationGroup::scheduled_for_cleanup() const {
return ScheduledForCleanupField::decode(flags());
}
void JSFinalizationGroup::set_scheduled_for_cleanup(
bool scheduled_for_cleanup) {
set_flags(ScheduledForCleanupField::update(flags(), scheduled_for_cleanup));
}
Object JSFinalizationGroup::PopClearedCellHoldings(
Handle<JSFinalizationGroup> finalization_group, Isolate* isolate) {
Handle<WeakCell> weak_cell =
handle(WeakCell::cast(finalization_group->cleared_cells()), isolate);
DCHECK(weak_cell->prev().IsUndefined(isolate));
finalization_group->set_cleared_cells(weak_cell->next());
weak_cell->set_next(ReadOnlyRoots(isolate).undefined_value());
if (finalization_group->cleared_cells().IsWeakCell()) {
WeakCell cleared_cells_head =
WeakCell::cast(finalization_group->cleared_cells());
DCHECK_EQ(cleared_cells_head.prev(), *weak_cell);
cleared_cells_head.set_prev(ReadOnlyRoots(isolate).undefined_value());
} else {
DCHECK(finalization_group->cleared_cells().IsUndefined(isolate));
}
// Also remove the WeakCell from the key_map (if it's there).
if (!weak_cell->key().IsUndefined(isolate)) {
if (weak_cell->key_list_prev().IsUndefined(isolate) &&
weak_cell->key_list_next().IsUndefined(isolate)) {
// weak_cell is the only one associated with its key; remove the key
// from the hash table.
Handle<ObjectHashTable> key_map =
handle(ObjectHashTable::cast(finalization_group->key_map()), isolate);
Handle<Object> key = handle(weak_cell->key(), isolate);
bool was_present;
key_map = ObjectHashTable::Remove(isolate, key_map, key, &was_present);
DCHECK(was_present);
finalization_group->set_key_map(*key_map);
} else if (weak_cell->key_list_prev().IsUndefined()) {
// weak_cell is the list head for its key; we need to change the value of
// the key in the hash table.
Handle<ObjectHashTable> key_map =
handle(ObjectHashTable::cast(finalization_group->key_map()), isolate);
Handle<Object> key = handle(weak_cell->key(), isolate);
Handle<WeakCell> next =
handle(WeakCell::cast(weak_cell->key_list_next()), isolate);
DCHECK_EQ(next->key_list_prev(), *weak_cell);
next->set_key_list_prev(ReadOnlyRoots(isolate).undefined_value());
weak_cell->set_key_list_next(ReadOnlyRoots(isolate).undefined_value());
key_map = ObjectHashTable::Put(key_map, key, next);
finalization_group->set_key_map(*key_map);
} else {
// weak_cell is somewhere in the middle of its key list.
WeakCell prev = WeakCell::cast(weak_cell->key_list_prev());
prev.set_key_list_next(weak_cell->key_list_next());
if (!weak_cell->key_list_next().IsUndefined()) {
WeakCell next = WeakCell::cast(weak_cell->key_list_next());
next.set_key_list_prev(weak_cell->key_list_prev());
}
}
}
return weak_cell->holdings();
}
void WeakCell::Nullify(
Isolate* isolate,
std::function<void(HeapObject object, ObjectSlot slot, Object target)>
gc_notify_updated_slot) {
// Remove from the WeakCell from the "active_cells" list of its
// JSFinalizationGroup and insert it into the "cleared_cells" list. This is
// only called for WeakCells which haven't been unregistered yet, so they will
// be in the active_cells list. (The caller must guard against calling this
// for unregistered WeakCells by checking that the target is not undefined.)
DCHECK(target().IsJSReceiver());
set_target(ReadOnlyRoots(isolate).undefined_value());
JSFinalizationGroup fg = JSFinalizationGroup::cast(finalization_group());
if (prev().IsWeakCell()) {
DCHECK_NE(fg.active_cells(), *this);
WeakCell prev_cell = WeakCell::cast(prev());
prev_cell.set_next(next());
gc_notify_updated_slot(prev_cell, prev_cell.RawField(WeakCell::kNextOffset),
next());
} else {
DCHECK_EQ(fg.active_cells(), *this);
fg.set_active_cells(next());
gc_notify_updated_slot(
fg, fg.RawField(JSFinalizationGroup::kActiveCellsOffset), next());
}
if (next().IsWeakCell()) {
WeakCell next_cell = WeakCell::cast(next());
next_cell.set_prev(prev());
gc_notify_updated_slot(next_cell, next_cell.RawField(WeakCell::kPrevOffset),
prev());
}
set_prev(ReadOnlyRoots(isolate).undefined_value());
Object cleared_head = fg.cleared_cells();
if (cleared_head.IsWeakCell()) {
WeakCell cleared_head_cell = WeakCell::cast(cleared_head);
cleared_head_cell.set_prev(*this);
gc_notify_updated_slot(cleared_head_cell,
cleared_head_cell.RawField(WeakCell::kPrevOffset),
*this);
}
set_next(fg.cleared_cells());
gc_notify_updated_slot(*this, RawField(WeakCell::kNextOffset), next());
fg.set_cleared_cells(*this);
gc_notify_updated_slot(
fg, fg.RawField(JSFinalizationGroup::kClearedCellsOffset), *this);
}
void WeakCell::RemoveFromFinalizationGroupCells(Isolate* isolate) {
// Remove the WeakCell from the list it's in (either "active_cells" or
// "cleared_cells" of its JSFinalizationGroup).
// It's important to set_target to undefined here. This guards that we won't
// call Nullify (which assumes that the WeakCell is in active_cells).
DCHECK(target().IsUndefined() || target().IsJSReceiver());
set_target(ReadOnlyRoots(isolate).undefined_value());
JSFinalizationGroup fg = JSFinalizationGroup::cast(finalization_group());
if (fg.active_cells() == *this) {
DCHECK(prev().IsUndefined(isolate));
fg.set_active_cells(next());
} else if (fg.cleared_cells() == *this) {
DCHECK(!prev().IsWeakCell());
fg.set_cleared_cells(next());
} else {
DCHECK(prev().IsWeakCell());
WeakCell prev_cell = WeakCell::cast(prev());
prev_cell.set_next(next());
}
if (next().IsWeakCell()) {
WeakCell next_cell = WeakCell::cast(next());
next_cell.set_prev(prev());
}
set_prev(ReadOnlyRoots(isolate).undefined_value());
set_next(ReadOnlyRoots(isolate).undefined_value());
}
} // namespace internal
} // namespace v8
#include "src/objects/object-macros-undef.h"
#endif // V8_OBJECTS_JS_WEAK_REFS_INL_H_
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