builtins-weak-refs.cc

// 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.

#include "src/builtins/builtins-utils-inl.h"
#include "src/counters.h"
#include "src/objects/js-weak-refs-inl.h"

namespace v8 {
namespace internal {

BUILTIN(WeakFactoryConstructor) {
  HandleScope scope(isolate);
  Handle<JSFunction> target = args.target();
  if (args.new_target()->IsUndefined(isolate)) {  // [[Call]]
    THROW_NEW_ERROR_RETURN_FAILURE(
        isolate, NewTypeError(MessageTemplate::kConstructorNotFunction,
                              handle(target->shared()->Name(), isolate)));
  }
  // [[Construct]]
  Handle<JSReceiver> new_target = Handle<JSReceiver>::cast(args.new_target());
  Handle<Object> cleanup = args.atOrUndefined(isolate, 1);

  if (!cleanup->IsCallable()) {
    THROW_NEW_ERROR_RETURN_FAILURE(
        isolate, NewTypeError(MessageTemplate::kWeakRefsCleanupMustBeCallable));
  }

  Handle<JSObject> result;
  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
      isolate, result,
      JSObject::New(target, new_target, Handle<AllocationSite>::null()));

  Handle<JSWeakFactory> weak_factory = Handle<JSWeakFactory>::cast(result);
  weak_factory->set_native_context(*isolate->native_context());
  weak_factory->set_cleanup(*cleanup);
  weak_factory->set_flags(
      JSWeakFactory::ScheduledForCleanupField::encode(false));
  return *weak_factory;
}

BUILTIN(WeakFactoryMakeCell) {
  HandleScope scope(isolate);
  const char* method_name = "WeakFactory.prototype.makeCell";

  CHECK_RECEIVER(JSWeakFactory, weak_factory, method_name);

  Handle<Object> target = args.atOrUndefined(isolate, 1);
  if (!target->IsJSReceiver()) {
    THROW_NEW_ERROR_RETURN_FAILURE(
        isolate,
        NewTypeError(MessageTemplate::kWeakRefsMakeCellTargetMustBeObject));
  }
  Handle<JSReceiver> target_receiver = Handle<JSReceiver>::cast(target);
  Handle<Object> holdings = args.atOrUndefined(isolate, 2);
  if (target->SameValue(*holdings)) {
    THROW_NEW_ERROR_RETURN_FAILURE(
        isolate,
        NewTypeError(
            MessageTemplate::kWeakRefsMakeCellTargetAndHoldingsMustNotBeSame));
  }

  // TODO(marja): Realms.

  Handle<Map> weak_cell_map(isolate->native_context()->js_weak_cell_map(),
                            isolate);

  // Allocate the JSWeakCell object in the old space, because 1) JSWeakCell
  // weakness handling is only implemented in the old space 2) they're
  // supposedly long-living. TODO(marja): Support JSWeakCells in Scavenger.
  Handle<JSWeakCell> weak_cell =
      Handle<JSWeakCell>::cast(isolate->factory()->NewJSObjectFromMap(
          weak_cell_map, TENURED, Handle<AllocationSite>::null()));
  weak_cell->set_target(*target_receiver);
  weak_cell->set_holdings(*holdings);
  weak_factory->AddWeakCell(*weak_cell);
  return *weak_cell;
}

BUILTIN(WeakFactoryMakeRef) {
  HandleScope scope(isolate);
  const char* method_name = "WeakFactory.prototype.makeRef";

  CHECK_RECEIVER(JSWeakFactory, weak_factory, method_name);

  Handle<Object> target = args.atOrUndefined(isolate, 1);
  if (!target->IsJSReceiver()) {
    THROW_NEW_ERROR_RETURN_FAILURE(
        isolate,
        NewTypeError(MessageTemplate::kWeakRefsMakeRefTargetMustBeObject));
  }
  Handle<JSReceiver> target_receiver = Handle<JSReceiver>::cast(target);
  Handle<Object> holdings = args.atOrUndefined(isolate, 2);
  if (target->SameValue(*holdings)) {
    THROW_NEW_ERROR_RETURN_FAILURE(
        isolate,
        NewTypeError(
            MessageTemplate::kWeakRefsMakeRefTargetAndHoldingsMustNotBeSame));
  }

  // TODO(marja): Realms.

  Handle<Map> weak_ref_map(isolate->native_context()->js_weak_ref_map(),
                           isolate);

  Handle<JSWeakRef> weak_ref =
      Handle<JSWeakRef>::cast(isolate->factory()->NewJSObjectFromMap(
          weak_ref_map, TENURED, Handle<AllocationSite>::null()));
  weak_ref->set_target(*target_receiver);
  weak_ref->set_holdings(*holdings);
  weak_factory->AddWeakCell(*weak_ref);

  isolate->heap()->AddKeepDuringJobTarget(target_receiver);

  return *weak_ref;
}

BUILTIN(WeakFactoryCleanupSome) {
  HandleScope scope(isolate);
  const char* method_name = "WeakFactory.prototype.cleanupSome";

  CHECK_RECEIVER(JSWeakFactory, weak_factory, method_name);

  // Don't do set_scheduled_for_cleanup(false); we still have the microtask
  // scheduled and don't want to schedule another one in case the user never
  // executes microtasks.
  JSWeakFactory::Cleanup(weak_factory, isolate);
  return ReadOnlyRoots(isolate).undefined_value();
}

BUILTIN(WeakFactoryCleanupIteratorNext) {
  HandleScope scope(isolate);
  CHECK_RECEIVER(JSWeakFactoryCleanupIterator, iterator, "next");

  Handle<JSWeakFactory> weak_factory(iterator->factory(), isolate);
  if (!weak_factory->NeedsCleanup()) {
    return *isolate->factory()->NewJSIteratorResult(
        handle(ReadOnlyRoots(isolate).undefined_value(), isolate), true);
  }
  Handle<JSWeakCell> weak_cell_object =
      handle(weak_factory->PopClearedCell(isolate), isolate);

  return *isolate->factory()->NewJSIteratorResult(weak_cell_object, false);
}

BUILTIN(WeakCellHoldingsGetter) {
  HandleScope scope(isolate);
  CHECK_RECEIVER(JSWeakCell, weak_cell, "get WeakCell.holdings");
  return weak_cell->holdings();
}

BUILTIN(WeakCellClear) {
  HandleScope scope(isolate);
  CHECK_RECEIVER(JSWeakCell, weak_cell, "WeakCell.prototype.clear");
  weak_cell->Clear(isolate);
  return ReadOnlyRoots(isolate).undefined_value();
}

BUILTIN(WeakRefDeref) {
  HandleScope scope(isolate);
  CHECK_RECEIVER(JSWeakRef, weak_ref, "WeakRef.prototype.deref");
  if (weak_ref->target()->IsJSReceiver()) {
    Handle<JSReceiver> target =
        handle(JSReceiver::cast(weak_ref->target()), isolate);
    // AddKeepDuringJobTarget might allocate and cause a GC, but it won't clear
    // weak_ref since we hold a Handle to its target.
    isolate->heap()->AddKeepDuringJobTarget(target);
  } else {
    DCHECK(weak_ref->target()->IsUndefined(isolate));
  }
  return weak_ref->target();
}

}  // namespace internal
}  // namespace v8