text: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   * vim: set ts=8 sts=4 et sw=4 tw=99:
   * 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/. */
  
  #include "vm/ReceiverGuard.h"
  
  #include "builtin/TypedObject.h"
  #include "vm/UnboxedObject.h"
  #include "jsobjinlines.h"
  
  using namespace js;
  
  ReceiverGuard::ReceiverGuard(JSObject* obj)
    : group(nullptr), shape(nullptr)
  {
      if (obj) {
          if (obj->is<UnboxedPlainObject>()) {
              group = obj->group();
              if (UnboxedExpandoObject* expando = obj->as<UnboxedPlainObject>().maybeExpando())
                  shape = expando->lastProperty();
          } else if (obj->is<UnboxedArrayObject>() || obj->is<TypedObject>()) {
              group = obj->group();
          } else {
              shape = obj->maybeShape();
          }
      }
  }
  
  ReceiverGuard::ReceiverGuard(ObjectGroup* group, Shape* shape)
    : group(group), shape(shape)
  {
      if (group) {
          const Class* clasp = group->clasp();
          if (clasp == &UnboxedPlainObject::class_) {
              // Keep both group and shape.
          } else if (clasp == &UnboxedArrayObject::class_ || IsTypedObjectClass(clasp)) {
              this->shape = nullptr;
          } else {
              this->group = nullptr;
          }
      }
  }
  
  /* static */ int32_t
  HeapReceiverGuard::keyBits(JSObject* obj)
  {
      if (obj->is<UnboxedPlainObject>()) {
          // Both the group and shape need to be guarded for unboxed plain objects.
          return obj->as<UnboxedPlainObject>().maybeExpando() ? 0 : 1;
      }
      if (obj->is<UnboxedArrayObject>() || obj->is<TypedObject>()) {
          // Only the group needs to be guarded for unboxed arrays and typed objects.
          return 2;
      }
      // Other objects only need the shape to be guarded.
      return 3;
  }
  
  void
  HeapReceiverGuard::trace(JSTracer* trc)
  {
      if (shape_)
          TraceEdge(trc, &shape_, "receiver_guard_shape");
      if (group_)
          TraceEdge(trc, &group_, "receiver_guard_group");
  }
  