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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
       2             :  * vim: set ts=8 sts=4 et sw=4 tw=99:
       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 vm_ReceiverGuard_h
       8             : #define vm_ReceiverGuard_h
       9             : 
      10             : #include "vm/Shape.h"
      11             : 
      12             : namespace js {
      13             : 
      14             : // A ReceiverGuard encapsulates the information about an object that needs to
      15             : // be tested to determine if it has the same 'structure' as another object.
      16             : // The guard includes the shape and/or group of the object, and which of these
      17             : // is tested, as well as the meaning here of 'structure', depends on the kind
      18             : // of object being tested:
      19             : //
      20             : // NativeObject: The structure of a native object is determined by its shape.
      21             : //   Two objects with the same shape have the same class, prototype, flags,
      22             : //   and all properties except those stored in dense elements.
      23             : //
      24             : // ProxyObject: The structure of a proxy object is determined by its shape.
      25             : //   Proxies with the same shape have the same class and prototype, but no
      26             : //   other commonality is guaranteed.
      27             : //
      28             : // TypedObject: The structure of a typed object is determined by its group.
      29             : //   All typed objects with the same group have the same class, prototype, and
      30             : //   own properties.
      31             : //
      32             : // UnboxedPlainObject: The structure of an unboxed plain object is determined
      33             : //   by its group and its expando object's shape, if there is one. All unboxed
      34             : //   plain objects with the same group and expando shape have the same
      35             : //   properties except those stored in the expando's dense elements.
      36             : 
      37             : class HeapReceiverGuard;
      38             : 
      39             : class ReceiverGuard
      40             : {
      41             :   public:
      42             :     ObjectGroup* group;
      43             :     Shape* shape;
      44             : 
      45         165 :     ReceiverGuard()
      46         165 :       : group(nullptr), shape(nullptr)
      47         165 :     {}
      48             : 
      49             :     inline MOZ_IMPLICIT ReceiverGuard(const HeapReceiverGuard& guard);
      50             : 
      51             :     explicit MOZ_ALWAYS_INLINE ReceiverGuard(JSObject* obj);
      52             :     MOZ_ALWAYS_INLINE ReceiverGuard(ObjectGroup* group, Shape* shape);
      53             : 
      54         131 :     bool operator ==(const ReceiverGuard& other) const {
      55         131 :         return group == other.group && shape == other.shape;
      56             :     }
      57             : 
      58          64 :     bool operator !=(const ReceiverGuard& other) const {
      59          64 :         return !(*this == other);
      60             :     }
      61             : 
      62         184 :     uintptr_t hash() const {
      63         184 :         return (uintptr_t(group) >> 3) ^ (uintptr_t(shape) >> 3);
      64             :     }
      65             : };
      66             : 
      67             : class HeapReceiverGuard
      68             : {
      69             :     GCPtrObjectGroup group_;
      70             :     GCPtrShape shape_;
      71             : 
      72             :   public:
      73             :     explicit HeapReceiverGuard(const ReceiverGuard& guard)
      74             :       : group_(guard.group), shape_(guard.shape)
      75             :     {}
      76             : 
      77         117 :     void init(const ReceiverGuard& other) {
      78         117 :         group_.init(other.group);
      79         117 :         shape_.init(other.shape);
      80         117 :     }
      81             : 
      82             :     void trace(JSTracer* trc);
      83             : 
      84          67 :     Shape* shape() const {
      85          67 :         return shape_;
      86             :     }
      87          67 :     ObjectGroup* group() const {
      88          67 :         return group_;
      89             :     }
      90             : };
      91             : 
      92             : inline
      93          67 : ReceiverGuard::ReceiverGuard(const HeapReceiverGuard& guard)
      94          67 :   : group(guard.group()), shape(guard.shape())
      95          67 : {}
      96             : 
      97             : } // namespace js
      98             : 
      99             : #endif /* vm_ReceiverGuard_h */