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/* -*- 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/. */
#ifndef vm_ReceiverGuard_h
#define vm_ReceiverGuard_h
#include "vm/Shape.h"
namespace js {
// [SMDOC] Receiver Guard
//
// A ReceiverGuard encapsulates the information about an object that needs to
// be tested to determine if it has the same 'structure' as another object.
// The guard includes the shape and/or group of the object, and which of these
// is tested, as well as the meaning here of 'structure', depends on the kind
// of object being tested:
//
// NativeObject: The structure of a native object is determined by its shape.
// Two objects with the same shape have the same class, prototype, flags,
// and all properties except those stored in dense elements.
//
// ProxyObject: The structure of a proxy object is determined by its shape.
// Proxies with the same shape have the same class and prototype, but no
// other commonality is guaranteed.
//
// TypedObject: The structure of a typed object is determined by its group.
// All typed objects with the same group have the same class, prototype, and
// own properties.
//
// In all cases, a ReceiverGuard has *either* a shape or a group active, and
// never both.
class ReceiverGuard {
ObjectGroup* group_;
Shape* shape_;
public:
ReceiverGuard() : group_(nullptr), shape_(nullptr) {}
explicit MOZ_ALWAYS_INLINE ReceiverGuard(JSObject* obj);
bool operator==(const ReceiverGuard& other) const {
return group_ == other.group_ && shape_ == other.shape_;
}
bool operator!=(const ReceiverGuard& other) const {
return !(*this == other);
}
uintptr_t hash() const {
return (uintptr_t(group_) >> 3) ^ (uintptr_t(shape_) >> 3);
}
Shape* getShape() const { return shape_; }
ObjectGroup* getGroup() const { return group_; }
};
// Heap storage for ReceiverGuards.
//
// This is a storage only class -- all computation is actually
// done by converting this back to a RecieverGuard, hence why
// there are no accessors.
class HeapReceiverGuard {
friend class ReceiverGuard;
const GCPtrObjectGroup group_;
const GCPtrShape shape_;
public:
explicit HeapReceiverGuard(const ReceiverGuard& guard)
: group_(guard.getGroup()), shape_(guard.getShape()) {}
void trace(JSTracer* trc);
};
} // namespace js
#endif /* vm_ReceiverGuard_h */
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