1/*
2 * Copyright (C) 2016 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28namespace JSC {
29
30class JSCell;
31class VM;
32
33// An Auxiliary barrier is a barrier that does not try to reason about the value being stored into
34// it, other than interpreting a falsy value as not needing a barrier. It's OK to use this for either
35// JSCells or any other kind of data, so long as it responds to operator!().
36template<typename T>
37class AuxiliaryBarrier {
38public:
39 typedef T Type;
40
41 AuxiliaryBarrier(): m_value() { }
42
43 template<typename U>
44 AuxiliaryBarrier(VM&, JSCell*, U&&);
45
46 void clear() { m_value = T(); }
47
48 template<typename U>
49 void set(VM&, JSCell*, U&&);
50
51 const T& get() const { return m_value; }
52
53 T* slot() { return &m_value; }
54
55 explicit operator bool() const { return !!m_value; }
56
57 template<typename U>
58 void setWithoutBarrier(U&& value) { m_value = std::forward<U>(value); }
59
60 T operator->() const { return get(); }
61
62private:
63 T m_value;
64};
65
66} // namespace JSC
67