1/*
2 * Copyright (C) 2014 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#ifndef CopyWriteBarrier_h
27#define CopyWriteBarrier_h
28
29#include "Heap.h"
30
31namespace JSC {
32
33template <typename T>
34class CopyWriteBarrier {
35public:
36    CopyWriteBarrier()
37        : m_value(0)
38    {
39    }
40
41    CopyWriteBarrier(VM& vm, const JSCell* owner, T& value)
42    {
43        this->set(vm, owner, &value);
44    }
45
46    CopyWriteBarrier(VM& vm, const JSCell* owner, T* value)
47    {
48        this->set(vm, owner, value);
49    }
50
51    bool operator!() const { return !m_value; }
52
53    typedef T* (CopyWriteBarrier::*UnspecifiedBoolType);
54    operator UnspecifiedBoolType*() const { return m_value ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0; }
55
56    T* get() const
57    {
58        return m_value;
59    }
60
61    T* operator*() const
62    {
63        return get();
64    }
65
66    T* operator->() const
67    {
68        return get();
69    }
70
71    void set(VM& vm, const JSCell* owner, T* value)
72    {
73        this->m_value = value;
74        vm.heap.writeBarrier(owner);
75    }
76
77    void setWithoutWriteBarrier(T* value)
78    {
79        this->m_value = value;
80    }
81
82    void clear() { m_value = 0; }
83
84private:
85    T* m_value;
86};
87
88} // namespace JSC
89
90#endif // CopyWriteBarrier_h
91