1/*
2 * Copyright (C) 2011 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
28#include <wtf/Assertions.h>
29#include "Handle.h"
30#include "HandleSet.h"
31
32namespace JSC {
33
34class VM;
35
36// A strongly referenced handle that prevents the object it points to from being garbage collected.
37template <typename T> class Strong : public Handle<T> {
38 using Handle<T>::slot;
39 using Handle<T>::setSlot;
40 template <typename U> friend class Strong;
41
42public:
43 typedef typename Handle<T>::ExternalType ExternalType;
44
45 Strong()
46 : Handle<T>()
47 {
48 }
49
50 Strong(VM&, ExternalType = ExternalType());
51
52 Strong(VM&, Handle<T>);
53
54 Strong(const Strong& other)
55 : Handle<T>()
56 {
57 if (!other.slot())
58 return;
59 setSlot(HandleSet::heapFor(other.slot())->allocate());
60 set(other.get());
61 }
62
63 template <typename U> Strong(const Strong<U>& other)
64 : Handle<T>()
65 {
66 if (!other.slot())
67 return;
68 setSlot(HandleSet::heapFor(other.slot())->allocate());
69 set(other.get());
70 }
71
72 enum HashTableDeletedValueTag { HashTableDeletedValue };
73 bool isHashTableDeletedValue() const { return slot() == hashTableDeletedValue(); }
74 Strong(HashTableDeletedValueTag)
75 : Handle<T>(hashTableDeletedValue())
76 {
77 }
78
79 ~Strong()
80 {
81 clear();
82 }
83
84 bool operator!() const { return !slot() || !*slot(); }
85
86 explicit operator bool() const { return !!*this; }
87
88 void swap(Strong& other)
89 {
90 Handle<T>::swap(other);
91 }
92
93 ExternalType get() const { return HandleTypes<T>::getFromSlot(this->slot()); }
94
95 void set(VM&, ExternalType);
96
97 template <typename U> Strong& operator=(const Strong<U>& other)
98 {
99 if (!other.slot()) {
100 clear();
101 return *this;
102 }
103
104 set(*HandleSet::heapFor(other.slot())->vm(), other.get());
105 return *this;
106 }
107
108 Strong& operator=(const Strong& other)
109 {
110 if (!other.slot()) {
111 clear();
112 return *this;
113 }
114
115 set(*HandleSet::heapFor(other.slot())->vm(), other.get());
116 return *this;
117 }
118
119 void clear()
120 {
121 if (!slot())
122 return;
123 HandleSet::heapFor(slot())->deallocate(slot());
124 setSlot(0);
125 }
126
127private:
128 static HandleSlot hashTableDeletedValue() { return reinterpret_cast<HandleSlot>(-1); }
129
130 void set(ExternalType externalType)
131 {
132 ASSERT(slot());
133 JSValue value = HandleTypes<T>::toJSValue(externalType);
134 HandleSet::heapFor(slot())->writeBarrier(slot(), value);
135 *slot() = value;
136 }
137};
138
139template<class T> inline void swap(Strong<T>& a, Strong<T>& b)
140{
141 a.swap(b);
142}
143
144} // namespace JSC
145
146namespace WTF {
147
148template<typename T> struct VectorTraits<JSC::Strong<T>> : SimpleClassVectorTraits {
149 static const bool canCompareWithMemcmp = false;
150};
151
152template<typename P> struct HashTraits<JSC::Strong<P>> : SimpleClassHashTraits<JSC::Strong<P>> { };
153
154} // namespace WTF
155