1 /*
2 * Copyright (C) 2009 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 WeakGCPtr_h
27 #define WeakGCPtr_h
28
29 #include "Collector.h"
30 #include <wtf/Noncopyable.h>
31
32 namespace JSC {
33
34 // A smart pointer whose get() function returns 0 for cells awaiting destruction.
35 template <typename T> class WeakGCPtr : Noncopyable {
36 public:
WeakGCPtr()37 WeakGCPtr() : m_ptr(0) { }
WeakGCPtr(T * ptr)38 WeakGCPtr(T* ptr) { assign(ptr); }
39
get()40 T* get() const
41 {
42 if (!m_ptr || !Heap::isCellMarked(m_ptr))
43 return 0;
44 return m_ptr;
45 }
46
clear(JSCell * ptr)47 void clear(JSCell* ptr)
48 {
49 if (ptr == m_ptr)
50 m_ptr = 0;
51 }
52
53 T& operator*() const { return *get(); }
54 T* operator->() const { return get(); }
55
56 bool operator!() const { return !get(); }
57
58 // This conversion operator allows implicit conversion to bool but not to other integer types.
59 #if COMPILER(WINSCW)
60 operator bool() const { return m_ptr; }
61 #else
62 typedef T* WeakGCPtr::*UnspecifiedBoolType;
UnspecifiedBoolType()63 operator UnspecifiedBoolType() const { return get() ? &WeakGCPtr::m_ptr : 0; }
64 #endif
65
66 WeakGCPtr& operator=(T*);
67
68 private:
assign(T * ptr)69 void assign(T* ptr)
70 {
71 if (ptr)
72 Heap::markCell(ptr);
73 m_ptr = ptr;
74 }
75
76 T* m_ptr;
77 };
78
79 template <typename T> inline WeakGCPtr<T>& WeakGCPtr<T>::operator=(T* optr)
80 {
81 assign(optr);
82 return *this;
83 }
84
85 template <typename T, typename U> inline bool operator==(const WeakGCPtr<T>& a, const WeakGCPtr<U>& b)
86 {
87 return a.get() == b.get();
88 }
89
90 template <typename T, typename U> inline bool operator==(const WeakGCPtr<T>& a, U* b)
91 {
92 return a.get() == b;
93 }
94
95 template <typename T, typename U> inline bool operator==(T* a, const WeakGCPtr<U>& b)
96 {
97 return a == b.get();
98 }
99
100 template <typename T, typename U> inline bool operator!=(const WeakGCPtr<T>& a, const WeakGCPtr<U>& b)
101 {
102 return a.get() != b.get();
103 }
104
105 template <typename T, typename U> inline bool operator!=(const WeakGCPtr<T>& a, U* b)
106 {
107 return a.get() != b;
108 }
109
110 template <typename T, typename U> inline bool operator!=(T* a, const WeakGCPtr<U>& b)
111 {
112 return a != b.get();
113 }
114
static_pointer_cast(const WeakGCPtr<U> & p)115 template <typename T, typename U> inline WeakGCPtr<T> static_pointer_cast(const WeakGCPtr<U>& p)
116 {
117 return WeakGCPtr<T>(static_cast<T*>(p.get()));
118 }
119
const_pointer_cast(const WeakGCPtr<U> & p)120 template <typename T, typename U> inline WeakGCPtr<T> const_pointer_cast(const WeakGCPtr<U>& p)
121 {
122 return WeakGCPtr<T>(const_cast<T*>(p.get()));
123 }
124
getPtr(const WeakGCPtr<T> & p)125 template <typename T> inline T* getPtr(const WeakGCPtr<T>& p)
126 {
127 return p.get();
128 }
129
130 } // namespace JSC
131
132 #endif // WeakGCPtr_h
133