runtime/WeakGCPtr.h

   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:
  37     WeakGCPtr() : m_ptr(0) { }
  38     WeakGCPtr(T* ptr) { assign(ptr); }
  39
  40     T* get() const
  41     {
  42         if (!m_ptr || !Heap::isCellMarked(m_ptr))
  43             return 0;
  44         return m_ptr;
  45     }
  46
  47     bool clear(JSCell* ptr)
  48     {
  49         if (ptr == m_ptr) {
  50             m_ptr = 0;
  51             return true;
  52         }
  53         return false;
  54     }
  55
  56     T& operator*() const { return *get(); }
  57     T* operator->() const { return get(); }
  58
  59     bool operator!() const { return !get(); }
  60
  61     // This conversion operator allows implicit conversion to bool but not to other integer types.
  62 #if COMPILER(WINSCW)
  63     operator bool() const { return m_ptr; }
  64 #else
  65     typedef T* WeakGCPtr::*UnspecifiedBoolType;
  66     operator UnspecifiedBoolType() const { return get() ? &WeakGCPtr::m_ptr : 0; }
  67 #endif
  68
  69     WeakGCPtr& operator=(T*);
  70
  71 #if !ASSERT_DISABLED
  72     bool hasDeadObject() const { return !!m_ptr; }
  73 #endif
  74
  75 private:
  76     void assign(T* ptr)
  77     {
  78         ASSERT(ptr);
  79         Heap::markCell(ptr);
  80         m_ptr = ptr;
  81     }
  82
  83     T* m_ptr;
  84 };
  85
  86 template <typename T> inline WeakGCPtr<T>& WeakGCPtr<T>::operator=(T* optr)
  87 {
  88     assign(optr);
  89     return *this;
  90 }
  91
  92 template <typename T, typename U> inline bool operator==(const WeakGCPtr<T>& a, const WeakGCPtr<U>& b)
  93 {
  94     return a.get() == b.get();
  95 }
  96
  97 template <typename T, typename U> inline bool operator==(const WeakGCPtr<T>& a, U* b)
  98 {
  99     return a.get() == b;
 100 }
 101
 102 template <typename T, typename U> inline bool operator==(T* a, const WeakGCPtr<U>& b)
 103 {
 104     return a == b.get();
 105 }
 106
 107 template <typename T, typename U> inline bool operator!=(const WeakGCPtr<T>& a, const WeakGCPtr<U>& b)
 108 {
 109     return a.get() != b.get();
 110 }
 111
 112 template <typename T, typename U> inline bool operator!=(const WeakGCPtr<T>& a, U* b)
 113 {
 114     return a.get() != b;
 115 }
 116
 117 template <typename T, typename U> inline bool operator!=(T* a, const WeakGCPtr<U>& b)
 118 {
 119     return a != b.get();
 120 }
 121
 122 template <typename T, typename U> inline WeakGCPtr<T> static_pointer_cast(const WeakGCPtr<U>& p)
 123 {
 124     return WeakGCPtr<T>(static_cast<T*>(p.get()));
 125 }
 126
 127 template <typename T, typename U> inline WeakGCPtr<T> const_pointer_cast(const WeakGCPtr<U>& p)
 128 {
 129     return WeakGCPtr<T>(const_cast<T*>(p.get()));
 130 }
 131
 132 template <typename T> inline T* getPtr(const WeakGCPtr<T>& p)
 133 {
 134     return p.get();
 135 }
 136
 137 } // namespace JSC
 138
 139 #endif // WeakGCPtr_h