heap/PassWeak.h

   1 /*
   2  * Copyright (C) 2012, 2013 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. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef PassWeak_h
  27 #define PassWeak_h
  28
  29 #include "JSCell.h"
  30 #include "WeakSetInlines.h"
  31 #include <wtf/Assertions.h>
  32 #include <wtf/NullPtr.h>
  33 #include <wtf/TypeTraits.h>
  34
  35 namespace JSC {
  36
  37 template<typename T> class PassWeak;
  38 template<typename T> PassWeak<T> adoptWeak(WeakImpl*);
  39
  40 template<typename T> class PassWeak {
  41 public:
  42     PassWeak();
  43     PassWeak(std::nullptr_t);
  44     PassWeak(T*, WeakHandleOwner* = 0, void* context = 0);
  45
  46     // It somewhat breaks the type system to allow transfer of ownership out of
  47     // a const PassWeak. However, it makes it much easier to work with PassWeak
  48     // temporaries, and we don't have a need to use real const PassWeaks anyway.
  49     PassWeak(const PassWeak&);
  50     template<typename U> PassWeak(const PassWeak<U>&);
  51
  52     ~PassWeak();
  53
  54     T* operator->() const;
  55     T& operator*() const;
  56     T* get() const;
  57
  58     bool operator!() const;
  59
  60     // This conversion operator allows implicit conversion to bool but not to other integer types.
  61     typedef void* (PassWeak::*UnspecifiedBoolType);
  62     operator UnspecifiedBoolType*() const;
  63
  64     WeakImpl* leakImpl() const WARN_UNUSED_RETURN;
  65
  66 private:
  67     friend PassWeak adoptWeak<T>(WeakImpl*);
  68     explicit PassWeak(WeakImpl*);
  69
  70     WeakImpl* m_impl;
  71 };
  72
  73 template<typename T> inline PassWeak<T>::PassWeak()
  74     : m_impl(0)
  75 {
  76 }
  77
  78 template<typename T> inline PassWeak<T>::PassWeak(std::nullptr_t)
  79     : m_impl(0)
  80 {
  81 }
  82
  83 template<typename T> inline PassWeak<T>::PassWeak(T* cell, WeakHandleOwner* weakOwner, void* context)
  84     : m_impl(cell ? WeakSet::allocate(cell, weakOwner, context) : 0)
  85 {
  86 }
  87
  88 template<typename T> inline PassWeak<T>::PassWeak(const PassWeak& o)
  89     : m_impl(o.leakImpl())
  90 {
  91 }
  92
  93 template<typename T> template<typename U> inline PassWeak<T>::PassWeak(const PassWeak<U>& o)
  94     : m_impl(o.leakImpl())
  95 {
  96 }
  97
  98 template<typename T> inline PassWeak<T>::~PassWeak()
  99 {
 100     if (!m_impl)
 101         return;
 102     WeakSet::deallocate(m_impl);
 103 }
 104
 105 template<typename T> inline T* PassWeak<T>::operator->() const
 106 {
 107     ASSERT(m_impl && m_impl->state() == WeakImpl::Live);
 108     return jsCast<T*>(m_impl->jsValue().asCell());
 109 }
 110
 111 template<typename T> inline T& PassWeak<T>::operator*() const
 112 {
 113     ASSERT(m_impl && m_impl->state() == WeakImpl::Live);
 114     return *jsCast<T*>(m_impl->jsValue().asCell());
 115 }
 116
 117 template<typename T> inline T* PassWeak<T>::get() const
 118 {
 119     if (!m_impl || m_impl->state() != WeakImpl::Live)
 120         return 0;
 121     return jsCast<T*>(m_impl->jsValue().asCell());
 122 }
 123
 124 template<typename T> inline bool PassWeak<T>::operator!() const
 125 {
 126     return !m_impl || m_impl->state() != WeakImpl::Live || !m_impl->jsValue();
 127 }
 128
 129 template<typename T> inline PassWeak<T>::operator UnspecifiedBoolType*() const
 130 {
 131     return reinterpret_cast<UnspecifiedBoolType*>(!!*this);
 132 }
 133
 134 template<typename T> inline PassWeak<T>::PassWeak(WeakImpl* impl)
 135 : m_impl(impl)
 136 {
 137 }
 138
 139 template<typename T> inline WeakImpl* PassWeak<T>::leakImpl() const
 140 {
 141     WeakImpl* tmp = 0;
 142     std::swap(tmp, const_cast<WeakImpl*&>(m_impl));
 143     return tmp;
 144 }
 145
 146 template<typename T> PassWeak<T> inline adoptWeak(WeakImpl* impl)
 147 {
 148     return PassWeak<T>(impl);
 149 }
 150
 151 template<typename T, typename U> inline bool operator==(const PassWeak<T>& a, const PassWeak<U>& b)
 152 {
 153     return a.get() == b.get();
 154 }
 155
 156 template<typename T, typename U> inline bool operator==(const PassWeak<T>& a, const Weak<U>& b)
 157 {
 158     return a.get() == b.get();
 159 }
 160
 161 template<typename T, typename U> inline bool operator==(const Weak<T>& a, const PassWeak<U>& b)
 162 {
 163     return a.get() == b.get();
 164 }
 165
 166 template<typename T, typename U> inline bool operator==(const PassWeak<T>& a, U* b)
 167 {
 168     return a.get() == b;
 169 }
 170
 171 template<typename T, typename U> inline bool operator==(T* a, const PassWeak<U>& b)
 172 {
 173     return a == b.get();
 174 }
 175
 176 template<typename T, typename U> inline bool operator!=(const PassWeak<T>& a, const PassWeak<U>& b)
 177 {
 178     return a.get() != b.get();
 179 }
 180
 181 template<typename T, typename U> inline bool operator!=(const PassWeak<T>& a, const Weak<U>& b)
 182 {
 183     return a.get() != b.get();
 184 }
 185
 186 template<typename T, typename U> inline bool operator!=(const Weak<T>& a, const PassWeak<U>& b)
 187 {
 188     return a.get() != b.get();
 189 }
 190
 191 template<typename T, typename U> inline bool operator!=(const PassWeak<T>& a, U* b)
 192 {
 193     return a.get() != b;
 194 }
 195
 196 template<typename T, typename U> inline bool operator!=(T* a, const PassWeak<U>& b)
 197 {
 198     return a != b.get();
 199 }
 200
 201 } // namespace JSC
 202
 203 #endif // PassWeak_h