heap/PassWeak.h

   1 /*
   2  * Copyright (C) 2012 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 Weak;
  38 template<typename T> class PassWeak;
  39 template<typename T> PassWeak<T> adoptWeak(WeakImpl*);
  40
  41 template<typename Base, typename T> class WeakImplAccessor {
  42 public:
  43     typedef T* GetType;
  44
  45     T* operator->() const;
  46     T& operator*() const;
  47     GetType get() const;
  48
  49 #if !ASSERT_DISABLED
  50     bool was(GetType) const;
  51 #endif
  52 };
  53
  54 template<typename T> class PassWeak : public WeakImplAccessor<PassWeak<T>, T> {
  55 public:
  56     friend class WeakImplAccessor<PassWeak<T>, T>;
  57     typedef typename WeakImplAccessor<PassWeak<T>, T>::GetType GetType;
  58
  59     PassWeak();
  60     PassWeak(std::nullptr_t);
  61     PassWeak(GetType, WeakHandleOwner* = 0, void* context = 0);
  62
  63     // It somewhat breaks the type system to allow transfer of ownership out of
  64     // a const PassWeak. However, it makes it much easier to work with PassWeak
  65     // temporaries, and we don't have a need to use real const PassWeaks anyway.
  66     PassWeak(const PassWeak&);
  67     template<typename U> PassWeak(const PassWeak<U>&);
  68
  69     ~PassWeak();
  70
  71     bool operator!() const;
  72
  73     // This conversion operator allows implicit conversion to bool but not to other integer types.
  74     typedef JSValue (PassWeak::*UnspecifiedBoolType);
  75     operator UnspecifiedBoolType*() const;
  76
  77     WeakImpl* leakImpl() const WARN_UNUSED_RETURN;
  78
  79 private:
  80     friend PassWeak adoptWeak<T>(WeakImpl*);
  81     explicit PassWeak(WeakImpl*);
  82
  83     WeakImpl* m_impl;
  84 };
  85
  86 template<typename Base, typename T> inline T* WeakImplAccessor<Base, T>::operator->() const
  87 {
  88     ASSERT(static_cast<const Base*>(this)->m_impl && static_cast<const Base*>(this)->m_impl->state() == WeakImpl::Live);
  89     return jsCast<T*>(static_cast<const Base*>(this)->m_impl->jsValue().asCell());
  90 }
  91
  92 template<typename Base, typename T> inline T& WeakImplAccessor<Base, T>::operator*() const
  93 {
  94     ASSERT(static_cast<const Base*>(this)->m_impl && static_cast<const Base*>(this)->m_impl->state() == WeakImpl::Live);
  95     return *jsCast<T*>(static_cast<const Base*>(this)->m_impl->jsValue().asCell());
  96 }
  97
  98 template<typename Base, typename T> inline typename WeakImplAccessor<Base, T>::GetType WeakImplAccessor<Base, T>::get() const
  99 {
 100     if (!static_cast<const Base*>(this)->m_impl || static_cast<const Base*>(this)->m_impl->state() != WeakImpl::Live)
 101         return GetType();
 102     return jsCast<T*>(static_cast<const Base*>(this)->m_impl->jsValue().asCell());
 103 }
 104
 105 #if !ASSERT_DISABLED
 106 template<typename Base, typename T> inline bool WeakImplAccessor<Base, T>::was(typename WeakImplAccessor<Base, T>::GetType other) const
 107 {
 108     return jsCast<T*>(static_cast<const Base*>(this)->m_impl->jsValue().asCell()) == other;
 109 }
 110 #endif
 111
 112 template<typename T> inline PassWeak<T>::PassWeak()
 113     : m_impl(0)
 114 {
 115 }
 116
 117 template<typename T> inline PassWeak<T>::PassWeak(std::nullptr_t)
 118     : m_impl(0)
 119 {
 120 }
 121
 122 template<typename T> inline PassWeak<T>::PassWeak(typename PassWeak<T>::GetType getType, WeakHandleOwner* weakOwner, void* context)
 123     : m_impl(getType ? WeakSet::allocate(getType, weakOwner, context) : 0)
 124 {
 125 }
 126
 127 template<typename T> inline PassWeak<T>::PassWeak(const PassWeak& o)
 128     : m_impl(o.leakImpl())
 129 {
 130 }
 131
 132 template<typename T> template<typename U> inline PassWeak<T>::PassWeak(const PassWeak<U>& o)
 133     : m_impl(o.leakImpl())
 134 {
 135 }
 136
 137 template<typename T> inline PassWeak<T>::~PassWeak()
 138 {
 139     if (!m_impl)
 140         return;
 141     WeakSet::deallocate(m_impl);
 142 }
 143
 144 template<typename T> inline bool PassWeak<T>::operator!() const
 145 {
 146     return !m_impl || m_impl->state() != WeakImpl::Live || !m_impl->jsValue();
 147 }
 148
 149 template<typename T> inline PassWeak<T>::operator UnspecifiedBoolType*() const
 150 {
 151     return reinterpret_cast<UnspecifiedBoolType*>(!!*this);
 152 }
 153
 154 template<typename T> inline PassWeak<T>::PassWeak(WeakImpl* impl)
 155 : m_impl(impl)
 156 {
 157 }
 158
 159 template<typename T> inline WeakImpl* PassWeak<T>::leakImpl() const
 160 {
 161     WeakImpl* tmp = 0;
 162     std::swap(tmp, const_cast<WeakImpl*&>(m_impl));
 163     return tmp;
 164 }
 165
 166 template<typename T> PassWeak<T> inline adoptWeak(WeakImpl* impl)
 167 {
 168     return PassWeak<T>(impl);
 169 }
 170
 171 template<typename T, typename U> inline bool operator==(const PassWeak<T>& a, const PassWeak<U>& b)
 172 {
 173     return a.get() == b.get();
 174 }
 175
 176 template<typename T, typename U> inline bool operator==(const PassWeak<T>& a, const Weak<U>& b)
 177 {
 178     return a.get() == b.get();
 179 }
 180
 181 template<typename T, typename U> inline bool operator==(const Weak<T>& a, const PassWeak<U>& b)
 182 {
 183     return a.get() == b.get();
 184 }
 185
 186 template<typename T, typename U> inline bool operator==(const PassWeak<T>& a, U* b)
 187 {
 188     return a.get() == b;
 189 }
 190
 191 template<typename T, typename U> inline bool operator==(T* a, const PassWeak<U>& b)
 192 {
 193     return a == b.get();
 194 }
 195
 196 template<typename T, typename U> inline bool operator!=(const PassWeak<T>& a, const PassWeak<U>& b)
 197 {
 198     return a.get() != b.get();
 199 }
 200
 201 template<typename T, typename U> inline bool operator!=(const PassWeak<T>& a, const Weak<U>& b)
 202 {
 203     return a.get() != b.get();
 204 }
 205
 206 template<typename T, typename U> inline bool operator!=(const Weak<T>& a, const PassWeak<U>& b)
 207 {
 208     return a.get() != b.get();
 209 }
 210
 211 template<typename T, typename U> inline bool operator!=(const PassWeak<T>& a, U* b)
 212 {
 213     return a.get() != b;
 214 }
 215
 216 template<typename T, typename U> inline bool operator!=(T* a, const PassWeak<U>& b)
 217 {
 218     return a != b.get();
 219 }
 220
 221 } // namespace JSC
 222
 223 #endif // PassWeak_h