heap/WeakImpl.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. 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 WeakImpl_h
  27 #define WeakImpl_h
  28
  29 #include "JSValue.h"
  30
  31 namespace JSC {
  32
  33 class WeakHandleOwner;
  34
  35 class WeakImpl {
  36 public:
  37     enum State {
  38         Live        = 0x0,
  39         Dead        = 0x1,
  40         Finalized   = 0x2,
  41         Deallocated = 0x3
  42     };
  43
  44     enum {
  45         StateMask   = 0x3
  46     };
  47
  48     WeakImpl();
  49     WeakImpl(JSValue, WeakHandleOwner*, void* context);
  50
  51     State state();
  52     void setState(State);
  53
  54     const JSValue& jsValue();
  55     WeakHandleOwner* weakHandleOwner();
  56     void* context();
  57
  58     static WeakImpl* asWeakImpl(JSValue*);
  59
  60 private:
  61     const JSValue m_jsValue;
  62     WeakHandleOwner* m_weakHandleOwner;
  63     void* m_context;
  64 };
  65
  66 inline WeakImpl::WeakImpl()
  67     : m_weakHandleOwner(0)
  68     , m_context(0)
  69 {
  70     setState(Deallocated);
  71 }
  72
  73 inline WeakImpl::WeakImpl(JSValue jsValue, WeakHandleOwner* weakHandleOwner, void* context)
  74     : m_jsValue(jsValue)
  75     , m_weakHandleOwner(weakHandleOwner)
  76     , m_context(context)
  77 {
  78     ASSERT(state() == Live);
  79     ASSERT(m_jsValue && m_jsValue.isCell());
  80 }
  81
  82 inline WeakImpl::State WeakImpl::state()
  83 {
  84     return static_cast<State>(reinterpret_cast<uintptr_t>(m_weakHandleOwner) & StateMask);
  85 }
  86
  87 inline void WeakImpl::setState(WeakImpl::State state)
  88 {
  89     ASSERT(state >= this->state());
  90     m_weakHandleOwner = reinterpret_cast<WeakHandleOwner*>((reinterpret_cast<uintptr_t>(m_weakHandleOwner) & ~StateMask) | state);
  91 }
  92
  93 inline const JSValue& WeakImpl::jsValue()
  94 {
  95     return m_jsValue;
  96 }
  97
  98 inline WeakHandleOwner* WeakImpl::weakHandleOwner()
  99 {
 100     return reinterpret_cast<WeakHandleOwner*>((reinterpret_cast<uintptr_t>(m_weakHandleOwner) & ~StateMask));
 101 }
 102
 103 inline void* WeakImpl::context()
 104 {
 105     return m_context;
 106 }
 107
 108 inline WeakImpl* WeakImpl::asWeakImpl(JSValue* slot)
 109 {
 110     return reinterpret_cast<WeakImpl*>(reinterpret_cast<char*>(slot) + OBJECT_OFFSETOF(WeakImpl, m_jsValue));
 111 }
 112
 113 } // namespace JSC
 114
 115 #endif // WeakImpl_h