heap/Handle.h

   1 /*
   2  * Copyright (C) 2011 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 Handle_h
  27 #define Handle_h
  28
  29 #include "HandleTypes.h"
  30
  31 namespace JSC {
  32
  33 /*
  34     A Handle is a smart pointer that updates automatically when the garbage
  35     collector moves the object to which it points.
  36
  37     The base Handle class represents a temporary reference to a pointer whose
  38     lifetime is guaranteed by something else.
  39 */
  40
  41 template <class T> class Handle;
  42
  43 // Creating a JSValue Handle is invalid
  44 template <> class Handle<JSValue>;
  45
  46 // Forward declare WeakGCMap
  47 template<typename KeyType, typename MappedType, typename FinalizerCallback, typename HashArg, typename KeyTraitsArg> class WeakGCMap;
  48
  49 class HandleBase {
  50     template <typename T> friend class Weak;
  51     friend class HandleSet;
  52     friend struct JSCallbackObjectData;
  53     template <typename KeyType, typename MappedType, typename FinalizerCallback, typename HashArg, typename KeyTraitsArg> friend class WeakGCMap;
  54
  55 public:
  56     bool operator!() const { return !m_slot || !*m_slot; }
  57
  58     // This conversion operator allows implicit conversion to bool but not to other integer types.
  59     typedef JSValue (HandleBase::*UnspecifiedBoolType);
  60     operator UnspecifiedBoolType*() const { return (m_slot && *m_slot) ? reinterpret_cast<UnspecifiedBoolType*>(1) : 0; }
  61
  62     HandleSlot slot() const { return m_slot; }
  63
  64 protected:
  65     HandleBase(HandleSlot slot)
  66         : m_slot(slot)
  67     {
  68     }
  69
  70     void swap(HandleBase& other) { std::swap(m_slot, other.m_slot); }
  71
  72     void setSlot(HandleSlot slot)
  73     {
  74         m_slot = slot;
  75     }
  76
  77 private:
  78     HandleSlot m_slot;
  79 };
  80
  81 template <typename Base, typename T> struct HandleConverter {
  82     T* operator->()
  83     {
  84         return static_cast<Base*>(this)->get();
  85     }
  86     const T* operator->() const
  87     {
  88         return static_cast<const Base*>(this)->get();
  89     }
  90
  91     T* operator*()
  92     {
  93         return static_cast<Base*>(this)->get();
  94     }
  95     const T* operator*() const
  96     {
  97         return static_cast<const Base*>(this)->get();
  98     }
  99 };
 100
 101 template <typename Base> struct HandleConverter<Base, Unknown> {
 102     Handle<JSObject> asObject() const;
 103     bool isObject() const { return jsValue().isObject(); }
 104     bool getNumber(double number) const { return jsValue().getNumber(number); }
 105     UString getString(ExecState*) const;
 106     bool isUndefinedOrNull() const { return jsValue().isUndefinedOrNull(); }
 107
 108 private:
 109     JSValue jsValue() const
 110     {
 111         return static_cast<const Base*>(this)->get();
 112     }
 113 };
 114
 115 template <typename T> class Handle : public HandleBase, public HandleConverter<Handle<T>, T> {
 116 public:
 117     template <typename A, typename B> friend class HandleConverter;
 118     typedef typename HandleTypes<T>::ExternalType ExternalType;
 119     template <typename U> Handle(Handle<U> o)
 120     {
 121         typename HandleTypes<T>::template validateUpcast<U>();
 122         setSlot(o.slot());
 123     }
 124
 125     void swap(Handle& other) { HandleBase::swap(other); }
 126
 127     ExternalType get() const { return HandleTypes<T>::getFromSlot(this->slot()); }
 128
 129 protected:
 130     Handle(HandleSlot slot = 0)
 131         : HandleBase(slot)
 132     {
 133     }
 134
 135 private:
 136     friend class HandleSet;
 137     friend class WeakBlock;
 138
 139     static Handle<T> wrapSlot(HandleSlot slot)
 140     {
 141         return Handle<T>(slot);
 142     }
 143 };
 144
 145 template <typename Base> Handle<JSObject> HandleConverter<Base, Unknown>::asObject() const
 146 {
 147     return Handle<JSObject>::wrapSlot(static_cast<const Base*>(this)->slot());
 148 }
 149
 150 template <typename T, typename U> inline bool operator==(const Handle<T>& a, const Handle<U>& b)
 151 {
 152     return a.get() == b.get();
 153 }
 154
 155 template <typename T, typename U> inline bool operator==(const Handle<T>& a, U* b)
 156 {
 157     return a.get() == b;
 158 }
 159
 160 template <typename T, typename U> inline bool operator==(T* a, const Handle<U>& b)
 161 {
 162     return a == b.get();
 163 }
 164
 165 template <typename T, typename U> inline bool operator!=(const Handle<T>& a, const Handle<U>& b)
 166 {
 167     return a.get() != b.get();
 168 }
 169
 170 template <typename T, typename U> inline bool operator!=(const Handle<T>& a, U* b)
 171 {
 172     return a.get() != b;
 173 }
 174
 175 template <typename T, typename U> inline bool operator!=(T* a, const Handle<U>& b)
 176 {
 177     return a != b.get();
 178 }
 179
 180 template <typename T, typename U> inline bool operator!=(const Handle<T>& a, JSValue b)
 181 {
 182     return a.get() != b;
 183 }
 184
 185 template <typename T, typename U> inline bool operator!=(JSValue a, const Handle<U>& b)
 186 {
 187     return a != b.get();
 188 }
 189
 190 }
 191
 192 #endif