third_party/WebKit/Source/wtf/PassRefPtr.h

   1 /*
   2  *  Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
   3  *
   4  *  This library is free software; you can redistribute it and/or
   5  *  modify it under the terms of the GNU Library General Public
   6  *  License as published by the Free Software Foundation; either
   7  *  version 2 of the License, or (at your option) any later version.
   8  *
   9  *  This library is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  *  Library General Public License for more details.
  13  *
  14  *  You should have received a copy of the GNU Library General Public License
  15  *  along with this library; see the file COPYING.LIB.  If not, write to
  16  *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  17  *  Boston, MA 02110-1301, USA.
  18  *
  19  */
  20
  21 #ifndef WTF_PassRefPtr_h
  22 #define WTF_PassRefPtr_h
  23
  24 #include "wtf/Assertions.h"
  25 #include "wtf/NullPtr.h"
  26 #include "wtf/RawPtr.h"
  27 #include "wtf/TypeTraits.h"
  28
  29 namespace WTF {
  30
  31     template<typename T> class RefPtr;
  32     template<typename T> class PassRefPtr;
  33     template<typename T> PassRefPtr<T> adoptRef(T*);
  34
  35     inline void adopted(const void*) { }
  36
  37     // requireAdoption() is not overloaded for WTF::RefCounted, which has a
  38     // built-in assumption that adoption is required. requireAdoption() is
  39     // for bootstrapping alternate reference count classes that are compatible
  40     // with ReftPtr/PassRefPtr but cannot have adoption checks enabled
  41     // by default, such as skia's SkRefCnt. The purpose of requireAdoption()
  42     // is to enable adoption checks only once it is known that the object will
  43     // be used with RefPtr/PassRefPtr.
  44     inline void requireAdoption(const void*) { }
  45
  46     template<typename T> ALWAYS_INLINE void refIfNotNull(T* ptr)
  47     {
  48         if (LIKELY(ptr != 0)) {
  49             requireAdoption(ptr);
  50             ptr->ref();
  51         }
  52     }
  53
  54     template<typename T> ALWAYS_INLINE void derefIfNotNull(T* ptr)
  55     {
  56         if (LIKELY(ptr != 0))
  57             ptr->deref();
  58     }
  59
  60     template<typename T> class PassRefPtr {
  61     public:
  62         PassRefPtr() : m_ptr(0) { }
  63         PassRefPtr(std::nullptr_t) : m_ptr(0) { }
  64         PassRefPtr(T* ptr) : m_ptr(ptr) { refIfNotNull(ptr); }
  65         template<typename U> PassRefPtr(const RawPtr<U>& ptr, EnsurePtrConvertibleArgDecl(U, T)) : m_ptr(ptr.get()) { refIfNotNull(m_ptr); }
  66         explicit PassRefPtr(T& ptr) : m_ptr(&ptr) { m_ptr->ref(); }
  67         // It somewhat breaks the type system to allow transfer of ownership out of
  68         // a const PassRefPtr. However, it makes it much easier to work with PassRefPtr
  69         // temporaries, and we don't have a need to use real const PassRefPtrs anyway.
  70         PassRefPtr(const PassRefPtr& o) : m_ptr(o.leakRef()) { }
  71         template<typename U> PassRefPtr(const PassRefPtr<U>& o, EnsurePtrConvertibleArgDecl(U, T)) : m_ptr(o.leakRef()) { }
  72
  73         ALWAYS_INLINE ~PassRefPtr() { derefIfNotNull(m_ptr); }
  74
  75         template<typename U> PassRefPtr(const RefPtr<U>&, EnsurePtrConvertibleArgDecl(U, T));
  76
  77         T* get() const { return m_ptr; }
  78
  79         T* leakRef() const WARN_UNUSED_RETURN;
  80
  81         T& operator*() const { return *m_ptr; }
  82         T* operator->() const { return m_ptr; }
  83
  84         bool operator!() const { return !m_ptr; }
  85
  86         // This conversion operator allows implicit conversion to bool but not to other integer types.
  87         typedef T* (PassRefPtr::*UnspecifiedBoolType);
  88         operator UnspecifiedBoolType() const { return m_ptr ? &PassRefPtr::m_ptr : 0; }
  89
  90         friend PassRefPtr adoptRef<T>(T*);
  91
  92     private:
  93         enum AdoptRefTag { AdoptRef };
  94         PassRefPtr(T* ptr, AdoptRefTag) : m_ptr(ptr) { }
  95
  96         PassRefPtr& operator=(const PassRefPtr&) { static_assert(!sizeof(T*), "PassRefPtr should never be assigned to"); return *this; }
  97
  98         mutable T* m_ptr;
  99     };
 100
 101     template<typename T> template<typename U> inline PassRefPtr<T>::PassRefPtr(const RefPtr<U>& o, EnsurePtrConvertibleArgDefn(U, T))
 102         : m_ptr(o.get())
 103     {
 104         T* ptr = m_ptr;
 105         refIfNotNull(ptr);
 106     }
 107
 108     template<typename T> inline T* PassRefPtr<T>::leakRef() const
 109     {
 110         T* ptr = m_ptr;
 111         m_ptr = 0;
 112         return ptr;
 113     }
 114
 115     template<typename T, typename U> inline bool operator==(const PassRefPtr<T>& a, const PassRefPtr<U>& b)
 116     {
 117         return a.get() == b.get();
 118     }
 119
 120     template<typename T, typename U> inline bool operator==(const PassRefPtr<T>& a, const RefPtr<U>& b)
 121     {
 122         return a.get() == b.get();
 123     }
 124
 125     template<typename T, typename U> inline bool operator==(const RefPtr<T>& a, const PassRefPtr<U>& b)
 126     {
 127         return a.get() == b.get();
 128     }
 129
 130     template<typename T, typename U> inline bool operator==(const PassRefPtr<T>& a, U* b)
 131     {
 132         return a.get() == b;
 133     }
 134
 135     template<typename T, typename U> inline bool operator==(T* a, const PassRefPtr<U>& b)
 136     {
 137         return a == b.get();
 138     }
 139
 140     template<typename T, typename U> inline bool operator==(const PassRefPtr<T>& a, const RawPtr<U>& b)
 141     {
 142         return a.get() == b.get();
 143     }
 144
 145     template<typename T, typename U> inline bool operator==(const RawPtr<T>& a, const PassRefPtr<U>& b)
 146     {
 147         return a.get() == b.get();
 148     }
 149
 150     template<typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, const PassRefPtr<U>& b)
 151     {
 152         return a.get() != b.get();
 153     }
 154
 155     template<typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, const RefPtr<U>& b)
 156     {
 157         return a.get() != b.get();
 158     }
 159
 160     template<typename T, typename U> inline bool operator!=(const RefPtr<T>& a, const PassRefPtr<U>& b)
 161     {
 162         return a.get() != b.get();
 163     }
 164
 165     template<typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, U* b)
 166     {
 167         return a.get() != b;
 168     }
 169
 170     template<typename T, typename U> inline bool operator!=(T* a, const PassRefPtr<U>& b)
 171     {
 172         return a != b.get();
 173     }
 174
 175     template<typename T, typename U> inline bool operator!=(const PassRefPtr<T>& a, const RawPtr<U>& b)
 176     {
 177         return a.get() != b.get();
 178     }
 179
 180     template<typename T, typename U> inline bool operator!=(const RawPtr<T>& a, const PassRefPtr<U>& b)
 181     {
 182         return a.get() != b.get();
 183     }
 184
 185     template<typename T> PassRefPtr<T> adoptRef(T* p)
 186     {
 187         adopted(p);
 188         return PassRefPtr<T>(p, PassRefPtr<T>::AdoptRef);
 189     }
 190
 191     template<typename T, typename U> inline PassRefPtr<T> static_pointer_cast(const PassRefPtr<U>& p)
 192     {
 193         return adoptRef(static_cast<T*>(p.leakRef()));
 194     }
 195
 196     template<typename T> inline T* getPtr(const PassRefPtr<T>& p)
 197     {
 198         return p.get();
 199     }
 200
 201 } // namespace WTF
 202
 203 using WTF::PassRefPtr;
 204 using WTF::adoptRef;
 205 using WTF::static_pointer_cast;
 206
 207 #endif // WTF_PassRefPtr_h