wtf/PassOwnPtr.h

   1 /*
   2  * Copyright (C) 2009, 2010 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 WTF_PassOwnPtr_h
  27 #define WTF_PassOwnPtr_h
  28
  29 #include "Assertions.h"
  30 #include "NullPtr.h"
  31 #include "OwnPtrCommon.h"
  32 #include "TypeTraits.h"
  33
  34 #if !PLATFORM(CHROMIUM) && !PLATFORM(WIN) && !PLATFORM(MAC) && !PLATFORM(QT)
  35 // Remove this once we make all WebKit code compatible with stricter rules about PassOwnPtr.
  36 #define LOOSE_PASS_OWN_PTR
  37 #endif
  38
  39 namespace WTF {
  40
  41     // Unlike most of our smart pointers, PassOwnPtr can take either the pointer type or the pointed-to type.
  42
  43     template<typename T> class OwnPtr;
  44     template<typename T> class PassOwnPtr;
  45     template<typename T> PassOwnPtr<T> adoptPtr(T*);
  46
  47     template<typename T> class PassOwnPtr {
  48     public:
  49         typedef typename RemovePointer<T>::Type ValueType;
  50         typedef ValueType* PtrType;
  51
  52         PassOwnPtr() : m_ptr(0) { }
  53         PassOwnPtr(std::nullptr_t) : m_ptr(0) { }
  54
  55         // It somewhat breaks the type system to allow transfer of ownership out of
  56         // a const PassOwnPtr. However, it makes it much easier to work with PassOwnPtr
  57         // temporaries, and we don't have a need to use real const PassOwnPtrs anyway.
  58         PassOwnPtr(const PassOwnPtr& o) : m_ptr(o.leakPtr()) { }
  59         template<typename U> PassOwnPtr(const PassOwnPtr<U>& o) : m_ptr(o.leakPtr()) { }
  60
  61         ~PassOwnPtr() { deleteOwnedPtr(m_ptr); }
  62
  63         PtrType get() const { return m_ptr; }
  64
  65         void clear();
  66         PtrType leakPtr() const WARN_UNUSED_RETURN;
  67
  68         ValueType& operator*() const { ASSERT(m_ptr); return *m_ptr; }
  69         PtrType operator->() const { ASSERT(m_ptr); return m_ptr; }
  70
  71         bool operator!() const { return !m_ptr; }
  72
  73         // This conversion operator allows implicit conversion to bool but not to other integer types.
  74         typedef PtrType PassOwnPtr::*UnspecifiedBoolType;
  75         operator UnspecifiedBoolType() const { return m_ptr ? &PassOwnPtr::m_ptr : 0; }
  76
  77         PassOwnPtr& operator=(const PassOwnPtr<T>&);
  78 #if !defined(LOOSE_PASS_OWN_PTR) || !HAVE(NULLPTR)
  79         PassOwnPtr& operator=(std::nullptr_t) { clear(); return *this; }
  80 #endif
  81         template<typename U> PassOwnPtr& operator=(const PassOwnPtr<U>&);
  82
  83         template<typename U> friend PassOwnPtr<U> adoptPtr(U*);
  84
  85 #ifdef LOOSE_PASS_OWN_PTR
  86         PassOwnPtr(PtrType ptr) : m_ptr(ptr) { }
  87         PassOwnPtr& operator=(PtrType);
  88 #endif
  89
  90     private:
  91 #ifndef LOOSE_PASS_OWN_PTR
  92         explicit PassOwnPtr(PtrType ptr) : m_ptr(ptr) { }
  93 #endif
  94
  95         // We should never have two OwnPtrs for the same underlying object (otherwise we'll get
  96         // double-destruction), so these equality operators should never be needed.
  97         template<typename U> bool operator==(const PassOwnPtr<U>&) { COMPILE_ASSERT(!sizeof(U*), OwnPtrs_should_never_be_equal); return false; }
  98         template<typename U> bool operator!=(const PassOwnPtr<U>&) { COMPILE_ASSERT(!sizeof(U*), OwnPtrs_should_never_be_equal); return false; }
  99         template<typename U> bool operator==(const OwnPtr<U>&) { COMPILE_ASSERT(!sizeof(U*), OwnPtrs_should_never_be_equal); return false; }
 100         template<typename U> bool operator!=(const OwnPtr<U>&) { COMPILE_ASSERT(!sizeof(U*), OwnPtrs_should_never_be_equal); return false; }
 101
 102         mutable PtrType m_ptr;
 103     };
 104
 105     template<typename T> inline void PassOwnPtr<T>::clear()
 106     {
 107         PtrType ptr = m_ptr;
 108         m_ptr = 0;
 109         deleteOwnedPtr(ptr);
 110     }
 111
 112     template<typename T> inline typename PassOwnPtr<T>::PtrType PassOwnPtr<T>::leakPtr() const
 113     {
 114         PtrType ptr = m_ptr;
 115         m_ptr = 0;
 116         return ptr;
 117     }
 118
 119 #ifdef LOOSE_PASS_OWN_PTR
 120     template<typename T> inline PassOwnPtr<T>& PassOwnPtr<T>::operator=(PtrType optr)
 121     {
 122         PtrType ptr = m_ptr;
 123         m_ptr = optr;
 124         ASSERT(!ptr || m_ptr != ptr);
 125         if (ptr)
 126             deleteOwnedPtr(ptr);
 127         return *this;
 128     }
 129 #endif
 130
 131     template<typename T> inline PassOwnPtr<T>& PassOwnPtr<T>::operator=(const PassOwnPtr<T>& optr)
 132     {
 133         PtrType ptr = m_ptr;
 134         m_ptr = optr.leakPtr();
 135         ASSERT(!ptr || m_ptr != ptr);
 136         if (ptr)
 137             deleteOwnedPtr(ptr);
 138         return *this;
 139     }
 140
 141     template<typename T> template<typename U> inline PassOwnPtr<T>& PassOwnPtr<T>::operator=(const PassOwnPtr<U>& optr)
 142     {
 143         PtrType ptr = m_ptr;
 144         m_ptr = optr.leakPtr();
 145         ASSERT(!ptr || m_ptr != ptr);
 146         if (ptr)
 147             deleteOwnedPtr(ptr);
 148         return *this;
 149     }
 150
 151     template<typename T, typename U> inline bool operator==(const PassOwnPtr<T>& a, const PassOwnPtr<U>& b)
 152     {
 153         return a.get() == b.get();
 154     }
 155
 156     template<typename T, typename U> inline bool operator==(const PassOwnPtr<T>& a, const OwnPtr<U>& b)
 157     {
 158         return a.get() == b.get();
 159     }
 160
 161     template<typename T, typename U> inline bool operator==(const OwnPtr<T>& a, const PassOwnPtr<U>& b)
 162     {
 163         return a.get() == b.get();
 164     }
 165
 166     template<typename T, typename U> inline bool operator==(const PassOwnPtr<T>& a, U* b)
 167     {
 168         return a.get() == b;
 169     }
 170
 171     template<typename T, typename U> inline bool operator==(T* a, const PassOwnPtr<U>& b)
 172     {
 173         return a == b.get();
 174     }
 175
 176     template<typename T, typename U> inline bool operator!=(const PassOwnPtr<T>& a, const PassOwnPtr<U>& b)
 177     {
 178         return a.get() != b.get();
 179     }
 180
 181     template<typename T, typename U> inline bool operator!=(const PassOwnPtr<T>& a, const OwnPtr<U>& b)
 182     {
 183         return a.get() != b.get();
 184     }
 185
 186     template<typename T, typename U> inline bool operator!=(const OwnPtr<T>& a, const PassOwnPtr<U>& b)
 187     {
 188         return a.get() != b.get();
 189     }
 190
 191     template<typename T, typename U> inline bool operator!=(const PassOwnPtr<T>& a, U* b)
 192     {
 193         return a.get() != b;
 194     }
 195
 196     template<typename T, typename U> inline bool operator!=(T* a, const PassOwnPtr<U>& b)
 197     {
 198         return a != b.get();
 199     }
 200
 201     template<typename T> inline PassOwnPtr<T> adoptPtr(T* ptr)
 202     {
 203         return PassOwnPtr<T>(ptr);
 204     }
 205
 206     template<typename T, typename U> inline PassOwnPtr<T> static_pointer_cast(const PassOwnPtr<U>& p)
 207     {
 208         return adoptPtr(static_cast<T*>(p.leakPtr()));
 209     }
 210
 211     template<typename T, typename U> inline PassOwnPtr<T> const_pointer_cast(const PassOwnPtr<U>& p)
 212     {
 213         return adoptPtr(const_cast<T*>(p.leakPtr()));
 214     }
 215
 216     template<typename T> inline T* getPtr(const PassOwnPtr<T>& p)
 217     {
 218         return p.get();
 219     }
 220
 221 } // namespace WTF
 222
 223 using WTF::PassOwnPtr;
 224 using WTF::adoptPtr;
 225 using WTF::const_pointer_cast;
 226 using WTF::static_pointer_cast;
 227
 228 #endif // WTF_PassOwnPtr_h