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      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 "wtf/Assertions.h"
     30 #include "wtf/NullPtr.h"
     31 #include "wtf/OwnPtrCommon.h"
     32 #include "wtf/TypeTraits.h"
     33 
     34 namespace WTF {
     35 
     36     // Unlike most of our smart pointers, PassOwnPtr can take either the pointer type or the pointed-to type.
     37 
     38     template<typename T> class OwnPtr;
     39     template<typename T> class PassOwnPtr;
     40     template<typename T> PassOwnPtr<T> adoptPtr(T*);
     41 
     42     template<typename T> class PassOwnPtr {
     43         WTF_DISALLOW_CONSTRUCTION_FROM_ZERO(PassOwnPtr);
     44     public:
     45         typedef typename RemovePointer<T>::Type ValueType;
     46         typedef ValueType* PtrType;
     47 
     48         PassOwnPtr() : m_ptr(0) { }
     49         PassOwnPtr(std::nullptr_t) : m_ptr(0) { }
     50 
     51         // It somewhat breaks the type system to allow transfer of ownership out of
     52         // a const PassOwnPtr. However, it makes it much easier to work with PassOwnPtr
     53         // temporaries, and we don't have a need to use real const PassOwnPtrs anyway.
     54         PassOwnPtr(const PassOwnPtr& o) : m_ptr(o.leakPtr()) { }
     55         template<typename U> PassOwnPtr(const PassOwnPtr<U>& o) : m_ptr(o.leakPtr()) { }
     56 
     57         ~PassOwnPtr() { deleteOwnedPtr(m_ptr); }
     58 
     59         PtrType get() const { return m_ptr; }
     60 
     61         PtrType leakPtr() const WARN_UNUSED_RETURN;
     62 
     63         ValueType& operator*() const { ASSERT(m_ptr); return *m_ptr; }
     64         PtrType operator->() const { ASSERT(m_ptr); return m_ptr; }
     65 
     66         bool operator!() const { return !m_ptr; }
     67 
     68         // This conversion operator allows implicit conversion to bool but not to other integer types.
     69         typedef PtrType PassOwnPtr::*UnspecifiedBoolType;
     70         operator UnspecifiedBoolType() const { return m_ptr ? &PassOwnPtr::m_ptr : 0; }
     71 
     72         PassOwnPtr& operator=(const PassOwnPtr&) { COMPILE_ASSERT(!sizeof(T*), PassOwnPtr_should_never_be_assigned_to); return *this; }
     73 
     74         template<typename U> friend PassOwnPtr<U> adoptPtr(U*);
     75 
     76     private:
     77         explicit PassOwnPtr(PtrType ptr) : m_ptr(ptr) { }
     78 
     79         // We should never have two OwnPtrs for the same underlying object (otherwise we'll get
     80         // double-destruction), so these equality operators should never be needed.
     81         template<typename U> bool operator==(const PassOwnPtr<U>&) { COMPILE_ASSERT(!sizeof(U*), OwnPtrs_should_never_be_equal); return false; }
     82         template<typename U> bool operator!=(const PassOwnPtr<U>&) { COMPILE_ASSERT(!sizeof(U*), OwnPtrs_should_never_be_equal); return false; }
     83         template<typename U> bool operator==(const OwnPtr<U>&) { COMPILE_ASSERT(!sizeof(U*), OwnPtrs_should_never_be_equal); return false; }
     84         template<typename U> bool operator!=(const OwnPtr<U>&) { COMPILE_ASSERT(!sizeof(U*), OwnPtrs_should_never_be_equal); return false; }
     85 
     86         mutable PtrType m_ptr;
     87     };
     88 
     89     template<typename T> inline typename PassOwnPtr<T>::PtrType PassOwnPtr<T>::leakPtr() const
     90     {
     91         PtrType ptr = m_ptr;
     92         m_ptr = 0;
     93         return ptr;
     94     }
     95 
     96     template<typename T, typename U> inline bool operator==(const PassOwnPtr<T>& a, const PassOwnPtr<U>& b)
     97     {
     98         return a.get() == b.get();
     99     }
    100 
    101     template<typename T, typename U> inline bool operator==(const PassOwnPtr<T>& a, const OwnPtr<U>& b)
    102     {
    103         return a.get() == b.get();
    104     }
    105 
    106     template<typename T, typename U> inline bool operator==(const OwnPtr<T>& a, const PassOwnPtr<U>& b)
    107     {
    108         return a.get() == b.get();
    109     }
    110 
    111     template<typename T, typename U> inline bool operator==(const PassOwnPtr<T>& a, U* b)
    112     {
    113         return a.get() == b;
    114     }
    115 
    116     template<typename T, typename U> inline bool operator==(T* a, const PassOwnPtr<U>& b)
    117     {
    118         return a == b.get();
    119     }
    120 
    121     template<typename T, typename U> inline bool operator!=(const PassOwnPtr<T>& a, const PassOwnPtr<U>& b)
    122     {
    123         return a.get() != b.get();
    124     }
    125 
    126     template<typename T, typename U> inline bool operator!=(const PassOwnPtr<T>& a, const OwnPtr<U>& b)
    127     {
    128         return a.get() != b.get();
    129     }
    130 
    131     template<typename T, typename U> inline bool operator!=(const OwnPtr<T>& a, const PassOwnPtr<U>& b)
    132     {
    133         return a.get() != b.get();
    134     }
    135 
    136     template<typename T, typename U> inline bool operator!=(const PassOwnPtr<T>& a, U* b)
    137     {
    138         return a.get() != b;
    139     }
    140 
    141     template<typename T, typename U> inline bool operator!=(T* a, const PassOwnPtr<U>& b)
    142     {
    143         return a != b.get();
    144     }
    145 
    146     template<typename T> inline PassOwnPtr<T> adoptPtr(T* ptr)
    147     {
    148         return PassOwnPtr<T>(ptr);
    149     }
    150 
    151     template<typename T, typename U> inline PassOwnPtr<T> static_pointer_cast(const PassOwnPtr<U>& p)
    152     {
    153         return adoptPtr(static_cast<T*>(p.leakPtr()));
    154     }
    155 
    156     template<typename T, typename U> inline PassOwnPtr<T> const_pointer_cast(const PassOwnPtr<U>& p)
    157     {
    158         return adoptPtr(const_cast<T*>(p.leakPtr()));
    159     }
    160 
    161     template<typename T> inline T* getPtr(const PassOwnPtr<T>& p)
    162     {
    163         return p.get();
    164     }
    165 
    166 } // namespace WTF
    167 
    168 using WTF::PassOwnPtr;
    169 using WTF::adoptPtr;
    170 using WTF::const_pointer_cast;
    171 using WTF::static_pointer_cast;
    172 
    173 #endif // WTF_PassOwnPtr_h
    174