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      1 /*
      2  * Copyright (C) 2014 Google 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 are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef WTF_RawPtr_h
     32 #define WTF_RawPtr_h
     33 
     34 #include <algorithm>
     35 #include <stdint.h>
     36 
     37 #include "wtf/HashTableDeletedValueType.h"
     38 
     39 // RawPtr is a simple wrapper for a raw pointer that provides the
     40 // interface (get, clear) of other pointer types such as RefPtr,
     41 // Persistent and Member. This is used for the Blink garbage
     42 // collection work in order to be able to write shared code that will
     43 // use reference counting or garbage collection based on a
     44 // compile-time flag.
     45 
     46 namespace WTF {
     47 
     48 template<typename T>
     49 class RawPtr {
     50     WTF_DISALLOW_CONSTRUCTION_FROM_ZERO(RawPtr);
     51     WTF_DISALLOW_ZERO_ASSIGNMENT(RawPtr);
     52 public:
     53     RawPtr()
     54     {
     55 #if ENABLE(ASSERT)
     56         m_ptr = reinterpret_cast<T*>(rawPtrZapValue);
     57 #endif
     58     }
     59     RawPtr(std::nullptr_t) : m_ptr(0) { }
     60     RawPtr(T* ptr) : m_ptr(ptr) { }
     61     explicit RawPtr(T& reference) : m_ptr(&reference) { }
     62     RawPtr(const RawPtr& other)
     63         : m_ptr(other.get())
     64     {
     65     }
     66 
     67     template<typename U>
     68     RawPtr(const RawPtr<U>& other)
     69         : m_ptr(other.get())
     70     {
     71     }
     72 
     73     // Hash table deleted values, which are only constructed and never copied or destroyed.
     74     RawPtr(HashTableDeletedValueType) : m_ptr(hashTableDeletedValue()) { }
     75     bool isHashTableDeletedValue() const { return m_ptr == hashTableDeletedValue(); }
     76 
     77     T* get() const { return m_ptr; }
     78     void clear() { m_ptr = 0; }
     79     // FIXME: oilpan: Remove release and leakRef once we remove RefPtrWillBeRawPtr.
     80     RawPtr<T> release()
     81     {
     82         RawPtr<T> tmp = m_ptr;
     83         m_ptr = 0;
     84         return tmp;
     85     }
     86     T* leakRef()
     87     {
     88         T* ptr = m_ptr;
     89         m_ptr = 0;
     90         return ptr;
     91     }
     92     T* leakPtr()
     93     {
     94         T* ptr = m_ptr;
     95         m_ptr = 0;
     96         return ptr;
     97     }
     98 
     99     template<typename U>
    100     RawPtr& operator=(U* ptr)
    101     {
    102         m_ptr = ptr;
    103         return *this;
    104     }
    105 
    106     template<typename U>
    107     RawPtr& operator=(RawPtr<U> ptr)
    108     {
    109         m_ptr = ptr.get();
    110         return *this;
    111     }
    112 
    113     RawPtr& operator=(std::nullptr_t)
    114     {
    115         m_ptr = 0;
    116         return *this;
    117     }
    118 
    119     operator T*() const { return m_ptr; }
    120     T& operator*() const { return *m_ptr; }
    121     T* operator->() const { return m_ptr; }
    122     bool operator!() const { return !m_ptr; }
    123 
    124     void swap(RawPtr& o)
    125     {
    126         std::swap(m_ptr, o.m_ptr);
    127     }
    128 
    129     static T* hashTableDeletedValue() { return reinterpret_cast<T*>(-1); }
    130 
    131 private:
    132     static const uintptr_t rawPtrZapValue = 0x3a3a3a3a;
    133     T* m_ptr;
    134 };
    135 
    136 template<typename T, typename U> inline RawPtr<T> static_pointer_cast(const RawPtr<U>& p)
    137 {
    138     return RawPtr<T>(static_cast<T*>(p.get()));
    139 }
    140 
    141 template<typename T> inline T* getPtr(const RawPtr<T>& p)
    142 {
    143     return p.get();
    144 }
    145 
    146 } // namespace WTF
    147 
    148 using WTF::RawPtr;
    149 
    150 #endif
    151