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      1 /*
      2  * Copyright (C) 2010 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 WebPrivatePtr_h
     32 #define WebPrivatePtr_h
     33 
     34 #include "WebCommon.h"
     35 
     36 #if INSIDE_BLINK
     37 #include "wtf/PassRefPtr.h"
     38 #endif
     39 
     40 namespace blink {
     41 
     42 // This class is an implementation detail of the WebKit API.  It exists
     43 // to help simplify the implementation of WebKit interfaces that merely
     44 // wrap a reference counted WebCore class.
     45 //
     46 // A typical implementation of a class which uses WebPrivatePtr might look like
     47 // this:
     48 //    class WebFoo {
     49 //    public:
     50 //        virtual ~WebFoo() { }  // Only necessary if WebFoo will be used as a
     51 //                               // base class.
     52 //        WebFoo() { }
     53 //        WebFoo(const WebFoo& other) { assign(other); }
     54 //        WebFoo& operator=(const WebFoo& other)
     55 //        {
     56 //            assign(other);
     57 //            return *this;
     58 //        }
     59 //        BLINK_EXPORT void assign(const WebFoo&);  // Implemented in the body.
     60 //
     61 //        // Methods that are exposed to Chromium and which are specific to
     62 //        // WebFoo go here.
     63 //        BLINK_EXPORT doWebFooThing();
     64 //
     65 //        // Methods that are used only by other WebKit/chromium API classes
     66 //        // should only be declared when INSIDE_BLINK is set.
     67 //    #if INSIDE_BLINK
     68 //        WebFoo(const WTF::PassRefPtr<WebCore::Foo>&);
     69 //    #endif
     70 //
     71 //    private:
     72 //        WebPrivatePtr<WebCore::Foo> m_private;
     73 //    };
     74 //
     75 template <typename T>
     76 class WebPrivatePtr {
     77 public:
     78     WebPrivatePtr() : m_ptr(0) { }
     79     ~WebPrivatePtr() { BLINK_ASSERT(!m_ptr); }
     80 
     81     bool isNull() const { return !m_ptr; }
     82 
     83 #if INSIDE_BLINK
     84     WebPrivatePtr(const PassRefPtr<T>& prp)
     85         : m_ptr(prp.leakRef())
     86     {
     87     }
     88 
     89     void reset()
     90     {
     91         assign(0);
     92     }
     93 
     94     WebPrivatePtr<T>& operator=(const WebPrivatePtr<T>& other)
     95     {
     96         T* p = other.m_ptr;
     97         if (p)
     98             p->ref();
     99         assign(p);
    100         return *this;
    101     }
    102 
    103     WebPrivatePtr<T>& operator=(const PassRefPtr<T>& prp)
    104     {
    105         assign(prp.leakRef());
    106         return *this;
    107     }
    108 
    109     T* get() const
    110     {
    111         return m_ptr;
    112     }
    113 
    114     T* operator->() const
    115     {
    116         ASSERT(m_ptr);
    117         return m_ptr;
    118     }
    119 #endif
    120 
    121 private:
    122 #if INSIDE_BLINK
    123     void assign(T* p)
    124     {
    125         // p is already ref'd for us by the caller
    126         if (m_ptr)
    127             m_ptr->deref();
    128         m_ptr = p;
    129     }
    130 #else
    131     // Disable the assignment operator; we define it above for when
    132     // INSIDE_BLINK is set, but we need to make sure that it is not
    133     // used outside there; the compiler-provided version won't handle reference
    134     // counting properly.
    135     WebPrivatePtr<T>& operator=(const WebPrivatePtr<T>& other);
    136 #endif
    137     // Disable the copy constructor; classes that contain a WebPrivatePtr
    138     // should implement their copy constructor using assign().
    139     WebPrivatePtr(const WebPrivatePtr<T>&);
    140 
    141     T* m_ptr;
    142 };
    143 
    144 } // namespace blink
    145 
    146 #endif
    147