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      1 /*
      2  * libjingle
      3  * Copyright 2011, Google Inc.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are met:
      7  *
      8  *  1. Redistributions of source code must retain the above copyright notice,
      9  *     this list of conditions and the following disclaimer.
     10  *  2. Redistributions in binary form must reproduce the above copyright notice,
     11  *     this list of conditions and the following disclaimer in the documentation
     12  *     and/or other materials provided with the distribution.
     13  *  3. The name of the author may not be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 // Originally these classes are from Chromium.
     29 // http://src.chromium.org/viewvc/chrome/trunk/src/base/memory/ref_counted.h?view=markup
     30 
     31 //
     32 // A smart pointer class for reference counted objects.  Use this class instead
     33 // of calling AddRef and Release manually on a reference counted object to
     34 // avoid common memory leaks caused by forgetting to Release an object
     35 // reference.  Sample usage:
     36 //
     37 //   class MyFoo : public RefCounted<MyFoo> {
     38 //    ...
     39 //   };
     40 //
     41 //   void some_function() {
     42 //     scoped_refptr<MyFoo> foo = new MyFoo();
     43 //     foo->Method(param);
     44 //     // |foo| is released when this function returns
     45 //   }
     46 //
     47 //   void some_other_function() {
     48 //     scoped_refptr<MyFoo> foo = new MyFoo();
     49 //     ...
     50 //     foo = NULL;  // explicitly releases |foo|
     51 //     ...
     52 //     if (foo)
     53 //       foo->Method(param);
     54 //   }
     55 //
     56 // The above examples show how scoped_refptr<T> acts like a pointer to T.
     57 // Given two scoped_refptr<T> classes, it is also possible to exchange
     58 // references between the two objects, like so:
     59 //
     60 //   {
     61 //     scoped_refptr<MyFoo> a = new MyFoo();
     62 //     scoped_refptr<MyFoo> b;
     63 //
     64 //     b.swap(a);
     65 //     // now, |b| references the MyFoo object, and |a| references NULL.
     66 //   }
     67 //
     68 // To make both |a| and |b| in the above example reference the same MyFoo
     69 // object, simply use the assignment operator:
     70 //
     71 //   {
     72 //     scoped_refptr<MyFoo> a = new MyFoo();
     73 //     scoped_refptr<MyFoo> b;
     74 //
     75 //     b = a;
     76 //     // now, |a| and |b| each own a reference to the same MyFoo object.
     77 //   }
     78 //
     79 
     80 #ifndef TALK_BASE_SCOPED_REF_PTR_H_
     81 #define TALK_BASE_SCOPED_REF_PTR_H_
     82 
     83 namespace talk_base {
     84 
     85 template <class T>
     86 class scoped_refptr {
     87  public:
     88   scoped_refptr() : ptr_(NULL) {
     89   }
     90 
     91   scoped_refptr(T* p) : ptr_(p) {
     92     if (ptr_)
     93       ptr_->AddRef();
     94   }
     95 
     96   scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
     97     if (ptr_)
     98       ptr_->AddRef();
     99   }
    100 
    101   template <typename U>
    102   scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
    103     if (ptr_)
    104       ptr_->AddRef();
    105   }
    106 
    107   ~scoped_refptr() {
    108     if (ptr_)
    109       ptr_->Release();
    110   }
    111 
    112   T* get() const { return ptr_; }
    113   operator T*() const { return ptr_; }
    114   T* operator->() const { return ptr_; }
    115 
    116   // Release a pointer.
    117   // The return value is the current pointer held by this object.
    118   // If this object holds a NULL pointer, the return value is NULL.
    119   // After this operation, this object will hold a NULL pointer,
    120   // and will not own the object any more.
    121   T* release() {
    122     T* retVal = ptr_;
    123     ptr_ = NULL;
    124     return retVal;
    125   }
    126 
    127   scoped_refptr<T>& operator=(T* p) {
    128     // AddRef first so that self assignment should work
    129     if (p)
    130       p->AddRef();
    131     if (ptr_ )
    132       ptr_ ->Release();
    133     ptr_ = p;
    134     return *this;
    135   }
    136 
    137   scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
    138     return *this = r.ptr_;
    139   }
    140 
    141   template <typename U>
    142   scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
    143     return *this = r.get();
    144   }
    145 
    146   void swap(T** pp) {
    147     T* p = ptr_;
    148     ptr_ = *pp;
    149     *pp = p;
    150   }
    151 
    152   void swap(scoped_refptr<T>& r) {
    153     swap(&r.ptr_);
    154   }
    155 
    156  protected:
    157   T* ptr_;
    158 };
    159 
    160 }  // namespace talk_base
    161 
    162 #endif  // TALK_BASE_SCOPED_REF_PTR_H_
    163