include/AD/generic/ref.h

   1 //////////////////////////////////////////////////////////////////////////////
   2 // NOTICE:
   3 //
   4 // ADLib, Prop and their related set of tools and documentation are in the
   5 // public domain.   The author(s) of this software reserve no copyrights on
   6 // the source code and any code generated using the tools.  You are encouraged
   7 // to use ADLib and Prop to develop software, in both academic and commercial
   8 // settings, and are free to incorporate any part of ADLib and Prop into
   9 // your programs.
  10 //
  11 // Although you are under no obligation to do so, we strongly recommend that
  12 // you give away all software developed using our tools.
  13 //
  14 // We also ask that credit be given to us when ADLib and/or Prop are used in
  15 // your programs, and that this notice be preserved intact in all the source
  16 // code.
  17 //
  18 // This software is still under development and we welcome any suggestions
  19 // and help from the users.
  20 //
  21 // Allen Leung
  22 // 1994
  23 //////////////////////////////////////////////////////////////////////////////
  24
  25 #ifndef reference_counting_pointer_h
  26 #define reference_counting_pointer_h
  27
  28 //
  29 //  Class Ref<Type> takes a pointer to an object and
  30 //  performs transparent reference counting on it.
  31 //  Assignment and initialization will change its reference.
  32 //  When the reference count of the object reaches 0, it
  33 //  will be automatically deleted.
  34 //
  35 //  Warning: circular objects built from this type will be not
  36 //  be reference counted correctly and space leak will result.
  37 //
  38
  39 template<class Type>
  40    class Ref {
  41       Type * object;    // The object itself
  42       int * refCount;   // number of Ref's in existence
  43    public:
  44       Ref(const Ref & r) : object(r.object), refCount(r.refCount)
  45          { ++*refCount; }
  46       Ref(Type * obj) : object(obj), refCount(new int) {}
  47       ~Ref() { if (--(*refCount) == 0) { delete object; delete refCount; }}
  48
  49       Type * operator -> () { return object; }
  50       Type * operator * () { return object; }
  51
  52       Ref& operator = (const Ref& r);
  53    };
  54
  55 template<class Type>
  56    Ref<Type>& Ref<Type>::operator = (const Ref<Type>& r)
  57    {  if (this != &r) {
  58          if (--*refCount == 0) { delete object; delete refCount; }
  59          object = r.object; refCount = r.refCount; ++*refCount;
  60       }
  61       return *this;
  62    }
  63
  64 #endif