# gdcmObject.h

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    00001 /*=========================================================================
    00002
    00003   Program: GDCM (Grassroots DICOM). A DICOM library
    00004   Module:  $URL$
    00005
    00006   Copyright (c) 2006-2009 Mathieu Malaterre
    00007   All rights reserved.
    00008   See Copyright.txt or http://gdcm.sourceforge.net/Copyright.html for details.
    00009
    00010      This software is distributed WITHOUT ANY WARRANTY; without even
    00011      the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
    00012      PURPOSE.  See the above copyright notice for more information.
    00013
    00014 =========================================================================*/
    00015 #ifndef __gdcmObject_h
    00016 #define __gdcmObject_h
    00017
    00018 #include "gdcmTypes.h"
    00019
    00020 #include <assert.h>
    00021 #include <iostream> // grrrr
    00022
    00023 //namespace std { class ostream; }
    00024 namespace gdcm
    00025 {
    00026
    00027 template<class ObjectType> class SmartPointer;
    00028
    00037 class GDCM_EXPORT Object
    00038 {
    00039   template <class ObjectType> friend class SmartPointer;
    00040   friend std::ostream& operator<<(std::ostream &os, const Object &obj);
    00041
    00042 public:
    00043   Object():ReferenceCount(0) {}
    00044
    00045   // Implementation note:
    00046   // If I move ~Object in the protected section I can prevent people
    00047   // from writing:
    00048   // SmartPointer<Object> p = new Object;
    00049   // delete p; // due to SmartPointer::operator ObjectType * () const
    00050   // but on the other hand one could not define an Object on the stack
    00051   // Object obj;
    00052   // Furthermore it would not prevent anyone from doing:
    00053   // class MyObject : public Object {};
    00054   // SmartPointer<MyObject> o = new MyObject;
    00055   // delete o; // grrrrrr
    00056   virtual ~Object() {
    00057     // If your debugger reach here it means you are doing something silly
    00058     // like using SmartPointer on object allocated on the stack (vs heap)
    00059     assert(ReferenceCount == 0);
    00060     }
    00061
    00062   // http://www.parashift.com/c++-faq-lite/freestore-mgmt.html#faq-16.24
    00063   // Set the ref count to 0
    00064   // Do NOT copy the reference count !
    00066   Object(const Object&):ReferenceCount(0){}
    00067   void operator=(const Object&){}
    00068
    00069   //static Object* New() { return new Object; }
    00070
    00071 protected:
    00072   // For the purpose of the invasive SmartPointer implementation
    00073   void Register() {
    00074     ReferenceCount++;
    00075     assert( ReferenceCount > 0 );
    00076   }
    00077   void UnRegister() {
    00078     assert( ReferenceCount > 0 );
    00079     ReferenceCount--;
    00080     if(!ReferenceCount)
    00081       {
    00082       delete this;
    00083       }
    00084     }
    00085
    00086 public:
    00087   // For dealing with printing of object and polymorphism
    00088   virtual void Print(std::ostream &) const {}
    00089
    00090 private:
    00091   long ReferenceCount;
    00092 };
    00093
    00094 //----------------------------------------------------------------------------
    00095 // function do not carry vtable. Thus define in the base class the operator
    00096 // and use the member function ->Print() to call the appropriate function
    00097 // NOTE: All subclass of Object needs to implement the Print function
    00098 inline std::ostream& operator<<(std::ostream &os, const Object &obj)
    00099 {
    00100   obj.Print(os);
    00101   return os;
    00102 }
    00103
    00104 } // end namespace gdcm
    00105
    00106 #endif //__gdcmObject_h
    00107