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gdcmObject.h
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1 /*=========================================================================
2
3 Program: GDCM (Grassroots DICOM). A DICOM library
4
5 Copyright (c) 2006-2011 Mathieu Malaterre
6 All rights reserved.
7 See Copyright.txt or http://gdcm.sourceforge.net/Copyright.html for details.
8
9 This software is distributed WITHOUT ANY WARRANTY; without even
10 the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
11 PURPOSE. See the above copyright notice for more information.
12
13 =========================================================================*/
14 #ifndef GDCMOBJECT_H
15 #define GDCMOBJECT_H
16
17 #include "gdcmTypes.h"
18
19 #include <assert.h>
20 #include <iostream> // grrrr
21
22 //namespace std { class ostream; }
23 namespace gdcm
24 {
25
26 template<class ObjectType> class SmartPointer;
27
36 class GDCM_EXPORT Object
37 {
38 template <class ObjectType> friend class SmartPointer;
39 friend std::ostream& operator<<(std::ostream &os, const Object &obj);
40
41 public:
42 Object():ReferenceCount(0) {}
43
44 // Implementation note:
45 // If I move ~Object in the protected section I can prevent people
46 // from writing:
47 // SmartPointer<Object> p = new Object;
48 // delete p; // due to SmartPointer::operator ObjectType * () const
49 // but on the other hand one could not define an Object on the stack
50 // Object obj;
51 // Furthermore it would not prevent anyone from doing:
52 // class MyObject : public Object {};
53 // SmartPointer<MyObject> o = new MyObject;
54 // delete o; // grrrrrr
55 virtual ~Object() {
56 // If your debugger reach here it means you are doing something silly
57 // like using SmartPointer on object allocated on the stack (vs heap)
58 assert(ReferenceCount == 0);
59 }
60
61 // http://www.parashift.com/c++-faq-lite/freestore-mgmt.html#faq-16.24
62 // Set the ref count to 0
63 // Do NOT copy the reference count !
65 Object(const Object&):ReferenceCount(0){}
66 void operator=(const Object&){}
67
68 //static Object* New() { return new Object; }
69
70 protected:
71 // For the purpose of the invasive SmartPointer implementation
72 void Register() {
73 ReferenceCount++;
74 assert( ReferenceCount > 0 );
75 }
76 void UnRegister() {
77 assert( ReferenceCount > 0 );
78 ReferenceCount--;
79 if(!ReferenceCount)
80 {
81 delete this;
82 }
83 }
84
85 public:
86 // For dealing with printing of object and polymorphism
87 virtual void Print(std::ostream &) const {}
88
89 private:
90 long ReferenceCount;
91 };
92
93 //----------------------------------------------------------------------------
94 // function do not carry vtable. Thus define in the base class the operator
95 // and use the member function ->Print() to call the appropriate function
96 // NOTE: All subclass of Object needs to implement the Print function
97 inline std::ostream& operator<<(std::ostream &os, const Object &obj)
98 {
99 obj.Print(os);
100 return os;
101 }
102
103 } // end namespace gdcm
104
105 #endif //GDCMOBJECT_H