LiteSQL
counted_ptr.hpp
1 /*
2  * counted_ptr - simple reference counted pointer.
3  *
4  * The is a non-intrusive implementation that allocates an additional
5  * int and pointer for every counted object.
6  */
7 
8 #ifndef COUNTED_PTR_HPP
9 #define COUNTED_PTR_HPP
10 
11 /* For ANSI-challenged compilers, you may want to #define
12  * NO_MEMBER_TEMPLATES or explicit */
13 
14 template <class X> class counted_ptr
15 {
16 public:
17  typedef X element_type;
18 
19  explicit counted_ptr(X* p = 0) // allocate a new counter
20  : itsCounter(0) {if (p) itsCounter = new counter(p);}
21  ~counted_ptr()
22  {release();}
23  counted_ptr(const counted_ptr& r) throw()
24  {acquire(r.itsCounter);}
25  counted_ptr& operator=(const counted_ptr& r)
26  {
27  if (this != &r) {
28  release();
29  acquire(r.itsCounter);
30  }
31  return *this;
32  }
33 
34 #ifndef NO_MEMBER_TEMPLATES
35  template <class Y> friend class counted_ptr<Y>;
36  template <class Y> counted_ptr(const counted_ptr<Y>& r) throw()
37  {acquire(r.itsCounter);}
38  template <class Y> counted_ptr& operator=(const counted_ptr<Y>& r)
39  {
40  if (this != &r) {
41  release();
42  acquire(r.itsCounter);
43  }
44  return *this;
45  }
46 #endif // NO_MEMBER_TEMPLATES
47 
48  X& operator*() const throw() {return *itsCounter->ptr;}
49  X* operator->() const throw() {return itsCounter->ptr;}
50  X* get() const throw() {return itsCounter ? itsCounter->ptr : 0;}
51  bool unique() const throw()
52  {return (itsCounter ? itsCounter->count == 1 : true);}
53 
54 private:
55 
56  struct counter {
57  counter(X* p = 0, unsigned c = 1) : ptr(p), count(c) {}
58  X* ptr;
59  unsigned count;
60  }* itsCounter;
61 
62  void acquire(counter* c) throw()
63  { // increment the count
64  itsCounter = c;
65  if (c) ++c->count;
66  }
67 
68  void release()
69  { // decrement the count, delete if it is 0
70  if (itsCounter) {
71  if (--itsCounter->count == 0) {
72  delete itsCounter->ptr;
73  delete itsCounter;
74  }
75  itsCounter = 0;
76  }
77  }
78 };
79 
80 #endif // COUNTED_PTR_HPP
counted_ptr
Definition: counted_ptr.hpp:15

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