-
Notifications
You must be signed in to change notification settings - Fork 1
/
p444 ScreenPtr.cpp
47 lines (38 loc) · 1.28 KB
/
p444 ScreenPtr.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
//
#include <cstddef>
using std::size_t;
//#include "screen5.h"
//private class for use by ScreenPtr only
class ScrPtr {
friend class ScreenPtr;
Screen *sp;
size_t use;
ScrPtr(Screen *p): sp(p), use(1) { }
~ScrPtr() { delete sp; }
};
class ScreenPtr {
public:
// no default constructor: ScreenPtrs must be bound to an object
ScreenPtr(Screen *p): ptr(new ScrPtr(p)) { }
// copy members and increment the use count
ScreenPtr(const ScreenPtr &orig):
ptr(orig.ptr) { ++ptr->use; }
ScreenPtr& operator=(const ScreenPtr&);
// if use count goes to zero, delete the ScrPtr object
~ScreenPtr() { if (--ptr->use == 0) delete ptr; }
// constructor and copy control members as before
Screen &operator*() { return *ptr->sp; }
Screen *operator->() { return ptr->sp; }
const Screen &operator*() const { return *ptr->sp; }
const Screen *operator->() const { return ptr->sp; }
private:
ScrPtr *ptr; // points to use-counted ScrPtr class
};
ScreenPtr& ScreenPtr::operator=(const ScreenPtr &rhs)
{
++rhs.ptr->use; // increment use count on rhs first
if (--ptr->use == 0)
delete ptr; // if use count goes to 0 on this object, delete it
ptr = rhs.ptr; // copy the ScrPtr object
return *this;
}