Cracking the Coding Interview - Fooo

13 9 Write a smart pointer (smart_ptr) class
SOLUTION
Solutions to Chapter 13 | C++
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pg 76
Smart_ptr is the same as a normal pointer, but it provides safety via automatic memory It
avoids dangling pointers, memory leaks, allocation failures etc The smart pointer must maintain
a single reference count for all instances
1 template class SmartPointer {
2 public:
3 SmartPointer(T * ptr) {
4 ref = ptr;
5 ref_count = (unsigned*)malloc(sizeof(unsigned));
6 *ref_count = 1;
7 }
8 SmartPointer(SmartPointer & sptr) {
9 ref = sptr.ref;
10 ref_count = sptr.ref_count;
11 ++*ref_count;
12 }
13 SmartPointer & operator=(SmartPointer & sptr) {
14 if (this != &sptr) {
15 ref = sptr.ref;
16 ref_count = sptr.ref_count;
17 ++*ref_count;
18 }
19 return *this;
20 }
21 ~SmartPointer() {
22 --*ref_count;
23 if (*ref_count == 0) {
24 delete ref;
25 free(ref_count);
26 ref = NULL;
27 ref_count = NULL;
28 }
29 }
30 T getValue() { return *ref; }
31 protected:
32 T * ref;
33 unsigned * ref_count;
34 };
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