Function Overloading & Default Arguments(Chapter 7 of Thinking in C++)

时间：2010-11-12 来源：Ray Z

Mem.cpp 1 #include "Mem.h"
2 #include <cstring>
3 using namespace std;
4
5 Mem::Mem()
6 {
7     mem = 0;
8     size = 0;
9 }
10
11 Mem::Mem(int sz)
12 {
13     mem = 0;
14     size = 0;
15     ensureMinSize(sz);
16 }
17
18 Mem::~Mem()
19 {
20     delete []mem;
21 }
22
23 int Mem::msize()
24 {
25     return size;
26 }
27
28 void Mem::ensureMinSize(int minSize)
29 {
30     if(size < minSize)
31     {
32         byte* newmem = new byte[minSize];
33         memset(newmem+size, 0, minSize - size);
34         memcpy(newmem, mem, size);
35
36         delete []mem;
37         mem = newmem;
38         size = minSize;
39     }
40 }
41
42 byte* Mem::pointer()
43 {
44     return mem;
45 }
46
47 byte* Mem::pointer(int memSize)
48 {
49     ensureMinSize(memSize);
50     return mem;
51 }

MemTest.cpp 1 #include "Mem.h"
2 #include <cstring>
3 #include <iostream>
4 using namespace std;
5
6 class MyString
7 {
8     Mem* buf;
9     public:
10         MyString();
11         MyString(char* str);
12         ~MyString();
13         void concat(char* str);
14         void print(ostream& os);
15 };
16
17 MyString::MyString()
18 {
19     buf = 0;
20 }
21
22 MyString::MyString(char* str)
23 {
24     buf = new Mem(strlen(str) + 1);
25     strcpy((char*)buf->pointer(), str);
26 }
27
28 void MyString::concat(char* str)
29 {
30     if(!buf)
31     {
32         buf = new Mem;
33     }
34
35     strcat((char*)buf->pointer(buf->msize() + strlen(str) + 1), str);
36 }
37
38 void MyString::print(ostream& os)
39 {
40     if(!buf)
41     {
42         return;
43     }
44     os << buf->pointer() << endl;
45 }
46
47 MyString::~MyString()
48 {
49     delete []buf;
50 }
51
52 int main()
53 {
54     MyString s("My test string");
55     s.print(cout);
56     s.concat(" some additional stuff");
57     s.print(cout);
58     MyString s2;
59     s2.concat("Using default constructor");
60     s2.print(cout);
61
62     cin.get();
63 }