c++;jstring類 寫時拷貝 簡單實現

c++;jstring類 寫時拷貝 簡單實現

#include<iostream>//頭文件
#pragma once
 
using namespace std;
class String
{
private:
    char* _string;
    int*  _strCount;
    size_t _size;
    size_t _capacity;
public:
    String(const char* str = "\0");
    String(const String& str);
    ~String();
    char& operator[](int index);
    char* GetChar();
    void operator =(String & str);
};
 
#include<iostream>//函數文件
#include"string.h"
 
using namespace std;
String::String(const char* str)
{
    _string = new char[strlen(str) + 5];
    _strCount=(int*)_string ;
    _string = _string + 4;
    strcpy(_string, str); 
    *_strCount = 1;
    _size = (strlen(str));
    _capacity = _size + 1;
}
 
String::String(const String& str)
{
    _string = str._string;
    ++*(str._strCount);
    _strCount = str._strCount;
    _size = str._size;
    _capacity = str._capacity;
}
 
String::~String()
{
    if (*_strCount > 1)
        --(*_strCount);
    else
        delete[] _strCount;
}
 
char& String:: operator[](int index)
{
    if (*_strCount != 1)
    {
        --*_strCount;
        char* tmp = new char[strlen(_string) + 5];
        strcpy(tmp + 4, _string);
        _strCount = (int*)tmp;
        *_strCount = 1;
        _size = strlen(_string);
        _capacity = _size + 1;
        _string = tmp + 4;
    }
    return _string[index];
}
 
char* String::GetChar()
{
    return _string;
}
 
void String::operator =(String & str)
{
    _string = str._string;
    ++*(str._strCount);
    _strCount = str._strCount;
    _size = str._size;
    _capacity = str._capacity;
 
}
 
#include<iostream>//主函數  測試文件
#include"string.h"
 
using namespace std;
void test1()
{
    String s1("woshishuaige");
    String s2(s1);
    String s3;
    cout << s1.GetChar() << endl;
    cout << s2.GetChar() << endl;
    cout << s3.GetChar() << endl;
    s2[0] = 1;
    cout << s2.GetChar() << endl;
 
}
 
int main()
{
    test1();
    return 0;
}