[C++] #include <string> 직접 구현!

#define _CRT_SECURE_NO_WARNINGS
//#pragma warning(disable:4996)
#include <iostream>
#include <cstring>
 
using namespace std;
 
 
class MyString
{
    char *_str; //문자 메모리 공간 할당 변수
    int _len;   //
public:
    MyString() { _str = NULL; _len = -1; }
 
    MyString(const char *str) {
        _len = strlen(str) + 1;
        _str = new char[_len];
        strcpy(_str, str);
    }
    MyString(int len) {
        _str = new char[len + 1];
        _len = len;
    }
    MyString(int len, const char str) {
        _str = new char[len + 1];
 
        for (int i = 0; i < len; i++)
            _str[i] = str;
 
        _str[len] = '\0';
    }
 
    MyString(const char *str, int len) {
        _len = len + 1;
        _str = new char[_len];
        strncpy(_str, str, len);
        _str[len] = '\0';
    }
 
    MyString(const MyString &ms)
    {
        _len = strlen(ms._str) + 1;
        _str = new char[_len];
        strcpy(_str, ms._str);
    }
 
    MyString(char *p1, char *p2)
    {
        _len = p2 - p1;
 
        _str = new char[_len + 1];
 
        for (int i = 0; i < _len; i++) _str[i] = p1[i];
 
        _str[_len] = '\0';
    }
 
    ~MyString() { delete[] _str; }
 
    friend ostream& operator << (ostream &out, const MyString &obj);
    friend istream& operator >> (istream &cin, MyString &ms);
 
    void operator += (const char *str)  // one+="oops"
    {
        _len += strlen(str);
        char *temp = new char[_len];
 
        strcpy(temp, _str);
        strcat(temp, str);
 
        delete[] _str;
 
        _str = temp;
    }
 
    MyString operator+(MyString& ms) // four = two + three;  four.operator=(two.operator+(three))
    {
        MyString *tempMs;
        tempMs = new MyString(_len + ms._len+1);
        strcpy(tempMs->_str, _str);
        strcat(tempMs->_str, ms._str);
 
        //tempMs->_len = _len + ms._len;
        
        // 아래 코드가 문제임
        //tempMs->_str = strcat(_str, ms._str);
        
        return *tempMs;
    }
 
    MyString& operator=(const MyString& ms)
    {
        /* cout << ms._len << endl;
        exit(-1);*/
        _len = ms._len;
 
        delete[] _str;
 
        _str = new char[_len];
        strcpy(_str, ms._str);
 
        return *this;
    }
 
    MyString& operator=(const char *ms)
    {
        _len = strlen(ms) + 1;
 
        delete[] _str;
 
        _str = new char[_len];
        strcpy(_str, ms);
 
        return *this;
    }
 
    char& operator [] (int index)
    {
        return _str[index];
    }
};
 
ostream& operator << (ostream &out, const MyString &obj)
{
    out << obj._str;
    return out;
}
 
 
istream& operator >> (istream &in, MyString &ms)
{
 
    /*char *buf = new char[BUFSIZ];
    in >> buf;
    ms.len = strlen(buf) + 1;
    obj.str = new char[obj.len];

    strcpy(obj.str, buf);

    delete[]buf;
    return in;*/
 
    char *tmpStr = new char[BUFSIZ];
    in >> tmpStr;
    ms._len = strlen(tmpStr) + 1;
    ms._str = new char[ms._len];
    strcpy(ms._str, tmpStr);
 
    delete[]tmpStr;
    return in;
 
    //cout << tmpStr;
    //exit(-1);
    //ms._len = strlen(tmpStr) + 1;
    //tmpStr = new char[ms._len];
 
 
 
    /*char tmpStr[BUFSIZ];
    cin >> tmpStr;

    ms._len = strlen(tmpStr) + 1;
    ms._str = new char[ms._len];

    strcpy(ms._str, tmpStr);
    return cin;*/
}
 
int main()
{
    /* 1 */
    MyString one("lottery winner!");//생성자함수호출
    cout << one << endl;  //출력연산자함수호출
 
    MyString two(20, '$');//생성자함수호출
    cout << two << endl;//출력연산자함수호출
 
    MyString three(one); // 복사생성자호출
    cout << three << endl; //출력연산자함수호출
 
    one += "oops"; // +=연산자함수호출 ( strcat함수 )
    cout << one << endl;//문자열결합 
 
    two = "sorry!that was";//대입연산자함수 호출 
    cout << two << endl;
 
    three[0] = 'p';//[]첨자연산자함수 호출 
    cout << three << endl;
    
    MyString four;
    four = two + three;
    cout << four << endl;
 
    char alls[] = "all's well that ends well";
    MyString five(alls, 20); //생성자호출
    cout << five << "!\n";
 
 
    MyString six(alls + 6, alls + 10);  //생성자
    cout << six << ",";
    
    MyString seven(&five[6], &five[10]);  //생성자
    cout << seven << "...\n";
 
    
    MyString eight;
    cout << "문자열 입력하세요 :";
    cin >> eight;  // >>연산자호출
    cout << " 입력한 문자열은 \"" << eight << "\" 입니다 " << endl;
    
    return 0;
}