22 string 클래스 - 직접 일부 구현

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#include <iostream>
#include <string>
#include <cstring>
 
namespace mystd
{
    using std::cout;
    using std::cin;
    using std::endl;
    using std::printf;
    using std::ostream;
    using std::istream;
 
    class string
    {
    private:
        char * str;
        int str_len;
    public:
        string();
        string(const string& r_string);
        string(const char * str);
        ~string();
 
        string& operator=(const string& r_string);
        string& operator=(const char * str);
        const string operator+(const char * str);
        const string operator+(const string& r_string);
        string& operator+=(const char * str);
        string& operator+=(const string& r_string);
        bool operator== (const string& r_string);
        bool operator== (const char * str);
 
        friend ostream& operator<<(ostream& os, const string& r_string);
        friend const string operator+(const char * str, const string& r_string);
        friend char * operator+=(char * str, const string& r_string);
        friend bool operator==(const char * str, const string& r_string);
    };
    istream& operator>> (istream& is, string& r_string);
    ostream& operator<< (ostream& os, const string& r_string);
    const string operator+(const char * str, const string& r_string);
    char * operator+=(char * str, const string& r_string);
    bool operator==(const char * str, const string& r_string);
};
 
using namespace mystd;
 
int main(void)
{
    string str1 = "I like "; // 복사 생성자
    string str2 = "string class"; // 복사 생성자
    string str3 = str1 + str2; // 복사 생성자, + 연산자 오버로딩
 
    cout<<"------ str1 ------"<<endl;
    cout<<str1<<endl; // << 연산자 오버로딩 전역
    cout<<"------ str2 ------"<<endl;
    cout<<str2<<endl; // << 연산자 오버로딩 전역
    cout<<"------ str3 ------"<<endl;
    cout<<str3<<endl; // << 연산자 오버로딩 전역
 
    string str4;
    str4 = "HELLO";
    cout<<"------ str4 ------"<<endl;
    cout<<str4<<endl;
 
    string str5;
    str5 = str3 + str4 ;
    cout<<"------ str5 ------"<<endl;
    cout<<str5<<endl;
 
    string str6;
    str6 = str4 + " AAA" ;
    cout<<"------ str6 ------"<<endl;
    cout<<str6<<endl;
 
    string str7;
    str7 =  "AAA " + str4 ;
    cout<<"------ str7 ------"<<endl;
    cout<<str7<<endl;
 
    string str8 = "asdf";
    string str9 = "fdsa";
 
    str8 += str9;
    str9 += "asdf";
    cout<<"------ str8 ------"<<endl;
    cout<<str8<<endl;
    cout<<"------ str9 ------"<<endl;
    cout<<str9<<endl;
 
    cout<<"------ str11 ------"<<endl;
    string str10="222222222";
    char str11[30] = "fdjskalfjklsaf";
    str11+=str10;
    printf("%s\n",str11+=str10);
 
    string str12 = "ZXC1";
    string str13 = "ZXC";
    if(str12 == str13)
        cout<<"동일한 문자열이다1"<<endl;
    else
        cout<<"동일하지 않은 문자열이다1"<<endl;
 
    char str14[10] = "ZXC";
    if(str12 == str14)
        cout<<"동일한 문자열이다2"<<endl;
    else
        cout<<"동일하지 않은 문자열이다2"<<endl;
 
    if(str14 == str12)
        cout<<"동일한 문자열이다3"<<endl;
    else
        cout<<"동일하지 않은 문자열이다3"<<endl;
 
    cout<<"문자열 입력 : ";
    cin>>str4; // >> 연산자 오버로딩 전역
    cout<<"입력한 문자열 : "<<str4<<endl; // << 연산자 오버로딩 전역
 
    return 0;
}
 
 
mystd::string::string() : str(NULL), str_len(0) { }
mystd::string::string(const string& r_string) : str_len(r_string.str_len)
{
    this->str = new char[r_string.str_len+1];
    strcpy(this->str, r_string.str);
}
mystd::string::string(const char * str) : str_len(strlen(str))
{
    this->str = new char[strlen(str)+1];
    strcpy(this->str, str);
}
mystd::string::~string()
{
    delete []this->str;
}
 
string& mystd::string::operator=(const string& r_string)
{
    this->str_len = r_string.str_len;
 
    if(this->str == NULL)
    {
        this->str = new char[this->str_len+1];
    }
    else
    {
        delete []this->str;
        this->str = new char[this->str_len+1];
    }
    strcpy(this->str, r_string.str);
    return *this;
}
 
string& mystd::string::operator=(const char * str)
{
    this->str_len = strlen(str);
 
    if(this->str == NULL)
    {
        this->str = new char[this->str_len+1];
    }
    else
    {
        delete []this->str;
        this->str = new char[this->str_len+1];
    }
 
    strcpy(this->str, str);
    return *this;
}
const string mystd::string::operator+(const char * str)
{
    char * tmp_str = new char[this->str_len + strlen(str) + 1];
    string tmp;
 
    strcpy(tmp_str, this->str);
    strcpy(tmp_str + this->str_len, str);
 
    tmp = tmp_str; // 대입 연산자 오버로딩
    delete []tmp_str;
    return tmp;
}
const string mystd::string::operator+(const string& r_string)
{
    char * tmp_str = new char[this->str_len + r_string.str_len + 1];
    string tmp;
 
    strcpy(tmp_str, this->str);
    strcpy(tmp_str + this->str_len, r_string.str);
 
    tmp = tmp_str; // 대입 연산자 오버로딩
    delete []tmp_str;
    return tmp;
}
string& mystd::string::operator+=(const char * str)
{
    int tmp_strlen = this->str_len + strlen(str);
    char * tmp_str = new char[tmp_strlen + 1];
 
    strcpy(tmp_str, this->str);
    strcpy(tmp_str+this->str_len, str);
 
    if(this->str == NULL)
        this->str = new char[tmp_strlen + 1];
    else
    {
        delete []this->str;
        this->str = new char[tmp_strlen + 1];
    }
    strcpy(this->str, tmp_str);
    this->str_len = tmp_strlen;
 
    delete []tmp_str;
    return *this;
}
string& mystd::string::operator+=(const string& r_string)
{
    int tmp_strlen = this->str_len + r_string.str_len;
    char * tmp_str = new char[tmp_strlen + 1];
 
    strcpy(tmp_str, this->str);
    strcpy(tmp_str+this->str_len, r_string.str);
 
    if(this->str == NULL)
        this->str = new char[tmp_strlen + 1];
    else
    {
        delete []this->str;
        this->str = new char[tmp_strlen + 1];
    }
    strcpy(this->str, tmp_str);
    this->str_len = tmp_strlen;
 
    delete []tmp_str;
    return *this;
}
bool mystd::string::operator== (const string& r_string)
{
    if(!strcmp(this->str, r_string.str))
        return true;
    else
        return false;
}
bool mystd::string::operator== (const char * str)
{
    if(!strcmp(this->str, str))
        return true;
    else
        return false;
}
 
istream& mystd::operator>> (istream& is, string& r_string)
{
    char str[100];
    is>>str;
    r_string = string(str);
    return is;
}
ostream& mystd::operator<< (ostream& os, const string& r_string)
{
    os<<r_string.str;
    return os;
}
const string mystd::operator+(const char * str, const string& r_string)
{
    char * tmp_str = new char[r_string.str_len + strlen(str) + 1];
    string tmp;
 
    strcpy(tmp_str, str);
    strcpy(tmp_str + strlen(str), r_string.str);
 
    tmp = tmp_str; // 대입 연산자 오버로딩
    delete []tmp_str;
    return tmp;
}
char * mystd::operator+=(char * str, const string& r_string)
{
    int i = 0;
    int tmp_strlen = strlen(str) + r_string.str_len;
    char * tmp_str = new char[tmp_strlen + 1];
 
    strcpy(tmp_str, str);
    strcpy(tmp_str + strlen(str), r_string.str);
 
    while(str[i++]!=0); // str의 사이즈를 구한다.(i-2)
    strncpy(str,tmp_str,i-2); // str의 기존 사이즈만큼 복사한다. 짤리겠지.
    delete []tmp_str;
    return str;
}
bool mystd::operator==(const char * str, const string& r_string)
{
    if(!strcmp(str, r_string.str))
        return true;
    else
        return false;
}

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직접 구현해보았으나 설명 및 풀이를 시간이 나면 진행을 해보겠다.