mystring c++ 自己的string 封装

 1 /*************************************************************************
  > File Name: mystring.h
  > Author: lukey
  > Mail: lukey123@foxmail.com 
  > Created Time: Wed 17 Jun 2015 08:50:49 PM CST
 ************************************************************************/

#ifndef __MYSTRING__
#define __MYSTRING__

class String
{
    public:
        String();
        String(const char *);//有参构造函数
        String(const String & rhs);    //复制构造
        ~String();

        String & operator=(const String & rhs);//赋值运算符的两种情况
        String & operator=(const char *str);

        String & operator+=(const String & rhs);
        String & operator+=(const char * str);

        char & operator[](std::size_t index);
        const char & operator[](std::size_t index) const;

        std::size_t size() const;
        const char* c_str() const;
        void debug();

        //String 类和char相加的几个情况
        friend String operator+(const String & s1, const String & s2);
        friend String operator+(const String &, const char *);
        friend String operator+(const char *, const String &);

        friend bool operator==(const String &, const String &);
        friend bool operator!=(const String &, const String &);

        friend bool operator<(const String &, const String &);
        friend bool operator>(const String &, const String &);
        friend bool operator<=(const String &, const String &);
        friend bool operator>=(const String &, const String &);

        friend std::ostream & operator<<(std::ostream & os, const String &s);
        friend std::istream & operator>>(std::istream & is, String & s);

    private:
        char *pstr_;
};

#endif

/*************************************************************************
  > File Name: mystring.cc
  > Author: lukey
  > Mail: lukey123@foxmail.com 
  > Created Time: Wed 17 Jun 2015 09:18:55 PM CST
 ************************************************************************/

#include<iostream>
#include<cstring>
#include<stdlib.h>
#include"mystring.h"
using namespace std;
#if 0
class String
{
    public:
    private:
        char *pstr_;
};
#endif

//构造函数
String::String()
{
    std::cout << "String()" << std::endl;
    pstr_  = new char[1];//new 已经初始化了
}
String::String(const char *str)//有参构造函数
{
    std::cout << "String(const char * str)" << std::endl;
    pstr_ = new char[strlen(str)+1];
    strcpy(pstr_, str);
}
String::String(const String & rhs)    //复制构造，考虑自复制情况？
{
    std::cout << "String(const String & rhs)" << std::endl;
    pstr_ = new char[strlen(rhs.pstr_) + 1];
    strcpy(pstr_, rhs.pstr_);
}
String::~String()
{
    std::cout << "~String()" << std::endl;
    delete []pstr_;
}

String & String::operator=(const String & rhs)//赋值运算符的两种情况,考虑自赋值情况
{
    std::cout << "String & operator=(const String & rhs)" << std::endl;
    if(this == &rhs)
        return *this;
    delete []pstr_;
    pstr_ = new char[strlen(rhs.pstr_) + 1];
    strcpy(pstr_, rhs.pstr_);
    return *this;
}
String & String::operator=(const char *str)
{
    std::cout << "String & operator=(const char *str)" << std::endl;
    pstr_ = new char[strlen(str) + 1];
    strcpy(pstr_, str);
    return *this;
}

String & String::operator+=(const String & rhs)    //rhs连接到pstr_后面
{
    std::cout << "operator+=(const String & rhs)" << std::endl;
    int len = strlen(rhs.pstr_) + strlen(pstr_);
    pstr_ = (char *)realloc(pstr_, len + 1);
    strcat(pstr_, rhs.pstr_);
    return *this;
}
String & String::operator+=(const char * str)
{
    std::cout << "operator+=(const char * str)" << std::endl;
    int len = strlen(str) + strlen(pstr_);
    pstr_ = (char *)realloc(pstr_, len + 1);
    strcat(pstr_, str);
    return *this;
}

//下标运算符，非常量，可以修改值
char & String::operator[](std::size_t index)
{
    return pstr_[index];
}

//常量对象取下标，不能为其赋值
const char & String::operator[](std::size_t index) const
{
    return pstr_[index];
}

//字符串容量
std::size_t String::size() const
{
    return strlen(pstr_);
}

//转换成c类型字符串，以''结尾
const char* String::c_str() const
{
    int len = strlen(pstr_);

    pstr_[len + 1] = '';
    return pstr_;
}

//不懂？打印出字符串？
void String::debug()
{
    std::cout << pstr_ << std::endl;    
}

String operator+(const String & s1, const String & s2)
{
    std::cout << "operator+(const String & s1,const String & s2)" << std::endl;
    String ret_str = s1.pstr_;
    ret_str += s2.pstr_;
    return ret_str;
}

String operator+(const String & s, const char * str)
{
    std::cout << "operator+(String, char *)" << std::endl;
    String temp(str);
    return (s + temp);    //直接调用上面的(+)函数

}

String operator+(const char * str, const String & s)
{
    std::cout << "operator+( char *, String)" << std::endl;
    String temp(str);
    return (s + temp);    //直接调用上面的(+)函数
}

bool operator==(const String & lstr, const String & rstr)
{
    std::cout << "==" << std::endl;
    if(strcmp(lstr.pstr_, rstr.pstr_) == 0)
        return true;
    else
        return false;
}

bool operator!=(const String & lstr, const String & rstr)
{
    std::cout << "!=" << std::endl;
    return !(lstr == rstr);
}

bool operator<(const String & lstr, const String & rstr)
{
    std::cout << "<" << std::endl;
    if(strcmp(lstr.pstr_, rstr.pstr_) < 0)
        return true;
    else
        return false;
}

bool operator>(const String & lstr, const String & rstr)
{
    std::cout << ">" << std::endl;
    if(strcmp(lstr.pstr_, rstr.pstr_) > 0)
        return true;
    else
        return false;
}
bool operator<=(const String & lstr, const String & rstr)
{
    std::cout << "<=" << std::endl;
    if(strcmp(lstr.pstr_, rstr.pstr_) <= 0)
        return true;
    else
        return false;
}

bool operator>=(const String & lstr, const String & rstr)
{
    std::cout << ">=" << std::endl;
    if(strcmp(lstr.pstr_, rstr.pstr_) >= 0)
        return true;
    else
        return false;
}

std::ostream & operator<<(std::ostream & os, const String &s)
{
    os << s.pstr_ << " ";
    return os;
}
std::istream & operator>>(std::istream & is, String & s)
{
    is >> s.pstr_;
    return is;        //貌似有坑, 目前不能输入空格
}


//测试时每个函数调用都打印了信息
int main(void)
{
    String s1("hello");
    s1.debug();
    std::cout << s1;
    std::cout << std::endl;
    String s2("world");
    s2.debug();
    if(s1 > s2)
        std::cout << "s1 > s2" << std::endl;

    s1 = s2;
    s1.debug();
    String s3(s1);
    s3.debug();

    String s4 = s2 + s3;
    s4.debug();

    String s5;
    std::cout << s5 << std::endl;
    std::cin >> s5;
    std::cout << s5 << std::endl;
    return 0;
}