mystring c++ 自己的string 封装

 1 /*************************************************************************
   > File Name: mystring.h
   > Author: lukey
   > Mail: [e-mail]
   > 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: [e-mail]
   > 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[];//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)+];
     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_) + ];
     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_) + ];
     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) + ];
     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 + );
     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 + );
     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'\0'结尾
 const char* String::c_str() const
 {
     int len = strlen(pstr_);

     pstr_[len + ] = '\0';
     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_) == )
         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_) < )
         return true;
     else
         return false;
 }

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

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