C++ String类简单实现

#ifndef MYSTRING_H#define MYSTRING_H#include<iostream>using namespace std;class MyString {/*重载<<*/    friend ostream& operator<<(ostream& _cout, MyString& _MyString)    {        _cout << _MyString.string_address;        return _cout;    }/*重载>>*/    friend istream& operator>>(istream& _cin, MyString& _MyString)    {        if (_MyString.string_address) {            free(_MyString.string_address);            _MyString.string_address = NULL;        }        _MyString.string_address = (char*)calloc(1, 1024);        if (!_MyString.string_address)            cout << "分配内存失败" << endl;        _cin >> _MyString.string_address;        return _cin;    }public:/*默认无参构造*/    MyString() :string_address(NULL)     {    }/*默认有参构造*/    MyString(const char* const_string)    {        string_address = (char*)calloc(1, strlen(const_string) + 1);        if (!string_address)            cout << "内存分配失败" << endl;        strcpy(string_address, const_string);    }/*拷贝构造*/    MyString(const MyString& other_MyString)    {        string_address = (char*)calloc(1, strlen(other_MyString.string_address) + 1);        if (!string_address)            cout << "内存分配失败" << endl;        strcpy(string_address, other_MyString.string_address);    }/*析构函数*/    ~MyString()    {        if (string_address){            free(string_address);            string_address = NULL;        }       }/*普通成员函数*/    const char* c_str() const    {        return string_address;    }/*获取字符串长度*/    size_t length()    {        return strlen(string_address);    }    size_t size()    {        return strlen(string_address);    }/*重载=*/    MyString& operator=(const MyString& _MyString)    {        if (string_address) {            free(string_address);            string_address = NULL;        }        string_address = (char*)calloc(1, strlen(_MyString.string_address) + 1);        if (!string_address)            cout << "内存分配失败" << endl;        strcpy(string_address, _MyString.string_address);        return *this;    }    MyString& operator=(const char* const_string)    {        if (string_address) {            free(string_address);            string_address = NULL;        }        string_address = (char*)calloc(1, strlen(const_string) + 1);        if (!string_address)            cout << "内存分配失败" << endl;        strcpy(string_address, const_string);        return *this;    }/*重载[]*/    char& operator[](size_t index)    {        if (index >= length())            return string_address[length() - 1];        return string_address[index];    }/*重载+=*/    MyString& operator+=(MyString& _MyString)    {        if (string_address){            if (_MyString.string_address){                string_address = (char*)realloc(string_address, length() + strlen(_MyString.string_address) + 1);                if (!string_address)                     cout << "内存分配失败" << endl;                strcat(string_address, _MyString.string_address);            }        }        else {            if (_MyString.string_address){                string_address = (char*)calloc(1, strlen(_MyString.string_address + 1));                if (!string_address)                    cout << "内存分配失败" << endl;                strcpy(string_address, _MyString.string_address);            }        }        return *this;    }    MyString& operator+=(const char* const_string)    {        if (string_address) {            if (const_string) {                string_address = (char*)realloc(string_address,length() + strlen(const_string) + 1);                if (!string_address)                    cout << "内存分配失败" << endl;                strcat(string_address, const_string);            }        }        else {            if (const_string) {                string_address = (char*)calloc(1, strlen(const_string) + 1);                if (!string_address)                    cout << "内存分配失败" << endl;                strcpy(string_address, const_string);            }        }        return *this;    }/*重载+*/    MyString operator+(MyString& _MyString)    {        if (string_address) {            if (_MyString.string_address) {                string_address = (char*)realloc(string_address, length() + _MyString.length() + 1);                if (!string_address)                    cout << "内存分配失败" << endl;                strcat(string_address, _MyString.string_address);            }        }        else {            if (_MyString.string_address) {                string_address = (char*)calloc(1, _MyString.length() + 1);                if (!string_address)                    cout << "内存分配失败" << endl;                strcpy(string_address, _MyString.string_address);            }        }        return *this;    }    MyString operator+(const char* const_string)    {        if (string_address) {            if (const_string) {                string_address = (char*)realloc(string_address, length() + strlen(const_string) + 1);                if (!string_address)                    cout << "内存分配失败" << endl;                strcat(string_address, const_string);            }        }        else {            if (const_string) {                string_address = (char*)calloc(1, strlen(const_string) + 1);                if (!string_address)                    cout << "内存分配失败" << endl;                strcpy(string_address, const_string);            }        }        return *this;    }/*重载 ==*/    bool operator==(MyString& _MyString)    {        if (string_address)            if (_MyString.string_address)                if (!strcmp(string_address, _MyString.string_address))                    return true;        else            if (!_MyString.string_address)                return true;        return false;    }    bool operator==(const char* const_string)    {        if (string_address)            if (const_string)                if (!strcmp(string_address, const_string))                    return true;                else                    if (!const_string)                        return true;        return false;    }/*重载!=*/    bool operator!=(MyString& _MyString)    {        if (string_address)            if (_MyString.string_address)                if (strcmp(string_address, _MyString.string_address))                    return true;                else                    if (_MyString.string_address)                        return true;        return false;    }    bool operator!=(const char* const_string)    {        if (string_address)            if (const_string)                if (strcmp(string_address, const_string))                    return true;                else                    if (const_string)                        return true;        return false;    }private:    char* string_address;};#endif