class my_string{
public:
my_string(const char* str){
int len = strlen(str);
len_ = len;
buffer_ = new char[len_ + 1];
memset(buffer_, 0, len_ + 1);
memcpy(buffer_, str, len_);
}
~my_string(){
delete[]buffer_;
buffer_ = nullptr;
}
//拷貝構造函數淺拷貝
my_string(const my_string& str)
{
len_ = str.get_len();
if (len_ ==0){
return;
}
//語法沒錯,可能編譯會拋異常
buffer_ = new char[len_ + 1];
memset(buffer_, 0, len_ + 1);
memcpy(buffer_, str.data(), len_);
}
//賦值構造函數
my_string& operator=(const my_string& str)
{
if (this !=&str){
int len = str.get_len();
if (this->buffer_ != nullptr) {
delete[] buffer_;
buffer_ = nullptr;
}
len_ = len;
this->buffer_ = new char[len_ + 1];
memset(buffer_, 0, len_ + 1);
memcpy(buffer_, str.data(), len_);
}
return *this;
}
//移動構造函數
my_string(const my_string&& str) noexcept
{
len_ = str.get_len();
if (len_ == 0) {
return;
}
this->buffer_ = new char[len_ + 1];
memset(buffer_, 0, len_ + 1);
memcpy(buffer_, str.data(), len_);
}
//移動賦值
my_string& operator=(const my_string&& str) {
if (this != &str) {
int len = str.get_len();
if (this->buffer_ != nullptr) {
delete[] buffer_;
buffer_ = nullptr;
}
len_ = len;
this->buffer_ = new char[len_ + 1];
memset(buffer_, 0, len_ + 1);
memcpy(buffer_, str.data(), len_);
}
return *this;
}
std::size_t get_len()const {
return len_;
}
char* data() const{
return buffer_;
}
private:
char* buffer_;
std::size_t len_{1};
};
#include<iostream>
//const my_string getPerson()
//{
// my_string person("person in func");
// return std::move(person);
//}
//不能返回局部變量的引用
//const my_string& getPerson()
//{
// my_string person("person in func");
// return person;
//}
//所以臨時對象一定要std::move
const my_string getPerson()
{
my_string person("person in func");
return std::move(person);
}
int main()
{
//std::string str = "1234567";
//std::string str1 = "7895624";
//my_string mystr(str.c_str());
//my_string mystr2(str1.c_str());
////臨時對象
my_string mystr33(std::move(getPerson()));
////一定賦值
//mystr2 = std::move(mystr);
//臨時對象會執行移動構造函數
my_string mystr44(std::move(my_string("123")));
//forward也會講一個左值變右值
my_string mystr55(std::forward<my_string>(my_string("22222")));
//注意不會執行,移動構造函數
//它是一個左值拷貝
//my_string mystr55(my_string("123"));
return 0;
}