重写strncpy函数

#include "stdafx.h"
#include<iostream>
#include<string>
#include<cassert>
#include<malloc.h>
char* str_ncpy(char* des,const char* sr,std::size_t n)
{
    std::size_t t;
    for(t=0;t<n;t++)
    {
        *(des+t)=*(sr+t);
    }
    *(des+n)= '\0';//别忘了字符串结尾符号
    return des;//返回目标字符串首地址
}
int main(void )
{
    char* str_test = "hello world!";
    char* str_des =(char*) malloc( strlen(str_test)+1);//分配内存，足够大
     std::cout<<str_ncpy( str_des,str_test,strlen(str_test) )<<std::endl;
    free(str_des);

    system("pause");
    return 0;
}