strlen 函数 源码分析，为什么它比程序员自己写的快很多 C语言。

#include<iostream>
#include<cstring>
#include<time.h>
using namespace std;

int my_strlen(char * str){
char* start = str;
while(*(++str) !='\0') ;;
return str-start;
}

int main(){
clock_t startTime,endTime;
startTime = clock();
char * str = "nsfsfgdgsdgdsgdfgdfgdfg";
for(int i = 0;i< 1000000;i++)
my_strlen(str);
endTime = clock();
cout<< "my strlen function run time:"<<endTime-startTime<<endl;

startTime = clock();
for(int i = 0;i< 1000000;i++)
strlen(str);
endTime = clock();
cout<< "system strlen function run time:"<<endTime-startTime<<endl;

}

运行结果：

my strlen function run time:49467
system strlen function run time:2128

amazing!!!

标签：startTime,clock,int,C语言,char,源码,str,strlen
来源： https://www.cnblogs.com/daniel123/p/16380546.html