C语言实现strlen(char *str)

#include <stdio.h>

int mylen(char *str);

int main()
{
	char *str = "haha";
	printf("len = %d", mylen(str));
	return 0;
}

int mylen(char *str)
{
	if(str == NULL) return 0;
	int len = 0;
	for(; *str++ != '\0';)
	{
		len++;
	}
	return len;
}