strncpy函数模拟实现

strncpy函数在cplusplus网站中的定义

模拟实现源码

//模拟实现
#include <stdio.h>
#include <string.h>
#include <assert.h>

char* my_strncpy(char* destination, const char* source, size_t num)
{
	assert(destination && source);//对指针进行断言，确保不是NULL指针

	char* ret = destination;//保存目的地址

	while (num--)
	{
		*destination = *source;
		destination++;
		source++;
	}

	return ret;
}

int main()
{
	char arr1[] = "abcdef";
	char arr2[20] = "xxxxxxxxxxxxxxx";
	char arr3[20] = { 0 };

	char* ret1 = my_strncpy(arr2, arr1, 4);
	char* ret2 = my_strncpy(arr3, arr1, 4);

	printf("arr1:%s\n", arr1);
	printf("arr2:%s\n", arr2);
	printf("ret1:%s\n", ret1);
	printf("arr3:%s\n", arr3);
	printf("ret2:%s\n", ret2);

	return 0;
}

执行结果