C语言实现strncpy

strncpy --- 字符串拷贝 --- 拷贝num个字符

char* strncpy ( char* destination, const char* source, size_t num )

拷贝num个字符从源字符串到目标空间；

如果源字符串长度小于num，则拷贝完源字符串之后，在目标的后边追加’‘，直到num个.

#include
#include
#include
#include


char* my_strncpy(char* destination, const char* source,unsigned int num)
{
	assert(destination && source);
	char* ret = destination;
	while (num&&(*destination++ = *source++))
	{
		num--;
	}
	if (num != 0)
	{
		while (num)
		{
			*destination++ = '';
			num--;
		}
	}
	return ret;
}

int main()
{
	char arr1[30] = "abcdef";
	char arr2[] = "bit";
	my_strncpy(arr1, arr2,6);
	printf("%s",arr1);
	return 0;
}