strncpy字符串拷贝函数

摘自linux内核4.11.1 源码string.c
linux/lib/string.c
Copyright (C) 1991, 1992  Linus Torvalds

头文件：#include
作用：将源字符串src复制count个字节至目标存储区dest；如果源src超过count个字节，结果不是NUL终止的，在src的长度小于count的情况下，dest的其余部分将用％NUL填充。
参数：
dest：目标存储区
src：源字符串
count：复制的最大字节数
返回值：
dest 目标存储区的地址

/**
 * strncpy - Copy a length-limited, C-string
 * @dest: Where to copy the string to
 * @src: Where to copy the string from
 * @count: The maximum number of bytes to copy
 *
 * The result is not %NUL-terminated if the source exceeds
 * @count bytes.
 *
 * In the case where the length of @src is less than  that  of
 * count, the remainder of @dest will be padded with %NUL.
 *
 */
char *strncpy(char *dest, const char *src, size_t count)
{
	char *tmp = dest;


	while (count) {
		if ((*tmp = *src) != 0)
			src++;
		tmp++;
		count--;
	}
	return dest;
}