c strcpy function to achieve

char *strcpy(char* strDest, const char* strSrc)
{
	if ((strDest == NULL) || (strSrc == NULL))
	{
		return NULL;
	}

	char * strDestCopy = strDest; //保存目标字符串首地址

	while ((*strDest++ = *strSrc++) != 0);
	
	return strDestCopy;
}