c++ Convert struct to bytes

d:\stock\tskingfromgoogle\src\netts\tw.cpp

convert struct  to bytes

//convert struct  to bytes 2019/05/20 by freeman
int constructloginbuffer(byte* buffer, size_t maxlen, lpctstr lpszuser, lpctstr lpszpasswd)
{
	int nlen = 0;
	int nlenuser = strlen(lpszuser);
	int nlenpasswd = strlen(lpszpasswd);

	tw_login	packet;
	memset(&packet,0,sizeof(packet));
	packet.m_header.m_magic = tw_magic;
	if(maxlen < (int)(5 + sizeof(tw_header) + nlenuser + nlenpasswd))
	{
		nlen = 5 + sizeof(tw_header);
		return -1;
	}
	packet.m_name_len = (word)nlenuser;
	memcpy(packet.m_data, lpszuser, nlenuser);
	*(word*)(packet.m_data + nlenuser)	=	(word)nlenpasswd;
	memcpy(packet.m_data + nlenuser + sizeof(word), lpszpasswd, nlenpasswd);

	nlen = 5 + sizeof(tw_header) + nlenuser + nlenpasswd;
	constructlength(packet.m_header, nlen - sizeof(packet.m_header));

	if(buffer)
		memcpy(buffer, &packet, nlen);
	return nlen;
}