cnq3/code/client/cl_net_chan.cpp

/*
===========================================================================
Copyright (C) 1999-2005 Id Software, Inc.

This file is part of Quake III Arena source code.

Quake III Arena source code is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.

Quake III Arena source code is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Quake III Arena source code; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/

#include "../qcommon/q_shared.h"
#include "../qcommon/qcommon.h"
#include "client.h"

/*
==============
CL_Netchan_Encode

	// first 12 bytes of the data are always:
	long serverId;
	long messageAcknowledge;
	long reliableAcknowledge;

==============
*/
static void CL_Netchan_Encode( msg_t *msg )
{
	int i, index;
	byte key, *string;

	if ( msg->cursize <= CL_ENCODE_START ) {
		return;
	}

	qbool soob = msg->oob;
	int sbit = msg->bit;
	int srdc = msg->readcount;

	msg->bit = 0;
	msg->readcount = 0;
	msg->oob = qfalse;

	int serverId = MSG_ReadLong(msg);
	int messageAcknowledge = MSG_ReadLong(msg);
	int reliableAcknowledge = MSG_ReadLong(msg);

	msg->oob = soob;
	msg->bit = sbit;
	msg->readcount = srdc;

	string = (byte *)clc.serverCommands[ reliableAcknowledge & (MAX_RELIABLE_COMMANDS-1) ];
	index = 0;
	//
	key = clc.challenge ^ serverId ^ messageAcknowledge;
	for (i = CL_ENCODE_START; i < msg->cursize; i++) {
		// modify the key with the last received now acknowledged server command
		if (!string[index])
			index = 0;
		if (string[index] > 127 || string[index] == '%') {
			key ^= '.' << (i & 1);
		}
		else {
			key ^= string[index] << (i & 1);
		}
		index++;
		// encode the data with this key
		*(msg->data + i) = (*(msg->data + i)) ^ key;
	}
}

/*
==============
CL_Netchan_Decode

	// first four bytes of the data are always:
	long reliableAcknowledge;

==============
*/
static void CL_Netchan_Decode( msg_t *msg )
{
	long i, index;
	byte key, *string;

	qbool soob = msg->oob;
	int sbit = msg->bit;
	int srdc = msg->readcount;

	msg->oob = qfalse;
	long reliableAcknowledge = MSG_ReadLong(msg);

	msg->oob = soob;
	msg->bit = sbit;
	msg->readcount = srdc;

	string = (byte *) clc.reliableCommands[ reliableAcknowledge & (MAX_RELIABLE_COMMANDS-1) ];
	index = 0;
	// xor the client challenge with the netchan sequence number (need something that changes every message)
	key = clc.challenge ^ LittleLong( *(unsigned *)msg->data );
	for (i = msg->readcount + CL_DECODE_START; i < msg->cursize; i++) {
		// modify the key with the last sent and with this message acknowledged client command
		if (!string[index])
			index = 0;
		if (string[index] > 127 || string[index] == '%') {
			key ^= '.' << (i & 1);
		}
		else {
			key ^= string[index] << (i & 1);
		}
		index++;
		// decode the data with this key
		*(msg->data + i) = *(msg->data + i) ^ key;
	}
}

/*
=================
CL_Netchan_TransmitNextFragment
=================
*/
void CL_Netchan_TransmitNextFragment( netchan_t *chan ) {
	Netchan_TransmitNextFragment( chan );
}

/*
===============
CL_Netchan_Transmit
================
*/
void CL_Netchan_Transmit( netchan_t *chan, msg_t* msg ) {
	MSG_WriteByte( msg, clc_EOF );

	CL_Netchan_Encode( msg );
	Netchan_Transmit( chan, msg->cursize, msg->data );
}

/*
=================
CL_Netchan_Process
=================
*/
qbool CL_Netchan_Process( netchan_t *chan, msg_t *msg ) {
	int ret;

	ret = Netchan_Process( chan, msg );
	if (!ret)
		return qfalse;
	CL_Netchan_Decode( msg );
	return qtrue;
}