d_net.c

//
// Copyright (C) 1993-1996 Id Software, Inc.
// Copyright (C) 2023 Frenkel Smeijers
//
// This program 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.
//
// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
//

// d_net.c

#include "doomdef.h"

#define NCMD_EXIT               0x80000000
#define NCMD_RETRANSMIT 0x40000000
#define NCMD_SETUP              0x20000000
#define NCMD_KILL               0x10000000              // kill game
#define NCMD_CHECKSUM   0x0fffffff


doomcom_t               *doomcom;
static doomdata_t              *netbuffer;             // points inside doomcom


/*
==============================================================================

							NETWORKING

gametic is the tic about to (or currently being) run
maketic is the tick that hasn't had control made for it yet
nettics[] has the maketics for all players

a gametic cannot be run until nettics[] > gametic for all players

==============================================================================
*/

#define RESENDCOUNT     10
#define PL_DRONE        0x80                            // bit flag in doomdata->player

static ticcmd_t                localcmds[BACKUPTICS];

ticcmd_t        netcmds[MAXPLAYERS][BACKUPTICS];
static int32_t             nettics[MAXNETNODES];
static boolean                 nodeingame[MAXNETNODES];        // set false as nodes leave game
static boolean                 remoteresend[MAXNETNODES];      // set when local needs tics
static int32_t                             resendto[MAXNETNODES];                  // set when remote needs tics
static int32_t                             resendcount[MAXNETNODES];

static int32_t                             nodeforplayer[MAXPLAYERS];

int32_t             maketic;
static int32_t                             skiptics;
int32_t                             ticdup;
static int32_t                             maxsend;        // BACKUPTICS/(2*ticdup)-1

void D_ProcessEvents (void);
void G_BuildTiccmd (ticcmd_t *cmd);
void D_DoAdvanceDemo (void);

static boolean                 reboundpacket;
static doomdata_t              reboundstore;


static int32_t     NetbufferSize (void)
{
	return (int32_t)&(((doomdata_t *)0)->cmds[netbuffer->numtics]);
}

static uint32_t NetbufferChecksum (void)
{
	uint32_t                c;
	int32_t             i,l;

	c = 0x1234567;

	l = (NetbufferSize () - (int32_t)&(((doomdata_t *)0)->retransmitfrom))/4;
	for (i=0 ; i<l ; i++)
		c += ((uint32_t *)&netbuffer->retransmitfrom)[i] * (i+1);

	return c & NCMD_CHECKSUM;
}

static int32_t ExpandTics (int32_t low)
{
	int32_t     delta;

	delta = low - (maketic&0xff);

	if (delta >= -64 && delta <= 64)
		return (maketic&~0xff) + low;
	if (delta > 64)
		return (maketic&~0xff) - 256 + low;
	if (delta < -64)
		return (maketic&~0xff) + 256 + low;

	I_Error ("ExpandTics: strange value %i at maketic %i",low,maketic);
	return 0; // shut up warning
}


//============================================================================


/*
==============
=
= HSendPacket
=
==============
*/

static void HSendPacket (int32_t node, int32_t flags)
{
	netbuffer->checksum = NetbufferChecksum () | flags;

	if (!node)
	{
		reboundstore = *netbuffer;
		reboundpacket = true;
		return;
	}

	if (demoplayback)
		return;

	if (!netgame)
		I_Error ("Tried to transmit to another node");

	doomcom->command = CMD_SEND;
	doomcom->remotenode = node;
	doomcom->datalength = NetbufferSize ();

if (debugfile)
{
	int32_t             i;
	int32_t             realretrans;
	if (netbuffer->checksum & NCMD_RETRANSMIT)
		realretrans = ExpandTics (netbuffer->retransmitfrom);
	else
		realretrans = -1;
	fprintf (debugfile,"send (%i + %i, R %i) [%i] "
	,ExpandTics(netbuffer->starttic),netbuffer->numtics, realretrans, doomcom->datalength);
	for (i=0 ; i<doomcom->datalength ; i++)
		fprintf (debugfile,"%i ",((byte *)netbuffer)[i]);
	fprintf (debugfile,"\n");
}

	I_NetCmd ();
}

/*
==============
=
= HGetPacket
=
= Returns false if no packet is waiting
=
==============
*/

static boolean HGetPacket (void)
{
	if (reboundpacket)
	{
		*netbuffer = reboundstore;
		doomcom->remotenode = 0;
		reboundpacket = false;
		return true;
	}

	if (!netgame)
		return false;
	if (demoplayback)
		return false;

	doomcom->command = CMD_GET;
	I_NetCmd ();
	if (doomcom->remotenode == -1)
		return false;

	if (doomcom->datalength != NetbufferSize ())
	{
		if (debugfile)
			fprintf (debugfile,"bad packet length %i\n",doomcom->datalength);
		return false;
	}

	if (NetbufferChecksum () != (netbuffer->checksum&NCMD_CHECKSUM) )
	{
		if (debugfile)
			fprintf (debugfile,"bad packet checksum\n");
		return false;
	}

if (debugfile)
{
	int32_t             realretrans;
			int32_t     i;

	if (netbuffer->checksum & NCMD_SETUP)
		fprintf (debugfile,"setup packet\n");
	else
	{
		if (netbuffer->checksum & NCMD_RETRANSMIT)
			realretrans = ExpandTics (netbuffer->retransmitfrom);
		else
			realretrans = -1;
		fprintf (debugfile,"get %i = (%i + %i, R %i)[%i] ",doomcom->remotenode,
		ExpandTics(netbuffer->starttic),netbuffer->numtics, realretrans, doomcom->datalength);
		for (i=0 ; i<doomcom->datalength ; i++)
			fprintf (debugfile,"%i ",((byte *)netbuffer)[i]);
		fprintf (debugfile,"\n");
	}
}
	return true;
}


/*
===================
=
= GetPackets
=
===================
*/

static char    exitmsg[80];

static void GetPackets (void)
{
	int32_t         netconsole;
	int32_t         netnode;
	ticcmd_t        *src, *dest;
	int32_t         realend;
	int32_t         realstart;

	while (HGetPacket ())
	{
		if (netbuffer->checksum & NCMD_SETUP)
			continue;               // extra setup packet

		netconsole = netbuffer->player & ~PL_DRONE;
		netnode = doomcom->remotenode;
		//
		// to save bytes, only the low byte of tic numbers are sent
		// Figure out what the rest of the bytes are
		//
		realstart = ExpandTics (netbuffer->starttic);
		realend = (realstart+netbuffer->numtics);

		//
		// check for exiting the game
		//
		if (netbuffer->checksum & NCMD_EXIT)
		{
			if (!nodeingame[netnode])
				continue;
			nodeingame[netnode] = false;
			playeringame[netconsole] = false;
			strcpy (exitmsg, "Player 1 left the game");
			exitmsg[7] += netconsole;
			players[consoleplayer].message = exitmsg;
			if (demorecording)
				G_CheckDemoStatus ();
			continue;
		}

		//
		// check for a remote game kill
		//
		if (netbuffer->checksum & NCMD_KILL)
			I_Error ("Killed by network driver");

		nodeforplayer[netconsole] = netnode;

		//
		// check for retransmit request
		//
		if ( resendcount[netnode] <= 0
		&& (netbuffer->checksum & NCMD_RETRANSMIT) )
		{
			resendto[netnode] = ExpandTics(netbuffer->retransmitfrom);
if (debugfile)
fprintf (debugfile,"retransmit from %i\n", resendto[netnode]);
			resendcount[netnode] = RESENDCOUNT;
		}
		else
			resendcount[netnode]--;

		//
		// check for out of order / duplicated packet
		//
		if (realend == nettics[netnode])
			continue;

		if (realend < nettics[netnode])
		{
if (debugfile)
fprintf (debugfile,"out of order packet (%i + %i)\n" ,realstart,netbuffer->numtics);
			continue;
		}

		//
		// check for a missed packet
		//
		if (realstart > nettics[netnode])
		{
		// stop processing until the other system resends the missed tics
if (debugfile)
fprintf (debugfile,"missed tics from %i (%i - %i)\n", netnode, realstart, nettics[netnode]);
			remoteresend[netnode] = true;
			continue;
		}

//
// update command store from the packet
//
{
	int32_t             start;

		remoteresend[netnode] = false;

		start = nettics[netnode] - realstart;
		src = &netbuffer->cmds[start];

		while (nettics[netnode] < realend)
		{
			dest = &netcmds[netconsole][nettics[netnode]%BACKUPTICS];
			nettics[netnode]++;
			*dest = *src;
			src++;
		}
	}
}

}

/*
=============
=
= NetUpdate
=
= Builds ticcmds for console player
= sends out a packet
=============
*/

static int32_t      gametime;

void NetUpdate (void)
{
	int32_t             nowtime;
	int32_t             newtics;
	int32_t                             i,j;
	int32_t                             realstart;
	int32_t                             gameticdiv;

//
// check time
//
	nowtime = I_GetTime ()/ticdup;
	newtics = nowtime - gametime;
	gametime = nowtime;

	if (newtics <= 0)                       // nothing new to update
		goto listen;

	if (skiptics <= newtics)
	{
		newtics -= skiptics;
		skiptics = 0;
	}
	else
	{
		skiptics -= newtics;
		newtics = 0;
	}


	netbuffer->player = consoleplayer;

//
// build new ticcmds for console player
//
	gameticdiv = gametic/ticdup;
	for (i=0 ; i<newtics ; i++)
	{
		I_StartTic ();
		D_ProcessEvents ();
		if (maketic - gameticdiv >= BACKUPTICS/2-1)
			break;          // can't hold any more
//printf ("mk:%i ",maketic);
		G_BuildTiccmd (&localcmds[maketic%BACKUPTICS]);
		maketic++;
	}


	if (singletics)
		return;         // singletic update is syncronous

//
// send the packet to the other nodes
//
	for (i=0 ; i<doomcom->numnodes ; i++)
		if (nodeingame[i])
		{
			netbuffer->starttic = realstart = resendto[i];
			netbuffer->numtics = maketic - realstart;
			if (netbuffer->numtics > BACKUPTICS)
				I_Error ("NetUpdate: netbuffer->numtics > BACKUPTICS");

			resendto[i] = maketic - doomcom->extratics;

			for (j=0 ; j< netbuffer->numtics ; j++)
				netbuffer->cmds[j] =
					localcmds[(realstart+j)%BACKUPTICS];

			if (remoteresend[i])
			{
				netbuffer->retransmitfrom = nettics[i];
				HSendPacket (i, NCMD_RETRANSMIT);
			}
			else
			{
				netbuffer->retransmitfrom = 0;
				HSendPacket (i, 0);
			}
		}

//
// listen for other packets
//
listen:

	GetPackets ();
}


/*
=====================
=
= CheckAbort
=
=====================
*/

static void CheckAbort (void)
{
	event_t *ev;
	int32_t             stoptic;

	stoptic = I_GetTime () + 2;
	while (I_GetTime() < stoptic)
		I_StartTic ();

	I_StartTic ();
	for ( ; eventtail != eventhead ; eventtail = (eventtail+1)&(MAXEVENTS-1) )
	{
		ev = &events[eventtail];
		if (ev->type == ev_keydown && ev->data1 == KEY_ESCAPE)
			I_Error ("Network game synchronization aborted.");
	}
}

/*
=====================
=
= D_ArbitrateNetStart
=
=====================
*/

static void D_ArbitrateNetStart (void)
{
	int32_t             i;
	boolean gotinfo[MAXNETNODES];

	autostart = true;
	memset (gotinfo,0,sizeof(gotinfo));

	if (doomcom->consoleplayer)
	{       // listen for setup info from key player
		mprintf ("listening for network start info...\n");
		while (1)
		{
			CheckAbort ();
			if (!HGetPacket ())
				continue;
			if (netbuffer->checksum & NCMD_SETUP)
			{
				if (netbuffer->player != VERSION)
#if APPVER_CHEX
					I_Error ("Different Chex(R) Quest versions cannot play a net quest!");
#else
					I_Error ("Different DOOM versions cannot play a net game!");
#endif
				startskill = netbuffer->retransmitfrom & 15;
				deathmatch = (netbuffer->retransmitfrom & 0xc0) >> 6;
				nomonsters = (netbuffer->retransmitfrom & 0x20) > 0;
				respawnparm = (netbuffer->retransmitfrom & 0x10) > 0;
				startmap = netbuffer->starttic & 0x3f;
				startepisode = netbuffer->starttic >> 6;
				return;
			}
		}
	}
	else
 	{       // key player, send the setup info
		mprintf ("sending network start info...\n");
		do
		{
			CheckAbort ();
			for (i=0 ; i<doomcom->numnodes ; i++)
			{
				netbuffer->retransmitfrom = startskill;
				if (deathmatch)
					netbuffer->retransmitfrom |= (deathmatch<<6);
				if (nomonsters)
					netbuffer->retransmitfrom |= 0x20;
				if (respawnparm)
					netbuffer->retransmitfrom |= 0x10;
				netbuffer->starttic = startepisode * 64 + startmap;
				netbuffer->player = VERSION;
				netbuffer->numtics = 0;
				HSendPacket (i, NCMD_SETUP);
			}

			for(i = 10 ; i  &&  HGetPacket(); --i)
			{
 if((netbuffer->player&0x7f) < MAXNETNODES)
				gotinfo[netbuffer->player&0x7f] = true;
			}

			for (i=1 ; i<doomcom->numnodes ; i++)
				if (!gotinfo[i])
					break;
		} while (i < doomcom->numnodes);
	}
}

/*
===================
=
= D_CheckNetGame
=
= Works out player numbers among the net participants
===================
*/

extern  int32_t                     viewangleoffset;

void D_CheckNetGame (void)
{
	int32_t             i;

	for (i=0 ; i<MAXNETNODES ; i++)
	{
		nodeingame[i] = false;
	nettics[i] = 0;
		remoteresend[i] = false;        // set when local needs tics
		resendto[i] = 0;                        // which tic to start sending
	}

// I_InitNetwork sets doomcom and netgame
	I_InitNetwork ();
	if (doomcom->id != DOOMCOM_ID)
		I_Error ("Doomcom buffer invalid!");
	netbuffer = &doomcom->data;
	consoleplayer = displayplayer = doomcom->consoleplayer;
	if (netgame)
		D_ArbitrateNetStart ();
	printf ("startskill %i  deathmatch: %i  startmap: %i  startepisode: %i\n", startskill, deathmatch, startmap, startepisode);

// read values out of doomcom
	ticdup = doomcom->ticdup;
	maxsend = BACKUPTICS/(2*ticdup)-1;
	if (maxsend<1)
		maxsend = 1;

	for (i=0 ; i<doomcom->numplayers ; i++)
		playeringame[i] = true;
	for (i=0 ; i<doomcom->numnodes ; i++)
		nodeingame[i] = true;

	printf ("player %i of %i (%i nodes)\n", consoleplayer+1, doomcom->numplayers, doomcom->numnodes);

}

/*
==================
=
= D_QuitNetGame
=
= Called before quitting to leave a net game without hanging the
= other players
=
==================
*/

void D_QuitNetGame (void)
{
	int32_t             i, j;

	if (debugfile)
		fclose (debugfile);

	if (!netgame || !usergame || consoleplayer == -1 || demoplayback)
		return;

// send a bunch of packets for security
	netbuffer->player = consoleplayer;
	netbuffer->numtics = 0;
	for (i=0 ; i<4 ; i++)
	{
		for (j=1 ; j<doomcom->numnodes ; j++)
			if (nodeingame[j])
				HSendPacket (j, NCMD_EXIT);
		I_WaitVBL (1);
	}
}



/*
===============
=
= TryRunTics
=
===============
*/

static int32_t     frameon;
static int32_t     frameskip[4];
static int32_t             oldnettics;
extern  boolean advancedemo;

void TryRunTics (void)
{
	int32_t             i;
	int32_t             lowtic;
	int32_t             entertic;
	static int32_t              oldentertics;
	int32_t                             realtics, availabletics;
	int32_t                             counts;
	int32_t                             numplaying;

//
// get real tics
//
	entertic = I_GetTime ()/ticdup;
	realtics = entertic - oldentertics;
	oldentertics = entertic;

//
// get available tics
//
	NetUpdate ();

	lowtic = MAXINT;
	numplaying = 0;
	for (i=0 ; i<doomcom->numnodes ; i++)
		if (nodeingame[i])
		{
			numplaying++;
			if (nettics[i] < lowtic)
				lowtic = nettics[i];
		}
	availabletics = lowtic - gametic/ticdup;


//
// decide how many tics to run
//
	if (realtics < availabletics-1)
		counts = realtics+1;
	else if (realtics < availabletics)
		counts = realtics;
	else
		counts = availabletics;
	if (counts < 1)
		counts = 1;

	frameon++;

	if (debugfile)
		fprintf (debugfile,"=======real: %i  avail: %i  game: %i\n",realtics, availabletics,counts);

	if (!demoplayback)
	{
	//=============================================================================
	//
	//      ideally nettics[0] should be 1 - 3 tics above lowtic
	//      if we are consistantly slower, speed up time
	//
		for (i=0 ; i<MAXPLAYERS ; i++)
			if (playeringame[i])
				break;
		if (consoleplayer == i)
		{       // the key player does not adapt
		}
		else
		{
			if (nettics[0] <= nettics[nodeforplayer[i]])
			{
				gametime--;
	//                      printf ("-");
			}
			frameskip[frameon&3] = (oldnettics > nettics[nodeforplayer[i]]);
			oldnettics = nettics[0];
			if (frameskip[0] && frameskip[1] && frameskip[2] && frameskip[3])
			{
				skiptics = 1;
	//                      printf ("+");
			}
		}
	//=============================================================================
	}       // demoplayback

	//
	// wait for new tics if needed
	//
		while (lowtic < gametic/ticdup + counts)
		{

			NetUpdate ();
			lowtic = MAXINT;

			for (i=0 ; i<doomcom->numnodes ; i++)
				if (nodeingame[i] && nettics[i] < lowtic)
					lowtic = nettics[i];

			if (lowtic < gametic/ticdup)
				I_Error ("TryRunTics: lowtic < gametic");

			// don't stay in here forever -- give the menu a chance to work
			if (I_GetTime ()/ticdup - entertic >= 20)
			{
				M_Ticker ();
				return;
			}
		}

//
// run the count * ticdup dics
//
	while (counts--)
	{
		for (i=0 ; i<ticdup ; i++)
		{
			if (gametic/ticdup > lowtic)
				I_Error ("gametic>lowtic");
			if (advancedemo)
				D_DoAdvanceDemo ();
			M_Ticker ();
			G_Ticker ();
			gametic++;
			//
			// modify command for duplicated tics
			//
			if (i != ticdup-1)
			{
				ticcmd_t        *cmd;
				int32_t                     buf;
				int32_t                     j;

				buf = (gametic/ticdup)%BACKUPTICS;
				for (j=0 ; j<MAXPLAYERS ; j++)
				{
					cmd = &netcmds[j][buf];
					cmd->chatchar = 0;
					if (cmd->buttons & BT_SPECIAL)
						cmd->buttons = 0;
				}
			}
		}
		NetUpdate ();                                   // check for new console commands
	}
}