quake3live/code/server/sv_netdemo.c

/*
===========================================================================
Server-side demo recording and playback (netdemo).

Records the full entity state array each server frame so that
demos can be played back from any viewpoint.  During playback the
recorded entities are injected into sv.gentities and the normal
snapshot pipeline delivers them to a spectator client.
===========================================================================
*/

#include "server.h"

// ---------------------------------------------------------------
//  File format
// ---------------------------------------------------------------
//
//  Header:
//    4 bytes   magic "SVDM"
//    4 bytes   version (1)
//    4 bytes   original sv_maxclients
//    4 bytes   original sv_fps
//    64 bytes  map name (null-padded)
//    Then: configstrings block
//      for each non-empty configstring:
//        2 bytes  index
//        2 bytes  string length (incl NUL)
//        N bytes  string data
//      2 bytes  index = 0xFFFF  (terminator)
//
//  Per frame:
//    4 bytes   serverTime
//    2 bytes   numEntities (how many entity records follow)
//    for each entity:
//      2 bytes   entity number
//      entityState_t              (fixed size, raw)
//      4 bytes   svFlags
//      4 bytes   linked
//      12 bytes  currentOrigin[3]
//      12 bytes  absmin[3]
//      12 bytes  absmax[3]
//    2 bytes   numConfigChanges
//    for each change:
//      2 bytes   index
//      2 bytes   string length (incl NUL)
//      N bytes   string data
//
//  Footer:
//    4 bytes   serverTime = -1  (end marker)
//

#define SVDEMO_MAGIC		(('S') | ('V' << 8) | ('D' << 16) | ('M' << 24))
#define SVDEMO_VERSION		1
#define SVDEMO_MAX_MAPNAME	64

// ---------------------------------------------------------------
//  State
// ---------------------------------------------------------------

// per-entity data stored for delta compression (entityState + PVS fields)
typedef struct {
	entityState_t	es;
	int				svFlags;
	qboolean		linked;
	vec3_t			currentOrigin;
	vec3_t			absmin;
	vec3_t			absmax;
	qboolean		active;			// was this entity present last frame?
} svdEntityState_t;

// per-player state for delta compression
typedef struct {
	playerState_t	ps;
	qboolean		active;
} svdPlayerState_t;

typedef struct {
	// recording
	fileHandle_t	recordFile;
	qboolean		recording;
	char			*lastConfigstrings[MAX_CONFIGSTRINGS];  // for delta detection
	svdEntityState_t	prevEntities[MAX_GENTITIES];  // previous frame for delta
	svdPlayerState_t	prevPlayers[MAX_CLIENTS];     // previous frame player states

	// playback
	fileHandle_t	playFile;
	qboolean		playing;
	int				playMaxClients;		// original maxclients from the recording
	int				playFps;			// original sv_fps
	char			*savedConfigstrings[MAX_CONFIGSTRINGS]; // from demo header, re-applied after map load
	char			playMapName[SVDEMO_MAX_MAPNAME];
	int				spectatorClientNum;	// which client slot is the demo spectator
	int				nextFrameTime;		// serverTime of next frame to read
	qboolean		endOfDemo;
	qboolean		needConfigstrings;	// apply saved configstrings on first frame
	svdEntityState_t	playPrevEntities[MAX_GENTITIES];  // previous frame for delta read
	svdPlayerState_t	playPrevPlayers[MAX_CLIENTS];     // previous frame player states
} svDemo_t;

static svDemo_t	demo;

// ---------------------------------------------------------------
//  Recording helpers
// ---------------------------------------------------------------

static void SVD_WriteInt( fileHandle_t f, int v ) {
	FS_Write( &v, 4, f );
}

static void SVD_WriteShort( fileHandle_t f, short v ) {
	FS_Write( &v, 2, f );
}

static int SVD_ReadInt( fileHandle_t f ) {
	int v = 0;
	FS_Read( &v, 4, f );
	return v;
}

static short SVD_ReadShort( fileHandle_t f ) {
	short v = 0;
	FS_Read( &v, 2, f );
	return v;
}

// ---------------------------------------------------------------
//  Write header
// ---------------------------------------------------------------

static void SVD_WriteHeader( fileHandle_t f ) {
	int i;
	char mapBuf[SVDEMO_MAX_MAPNAME];

	SVD_WriteInt( f, SVDEMO_MAGIC );
	SVD_WriteInt( f, SVDEMO_VERSION );
	SVD_WriteInt( f, sv_maxclients->integer );
	SVD_WriteInt( f, sv_fps->integer );

	// map name
	memset( mapBuf, 0, sizeof(mapBuf) );
	Q_strncpyz( mapBuf, sv.configstrings[CS_SERVERINFO], sizeof(mapBuf) );
	// actually store the mapname from CS_SERVERINFO... or just the map name
	{
		const char *mapname = Cvar_VariableString("mapname");
		memset( mapBuf, 0, sizeof(mapBuf) );
		Q_strncpyz( mapBuf, mapname, sizeof(mapBuf) );
	}
	FS_Write( mapBuf, SVDEMO_MAX_MAPNAME, f );

	// configstrings
	for ( i = 0; i < MAX_CONFIGSTRINGS; i++ ) {
		if ( sv.configstrings[i] && sv.configstrings[i][0] ) {
			int len = strlen( sv.configstrings[i] ) + 1;
			SVD_WriteShort( f, (short)i );
			SVD_WriteShort( f, (short)len );
			FS_Write( sv.configstrings[i], len, f );

			// store initial copy for delta detection
			if ( demo.lastConfigstrings[i] ) {
				Z_Free( demo.lastConfigstrings[i] );
			}
			demo.lastConfigstrings[i] = CopyString( sv.configstrings[i] );
		}
	}
	// terminator
	SVD_WriteShort( f, (short)0xFFFF );
}

// ---------------------------------------------------------------
//  Write one frame
// ---------------------------------------------------------------

static void SVD_WriteFrame( fileHandle_t f ) {
	int i;
	sharedEntity_t *ent;
	short numChanges;
	msg_t msg;
	byte msgBuf[MAX_GENTITIES * 64];  // delta-compressed entities are small
	int msgLen;

	SVD_WriteInt( f, svs.time );
	SVD_WriteShort( f, (short)sv.num_entities );

	// delta-compress all entities into a message buffer
	MSG_Init( &msg, msgBuf, sizeof(msgBuf) );

	for ( i = 0; i < sv.num_entities; i++ ) {
		qboolean active;
		ent = SV_GentityNum( i );
		active = ( ent->r.linked || ent->s.eType != 0 );

		if ( active ) {
			entityState_t baseline;
			entityState_t *from;
			if ( demo.prevEntities[i].active ) {
				from = &demo.prevEntities[i].es;
			} else {
				Com_Memset( &baseline, 0, sizeof(baseline) );
				baseline.number = i;
				from = &baseline;
			}
			MSG_WriteDeltaEntity( &msg, from, &ent->s, qtrue );

			// write PVS fields only if changed from previous frame
			{
				qboolean pvsChanged = !demo.prevEntities[i].active
					|| ent->r.svFlags != demo.prevEntities[i].svFlags
					|| ent->r.linked != demo.prevEntities[i].linked
					|| !VectorCompare( ent->r.currentOrigin, demo.prevEntities[i].currentOrigin )
					|| !VectorCompare( ent->r.absmin, demo.prevEntities[i].absmin )
					|| !VectorCompare( ent->r.absmax, demo.prevEntities[i].absmax );

				MSG_WriteBits( &msg, pvsChanged, 1 );
				if ( pvsChanged ) {
					MSG_WriteLong( &msg, ent->r.svFlags );
					MSG_WriteLong( &msg, ent->r.linked );
					MSG_WriteFloat( &msg, ent->r.currentOrigin[0] );
					MSG_WriteFloat( &msg, ent->r.currentOrigin[1] );
					MSG_WriteFloat( &msg, ent->r.currentOrigin[2] );
					MSG_WriteFloat( &msg, ent->r.absmin[0] );
					MSG_WriteFloat( &msg, ent->r.absmin[1] );
					MSG_WriteFloat( &msg, ent->r.absmin[2] );
					MSG_WriteFloat( &msg, ent->r.absmax[0] );
					MSG_WriteFloat( &msg, ent->r.absmax[1] );
					MSG_WriteFloat( &msg, ent->r.absmax[2] );
				}
			}

			// update prev state
			demo.prevEntities[i].es = ent->s;
			demo.prevEntities[i].svFlags = ent->r.svFlags;
			demo.prevEntities[i].linked = ent->r.linked;
			VectorCopy( ent->r.currentOrigin, demo.prevEntities[i].currentOrigin );
			VectorCopy( ent->r.absmin, demo.prevEntities[i].absmin );
			VectorCopy( ent->r.absmax, demo.prevEntities[i].absmax );
			demo.prevEntities[i].active = qtrue;
		} else if ( demo.prevEntities[i].active ) {
			// entity was removed — write a remove marker
			MSG_WriteDeltaEntity( &msg, &demo.prevEntities[i].es, NULL, qtrue );
			demo.prevEntities[i].active = qfalse;
		}
		// else: entity was inactive and still inactive — write nothing
	}

	// end of entities marker
	MSG_WriteBits( &msg, (MAX_GENTITIES - 1), GENTITYNUM_BITS );

	// write compressed entity message to file
	msgLen = msg.cursize;
	SVD_WriteInt( f, msgLen );
	FS_Write( msg.data, msgLen, f );

	// write player states (delta compressed)
	{
		msg_t psmsg;
		byte psBuf[MAX_CLIENTS * 256];
		int psCount = 0;

		MSG_Init( &psmsg, psBuf, sizeof(psBuf) );

		for ( i = 0; i < sv_maxclients->integer; i++ ) {
			playerState_t *ps = SV_GameClientNum( i );
			client_t *cl = &svs.clients[i];
			qboolean active = ( cl->state >= CS_ACTIVE );

			if ( active ) {
				playerState_t *from = demo.prevPlayers[i].active ? &demo.prevPlayers[i].ps : NULL;
				MSG_WriteBits( &psmsg, i, 6 );  // client number (0-63)
				MSG_WriteBits( &psmsg, 1, 1 );   // active flag
				MSG_WriteDeltaPlayerstate( &psmsg, from, ps );
				demo.prevPlayers[i].ps = *ps;
				demo.prevPlayers[i].active = qtrue;
				psCount++;
			} else if ( demo.prevPlayers[i].active ) {
				MSG_WriteBits( &psmsg, i, 6 );
				MSG_WriteBits( &psmsg, 0, 1 );   // inactive flag (player left)
				demo.prevPlayers[i].active = qfalse;
				psCount++;
			}
		}
		// terminator
		MSG_WriteBits( &psmsg, MAX_CLIENTS - 1, 6 );
		MSG_WriteBits( &psmsg, 0, 1 );

		msgLen = psmsg.cursize;
		SVD_WriteInt( f, msgLen );
		FS_Write( psmsg.data, msgLen, f );
	}

	// configstring changes
	numChanges = 0;
	for ( i = 0; i < MAX_CONFIGSTRINGS; i++ ) {
		const char *cur = sv.configstrings[i] ? sv.configstrings[i] : "";
		const char *old = demo.lastConfigstrings[i] ? demo.lastConfigstrings[i] : "";
		if ( strcmp( cur, old ) != 0 ) {
			numChanges++;
		}
	}
	SVD_WriteShort( f, numChanges );

	if ( numChanges > 0 ) {
		for ( i = 0; i < MAX_CONFIGSTRINGS; i++ ) {
			const char *cur = sv.configstrings[i] ? sv.configstrings[i] : "";
			const char *old = demo.lastConfigstrings[i] ? demo.lastConfigstrings[i] : "";
			if ( strcmp( cur, old ) != 0 ) {
				int len = strlen( cur ) + 1;
				SVD_WriteShort( f, (short)i );
				SVD_WriteShort( f, (short)len );
				FS_Write( cur, len, f );

				if ( demo.lastConfigstrings[i] ) {
					Z_Free( demo.lastConfigstrings[i] );
				}
				demo.lastConfigstrings[i] = CopyString( cur );
			}
		}
	}
}

// ---------------------------------------------------------------
//  Recording commands
// ---------------------------------------------------------------

void SVD_Record_f( void ) {
	char name[MAX_OSPATH];
	char *s;

	if ( demo.recording ) {
		Com_Printf( "Already recording a server demo.\n" );
		return;
	}

	if ( sv.state != SS_GAME ) {
		Com_Printf( "Not running a server.\n" );
		return;
	}

	s = Cmd_Argv(1);
	if ( !s[0] ) {
		Com_Printf( "Usage: svdemo_record <demoname>\n" );
		return;
	}

	Com_sprintf( name, sizeof(name), "svdemos/%s.svdm", s );

	demo.recordFile = FS_FOpenFileWrite( name );
	if ( !demo.recordFile ) {
		Com_Printf( "ERROR: couldn't open %s for writing.\n", name );
		return;
	}

	Com_Printf( "Recording server demo to %s\n", name );
	demo.recording = qtrue;

	// clear delta state for fresh recording
	Com_Memset( demo.prevEntities, 0, sizeof(demo.prevEntities) );

	SVD_WriteHeader( demo.recordFile );
}

void SVD_StopRecord_f( void ) {
	int i;

	if ( !demo.recording ) {
		Com_Printf( "Not recording a server demo.\n" );
		return;
	}

	// write end marker
	SVD_WriteInt( demo.recordFile, -1 );

	FS_FCloseFile( demo.recordFile );
	demo.recordFile = 0;
	demo.recording = qfalse;

	// free configstring tracking
	for ( i = 0; i < MAX_CONFIGSTRINGS; i++ ) {
		if ( demo.lastConfigstrings[i] ) {
			Z_Free( demo.lastConfigstrings[i] );
			demo.lastConfigstrings[i] = NULL;
		}
	}

	Com_Printf( "Server demo recording stopped.\n" );
}

/*
Called from SV_Frame() after the game has run its frame.
*/
void SVD_RecordFrame( void ) {
	if ( !demo.recording ) {
		return;
	}
	SVD_WriteFrame( demo.recordFile );
}

// ---------------------------------------------------------------
//  Playback: read header
// ---------------------------------------------------------------

static qboolean SVD_ReadHeader( fileHandle_t f ) {
	int magic, version;

	magic = SVD_ReadInt( f );
	if ( magic != SVDEMO_MAGIC ) {
		Com_Printf( "Not a valid server demo file.\n" );
		return qfalse;
	}

	version = SVD_ReadInt( f );
	if ( version != SVDEMO_VERSION ) {
		Com_Printf( "Unsupported server demo version %d.\n", version );
		return qfalse;
	}

	demo.playMaxClients = SVD_ReadInt( f );
	demo.playFps = SVD_ReadInt( f );
	FS_Read( demo.playMapName, SVDEMO_MAX_MAPNAME, f );
	demo.playMapName[SVDEMO_MAX_MAPNAME - 1] = '\0';

	// read configstrings — store for re-application after map load
	{
		short idx;
		while (1) {
			idx = SVD_ReadShort( f );
			if ( idx == (short)0xFFFF ) {
				break;
			}
			{
				short len = SVD_ReadShort( f );
				char buf[BIG_INFO_STRING];
				if ( len > 0 && len < (short)sizeof(buf) ) {
					FS_Read( buf, len, f );
					buf[len - 1] = '\0';
					if ( demo.savedConfigstrings[idx] ) {
						Z_Free( demo.savedConfigstrings[idx] );
					}
					demo.savedConfigstrings[idx] = CopyString( buf );
				}
			}
		}
	}

	return qtrue;
}

/*
Re-apply recorded configstrings after the map has loaded.
Called after devmap finishes in SVD_Play_f.
*/
static void SVD_ApplyConfigstrings( void ) {
	int i;
	for ( i = 0; i < MAX_CONFIGSTRINGS; i++ ) {
		// skip CS_SERVERINFO and CS_SYSTEMINFO — they contain latched cvars
		// (sv_maxclients, sv_pure, etc.) that would trigger a map restart
		if ( i == CS_SERVERINFO || i == CS_SYSTEMINFO ) {
			continue;
		}
		if ( demo.savedConfigstrings[i] && demo.savedConfigstrings[i][0] ) {
			SV_SetConfigstring( i, demo.savedConfigstrings[i] );
		}
	}
}

// ---------------------------------------------------------------
//  Playback: read one frame, populate sv.gentities
// ---------------------------------------------------------------

static qboolean SVD_ReadFrame( fileHandle_t f ) {
	int serverTime;
	short numEnts, numChanges;
	int i, entNum, msgLen;
	sharedEntity_t *ent;
	msg_t msg;
	byte msgBuf[MAX_GENTITIES * 64];
	entityState_t newEs;

	serverTime = SVD_ReadInt( f );
	if ( serverTime == -1 ) {
		return qfalse;  // end of demo
	}

	svs.time = serverTime;
	numEnts = SVD_ReadShort( f );

	// read compressed message
	msgLen = SVD_ReadInt( f );
	if ( msgLen <= 0 || msgLen > (int)sizeof(msgBuf) ) {
		return qfalse;
	}
	FS_Read( msgBuf, msgLen, f );
	MSG_Init( &msg, msgBuf, sizeof(msgBuf) );
	msg.cursize = msgLen;

	// clear all non-spectator entities
	for ( i = 0; i < sv.num_entities; i++ ) {
		if ( i == demo.spectatorClientNum ) {
			continue;
		}
		ent = SV_GentityNum( i );
		if ( ent->r.linked ) {
			SV_UnlinkEntity( ent );
		}
		ent->s.eType = 0;
		ent->s.number = i;
	}

	// parse delta-compressed entities
	while ( 1 ) {
		entNum = MSG_ReadBits( &msg, GENTITYNUM_BITS );
		if ( entNum == MAX_GENTITIES - 1 ) {
			break;  // end of entities marker
		}
		if ( msg.readcount > msg.cursize ) {
			break;
		}

		{
			entityState_t baseline;
			entityState_t *from;
			Com_Memset( &newEs, 0, sizeof(newEs) );
			if ( demo.playPrevEntities[entNum].active ) {
				from = &demo.playPrevEntities[entNum].es;
			} else {
				Com_Memset( &baseline, 0, sizeof(baseline) );
				baseline.number = entNum;
				from = &baseline;
			}
			MSG_ReadDeltaEntity( &msg, from, &newEs, entNum );
		}

		if ( newEs.number == MAX_GENTITIES - 1 ) {
			// entity was removed
			demo.playPrevEntities[entNum].active = qfalse;
			continue;
		}

		// read PVS fields
		{
			qboolean pvsChanged = MSG_ReadBits( &msg, 1 );
			if ( pvsChanged ) {
				demo.playPrevEntities[entNum].svFlags = MSG_ReadLong( &msg );
				demo.playPrevEntities[entNum].linked = MSG_ReadLong( &msg );
				demo.playPrevEntities[entNum].currentOrigin[0] = MSG_ReadFloat( &msg );
				demo.playPrevEntities[entNum].currentOrigin[1] = MSG_ReadFloat( &msg );
				demo.playPrevEntities[entNum].currentOrigin[2] = MSG_ReadFloat( &msg );
				demo.playPrevEntities[entNum].absmin[0] = MSG_ReadFloat( &msg );
				demo.playPrevEntities[entNum].absmin[1] = MSG_ReadFloat( &msg );
				demo.playPrevEntities[entNum].absmin[2] = MSG_ReadFloat( &msg );
				demo.playPrevEntities[entNum].absmax[0] = MSG_ReadFloat( &msg );
				demo.playPrevEntities[entNum].absmax[1] = MSG_ReadFloat( &msg );
				demo.playPrevEntities[entNum].absmax[2] = MSG_ReadFloat( &msg );
			}
		}

		demo.playPrevEntities[entNum].es = newEs;
		demo.playPrevEntities[entNum].active = qtrue;

		// skip the spectator's slot
		if ( entNum == demo.spectatorClientNum ) {
			continue;
		}

		// apply to server entity
		ent = SV_GentityNum( entNum );
		ent->s = newEs;
		ent->s.number = entNum;
		ent->r.svFlags = demo.playPrevEntities[entNum].svFlags;
		ent->r.linked = demo.playPrevEntities[entNum].linked;
		VectorCopy( demo.playPrevEntities[entNum].currentOrigin, ent->r.currentOrigin );
		VectorCopy( demo.playPrevEntities[entNum].absmin, ent->r.absmin );
		VectorCopy( demo.playPrevEntities[entNum].absmax, ent->r.absmax );

		if ( ent->r.linked ) {
			SV_LinkEntity( ent );
		}

		if ( entNum + 1 > sv.num_entities ) {
			sv.num_entities = entNum + 1;
		}
	}

	// ensure spectator slot is counted
	if ( demo.spectatorClientNum + 1 > sv.num_entities ) {
		sv.num_entities = demo.spectatorClientNum + 1;
	}

	// read player states (delta compressed)
	{
		msg_t psmsg;
		byte psBuf[MAX_CLIENTS * 256];
		int psMsgLen;

		psMsgLen = SVD_ReadInt( f );
		if ( psMsgLen > 0 && psMsgLen <= (int)sizeof(psBuf) ) {
			FS_Read( psBuf, psMsgLen, f );
			MSG_Init( &psmsg, psBuf, sizeof(psBuf) );
			psmsg.cursize = psMsgLen;

			while ( 1 ) {
				int clientNum = MSG_ReadBits( &psmsg, 6 );
				int active = MSG_ReadBits( &psmsg, 1 );

				if ( clientNum == MAX_CLIENTS - 1 && !active ) {
					break;  // terminator
				}
				if ( psmsg.readcount > psmsg.cursize ) {
					break;
				}

				if ( active ) {
					playerState_t newPs;
					playerState_t *from;
					playerState_t baseline;

					if ( demo.playPrevPlayers[clientNum].active ) {
						from = &demo.playPrevPlayers[clientNum].ps;
					} else {
						Com_Memset( &baseline, 0, sizeof(baseline) );
						from = &baseline;
					}

					MSG_ReadDeltaPlayerstate( &psmsg, from, &newPs );
					demo.playPrevPlayers[clientNum].ps = newPs;
					demo.playPrevPlayers[clientNum].active = qtrue;

					// inject into game module's client state
					if ( clientNum != demo.spectatorClientNum ) {
						playerState_t *gamePs = SV_GameClientNum( clientNum );
						*gamePs = newPs;
					}
				} else {
					demo.playPrevPlayers[clientNum].active = qfalse;
					// clear game playerState so G_RunFrame sees commandTime=0
					if ( clientNum != demo.spectatorClientNum ) {
						playerState_t *gamePs = SV_GameClientNum( clientNum );
						Com_Memset( gamePs, 0, sizeof(*gamePs) );
					}
				}
			}
		}
	}

	// read configstring changes
	numChanges = SVD_ReadShort( f );
	for ( i = 0; i < numChanges; i++ ) {
		short idx = SVD_ReadShort( f );
		short len = SVD_ReadShort( f );
		char buf[BIG_INFO_STRING];
		if ( len > 0 && len < (short)sizeof(buf) ) {
			FS_Read( buf, len, f );
			buf[len - 1] = '\0';
			SV_SetConfigstring( idx, buf );
		}
	}

	return qtrue;
}

// ---------------------------------------------------------------
//  Playback commands
// ---------------------------------------------------------------

void SVD_Play_f( void ) {
	char name[MAX_OSPATH];
	char *s;
	int len;

	if ( demo.playing ) {
		Com_Printf( "Already playing a server demo.\n" );
		return;
	}

	s = Cmd_Argv(1);
	if ( !s[0] ) {
		Com_Printf( "Usage: svdemo_play <demoname>\n" );
		return;
	}

	Com_sprintf( name, sizeof(name), "svdemos/%s.svdm", s );

	len = FS_FOpenFileRead( name, &demo.playFile, qtrue );
	if ( !demo.playFile || len <= 0 ) {
		Com_Printf( "ERROR: couldn't open %s.\n", name );
		return;
	}

	// read the header (populates demo.playMapName etc.)
	memset( &demo, 0, sizeof(demo) );
	demo.playFile = 0; // re-open after memset
	len = FS_FOpenFileRead( name, &demo.playFile, qtrue );

	if ( !SVD_ReadHeader( demo.playFile ) ) {
		FS_FCloseFile( demo.playFile );
		demo.playFile = 0;
		return;
	}

	demo.playing = qtrue;
	demo.endOfDemo = qfalse;

	// The spectator gets the highest slot: MAX_CLIENTS - 1
	demo.spectatorClientNum = MAX_CLIENTS - 1;

	Com_Printf( "Playing server demo: map=%s maxclients=%d fps=%d\n",
		demo.playMapName, demo.playMaxClients, demo.playFps );

	// Load the map with maxclients = MAX_CLIENTS to avoid entity slot collisions.
	Cbuf_ExecuteText( EXEC_NOW, va("set sv_maxclients %d\n", MAX_CLIENTS) );
	Cbuf_ExecuteText( EXEC_NOW, va("set sv_fps %d\n", demo.playFps) );
	Cbuf_ExecuteText( EXEC_NOW, va("devmap %s\n", demo.playMapName) );

	// Signal demo mode to the game module AFTER map load
	Cvar_Set( "sv_demoplaying", "1" );

	// Reserve recorded player slots so the connecting spectator
	// doesn't land in slot 0 (which collides with recorded player 0).
	// Mark as CS_ZOMBIE (non-free, won't be reused by SV_DirectConnect).
	// Set rate and nextSnapshotTime so SV_SendClientMessages doesn't
	// crash on division by zero or try to send them snapshots.
	{
		int i;
		for ( i = 0; i < demo.playMaxClients; i++ ) {
			if ( svs.clients[i].state == CS_FREE ) {
				svs.clients[i].state = CS_ZOMBIE;
				svs.clients[i].rate = 10000;
				svs.clients[i].nextSnapshotTime = 0x7FFFFFFF;  // never send
				svs.clients[i].lastPacketTime = svs.time;
			}
		}
	}

	// Configstrings will be applied on the first playback frame,
	// after the map has fully loaded.
	demo.needConfigstrings = qtrue;
}

void SVD_StopPlay_f( void ) {
	int i;

	if ( !demo.playing ) {
		Com_Printf( "Not playing a server demo.\n" );
		return;
	}

	FS_FCloseFile( demo.playFile );

	// free saved configstrings
	for ( i = 0; i < MAX_CONFIGSTRINGS; i++ ) {
		if ( demo.savedConfigstrings[i] ) {
			Z_Free( demo.savedConfigstrings[i] );
		}
	}
	memset( &demo, 0, sizeof(demo) );

	Cvar_Set( "sv_demoplaying", "0" );
	Com_Printf( "Server demo playback stopped.\n" );
}

/*
Called from SV_Frame() to advance playback by one frame.
Returns qtrue if a frame was read, qfalse if demo ended.
*/
qboolean SVD_PlaybackFrame( void ) {
	if ( !demo.playing || demo.endOfDemo ) {
		return qfalse;
	}

	// apply recorded configstrings once after map load
	if ( demo.needConfigstrings ) {
		SVD_ApplyConfigstrings();
		demo.needConfigstrings = qfalse;
	}

	if ( !SVD_ReadFrame( demo.playFile ) ) {
		demo.endOfDemo = qtrue;
		Com_Printf( "Server demo playback finished.\n" );
		return qfalse;
	}

	return qtrue;
}

// ---------------------------------------------------------------
//  Queries
// ---------------------------------------------------------------

qboolean SVD_IsRecording( void ) {
	return demo.recording;
}

qboolean SVD_IsPlaying( void ) {
	return demo.playing;
}

int SVD_SpectatorClientNum( void ) {
	return demo.spectatorClientNum;
}