- Added selective compression of network packets. Interestingly, most packets

don't actually compress all that well, even the ones that aren't too short
  to possibly compress. (Maybe make the whole thing one long, never-ending
  zlib data stream with Z_SYNC_FLUSH used to chunk things at packet
  boundaries? That would probably help the compression ratio, but it would
  require changing the way the netcode determines sequence, which would be
  a much more invasive change.)


SVN r1438 (trunk)

docs/rh-log.txt

@@ -1,4 +1,13 @@
-February 21, 2009  (Changes by Graf Zahl)
+February 21, 2009
+- Added selective compression of network packets. Interestingly, most packets
+  don't actually compress all that well, even the ones that aren't too short
+  to possibly compress. (Maybe make the whole thing one long, never-ending
+  zlib data stream with Z_SYNC_FLUSH used to chunk things at packet
+  boundaries? That would probably help the compression ratio, but it would
+  require changing the way the netcode determines sequence, which would be
+  a much more invasive change.)
+
+February 21, 2009  (Changes by Graf Zahl)
 - Fixed: Heretic's fullscreen HUD crashed when the player had armor without
   a valid icon.
 - Fixed: The StrifePlayer was missing a RunHealth setting.

src/d_net.cpp

@@ -67,35 +67,6 @@ EXTERN_CVAR (Int, autosavecount)
 //#define SIMULATEERRORS		(RAND_MAX/3)
 #define SIMULATEERRORS			0
 
-#define NCMD_EXIT				0x80
-#define NCMD_RETRANSMIT 		0x40
-#define NCMD_SETUP				0x20
-#define NCMD_MULTI				0x10		// multiple players in this packet
-#define NCMD_QUITTERS			0x08		// one or more players just quit (packet server only)
-
-#define NCMD_XTICS				0x03		// packet contains >2 tics
-#define NCMD_2TICS				0x02		// packet contains 2 tics
-#define NCMD_1TICS				0x01		// packet contains 1 tic
-#define NCMD_0TICS				0x00		// packet contains 0 tics
-
-// [RH]
-// New generic packet structure:
-//
-// Header:
-//  One byte with above flags.
-//  One byte with starttic
-//  One byte with master's maketic (master -> slave only!)
-//  If NCMD_RETRANSMIT set, one byte with retransmitfrom
-//  If NCMD_XTICS set, one byte with number of tics (minus 3, so theoretically up to 258 tics in one packet)
-//  If NCMD_QUITTERS, one byte with number of players followed by one byte with each player's consolenum
-//  If NCMD_MULTI, one byte with number of players followed by one byte with each player's consolenum
-//     - The first player's consolenum is not included in this list, because it always matches the sender
-//
-// For each tic:
-//  Two bytes with consistancy check, followed by tic data
-//
-// Setup packets are different, and are described just before D_ArbitrateNetStart().
-
 extern BYTE		*demo_p;		// [RH] Special "ticcmds" get recorded in demos
 extern char		savedescription[SAVESTRINGSIZE];
 extern FString	savegamefile;

src/d_net.h

@@ -48,7 +48,7 @@
 // Probably not enough.
 #define MAX_MSGLEN		(BACKUPTICS*10)
 #else
-#define MAX_MSGLEN		1400
+#define MAX_MSGLEN		14000
 #endif
 
 #define CMD_SEND	1
@@ -144,4 +144,34 @@ extern	int 			nettics[MAXNETNODES];
 extern	ticcmd_t		netcmds[MAXPLAYERS][BACKUPTICS];
 extern	int 			ticdup;
 
+// [RH]
+// New generic packet structure:
+//
+// Header:
+//  One byte with following flags.
+//  One byte with starttic
+//  One byte with master's maketic (master -> slave only!)
+//  If NCMD_RETRANSMIT set, one byte with retransmitfrom
+//  If NCMD_XTICS set, one byte with number of tics (minus 3, so theoretically up to 258 tics in one packet)
+//  If NCMD_QUITTERS, one byte with number of players followed by one byte with each player's consolenum
+//  If NCMD_MULTI, one byte with number of players followed by one byte with each player's consolenum
+//     - The first player's consolenum is not included in this list, because it always matches the sender
+//
+// For each tic:
+//  Two bytes with consistancy check, followed by tic data
+//
+// Setup packets are different, and are described just before D_ArbitrateNetStart().
+
+#define NCMD_EXIT				0x80
+#define NCMD_RETRANSMIT 		0x40
+#define NCMD_SETUP				0x20
+#define NCMD_MULTI				0x10		// multiple players in this packet
+#define NCMD_QUITTERS			0x08		// one or more players just quit (packet server only)
+#define NCMD_COMPRESSED			0x04		// remainder of packet is compressed
+
+#define NCMD_XTICS				0x03		// packet contains >2 tics
+#define NCMD_2TICS				0x02		// packet contains 2 tics
+#define NCMD_1TICS				0x01		// packet contains 1 tic
+#define NCMD_0TICS				0x00		// packet contains 0 tics
+
 #endif

src/i_net.cpp

@@ -64,7 +64,9 @@
 
 #include "i_net.h"
 
-
+// As per http://support.microsoft.com/kb/q192599/ the standard
+// size for network buffers is 8k.
+#define TRANSMIT_SIZE		8000
 
 /* [Petteri] Get more portable: */
 #ifndef __WIN32__
@@ -133,6 +135,8 @@ struct PreGamePacket
 	} machines[MAXNETNODES];
 };
 
+BYTE TransmitBuffer[TRANSMIT_SIZE];
+
 //
 // UDPsocket
 //
@@ -191,11 +195,47 @@ void PacketSend (void)
 {
 	int c;
 
-	//printf ("sending %i\n",gametic);
+	// FIXME: Catch this before we've overflown the buffer. With long chat
-	c = sendto (mysocket , (const char*)doomcom.data, doomcom.datalength
+	// text and lots of backup tics, it could conceivably happen. (Though
-				,0,(sockaddr *)&sendaddress[doomcom.remotenode]
+	// apparently it hasn't yet, which is good.)
-				,sizeof(sendaddress[doomcom.remotenode]));
+	if (doomcom.datalength > MAX_MSGLEN)
+	{
+		I_FatalError("Netbuffer overflow!");
+	}
 
+	uLong size = TRANSMIT_SIZE - 1;
+	if (doomcom.datalength >= 10)
+	{
+		assert(!(doomcom.data[0] & NCMD_COMPRESSED));
+		TransmitBuffer[0] = doomcom.data[0] | NCMD_COMPRESSED;
+		c = compress2(TransmitBuffer + 1, &size, doomcom.data + 1, doomcom.datalength - 1, 9);
+		size += 1;
+	}
+	else
+	{
+		c = -1;	// Just some random error code to avoid sending the compressed buffer.
+	}
+	if (c == Z_OK && size < (uLong)doomcom.datalength)
+	{
+//		Printf("send %lu/%d\n", size, doomcom.datalength);
+		c = sendto(mysocket, (char *)TransmitBuffer, size,
+			0, (sockaddr *)&sendaddress[doomcom.remotenode],
+			sizeof(sendaddress[doomcom.remotenode]));
+	}
+	else
+	{
+		if (doomcom.datalength > TRANSMIT_SIZE)
+		{
+			I_Error("Net compression failed (zlib error %d)", c);
+		}
+		else
+		{
+//			Printf("send %d\n", doomcom.datalength);
+			c = sendto(mysocket, (char *)doomcom.data, doomcom.datalength,
+				0, (sockaddr *)&sendaddress[doomcom.remotenode],
+				sizeof(sendaddress[doomcom.remotenode]));
+		}
+	}
 	//	if (c == -1)
 	//			I_Error ("SendPacket error: %s",strerror(errno));
 }
@@ -212,8 +252,8 @@ void PacketGet (void)
 	int node;
 
 	fromlen = sizeof(fromaddress);
-	c = recvfrom (mysocket, (char*)doomcom.data, MAX_MSGLEN, 0
+	c = recvfrom (mysocket, (char*)TransmitBuffer, TRANSMIT_SIZE, 0,
-				  , (sockaddr *)&fromaddress, &fromlen);
+				  (sockaddr *)&fromaddress, &fromlen);
 	node = FindNode (&fromaddress);
 
 	if (node >= 0 && c == SOCKET_ERROR)
@@ -239,6 +279,26 @@ void PacketGet (void)
 			return;
 		}
 	}
+	else if (c > 0)
+	{
+		doomcom.data[0] = TransmitBuffer[0] & ~NCMD_COMPRESSED;
+		if (TransmitBuffer[0] & NCMD_COMPRESSED)
+		{
+			uLongf msgsize = MAX_MSGLEN - 1;
+			int err = uncompress(doomcom.data + 1, &msgsize, TransmitBuffer + 1, c - 1);
+//			Printf("recv %d/%lu\n", c, msgsize + 1);
+			if (err != Z_OK)
+			{
+				I_Error("Net decompression failed (zlib error %d)\n", err);
+			}
+			c = msgsize + 1;
+		}
+		else
+		{
+//			Printf("recv %d\n", c);
+			memcpy(doomcom.data + 1, TransmitBuffer + 1, c - 1);
+		}
+	}
 
 	doomcom.remotenode = node;
 	doomcom.datalength = (short)c;