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Revision: 1.87
Committed: Tue Nov 6 03:45:17 2012 UTC (13 years, 10 months ago) by root
Content type: text/plain
Branch: MAIN
Changes since 1.86: +119 -6 lines
Log Message:
websockets, a bit of them

File Contents

# User Rev Content
1 elmex 1.1 /*
2 root 1.62 * This file is part of Deliantra, the Roguelike Realtime MMORPG.
3 root 1.85 *
4 root 1.84 * Copyright (©) 2005,2006,2007,2008,2009,2010,2011,2012 Marc Alexander Lehmann / Robin Redeker / the Deliantra team
5 root 1.85 *
6 root 1.71 * Deliantra is free software: you can redistribute it and/or modify it under
7     * the terms of the Affero GNU General Public License as published by the
8     * Free Software Foundation, either version 3 of the License, or (at your
9     * option) any later version.
10 root 1.85 *
11 root 1.49 * This program is distributed in the hope that it will be useful,
12     * but WITHOUT ANY WARRANTY; without even the implied warranty of
13     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14     * GNU General Public License for more details.
15 root 1.85 *
16 root 1.71 * You should have received a copy of the Affero GNU General Public License
17     * and the GNU General Public License along with this program. If not, see
18     * <http://www.gnu.org/licenses/>.
19 root 1.85 *
20 root 1.62 * The authors can be reached via e-mail to <support@deliantra.net>
21 pippijn 1.32 */
22 root 1.42
23 elmex 1.1 using namespace std;
24    
25     #include <global.h>
26     #include <sproto.h>
27 root 1.11 #include <cstdarg>
28 elmex 1.1
29 root 1.45 #if HAVE_TCP_INFO
30 elmex 1.1 # include <sys/types.h>
31     # include <sys/socket.h>
32     # include <netinet/in.h>
33     # include <netinet/tcp.h>
34     #endif
35    
36 root 1.43 // force a packet when idle for more than this many seconds,
37     // forcing an ack regularly.
38     #define IDLE_PING 2.
39 elmex 1.1
40 root 1.5 void
41 root 1.22 client::flush ()
42 elmex 1.1 {
43 root 1.29 if (destroyed ())
44     return;
45    
46 root 1.20 /**
47     * Writes data to socket.
48     *
49     * When the socket is clear to write, and we have backlogged data, this
50     * is called to write it out.
51     */
52    
53 root 1.43 // write a nop to the socket at least every IDLE_NOP seconds.
54     if (!outputbuffer.len)
55     {
56 root 1.47 if (last_send + IDLE_PING <= NOW && pl && pl->active)
57 root 1.43 {
58 root 1.82 // this is a bit ugly, but map1a seems to be the only
59     // nop'able command and it is quite small.
60 root 1.80 packet sl ("map1a");
61 root 1.43 send_packet (sl);
62     }
63     else
64     return;
65     }
66    
67 root 1.63 if (socket_ev.poll () & EV_WRITE)
68 root 1.20 return;
69    
70 root 1.43 last_send = NOW;
71 root 1.20 write_outputbuffer ();
72     }
73 elmex 1.1
74 root 1.20 void
75 root 1.22 client::write_outputbuffer ()
76 root 1.20 {
77     while (outputbuffer.len)
78     {
79     int res = write (fd, outputbuffer.data + outputbuffer.start,
80     min (outputbuffer.len, SOCKETBUFSIZE - outputbuffer.start));
81 root 1.5
82 root 1.20 if (res > 0)
83     {
84     outputbuffer.start += res;
85     /* wrap back to start of buffer */
86     if (outputbuffer.start == SOCKETBUFSIZE)
87     outputbuffer.start = 0;
88    
89     outputbuffer.len -= res;
90     }
91     else if (res == 0)
92     {
93     LOG (llevError, "socket write failed, connection closed.\n");
94 root 1.23 destroy ();
95 root 1.20 return;
96     }
97     else if (errno == EINTR)
98     {
99     // just retry
100     }
101     else if (errno == EAGAIN)
102     {
103     // delay till ready
104 root 1.63 socket_ev.poll (socket_ev.poll () | EV_WRITE);
105 root 1.20 socket_ev.start ();
106     return;
107     }
108     else
109     {
110     LOG (llevError, "socket write failed: %s\n", strerror (errno));
111 root 1.23 destroy ();
112 root 1.20 return;
113     }
114     }
115    
116 root 1.63 socket_ev.poll (socket_ev.poll () & ~EV_WRITE);
117 elmex 1.1 }
118    
119 root 1.23 /******************************************************************************
120 elmex 1.1 *
121 root 1.23 * Start of read routines.
122 elmex 1.1 *
123 root 1.23 ******************************************************************************/
124 elmex 1.1
125 root 1.23 int
126     client::next_packet ()
127 elmex 1.1 {
128 root 1.23 if (inbuf_len >= 2)
129 root 1.11 {
130 root 1.23 int pkt_len = (inbuf [0] << 8) | inbuf [1];
131    
132     if (inbuf_len >= 2 + pkt_len)
133     return 2 + pkt_len;
134    
135     if (inbuf_len == sizeof (inbuf))
136 root 1.15 {
137 root 1.53 send_packet_printf ("drawinfo %d input buffer overflow - closing connection.", NDI_RED | NDI_REPLY);
138 root 1.23 destroy ();
139     return -1;
140 root 1.15 }
141 root 1.11 }
142 root 1.9
143 root 1.23 return 0;
144 root 1.11 }
145 root 1.9
146 root 1.23 void
147     client::skip_packet (int len)
148 root 1.11 {
149 root 1.23 inbuf_len -= len;
150     memmove (inbuf, inbuf + len, inbuf_len);
151 elmex 1.1 }
152    
153 root 1.23 /*****************************************************************************
154     * Start of command dispatch area.
155     * The commands here are protocol commands.
156     ****************************************************************************/
157    
158     // SocketCommand, PlayingCommand, should not exist with those ugly casts
159     #define SC(cb) (void *)static_cast<void (*)(char *, int, client *)>(cb),
160     #define PC(cb) (void *)static_cast<void (*)(char *, int, player *)>(cb), PF_PLAYER |
161    
162 root 1.76 static void
163     NopCmd (char *, int, client *)
164     {
165     // do nothing
166     }
167    
168 root 1.23 /**
169     * Dispatch table for the server.
170     */
171     static struct packet_type packets[] = {
172 root 1.33 {"ncom", PC(NewPlayerCmd) PF_PLAYING | PF_COMMAND6 },
173     {"command", PC(PlayerCmd) PF_PLAYING | PF_COMMAND0 },
174 root 1.23
175     {"examine", PC(ExamineCmd) PF_PLAYING },
176 root 1.39 {"ex", PC(ExCmd) PF_PLAYING },
177 root 1.23 {"apply", PC(ApplyCmd) PF_PLAYING },
178     {"lookat", PC(LookAt) PF_PLAYING },
179     {"lock", PC(LockItem) PF_PLAYING },
180     {"mark", PC(MarkItem) PF_PLAYING },
181     {"move", PC(MoveCmd) PF_PLAYING },
182 root 1.77 {"ext", PC(ExtCmd) 0 }, // CF+/Deliantra
183 root 1.39 {"mapredraw", PC(MapRedrawCmd) 0 },
184 root 1.77 {"mapinfo", PC(MapInfoCmd) 0 }, // CF+/Deliantra
185 root 1.23
186 root 1.28 {"reply", SC(ReplyCmd) 0 },
187 root 1.77 {"exti", SC(ExtiCmd) 0 }, // CF+/Deliantra
188 root 1.26 {"addme", SC(AddMeCmd) 0 },
189 root 1.36 {"askface", SC(AskFaceCmd) 0 },
190 root 1.26 {"requestinfo", SC(RequestInfo) 0 },
191     {"setsound", SC(SetSound) 0 },
192     {"setup", SC(SetUp) 0 },
193     {"version", SC(VersionCmd) 0 },
194 root 1.76
195 root 1.77 {"toggleextendedtext", SC(NopCmd) 0 }, // deliantra: disabled
196 root 1.23 };
197    
198     bool
199     client::may_execute (const packet_type *pkt) const
200 elmex 1.1 {
201 root 1.23 return (!(pkt->flags & PF_PLAYER) || pl)
202 root 1.29 && (!(pkt->flags & PF_PLAYING) || state == ST_PLAYING);
203 root 1.11 }
204 root 1.9
205 root 1.33 // HACK: some commands currently should be executed
206     // even when the player is frozen. this hack detects
207     // those commands. it should be folded into may_execute,
208     // but kept seperate to emphasise the hack aspect, i.e.
209     // do it better, then remove.
210     static bool
211     always_immediate (const client *ns, const packet_type *pkt, const char *data, int len)
212     {
213     if (!(pkt->flags & (PF_COMMAND0 | PF_COMMAND6)))
214     return false;
215    
216     if (!ns->pl || !ns->pl->ob || !ns->pl->ob->map)
217     return false;
218    
219     if (pkt->flags & PF_COMMAND6)
220     {
221     data += 6;
222     len -= 6;
223     }
224    
225 root 1.70 if (len > 4 && data [ 3] == ' ' && !strncmp (data, "say " , 4)) return true;
226     if (len > 5 && data [ 4] == ' ' && !strncmp (data, "chat " , 5)) return true;
227     if (len > 6 && data [ 5] == ' ' && !strncmp (data, "shout " , 6)) return true;
228     if (len > 8 && data [ 7] == ' ' && !strncmp (data, "suicide " , 8)) return true;
229     if (len > 18 && data [17] == ' ' && !strncmp (data, "accept-invitation ", 18)) return true;
230 root 1.61
231     if (len == 7 && !strcmp (data, "suicide")) return true;
232 root 1.33
233     return false;
234     }
235    
236 root 1.23 void
237     client::execute (const packet_type *pkt, char *data, int datalen)
238 root 1.11 {
239 root 1.33 if (may_execute (pkt) || always_immediate (this, pkt, data, datalen))
240 root 1.23 {
241     //TODO: only one format
242     if (pkt->flags & PF_PLAYER)
243 root 1.74 {
244     ((void (*)(char *, int, player *))pkt->cb)((char *)data, datalen, pl);
245     pl->need_updated_stats ();
246     }
247 root 1.23 else
248     ((void (*)(char *, int, client *))pkt->cb)((char *)data, datalen, this);
249     }
250     else
251 root 1.53 send_packet_printf ("drawinfo %d ERROR: you cannot execute '%s' now.", NDI_RED | NDI_REPLY, pkt->name);
252 elmex 1.1 }
253    
254 root 1.23 bool
255     client::handle_packet ()
256 root 1.10 {
257 root 1.23 int pkt_len = next_packet ();
258    
259     if (!pkt_len)
260     return false;
261     else if (pkt_len < 0)
262     {
263     LOG (llevError, "read error on player %s\n",
264     pl && pl->ob ? &pl->ob->name : "[anonymous]");
265     destroy ();
266     return false;
267     }
268    
269 root 1.72 uint8_t save_byte = inbuf [pkt_len]; // rather ugly
270     inbuf [pkt_len] = 0; /* temporarily terminate buffer - useful for string data */
271 root 1.23
272     /* First, break out beginning word. There are at least
273     * a few commands that do not have any paremeters. If
274     * we get such a command, don't worry about trying
275     * to break it up.
276     */
277     int datalen;
278     char *data = strchr ((char *)inbuf + 2, ' ');
279    
280     if (data)
281     {
282     *data++ = 0;
283     datalen = pkt_len - (data - (char *)inbuf);
284     }
285     else
286     {
287     data = (char *)inbuf + 2; // better read garbage than segfault
288     datalen = 0;
289     }
290 root 1.15
291 root 1.78 for (packet_type *pkt = packets; pkt < packets + array_length (packets); ++pkt)
292 root 1.23 if (!strcmp ((char *)inbuf + 2, pkt->name))
293     {
294 root 1.33 if (pkt->flags & PF_PLAYER && !always_immediate (this, pkt, data, datalen))
295 root 1.26 queue_command (pkt, data, datalen);
296     else
297 root 1.23 execute (pkt, data, datalen);
298    
299     goto next_packet;
300     }
301    
302 root 1.26 // If we get here, we didn't find a valid command.
303 root 1.53 send_packet_printf ("drawinfo %d ERROR: command '%s' not supported.", NDI_RED | NDI_REPLY, (char *)inbuf + 2);
304 root 1.72
305 root 1.23 next_packet:
306 root 1.72 inbuf [pkt_len] = save_byte; // rather ugly
307 root 1.23 skip_packet (pkt_len);
308 root 1.11
309 root 1.23 // input buffer has space again
310 root 1.63 socket_ev.poll (socket_ev.poll () | EV_READ);
311 root 1.10
312 root 1.23 return true;
313 root 1.10 }
314    
315 root 1.86 void
316     client::inbuf_handle ()
317     {
318     if (!handle_packet ())
319     return;
320    
321     while (handle_packet ())
322     ;
323    
324     flush ();
325     }
326    
327 root 1.23 // callback called when socket is either readable or writable
328     void
329 root 1.63 client::socket_cb (iow &w, int revents)
330 root 1.23 {
331     //TODO remove when we have better socket cleanup logic
332 root 1.29 if (destroyed ())
333 root 1.23 {
334     socket_ev.poll (0);
335     return;
336     }
337 elmex 1.1
338 root 1.63 if (revents & EV_WRITE)
339 root 1.5 {
340 root 1.23 write_outputbuffer ();
341    
342     if (!outputbuffer.len)
343 root 1.63 socket_ev.poll (socket_ev.poll () & ~EV_WRITE);
344 root 1.23 }
345 root 1.12
346 root 1.63 if (revents & EV_READ)
347 root 1.23 {
348     //TODO: rate-limit tcp connection in better ways, important
349 pippijn 1.8
350 root 1.12 int amount = sizeof (inbuf) - inbuf_len;
351    
352 root 1.23 if (!amount)
353 root 1.5 {
354 root 1.23 // input buffer full
355 root 1.87 LOG (llevError, "input buffer overflow.");
356     destroy ();
357 root 1.23 return;
358 root 1.3 }
359 elmex 1.1
360 root 1.87 if (ws_version)
361     {
362     if (ws_inbuf_len + 4096 > ws_inbuf_alloc)
363     ws_inbuf = (uint8 *)realloc (ws_inbuf, ws_inbuf_alloc += 4096);
364    
365     int len = read (fd, ws_inbuf + ws_inbuf_len, ws_inbuf_alloc - ws_inbuf_len);
366    
367     if (len > 0)
368     {
369     ws_inbuf_len += len;
370    
371     if (ws_inbuf_len < 2 + 4) // 6 is minimum length: op, len, mask
372     return;
373    
374     int d = 2;
375     int o = ws_inbuf [0] & 15;
376     int l = ws_inbuf [1] & 127;
377    
378     if (l == 126)
379     {
380     l = (ws_inbuf [2] << 8) | ws_inbuf [3];
381     d += 2;
382     }
383     else if (l == 127)
384     {
385     if (ws_inbuf_len < 2 + 8)
386     return;
387    
388     // we don't do extra long frames, if a browser wants to send >2**32 bytes,
389     // there are bigger issues to fix.
390     l = (ws_inbuf [6] << 24)
391     | (ws_inbuf [7] << 16)
392     | (ws_inbuf [8] << 8)
393     | ws_inbuf [9];
394     d += 8;
395     }
396    
397     // we only continue if we have a complete frame
398     if (ws_inbuf_len < d + 4 + l)
399     return;
400    
401     switch (o)
402     {
403     case 0: o = ws_inbuf_type; break; // continuation
404     case 1: ws_inbuf_type = 1; break; // utf-8
405     case 2: ws_inbuf_type = 2; break; // binary
406     }
407    
408     if (l > amount)
409     {
410     // input buffer full
411     LOG (llevError, "input buffer overflow (ws).");
412     destroy ();
413     return;
414     }
415    
416     for (int i = 0; i < l; ++i)
417     inbuf [inbuf_len + i] = ws_inbuf [d + 4 + i] ^ ws_inbuf [d + (i & 3)];
418    
419     // remove frame
420     ws_inbuf_len -= d + 4 + l;
421     memmove (ws_inbuf, ws_inbuf + d + 4 + l, ws_inbuf_len);
422    
423     switch (o)
424     {
425     case 1: // utf-8
426     //TODO
427     break;
428     case 2: // binary
429     break;
430    
431     case 9: // ping
432     {
433     // send pong - we assume ping messages are <64k
434     // as we can't handle >10k at the moment anyway.
435     uint8 hdr [] = { 0x8a, 126, l >> 8, l };
436     send (hdr, sizeof (hdr));
437     send (inbuf + inbuf_len, l);
438     }
439     return;
440    
441     case 10: // pong
442     return;
443    
444     case 8: // close
445     default:
446     destroy ();
447     return;
448     }
449    
450     amount = l;
451     }
452     else
453     amount = -1;
454     }
455     else
456     amount = read (fd, inbuf + inbuf_len, amount);
457 root 1.12
458     if (!amount)
459 root 1.5 {
460 root 1.23 destroy ();
461     return;
462 root 1.5 }
463 root 1.12 else if (amount < 0)
464 root 1.5 {
465 root 1.12 if (errno != EAGAIN && errno != EINTR)
466 root 1.5 {
467 root 1.20 LOG (llevError, "read error: %s\n", strerror (errno));
468 root 1.23 destroy ();
469     return;
470 root 1.3 }
471 root 1.12
472 root 1.23 // should not be here, normally
473 root 1.3 }
474 root 1.23 else
475     {
476     inbuf_len += amount;
477 root 1.86 inbuf_handle ();
478 root 1.23 }
479 root 1.5 }
480 root 1.12 }
481    
482 elmex 1.1 /*******************************************************************************
483     *
484     * Start of write related routines.
485     *
486     ******************************************************************************/
487    
488     /**
489     * Adds data to a socket buffer for whatever reason.
490     *
491     * ns is the socket we are adding the data to, buf is the start of the
492     * data, and len is the number of bytes to add.
493     */
494 root 1.20 void
495 root 1.22 client::send (void *buf_, int len)
496 root 1.20 {
497     char *buf = (char *)buf_;
498 elmex 1.1
499 root 1.29 if (destroyed () || !buf)
500 root 1.23 return;
501 elmex 1.1
502 root 1.31 if (len + outputbuffer.len > SOCKETBUFSIZE)
503 root 1.5 {
504 root 1.23 LOG (llevDebug, "socket on fd %d has overrun internal buffer - marking as dead\n", fd);
505 root 1.36 // shutdown the socket, this is safer than destroying it immediately
506     // as lots of code in the callchain might still access the map etc.
507     shutdown (fd, SHUT_RDWR);
508 root 1.5 return;
509     }
510    
511 root 1.20 int avail, end;
512    
513 root 1.5 /* data + end is where we start putting the new data. The last byte
514     * currently in use is actually data + end -1
515     */
516 root 1.20 end = outputbuffer.start + outputbuffer.len;
517 root 1.5 /* The buffer is already in a wrapped state, so adjust end */
518     if (end >= SOCKETBUFSIZE)
519     end -= SOCKETBUFSIZE;
520 root 1.7
521 root 1.5 avail = SOCKETBUFSIZE - end;
522 elmex 1.1
523 root 1.5 /* We can all fit it behind the current data without wrapping */
524     if (avail >= len)
525 root 1.20 memcpy (outputbuffer.data + end, buf, len);
526 root 1.5 else
527     {
528 root 1.20 memcpy (outputbuffer.data + end, buf, avail);
529     memcpy (outputbuffer.data, buf + avail, len - avail);
530 elmex 1.1 }
531 root 1.7
532 root 1.20 outputbuffer.len += len;
533 elmex 1.1 }
534    
535     /**
536     * Takes a string of data, and writes it out to the socket. A very handy
537     * shortcut function.
538     */
539 root 1.13 void
540 root 1.22 client::send_packet (packet &sl)
541 root 1.13 {
542 root 1.29 if (destroyed ())
543 root 1.19 return;
544    
545 root 1.55 if (sl.length () > MAXSOCKBUF)
546 root 1.19 {
547     LOG (llevError, "Trying to send a buffer beyond properly size, len =%d\n", sl.length ());
548     /* Almost certainly we've overflowed a buffer, so quit now to make
549     * it easier to debug.
550     */
551     abort ();
552     }
553    
554     if (!sl.length ())
555     return;
556    
557 root 1.87 if (ws_version == 8)
558     {
559     uint8 hdr [4] = { 0x81, 126, sl.length () >> 8, sl.length () };
560     // TODO: utf-8 encoding
561     send (hdr, 4);
562     send (sl.buf_ + sl.hdrlen, sl.cur - sl.buf_ - sl.hdrlen);
563     }
564     else if (ws_version == 13)
565     {
566     uint8 hdr [4] = { 0x82, 126, sl.length () >> 8, sl.length () };
567     send (hdr, 4);
568     send (sl.buf_ + sl.hdrlen, sl.cur - sl.buf_ - sl.hdrlen);
569     }
570     else
571     {
572     assert (sl.hdrlen == 2);
573 root 1.19
574 root 1.87 sl.buf_ [0] = sl.length () >> 8;
575     sl.buf_ [1] = sl.length () ;
576 root 1.19
577 root 1.87 send (sl.buf_, sl.length () + sl.hdrlen);
578     }
579 root 1.13 }
580    
581 root 1.5 void
582 root 1.22 client::send_packet (const char *buf, int len)
583 elmex 1.1 {
584 root 1.14 packet sl;
585 elmex 1.1
586 root 1.13 sl << data (buf, len);
587     send_packet (sl);
588 elmex 1.1 }
589    
590 root 1.13 void
591 root 1.22 client::send_packet (const char *buf)
592 root 1.13 {
593     send_packet (buf, strlen (buf));
594     }
595 elmex 1.1
596 root 1.23 void
597     client::send_packet_printf (const char *format, ...)
598     {
599     packet sl;
600    
601     va_list ap;
602     va_start (ap, format);
603     sl.vprintf (format, ap);
604     va_end (ap);
605    
606     send_packet (sl);
607     }
608    
609 root 1.40 void
610     client::send_msg (int color, const char *type, const char *msg)
611     {
612 root 1.58 if (!msg || !type) // it can happen (for example, missing attack messages cause this)
613     {
614     LOG (logBacktrace | llevError, "send_msg(%d,%p,%p) called with NULL msg or type.\n", color, type, msg);
615     return;
616     }
617    
618 root 1.59 int len = strlen (msg);
619    
620 root 1.66 if (!(color & NDI_VERBATIM)
621     && (msg_is_special (msg)
622     || (type [0] == 'c' && type [1] == '/') || len > (MAXSOCKBUF - 128)))
623 root 1.48 cfperl_send_msg (this, color, type, msg);
624 root 1.69 else
625 root 1.53 send_packet_printf ("msg %d %s %s", color & NDI_CLIENT_MASK, type, msg);
626 root 1.40 }
627    
628 root 1.48 void
629     client::send_drawinfo (const char *msg, int flags)
630     {
631     send_msg (flags, "log", msg);
632     }
633    
634 root 1.23 /***********************************************************************
635     *
636     * packet functions/utilities
637     *
638     **********************************************************************/
639    
640 root 1.27 packet::packet (const char *name)
641     {
642     reset ();
643    
644     int len = strlen (name);
645     memcpy (cur, name, len); cur += len;
646     *cur++ = ' ';
647     }
648    
649 root 1.37 packet &packet::operator <<(const ber32 v)
650     {
651 root 1.79 enum { maxlen = 32 / 7 + 1 };
652 root 1.37 uint8 buf[maxlen];
653     uint8 *p = buf + maxlen;
654     uint32 val = v.val;
655    
656 root 1.38 *--p = val & 0x7F;
657    
658 root 1.37 while (val > 0x7F)
659     {
660 root 1.38 val >>= 7;
661 root 1.37 *--p = (val & 0x7F) | 0x80;
662     }
663    
664     return *this << data (p, buf + maxlen - p);
665     }
666    
667 root 1.23 packet &packet::operator <<(const data &v)
668     {
669     if (room () < v.len)
670     reset ();
671     else
672     {
673     if (v.len)
674     {
675     memcpy (cur, v.ptr, v.len);
676     cur += v.len;
677     }
678     }
679    
680     return *this;
681     }
682    
683     packet &packet::operator <<(const data8 &v)
684     {
685     unsigned int len = min (v.len, 0x00FF);
686     return *this << uint8 (len) << data (v.ptr, len);
687     }
688    
689     packet &packet::operator <<(const data16 &v)
690     {
691     unsigned int len = min (v.len, 0xFFFF);
692     return *this << uint16 (len) << data (v.ptr, len);
693     }
694    
695     packet &packet::operator <<(const char *v)
696     {
697     return *this << data (v, strlen (v ? v : 0));
698     }
699    
700     void
701     packet::vprintf (const char *format, va_list ap)
702     {
703     int size = room ();
704    
705     int len = vsnprintf ((char *)cur, size, format, ap);
706    
707     if (len >= size)
708     return reset ();
709    
710     cur += len;
711     }
712