summaryrefslogtreecommitdiff
path: root/src/xcb_io.c
blob: 59873296c3db095a8661abf6c1bce62a10a4a52f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
/* Copyright (C) 2003-2006 Jamey Sharp, Josh Triplett
 * This file is licensed under the MIT license. See the file COPYING. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "Xlibint.h"
#include "locking.h"
#include "Xprivate.h"
#include "Xxcbint.h"
#include <xcb/xcbext.h>

#include <assert.h>
#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#endif
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif

#define xcb_fail_assert(_message, _var) { \
	unsigned int _var = 1; \
	fprintf(stderr, "[xcb] Aborting, sorry about that.\n"); \
	assert(!_var); \
}

#define throw_thread_fail_assert(_message, _var) { \
	fprintf(stderr, "[xcb] " _message "\n"); \
	fprintf(stderr, "[xcb] Most likely this is a multi-threaded client " \
	                "and XInitThreads has not been called\n"); \
	xcb_fail_assert(_message, _var); \
}

/* XXX: It would probably be most useful if we stored the last-processed
 *      request, so we could find the offender from the message. */
#define throw_extlib_fail_assert(_message, _var) { \
	fprintf(stderr, "[xcb] " _message "\n"); \
	fprintf(stderr, "[xcb] This is most likely caused by a broken X " \
	                "extension library\n"); \
	xcb_fail_assert(_message, _var); \
}

static void return_socket(void *closure)
{
	Display *dpy = closure;
	InternalLockDisplay(dpy, /* don't skip user locks */ 0);
	_XSend(dpy, NULL, 0);
	dpy->bufmax = dpy->buffer;
	UnlockDisplay(dpy);
}

static void require_socket(Display *dpy)
{
	if(dpy->bufmax == dpy->buffer)
	{
		uint64_t sent;
		int flags = 0;
		/* if we don't own the event queue, we have to ask XCB
		 * to set our errors aside for us. */
		if(dpy->xcb->event_owner != XlibOwnsEventQueue)
			flags = XCB_REQUEST_CHECKED;
		if(!xcb_take_socket(dpy->xcb->connection, return_socket, dpy,
		                    flags, &sent))
			_XIOError(dpy);
		/* Xlib uses unsigned long for sequence numbers.  XCB
		 * uses 64-bit internally, but currently exposes an
		 * unsigned int API.  If these differ, Xlib cannot track
		 * the full 64-bit sequence number if 32-bit wrap
		 * happens while Xlib does not own the socket.  A
		 * complete fix would be to make XCB's public API use
		 * 64-bit sequence numbers. */
		if (sizeof(unsigned long) > sizeof(unsigned int) &&
		    dpy->xcb->event_owner == XlibOwnsEventQueue &&
		    (sent - dpy->last_request_read >= (UINT64_C(1) << 32))) {
			throw_thread_fail_assert("Sequence number wrapped "
			                         "beyond 32 bits while Xlib "
						 "did not own the socket",
			                         xcb_xlib_seq_number_wrapped);
		}
		dpy->xcb->last_flushed = dpy->request = sent;
		dpy->bufmax = dpy->xcb->real_bufmax;
	}
}

/* Call internal connection callbacks for any fds that are currently
 * ready to read. This function will not block unless one of the
 * callbacks blocks.
 *
 * This code borrowed from _XWaitForReadable. Inverse call tree:
 * _XRead
 *  _XWaitForWritable
 *   _XFlush
 *   _XSend
 *  _XEventsQueued
 *  _XReadEvents
 *  _XRead[0-9]+
 *   _XAllocIDs
 *  _XReply
 *  _XEatData
 * _XReadPad
 */
static void check_internal_connections(Display *dpy)
{
	struct _XConnectionInfo *ilist;
	fd_set r_mask;
	struct timeval tv;
	int result;
	int highest_fd = -1;

	if(dpy->flags & XlibDisplayProcConni || !dpy->im_fd_info)
		return;

	FD_ZERO(&r_mask);
	for(ilist = dpy->im_fd_info; ilist; ilist = ilist->next)
	{
		assert(ilist->fd >= 0);
		FD_SET(ilist->fd, &r_mask);
		if(ilist->fd > highest_fd)
			highest_fd = ilist->fd;
	}
	assert(highest_fd >= 0);

	tv.tv_sec = 0;
	tv.tv_usec = 0;
	result = select(highest_fd + 1, &r_mask, NULL, NULL, &tv);

	if(result == -1)
	{
		if(errno == EINTR)
			return;
		_XIOError(dpy);
	}

	for(ilist = dpy->im_fd_info; result && ilist; ilist = ilist->next)
		if(FD_ISSET(ilist->fd, &r_mask))
		{
			_XProcessInternalConnection(dpy, ilist);
			--result;
		}
}

static PendingRequest *append_pending_request(Display *dpy, unsigned long sequence)
{
	PendingRequest *node = malloc(sizeof(PendingRequest));
	assert(node);
	node->next = NULL;
	node->sequence = sequence;
	node->reply_waiter = 0;
	if(dpy->xcb->pending_requests_tail)
	{
		if (XLIB_SEQUENCE_COMPARE(dpy->xcb->pending_requests_tail->sequence,
		                          >=, node->sequence))
			throw_thread_fail_assert("Unknown sequence number "
			                         "while appending request",
			                         xcb_xlib_unknown_seq_number);
		if (dpy->xcb->pending_requests_tail->next != NULL)
			throw_thread_fail_assert("Unknown request in queue "
			                         "while appending request",
			                         xcb_xlib_unknown_req_pending);
		dpy->xcb->pending_requests_tail->next = node;
	}
	else
		dpy->xcb->pending_requests = node;
	dpy->xcb->pending_requests_tail = node;
	return node;
}

static void dequeue_pending_request(Display *dpy, PendingRequest *req)
{
	if (req != dpy->xcb->pending_requests)
		throw_thread_fail_assert("Unknown request in queue while "
		                         "dequeuing",
		                         xcb_xlib_unknown_req_in_deq);

	dpy->xcb->pending_requests = req->next;
	if(!dpy->xcb->pending_requests)
	{
		if (req != dpy->xcb->pending_requests_tail)
			throw_thread_fail_assert("Unknown request in queue "
			                         "while dequeuing",
			                         xcb_xlib_unknown_req_in_deq);
		dpy->xcb->pending_requests_tail = NULL;
	}
	else if (XLIB_SEQUENCE_COMPARE(req->sequence, >=,
	                               dpy->xcb->pending_requests->sequence))
		throw_thread_fail_assert("Unknown sequence number while "
		                         "dequeuing request",
		                         xcb_xlib_threads_sequence_lost);

	free(req);
}

static int handle_error(Display *dpy, xError *err, Bool in_XReply)
{
	_XExtension *ext;
	int ret_code;
	/* Oddly, Xlib only allows extensions to suppress errors when
	 * those errors were seen by _XReply. */
	if(in_XReply)
		/*
		 * we better see if there is an extension who may
		 * want to suppress the error.
		 */
		for(ext = dpy->ext_procs; ext; ext = ext->next)
			if(ext->error && (*ext->error)(dpy, err, &ext->codes, &ret_code))
				return ret_code;
	_XError(dpy, err);
	return 0;
}

/* Widen a 32-bit sequence number into a native-word-size (unsigned long)
 * sequence number.  Treating the comparison as a 1 and shifting it avoids a
 * conditional branch, and shifting by 16 twice avoids a compiler warning when
 * sizeof(unsigned long) == 4. */
static void widen(unsigned long *wide, unsigned int narrow)
{
	unsigned long new = (*wide & ~0xFFFFFFFFUL) | narrow;
	*wide = new + ((unsigned long) (new < *wide) << 16 << 16);
}

/* Thread-safety rules:
 *
 * At most one thread can be reading from XCB's event queue at a time.
 * If you are not the current event-reading thread and you need to find
 * out if an event is available, you must wait.
 *
 * The same rule applies for reading replies.
 *
 * A single thread cannot be both the the event-reading and the
 * reply-reading thread at the same time.
 *
 * We always look at both the current event and the first pending reply
 * to decide which to process next.
 *
 * We always process all responses in sequence-number order, which may
 * mean waiting for another thread (either the event_waiter or the
 * reply_waiter) to handle an earlier response before we can process or
 * return a later one. If so, we wait on the corresponding condition
 * variable for that thread to process the response and wake us up.
 */

static xcb_generic_reply_t *poll_for_event(Display *dpy)
{
	/* Make sure the Display's sequence numbers are valid */
	require_socket(dpy);

	/* Precondition: This thread can safely get events from XCB. */
	assert(dpy->xcb->event_owner == XlibOwnsEventQueue && !dpy->xcb->event_waiter);

	if(!dpy->xcb->next_event)
		dpy->xcb->next_event = xcb_poll_for_event(dpy->xcb->connection);

	if(dpy->xcb->next_event)
	{
		PendingRequest *req = dpy->xcb->pending_requests;
		xcb_generic_event_t *event = dpy->xcb->next_event;
		unsigned long event_sequence = dpy->last_request_read;
		widen(&event_sequence, event->full_sequence);
		if(!req || XLIB_SEQUENCE_COMPARE(event_sequence, <, req->sequence)
		        || (event->response_type != X_Error && event_sequence == req->sequence))
		{
			if (XLIB_SEQUENCE_COMPARE(event_sequence, >,
			                          dpy->request))
			{
				throw_thread_fail_assert("Unknown sequence "
				                         "number while "
							 "processing queue",
				                xcb_xlib_threads_sequence_lost);
			}
			dpy->last_request_read = event_sequence;
			dpy->xcb->next_event = NULL;
			return (xcb_generic_reply_t *) event;
		}
	}
	return NULL;
}

static xcb_generic_reply_t *poll_for_response(Display *dpy)
{
	void *response;
	xcb_generic_error_t *error;
	PendingRequest *req;
	while(!(response = poll_for_event(dpy)) &&
	      (req = dpy->xcb->pending_requests) &&
	      !req->reply_waiter &&
	      xcb_poll_for_reply(dpy->xcb->connection, req->sequence, &response, &error))
	{
		if(XLIB_SEQUENCE_COMPARE(req->sequence, >, dpy->request))
		{
			throw_thread_fail_assert("Unknown sequence number "
			                         "while awaiting reply",
			                        xcb_xlib_threads_sequence_lost);
		}
		dpy->last_request_read = req->sequence;
		if(response)
			break;
		dequeue_pending_request(dpy, req);
		if(error)
			return (xcb_generic_reply_t *) error;
	}
	return response;
}

static void handle_response(Display *dpy, xcb_generic_reply_t *response, Bool in_XReply)
{
	_XAsyncHandler *async, *next;
	switch(response->response_type)
	{
	case X_Reply:
		for(async = dpy->async_handlers; async; async = next)
		{
			next = async->next;
			if(async->handler(dpy, (xReply *) response, (char *) response, sizeof(xReply) + (response->length << 2), async->data))
				break;
		}
		break;

	case X_Error:
		handle_error(dpy, (xError *) response, in_XReply);
		break;

	default: /* event */
		/* GenericEvents may be > 32 bytes. In this case, the
		 * event struct is trailed by the additional bytes. the
		 * xcb_generic_event_t struct uses 4 bytes for internal
		 * numbering, so we need to shift the trailing data to
		 * be after the first 32 bytes. */
		if(response->response_type == GenericEvent && ((xcb_ge_event_t *) response)->length)
		{
			xcb_ge_event_t *event = (xcb_ge_event_t *) response;
			memmove(&event->full_sequence, &event[1], event->length * 4);
		}
		_XEnq(dpy, (xEvent *) response);
		break;
	}
	free(response);
}

int _XEventsQueued(Display *dpy, int mode)
{
	xcb_generic_reply_t *response;
	if(dpy->flags & XlibDisplayIOError)
		return 0;
	if(dpy->xcb->event_owner != XlibOwnsEventQueue)
		return 0;

	if(mode == QueuedAfterFlush)
		_XSend(dpy, NULL, 0);
	else
		check_internal_connections(dpy);

	/* If another thread is blocked waiting for events, then we must
	 * let that thread pick up the next event. Since it blocked, we
	 * can reasonably claim there are no new events right now. */
	if(!dpy->xcb->event_waiter)
	{
		while((response = poll_for_response(dpy)))
			handle_response(dpy, response, False);
		if(xcb_connection_has_error(dpy->xcb->connection))
			_XIOError(dpy);
	}
	return dpy->qlen;
}

/* _XReadEvents - Flush the output queue,
 * then read as many events as possible (but at least 1) and enqueue them
 */
void _XReadEvents(Display *dpy)
{
	xcb_generic_reply_t *response;
	unsigned long serial;

	if(dpy->flags & XlibDisplayIOError)
		return;
	_XSend(dpy, NULL, 0);
	if(dpy->xcb->event_owner != XlibOwnsEventQueue)
		return;
	check_internal_connections(dpy);

	serial = dpy->next_event_serial_num;
	while(serial == dpy->next_event_serial_num || dpy->qlen == 0)
	{
		if(dpy->xcb->event_waiter)
		{
			ConditionWait(dpy, dpy->xcb->event_notify);
			/* Maybe the other thread got us an event. */
			continue;
		}

		if(!dpy->xcb->next_event)
		{
			xcb_generic_event_t *event;
			dpy->xcb->event_waiter = 1;
			UnlockDisplay(dpy);
			event = xcb_wait_for_event(dpy->xcb->connection);
			/* It appears that classic Xlib respected user
			 * locks when waking up after waiting for
			 * events. However, if this thread did not have
			 * any user locks, and another thread takes a
			 * user lock and tries to read events, then we'd
			 * deadlock. So we'll choose to let the thread
			 * that got in first consume events, despite the
			 * later thread's user locks. */
			InternalLockDisplay(dpy, /* ignore user locks */ 1);
			dpy->xcb->event_waiter = 0;
			ConditionBroadcast(dpy, dpy->xcb->event_notify);
			if(!event)
				_XIOError(dpy);
			dpy->xcb->next_event = event;
		}

		/* We've established most of the conditions for
		 * poll_for_response to return non-NULL. The exceptions
		 * are connection shutdown, and finding that another
		 * thread is waiting for the next reply we'd like to
		 * process. */

		response = poll_for_response(dpy);
		if(response)
			handle_response(dpy, response, False);
		else if(dpy->xcb->pending_requests->reply_waiter)
		{ /* need braces around ConditionWait */
			ConditionWait(dpy, dpy->xcb->reply_notify);
		}
		else
			_XIOError(dpy);
	}

	/* The preceding loop established that there is no
	 * event_waiter--unless we just called ConditionWait because of
	 * a reply_waiter, in which case another thread may have become
	 * the event_waiter while we slept unlocked. */
	if(!dpy->xcb->event_waiter)
		while((response = poll_for_response(dpy)))
			handle_response(dpy, response, False);
	if(xcb_connection_has_error(dpy->xcb->connection))
		_XIOError(dpy);
}

/*
 * _XSend - Flush the buffer and send the client data. 32 bit word aligned
 * transmission is used, if size is not 0 mod 4, extra bytes are transmitted.
 *
 * Note that the connection must not be read from once the data currently
 * in the buffer has been written.
 */
void _XSend(Display *dpy, const char *data, long size)
{
	static const xReq dummy_request;
	static char const pad[3];
	struct iovec vec[3];
	uint64_t requests;
	_XExtension *ext;
	xcb_connection_t *c = dpy->xcb->connection;
	if(dpy->flags & XlibDisplayIOError)
		return;

	if(dpy->bufptr == dpy->buffer && !size)
		return;

	/* iff we asked XCB to set aside errors, we must pick those up
	 * eventually. iff there are async handlers, we may have just
	 * issued requests that will generate replies. in either case,
	 * we need to remember to check later. */
	if(dpy->xcb->event_owner != XlibOwnsEventQueue || dpy->async_handlers)
	{
		uint64_t sequence;
		for(sequence = dpy->xcb->last_flushed + 1; sequence <= dpy->request; ++sequence)
			append_pending_request(dpy, sequence);
	}
	requests = dpy->request - dpy->xcb->last_flushed;
	dpy->xcb->last_flushed = dpy->request;

	vec[0].iov_base = dpy->buffer;
	vec[0].iov_len = dpy->bufptr - dpy->buffer;
	vec[1].iov_base = (char *)data;
	vec[1].iov_len = size;
	vec[2].iov_base = (char *)pad;
	vec[2].iov_len = -size & 3;

	for(ext = dpy->flushes; ext; ext = ext->next_flush)
	{
		int i;
		for(i = 0; i < 3; ++i)
			if(vec[i].iov_len)
				ext->before_flush(dpy, &ext->codes, vec[i].iov_base, vec[i].iov_len);
	}

	if(xcb_writev(c, vec, 3, requests) < 0)
		_XIOError(dpy);
	dpy->bufptr = dpy->buffer;
	dpy->last_req = (char *) &dummy_request;

	check_internal_connections(dpy);

	_XSetSeqSyncFunction(dpy);
}

/*
 * _XFlush - Flush the X request buffer.  If the buffer is empty, no
 * action is taken.
 */
void _XFlush(Display *dpy)
{
	require_socket(dpy);
	_XSend(dpy, NULL, 0);

	_XEventsQueued(dpy, QueuedAfterReading);
}

static const XID inval_id = ~0UL;

void _XIDHandler(Display *dpy)
{
	if (dpy->xcb->next_xid == inval_id)
		_XAllocIDs(dpy, &dpy->xcb->next_xid, 1);
}

/* _XAllocID - resource ID allocation routine. */
XID _XAllocID(Display *dpy)
{
	XID ret = dpy->xcb->next_xid;
	assert (ret != inval_id);
	dpy->xcb->next_xid = inval_id;
	_XSetPrivSyncFunction(dpy);
	return ret;
}

/* _XAllocIDs - multiple resource ID allocation routine. */
void _XAllocIDs(Display *dpy, XID *ids, int count)
{
	int i;
#ifdef XTHREADS
	if (dpy->lock)
		(*dpy->lock->user_lock_display)(dpy);
	UnlockDisplay(dpy);
#endif
	for (i = 0; i < count; i++)
		ids[i] = xcb_generate_id(dpy->xcb->connection);
#ifdef XTHREADS
	InternalLockDisplay(dpy, /* don't skip user locks */ 0);
	if (dpy->lock)
		(*dpy->lock->user_unlock_display)(dpy);
#endif
}

static void _XFreeReplyData(Display *dpy, Bool force)
{
	if(!force && dpy->xcb->reply_consumed < dpy->xcb->reply_length)
		return;
	free(dpy->xcb->reply_data);
	dpy->xcb->reply_data = NULL;
}

/*
 * _XReply - Wait for a reply packet and copy its contents into the
 * specified rep.
 * extra: number of 32-bit words expected after the reply
 * discard: should I discard data following "extra" words?
 */
Status _XReply(Display *dpy, xReply *rep, int extra, Bool discard)
{
	xcb_generic_error_t *error;
	xcb_connection_t *c = dpy->xcb->connection;
	char *reply;
	PendingRequest *current;

	if (dpy->xcb->reply_data)
		throw_extlib_fail_assert("Extra reply data still left in queue",
		                         xcb_xlib_extra_reply_data_left);

	if(dpy->flags & XlibDisplayIOError)
		return 0;

	_XSend(dpy, NULL, 0);
	if(dpy->xcb->pending_requests_tail && dpy->xcb->pending_requests_tail->sequence == dpy->request)
		current = dpy->xcb->pending_requests_tail;
	else
		current = append_pending_request(dpy, dpy->request);
	/* Don't let any other thread get this reply. */
	current->reply_waiter = 1;

	while(1)
	{
		PendingRequest *req = dpy->xcb->pending_requests;
		xcb_generic_reply_t *response;

		if(req != current && req->reply_waiter)
		{
			ConditionWait(dpy, dpy->xcb->reply_notify);
			/* Another thread got this reply. */
			continue;
		}
		req->reply_waiter = 1;
		UnlockDisplay(dpy);
		response = xcb_wait_for_reply(c, req->sequence, &error);
		/* Any user locks on another thread must have been taken
		 * while we slept in xcb_wait_for_reply. Classic Xlib
		 * ignored those user locks in this case, so we do too. */
		InternalLockDisplay(dpy, /* ignore user locks */ 1);

		/* We have the response we're looking for. Now, before
		 * letting anyone else process this sequence number, we
		 * need to process any events that should have come
		 * earlier. */

		if(dpy->xcb->event_owner == XlibOwnsEventQueue)
		{
			xcb_generic_reply_t *event;
			/* If some thread is already waiting for events,
			 * it will get the first one. That thread must
			 * process that event before we can continue. */
			/* FIXME: That event might be after this reply,
			 * and might never even come--or there might be
			 * multiple threads trying to get events. */
			while(dpy->xcb->event_waiter)
			{ /* need braces around ConditionWait */
				ConditionWait(dpy, dpy->xcb->event_notify);
			}
			while((event = poll_for_event(dpy)))
				handle_response(dpy, event, True);
		}

		req->reply_waiter = 0;
		ConditionBroadcast(dpy, dpy->xcb->reply_notify);
		if(XLIB_SEQUENCE_COMPARE(req->sequence, >, dpy->request)) {
			throw_thread_fail_assert("Unknown sequence number "
			                         "while processing reply",
			                        xcb_xlib_threads_sequence_lost);
		}
		dpy->last_request_read = req->sequence;
		if(!response)
			dequeue_pending_request(dpy, req);

		if(req == current)
		{
			reply = (char *) response;
			break;
		}

		if(error)
			handle_response(dpy, (xcb_generic_reply_t *) error, True);
		else if(response)
			handle_response(dpy, response, True);
	}
	check_internal_connections(dpy);

	if(dpy->xcb->next_event && dpy->xcb->next_event->response_type == X_Error)
	{
		xcb_generic_event_t *event = dpy->xcb->next_event;
		unsigned long event_sequence = dpy->last_request_read;
		widen(&event_sequence, event->full_sequence);
		if(event_sequence == dpy->last_request_read)
		{
			error = (xcb_generic_error_t *) event;
			dpy->xcb->next_event = NULL;
		}
	}

	if(error)
	{
		int ret_code;

		/* Xlib is evil and assumes that even errors will be
		 * copied into rep. */
		memcpy(rep, error, 32);

		/* do not die on "no such font", "can't allocate",
		   "can't grab" failures */
		switch(error->error_code)
		{
			case BadName:
				switch(error->major_code)
				{
					case X_LookupColor:
					case X_AllocNamedColor:
						free(error);
						return 0;
				}
				break;
			case BadFont:
				if(error->major_code == X_QueryFont) {
					free(error);
					return 0;
				}
				break;
			case BadAlloc:
			case BadAccess:
				free(error);
				return 0;
		}

		ret_code = handle_error(dpy, (xError *) error, True);
		free(error);
		return ret_code;
	}

	/* it's not an error, but we don't have a reply, so it's an I/O
	 * error. */
	if(!reply)
	{
		_XIOError(dpy);
		return 0;
	}

	/* there's no error and we have a reply. */
	dpy->xcb->reply_data = reply;
	dpy->xcb->reply_consumed = sizeof(xReply) + (extra * 4);
	dpy->xcb->reply_length = sizeof(xReply);
	if(dpy->xcb->reply_data[0] == 1)
		dpy->xcb->reply_length += (((xcb_generic_reply_t *) dpy->xcb->reply_data)->length * 4);

	/* error: Xlib asks too much. give them what we can anyway. */
	if(dpy->xcb->reply_length < dpy->xcb->reply_consumed)
		dpy->xcb->reply_consumed = dpy->xcb->reply_length;

	memcpy(rep, dpy->xcb->reply_data, dpy->xcb->reply_consumed);
	_XFreeReplyData(dpy, discard);
	return 1;
}

int _XRead(Display *dpy, char *data, long size)
{
	assert(size >= 0);
	if(size == 0)
		return 0;
	if(dpy->xcb->reply_data == NULL ||
	   dpy->xcb->reply_consumed + size > dpy->xcb->reply_length)
		throw_extlib_fail_assert("Too much data requested from _XRead",
		                         xcb_xlib_too_much_data_requested);
	memcpy(data, dpy->xcb->reply_data + dpy->xcb->reply_consumed, size);
	dpy->xcb->reply_consumed += size;
	_XFreeReplyData(dpy, False);
	return 0;
}

/*
 * _XReadPad - Read bytes from the socket taking into account incomplete
 * reads.  If the number of bytes is not 0 mod 4, read additional pad
 * bytes.
 */
void _XReadPad(Display *dpy, char *data, long size)
{
	_XRead(dpy, data, size);
	dpy->xcb->reply_consumed += -size & 3;
	_XFreeReplyData(dpy, False);
}

/* Read and discard "n" 8-bit bytes of data */
void _XEatData(Display *dpy, unsigned long n)
{
	dpy->xcb->reply_consumed += n;
	_XFreeReplyData(dpy, False);
}

/*
 * Read and discard "n" 32-bit words of data
 * Matches the units of the length field in X protocol replies, and provides
 * a single implementation of overflow checking to avoid having to replicate
 * those checks in every caller.
 */
void _XEatDataWords(Display *dpy, unsigned long n)
{
	if (n < ((INT_MAX - dpy->xcb->reply_consumed) >> 2))
		dpy->xcb->reply_consumed += (n << 2);
	else
		/* Overflow would happen, so just eat the rest of the reply */
		dpy->xcb->reply_consumed = dpy->xcb->reply_length;
	_XFreeReplyData(dpy, False);
}

unsigned long
_XNextRequest(Display *dpy)
{
    /* This will update dpy->request. The assumption is that the next thing
     * that the application will do is make a request so there's little
     * overhead.
     */
    require_socket(dpy);
    return NextRequest(dpy);
}