summaryrefslogtreecommitdiff
path: root/src/xcb_in.c
blob: 796b4e946a1ce56d411e109b466ff3e0d8fdff34 (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
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
/* Copyright (C) 2001-2004 Bart Massey and Jamey Sharp.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 * 
 * Except as contained in this notice, the names of the authors or their
 * institutions shall not be used in advertising or otherwise to promote the
 * sale, use or other dealings in this Software without prior written
 * authorization from the authors.
 */

/* Stuff that reads stuff from the server. */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>

#if USE_POLL
#include <poll.h>
#endif
#ifndef _WIN32
#include <sys/select.h>
#include <sys/socket.h>
#endif

#ifdef _WIN32
#include "xcb_windefs.h"
#endif /* _WIN32 */

#include "xcb.h"
#include "xcbext.h"
#include "xcbint.h"

#define XCB_ERROR 0
#define XCB_REPLY 1
#define XCB_XGE_EVENT 35

struct event_list {
    xcb_generic_event_t *event;
    struct event_list *next;
};

struct xcb_special_event {

    struct xcb_special_event *next;

    /* Match XGE events for the specific extension and event ID (the
     * first 32 bit word after evtype)
     */
    uint8_t     extension;
    uint32_t    eid;
    uint32_t    *stamp;

    struct event_list   *events;
    struct event_list   **events_tail;

    pthread_cond_t special_event_cond;
};

struct reply_list {
    void *reply;
    struct reply_list *next;
};

typedef struct pending_reply {
    uint64_t first_request;
    uint64_t last_request;
    enum workarounds workaround;
    int flags;
    struct pending_reply *next;
} pending_reply;

typedef struct reader_list {
    uint64_t request;
    pthread_cond_t *data;
    struct reader_list *next;
} reader_list;

typedef struct special_list {
    xcb_special_event_t *se;
    struct special_list *next;
} special_list;

static void remove_finished_readers(reader_list **prev_reader, uint64_t completed)
{
    while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, completed))
    {
        /* If you don't have what you're looking for now, you never
         * will. Wake up and leave me alone. */
        pthread_cond_signal((*prev_reader)->data);
        *prev_reader = (*prev_reader)->next;
    }
}

#if HAVE_SENDMSG
static int read_fds(xcb_connection_t *c, int *fds, int nfd)
{
    int *ifds = &c->in.in_fd.fd[c->in.in_fd.ifd];
    int infd = c->in.in_fd.nfd - c->in.in_fd.ifd;

    if (nfd > infd)
        return 0;
    memcpy(fds, ifds, nfd * sizeof (int));
    c->in.in_fd.ifd += nfd;
    return 1;
}
#endif

typedef struct xcb_ge_special_event_t {
    uint8_t  response_type; /**<  */
    uint8_t  extension; /**<  */
    uint16_t sequence; /**<  */
    uint32_t length; /**<  */
    uint16_t evtype; /**<  */
    uint8_t  pad0[2]; /**< */
    uint32_t eid; /**< */
    uint8_t  pad1[16]; /**<  */
} xcb_ge_special_event_t;

static int event_special(xcb_connection_t *c,
                         struct event_list *event)
{
    struct xcb_special_event *special_event;
    struct xcb_ge_special_event_t *ges = (void *) event->event;

    /* Special events are always XGE events */
    if ((ges->response_type & 0x7f) != XCB_XGE_EVENT)
        return 0;

    for (special_event = c->in.special_events;
         special_event;
         special_event = special_event->next)
    {
        if (ges->extension == special_event->extension &&
            ges->eid == special_event->eid)
        {
            *special_event->events_tail = event;
            special_event->events_tail = &event->next;
            if (special_event->stamp)
                ++(*special_event->stamp);
            pthread_cond_signal(&special_event->special_event_cond);
            return 1;
        }
    }

    return 0;
}

static int read_packet(xcb_connection_t *c)
{
    xcb_generic_reply_t genrep;
    uint64_t length = 32;
    uint64_t eventlength = 0; /* length after first 32 bytes for GenericEvents */
    int nfd = 0;         /* Number of file descriptors attached to the reply */
    uint64_t bufsize;
    void *buf;
    pending_reply *pend = 0;
    struct event_list *event;

    /* Wait for there to be enough data for us to read a whole packet */
    if(c->in.queue_len < length)
        return 0;

    /* Get the response type, length, and sequence number. */
    memcpy(&genrep, c->in.queue, sizeof(genrep));

    /* Compute 32-bit sequence number of this packet. */
    if((genrep.response_type & 0x7f) != XCB_KEYMAP_NOTIFY)
    {
        uint64_t lastread = c->in.request_read;
        c->in.request_read = (lastread & UINT64_C(0xffffffffffff0000)) | genrep.sequence;
        if(XCB_SEQUENCE_COMPARE(c->in.request_read, <, lastread))
            c->in.request_read += 0x10000;
        if(XCB_SEQUENCE_COMPARE(c->in.request_read, >, c->in.request_expected))
            c->in.request_expected = c->in.request_read;

        if(c->in.request_read != lastread)
        {
            if(c->in.current_reply)
            {
                _xcb_map_put(c->in.replies, lastread, c->in.current_reply);
                c->in.current_reply = 0;
                c->in.current_reply_tail = &c->in.current_reply;
            }
            c->in.request_completed = c->in.request_read - 1;
        }

        while(c->in.pending_replies &&
              c->in.pending_replies->workaround != WORKAROUND_EXTERNAL_SOCKET_OWNER &&
              XCB_SEQUENCE_COMPARE (c->in.pending_replies->last_request, <=, c->in.request_completed))
        {
            pending_reply *oldpend = c->in.pending_replies;
            c->in.pending_replies = oldpend->next;
            if(!oldpend->next)
                c->in.pending_replies_tail = &c->in.pending_replies;
            free(oldpend);
        }

        if(genrep.response_type == XCB_ERROR)
            c->in.request_completed = c->in.request_read;

        remove_finished_readers(&c->in.readers, c->in.request_completed);
    }

    if(genrep.response_type == XCB_ERROR || genrep.response_type == XCB_REPLY)
    {
        pend = c->in.pending_replies;
        if(pend &&
           !(XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->in.request_read) &&
             (pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER ||
              XCB_SEQUENCE_COMPARE(c->in.request_read, <=, pend->last_request))))
            pend = 0;
    }

    /* For reply packets, check that the entire packet is available. */
    if(genrep.response_type == XCB_REPLY)
    {
        if(pend && pend->workaround == WORKAROUND_GLX_GET_FB_CONFIGS_BUG)
        {
            uint32_t *p = (uint32_t *) c->in.queue;
            genrep.length = p[2] * p[3] * 2;
        }
        length += genrep.length * 4;

        /* XXX a bit of a hack -- we "know" that all FD replys place
         * the number of fds in the pad0 byte */
        if (pend && pend->flags & XCB_REQUEST_REPLY_FDS)
            nfd = genrep.pad0;
    }

    /* XGE events may have sizes > 32 */
    if ((genrep.response_type & 0x7f) == XCB_XGE_EVENT)
        eventlength = genrep.length * 4;

    bufsize = length + eventlength + nfd * sizeof(int)  +
        (genrep.response_type == XCB_REPLY ? 0 : sizeof(uint32_t));
    if (bufsize < INT32_MAX)
        buf = malloc((size_t) bufsize);
    else
        buf = NULL;
    if(!buf)
    {
        _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
        return 0;
    }

    if(_xcb_in_read_block(c, buf, length) <= 0)
    {
        free(buf);
        return 0;
    }

    /* pull in XGE event data if available, append after event struct */
    if (eventlength)
    {
        if(_xcb_in_read_block(c, &((xcb_generic_event_t*)buf)[1], eventlength) <= 0)
        {
            free(buf);
            return 0;
        }
    }

#if HAVE_SENDMSG
    if (nfd)
    {
        if (!read_fds(c, (int *) &((char *) buf)[length], nfd))
        {
            free(buf);
            return 0;
        }
    }
#endif

    if(pend && (pend->flags & XCB_REQUEST_DISCARD_REPLY))
    {
        free(buf);
        return 1;
    }

    if(genrep.response_type != XCB_REPLY)
        ((xcb_generic_event_t *) buf)->full_sequence = c->in.request_read;

    /* reply, or checked error */
    if( genrep.response_type == XCB_REPLY ||
       (genrep.response_type == XCB_ERROR && pend && (pend->flags & XCB_REQUEST_CHECKED)))
    {
        struct reply_list *cur = malloc(sizeof(struct reply_list));
        if(!cur)
        {
            _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
            free(buf);
            return 0;
        }
        cur->reply = buf;
        cur->next = 0;
        *c->in.current_reply_tail = cur;
        c->in.current_reply_tail = &cur->next;
        if(c->in.readers && c->in.readers->request == c->in.request_read)
            pthread_cond_signal(c->in.readers->data);
        return 1;
    }

    /* event, or unchecked error */
    event = malloc(sizeof(struct event_list));
    if(!event)
    {
        _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
        free(buf);
        return 0;
    }
    event->event = buf;
    event->next = 0;

    if (!event_special(c, event)) {
        *c->in.events_tail = event;
        c->in.events_tail = &event->next;
        pthread_cond_signal(&c->in.event_cond);
    }
    return 1; /* I have something for you... */
}

static xcb_generic_event_t *get_event(xcb_connection_t *c)
{
    struct event_list *cur = c->in.events;
    xcb_generic_event_t *ret;
    if(!c->in.events)
        return 0;
    ret = cur->event;
    c->in.events = cur->next;
    if(!cur->next)
        c->in.events_tail = &c->in.events;
    free(cur);
    return ret;
}

static void free_reply_list(struct reply_list *head)
{
    while(head)
    {
        struct reply_list *cur = head;
        head = cur->next;
        free(cur->reply);
        free(cur);
    }
}

static int read_block(const int fd, void *buf, const ssize_t len)
{
    int done = 0;
    while(done < len)
    {
        int ret = recv(fd, ((char *) buf) + done, len - done, 0);
        if(ret > 0)
            done += ret;
#ifndef _WIN32
        if(ret < 0 && errno == EAGAIN)
#else
        if(ret == SOCKET_ERROR && WSAGetLastError() == WSAEWOULDBLOCK)
#endif /* !_Win32 */
        {
#if USE_POLL
            struct pollfd pfd;
            pfd.fd = fd;
            pfd.events = POLLIN;
            pfd.revents = 0;
            do {
                ret = poll(&pfd, 1, -1);
            } while (ret == -1 && errno == EINTR);
#else
            fd_set fds;
            FD_ZERO(&fds);
            FD_SET(fd, &fds);

            /* Initializing errno here makes sure that for Win32 this loop will execute only once */
            errno = 0;
            do {
                ret = select(fd + 1, &fds, 0, 0, 0);
            } while (ret == -1 && errno == EINTR);
#endif /* USE_POLL */
        }
        if(ret <= 0)
            return ret;
    }
    return len;
}

static int poll_for_reply(xcb_connection_t *c, uint64_t request, void **reply, xcb_generic_error_t **error)
{
    struct reply_list *head;

    /* If an error occurred when issuing the request, fail immediately. */
    if(!request)
        head = 0;
    /* We've read requests past the one we want, so if it has replies we have
     * them all and they're in the replies map. */
    else if(XCB_SEQUENCE_COMPARE(request, <, c->in.request_read))
    {
        head = _xcb_map_remove(c->in.replies, request);
        if(head && head->next)
            _xcb_map_put(c->in.replies, request, head->next);
    }
    /* We're currently processing the responses to the request we want, and we
     * have a reply ready to return. So just return it without blocking. */
    else if(request == c->in.request_read && c->in.current_reply)
    {
        head = c->in.current_reply;
        c->in.current_reply = head->next;
        if(!head->next)
            c->in.current_reply_tail = &c->in.current_reply;
    }
    /* We know this request can't have any more replies, and we've already
     * established it doesn't have a reply now. Don't bother blocking. */
    else if(request == c->in.request_completed)
        head = 0;
    /* We may have more replies on the way for this request: block until we're
     * sure. */
    else
        return 0;

    if(error)
        *error = 0;
    *reply = 0;

    if(head)
    {
        if(((xcb_generic_reply_t *) head->reply)->response_type == XCB_ERROR)
        {
            if(error)
                *error = head->reply;
            else
                free(head->reply);
        }
        else
            *reply = head->reply;

        free(head);
    }

    return 1;
}

static void insert_reader(reader_list **prev_reader, reader_list *reader, uint64_t request, pthread_cond_t *cond)
{
    while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, request))
        prev_reader = &(*prev_reader)->next;
    reader->request = request;
    reader->data = cond;
    reader->next = *prev_reader;
    *prev_reader = reader;
}

static void remove_reader(reader_list **prev_reader, reader_list *reader)
{
    while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, reader->request))
        if(*prev_reader == reader)
        {
            *prev_reader = (*prev_reader)->next;
            break;
        }
}

static void insert_special(special_list **prev_special, special_list *special, xcb_special_event_t *se)
{
    special->se = se;
    special->next = *prev_special;
    *prev_special = special;
}

static void remove_special(special_list **prev_special, special_list *special)
{
    while(*prev_special)
    {
        if(*prev_special == special)
        {
            *prev_special = (*prev_special)->next;
            break;
        }
        prev_special = &(*prev_special)->next;
    }
}

static void *wait_for_reply(xcb_connection_t *c, uint64_t request, xcb_generic_error_t **e)
{
    void *ret = 0;

    /* If this request has not been written yet, write it. */
    if(c->out.return_socket || _xcb_out_flush_to(c, request))
    {
        pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
        reader_list reader;

        insert_reader(&c->in.readers, &reader, request, &cond);

        while(!poll_for_reply(c, request, &ret, e))
            if(!_xcb_conn_wait(c, &cond, 0, 0))
                break;

        remove_reader(&c->in.readers, &reader);
        pthread_cond_destroy(&cond);
    }

    _xcb_in_wake_up_next_reader(c);
    return ret;
}

static uint64_t widen(xcb_connection_t *c, unsigned int request)
{
    uint64_t widened_request = (c->out.request & UINT64_C(0xffffffff00000000)) | request;
    if(widened_request > c->out.request)
        widened_request -= UINT64_C(1) << 32;
    return widened_request;
}

/* Public interface */

void *xcb_wait_for_reply(xcb_connection_t *c, unsigned int request, xcb_generic_error_t **e)
{
    void *ret;
    if(e)
        *e = 0;
    if(c->has_error)
        return 0;

    pthread_mutex_lock(&c->iolock);
    ret = wait_for_reply(c, widen(c, request), e);
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

void *xcb_wait_for_reply64(xcb_connection_t *c, uint64_t request, xcb_generic_error_t **e)
{
    void *ret;
    if(e)
        *e = 0;
    if(c->has_error)
        return 0;

    pthread_mutex_lock(&c->iolock);
    ret = wait_for_reply(c, request, e);
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

int *xcb_get_reply_fds(xcb_connection_t *c, void *reply, size_t reply_size)
{
    return (int *) (&((char *) reply)[reply_size]);
}

static void insert_pending_discard(xcb_connection_t *c, pending_reply **prev_next, uint64_t seq)
{
    pending_reply *pend;
    pend = malloc(sizeof(*pend));
    if(!pend)
    {
        _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
        return;
    }

    pend->first_request = seq;
    pend->last_request = seq;
    pend->workaround = 0;
    pend->flags = XCB_REQUEST_DISCARD_REPLY;
    pend->next = *prev_next;
    *prev_next = pend;

    if(!pend->next)
        c->in.pending_replies_tail = &pend->next;
}

static void discard_reply(xcb_connection_t *c, uint64_t request)
{
    void *reply;
    pending_reply **prev_pend;

    /* Free any replies or errors that we've already read. Stop if
     * xcb_wait_for_reply would block or we've run out of replies. */
    while(poll_for_reply(c, request, &reply, 0) && reply)
        free(reply);

    /* If we've proven there are no more responses coming, we're done. */
    if(XCB_SEQUENCE_COMPARE(request, <=, c->in.request_completed))
        return;

    /* Walk the list of pending requests. Mark the first match for deletion. */
    for(prev_pend = &c->in.pending_replies; *prev_pend; prev_pend = &(*prev_pend)->next)
    {
        if(XCB_SEQUENCE_COMPARE((*prev_pend)->first_request, >, request))
            break;

        if((*prev_pend)->first_request == request)
        {
            /* Pending reply found. Mark for discard: */
            (*prev_pend)->flags |= XCB_REQUEST_DISCARD_REPLY;
            return;
        }
    }

    /* Pending reply not found (likely due to _unchecked request). Create one: */
    insert_pending_discard(c, prev_pend, request);
}

void xcb_discard_reply(xcb_connection_t *c, unsigned int sequence)
{
    if(c->has_error)
        return;

    /* If an error occurred when issuing the request, fail immediately. */
    if(!sequence)
        return;

    pthread_mutex_lock(&c->iolock);
    discard_reply(c, widen(c, sequence));
    pthread_mutex_unlock(&c->iolock);
}

void xcb_discard_reply64(xcb_connection_t *c, uint64_t sequence)
{
    if(c->has_error)
        return;

    /* If an error occurred when issuing the request, fail immediately. */
    if(!sequence)
        return;

    pthread_mutex_lock(&c->iolock);
    discard_reply(c, sequence);
    pthread_mutex_unlock(&c->iolock);
}

int xcb_poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply, xcb_generic_error_t **error)
{
    int ret;
    if(c->has_error)
    {
        *reply = 0;
        if(error)
            *error = 0;
        return 1; /* would not block */
    }
    assert(reply != 0);
    pthread_mutex_lock(&c->iolock);
    ret = poll_for_reply(c, widen(c, request), reply, error);
    if(!ret && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
        ret = poll_for_reply(c, widen(c, request), reply, error);
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

int xcb_poll_for_reply64(xcb_connection_t *c, uint64_t request, void **reply, xcb_generic_error_t **error)
{
    int ret;
    if(c->has_error)
    {
        *reply = 0;
        if(error)
            *error = 0;
        return 1; /* would not block */
    }
    assert(reply != 0);
    pthread_mutex_lock(&c->iolock);
    ret = poll_for_reply(c, request, reply, error);
    if(!ret && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
        ret = poll_for_reply(c, request, reply, error);
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

xcb_generic_event_t *xcb_wait_for_event(xcb_connection_t *c)
{
    xcb_generic_event_t *ret;
    if(c->has_error)
        return 0;
    pthread_mutex_lock(&c->iolock);
    /* get_event returns 0 on empty list. */
    while(!(ret = get_event(c)))
        if(!_xcb_conn_wait(c, &c->in.event_cond, 0, 0))
            break;

    _xcb_in_wake_up_next_reader(c);
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

static xcb_generic_event_t *poll_for_next_event(xcb_connection_t *c, int queued)
{
    xcb_generic_event_t *ret = 0;
    if(!c->has_error)
    {
        pthread_mutex_lock(&c->iolock);
        /* FIXME: follow X meets Z architecture changes. */
        ret = get_event(c);
        if(!ret && !queued && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
            ret = get_event(c);
        pthread_mutex_unlock(&c->iolock);
    }
    return ret;
}

xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c)
{
    return poll_for_next_event(c, 0);
}

xcb_generic_event_t *xcb_poll_for_queued_event(xcb_connection_t *c)
{
    return poll_for_next_event(c, 1);
}

xcb_generic_error_t *xcb_request_check(xcb_connection_t *c, xcb_void_cookie_t cookie)
{
    uint64_t request;
    xcb_generic_error_t *ret = 0;
    void *reply;
    if(c->has_error)
        return 0;
    pthread_mutex_lock(&c->iolock);
    request = widen(c, cookie.sequence);
    if(XCB_SEQUENCE_COMPARE(request, >=, c->in.request_expected)
       && XCB_SEQUENCE_COMPARE(request, >, c->in.request_completed))
    {
        _xcb_out_send_sync(c);
        _xcb_out_flush_to(c, c->out.request);
    }
    reply = wait_for_reply(c, request, &ret);
    assert(!reply);
    pthread_mutex_unlock(&c->iolock);
    return ret;
}

static xcb_generic_event_t *get_special_event(xcb_connection_t *c,
                                              xcb_special_event_t *se)
{
    xcb_generic_event_t *event = NULL;
    struct event_list *events;

    if ((events = se->events) != NULL) {
        event = events->event;
        if (!(se->events = events->next))
            se->events_tail = &se->events;
        free (events);
    }
    return event;
}

xcb_generic_event_t *xcb_poll_for_special_event(xcb_connection_t *c,
                                                xcb_special_event_t *se)
{
    xcb_generic_event_t *event;

    if(c->has_error)
        return 0;
    pthread_mutex_lock(&c->iolock);
    event = get_special_event(c, se);
    if(!event && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
        event = get_special_event(c, se);
    pthread_mutex_unlock(&c->iolock);
    return event;
}

xcb_generic_event_t *xcb_wait_for_special_event(xcb_connection_t *c,
                                                xcb_special_event_t *se)
{
    special_list special;
    xcb_generic_event_t *event;

    if(c->has_error)
        return 0;
    pthread_mutex_lock(&c->iolock);

    insert_special(&c->in.special_waiters, &special, se);

    /* get_special_event returns 0 on empty list. */
    while(!(event = get_special_event(c, se)))
        if(!_xcb_conn_wait(c, &se->special_event_cond, 0, 0))
            break;

    remove_special(&c->in.special_waiters, &special);

    _xcb_in_wake_up_next_reader(c);
    pthread_mutex_unlock(&c->iolock);
    return event;
}

xcb_special_event_t *
xcb_register_for_special_xge(xcb_connection_t *c,
                             xcb_extension_t *ext,
                             uint32_t eid,
                             uint32_t *stamp)
{
    xcb_special_event_t *se;
    const xcb_query_extension_reply_t   *ext_reply;

    if(c->has_error)
        return NULL;
    ext_reply = xcb_get_extension_data(c, ext);
    if (!ext_reply)
        return NULL;
    pthread_mutex_lock(&c->iolock);
    for (se = c->in.special_events; se; se = se->next) {
        if (se->extension == ext_reply->major_opcode &&
            se->eid == eid) {
            pthread_mutex_unlock(&c->iolock);
            return NULL;
        }
    }
    se = calloc(1, sizeof(xcb_special_event_t));
    if (!se) {
        pthread_mutex_unlock(&c->iolock);
        return NULL;
    }

    se->extension = ext_reply->major_opcode;
    se->eid = eid;

    se->events = NULL;
    se->events_tail = &se->events;
    se->stamp = stamp;

    pthread_cond_init(&se->special_event_cond, 0);

    se->next = c->in.special_events;
    c->in.special_events = se;
    pthread_mutex_unlock(&c->iolock);
    return se;
}

void
xcb_unregister_for_special_event(xcb_connection_t *c,
                                 xcb_special_event_t *se)
{
    xcb_special_event_t *s, **prev;
    struct event_list   *events, *next;

    if (!se)
        return;

    if (c->has_error)
        return;

    pthread_mutex_lock(&c->iolock);

    for (prev = &c->in.special_events; (s = *prev) != NULL; prev = &(s->next)) {
        if (s == se) {
            *prev = se->next;
            for (events = se->events; events; events = next) {
                next = events->next;
                free (events->event);
                free (events);
            }
            pthread_cond_destroy(&se->special_event_cond);
            free (se);
            break;
        }
    }
    pthread_mutex_unlock(&c->iolock);
}

/* Private interface */

int _xcb_in_init(_xcb_in *in)
{
    if(pthread_cond_init(&in->event_cond, 0))
        return 0;
    in->reading = 0;

    in->queue_len = 0;

    in->request_read = 0;
    in->request_completed = 0;

    in->replies = _xcb_map_new();
    if(!in->replies)
        return 0;

    in->current_reply_tail = &in->current_reply;
    in->events_tail = &in->events;
    in->pending_replies_tail = &in->pending_replies;

    return 1;
}

void _xcb_in_destroy(_xcb_in *in)
{
    pthread_cond_destroy(&in->event_cond);
    free_reply_list(in->current_reply);
    _xcb_map_delete(in->replies, (void (*)(void *)) free_reply_list);
    while(in->events)
    {
        struct event_list *e = in->events;
        in->events = e->next;
        free(e->event);
        free(e);
    }
    while(in->pending_replies)
    {
        pending_reply *pend = in->pending_replies;
        in->pending_replies = pend->next;
        free(pend);
    }
}

void _xcb_in_wake_up_next_reader(xcb_connection_t *c)
{
    int pthreadret;
    if(c->in.readers)
        pthreadret = pthread_cond_signal(c->in.readers->data);
    else if(c->in.special_waiters)
        pthreadret = pthread_cond_signal(&c->in.special_waiters->se->special_event_cond);
    else
        pthreadret = pthread_cond_signal(&c->in.event_cond);
    assert(pthreadret == 0);
}

int _xcb_in_expect_reply(xcb_connection_t *c, uint64_t request, enum workarounds workaround, int flags)
{
    pending_reply *pend = malloc(sizeof(pending_reply));
    assert(workaround != WORKAROUND_NONE || flags != 0);
    if(!pend)
    {
        _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
        return 0;
    }
    pend->first_request = pend->last_request = request;
    pend->workaround = workaround;
    pend->flags = flags;
    pend->next = 0;
    *c->in.pending_replies_tail = pend;
    c->in.pending_replies_tail = &pend->next;
    return 1;
}

void _xcb_in_replies_done(xcb_connection_t *c)
{
    struct pending_reply *pend;
    if (c->in.pending_replies_tail != &c->in.pending_replies)
    {
        pend = container_of(c->in.pending_replies_tail, struct pending_reply, next);
        if(pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER)
        {
            if (XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->out.request)) {
                pend->last_request = c->out.request;
                pend->workaround = WORKAROUND_NONE;
            } else {
                /* The socket was taken, but no requests were actually sent
                 * so just discard the pending_reply that was created.
                 */
                struct pending_reply **prev_next = &c->in.pending_replies;
                while (*prev_next != pend)
                    prev_next = &(*prev_next)->next;
                *prev_next = NULL;
                c->in.pending_replies_tail = prev_next;
                free(pend);
            }
        }
    }
}

int _xcb_in_read(xcb_connection_t *c)
{
    int n;

#if HAVE_SENDMSG
    struct iovec    iov = {
        .iov_base = c->in.queue + c->in.queue_len,
        .iov_len = sizeof(c->in.queue) - c->in.queue_len,
    };
    union {
        struct cmsghdr cmsghdr;
        char buf[CMSG_SPACE(XCB_MAX_PASS_FD * sizeof(int))];
    } cmsgbuf;
    struct msghdr msg = {
        .msg_name = NULL,
        .msg_namelen = 0,
        .msg_iov = &iov,
        .msg_iovlen = 1,
        .msg_control = cmsgbuf.buf,
        .msg_controllen = CMSG_SPACE(sizeof(int) * (XCB_MAX_PASS_FD - c->in.in_fd.nfd)),
    };
    n = recvmsg(c->fd, &msg, 0);

    /* Check for truncation errors. Only MSG_CTRUNC is
     * probably possible here, which would indicate that
     * the sender tried to transmit more than XCB_MAX_PASS_FD
     * file descriptors.
     */
    if (msg.msg_flags & (MSG_TRUNC|MSG_CTRUNC)) {
        _xcb_conn_shutdown(c, XCB_CONN_CLOSED_FDPASSING_FAILED);
        return 0;
    }
#else
    n = recv(c->fd, c->in.queue + c->in.queue_len, sizeof(c->in.queue) - c->in.queue_len, 0);
#endif
    if(n > 0) {
#if HAVE_SENDMSG
        struct cmsghdr *hdr;

        if (msg.msg_controllen >= sizeof (struct cmsghdr)) {
            for (hdr = CMSG_FIRSTHDR(&msg); hdr; hdr = CMSG_NXTHDR(&msg, hdr)) {
                if (hdr->cmsg_level == SOL_SOCKET && hdr->cmsg_type == SCM_RIGHTS) {
                    int nfd = (hdr->cmsg_len - CMSG_LEN(0)) / sizeof (int);
                    memcpy(&c->in.in_fd.fd[c->in.in_fd.nfd], CMSG_DATA(hdr), nfd * sizeof (int));
                    c->in.in_fd.nfd += nfd;
                }
            }
        }
#endif
        c->in.total_read += n;
        c->in.queue_len += n;
    }
    while(read_packet(c))
        /* empty */;
#if HAVE_SENDMSG
    if (c->in.in_fd.nfd) {
        c->in.in_fd.nfd -= c->in.in_fd.ifd;
        memmove(&c->in.in_fd.fd[0],
                &c->in.in_fd.fd[c->in.in_fd.ifd],
                c->in.in_fd.nfd * sizeof (int));
        c->in.in_fd.ifd = 0;

        /* If we have any left-over file descriptors after emptying
         * the input buffer, then the server sent some that we weren't
         * expecting.  Close them and mark the connection as broken;
         */
        if (c->in.queue_len == 0 && c->in.in_fd.nfd != 0) {
            int i;
            for (i = 0; i < c->in.in_fd.nfd; i++)
                close(c->in.in_fd.fd[i]);
            _xcb_conn_shutdown(c, XCB_CONN_CLOSED_FDPASSING_FAILED);
            return 0;
        }
    }
#endif
#ifndef _WIN32
    if((n > 0) || (n < 0 && (errno == EAGAIN || errno == EINTR)))
#else
    if((n > 0) || (n < 0 && WSAGetLastError() == WSAEWOULDBLOCK))
#endif /* !_WIN32 */
        return 1;
    _xcb_conn_shutdown(c, XCB_CONN_ERROR);
    return 0;
}

int _xcb_in_read_block(xcb_connection_t *c, void *buf, int len)
{
    int done = c->in.queue_len;
    if(len < done)
        done = len;

    memcpy(buf, c->in.queue, done);
    c->in.queue_len -= done;
    memmove(c->in.queue, c->in.queue + done, c->in.queue_len);

    if(len > done)
    {
        int ret = read_block(c->fd, (char *) buf + done, len - done);
        if(ret <= 0)
        {
            _xcb_conn_shutdown(c, XCB_CONN_ERROR);
            return ret;
        }
    }

    return len;
}