git.demorecorder.com Git - free-sw/xcb/libxcb/blob - src/xcb_in.c

   1 /* Copyright (C) 2001-2004 Bart Massey and Jamey Sharp.
   2  *
   3  * Permission is hereby granted, free of charge, to any person obtaining a
   4  * copy of this software and associated documentation files (the "Software"),
   5  * to deal in the Software without restriction, including without limitation
   6  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   7  * and/or sell copies of the Software, and to permit persons to whom the
   8  * Software is furnished to do so, subject to the following conditions:
   9  *
  10  * The above copyright notice and this permission notice shall be included in
  11  * all copies or substantial portions of the Software.
  12  *
  13  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  14  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  15  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  16  * AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  17  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  18  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  19  *
  20  * Except as contained in this notice, the names of the authors or their
  21  * institutions shall not be used in advertising or otherwise to promote the
  22  * sale, use or other dealings in this Software without prior written
  23  * authorization from the authors.
  24  */
  25
  26 /* Stuff that reads stuff from the server. */
  27
  28 #include <assert.h>
  29 #include <string.h>
  30 #include <stdlib.h>
  31 #include <unistd.h>
  32 #include <stdio.h>
  33 #include <errno.h>
  34
  35 #include "xcb.h"
  36 #include "xcbext.h"
  37 #include "xcbint.h"
  38 #if USE_POLL
  39 #include <poll.h>
  40 #else
  41 #include <sys/select.h>
  42 #endif
  43
  44 #define XCB_ERROR 0
  45 #define XCB_REPLY 1
  46 #define XCB_XGE_EVENT 35
  47
  48 struct event_list {
  49     xcb_generic_event_t *event;
  50     struct event_list *next;
  51 };
  52
  53 struct reply_list {
  54     void *reply;
  55     struct reply_list *next;
  56 };
  57
  58 typedef struct pending_reply {
  59     uint64_t first_request;
  60     uint64_t last_request;
  61     enum workarounds workaround;
  62     int flags;
  63     struct pending_reply *next;
  64 } pending_reply;
  65
  66 typedef struct reader_list {
  67     unsigned int request;
  68     pthread_cond_t *data;
  69     struct reader_list *next;
  70 } reader_list;
  71
  72 static void wake_up_next_reader(xcb_connection_t *c)
  73 {
  74     int pthreadret;
  75     if(c->in.readers)
  76         pthreadret = pthread_cond_signal(c->in.readers->data);
  77     else
  78         pthreadret = pthread_cond_signal(&c->in.event_cond);
  79     assert(pthreadret == 0);
  80 }
  81
  82 static int read_packet(xcb_connection_t *c)
  83 {
  84     xcb_generic_reply_t genrep;
  85     int length = 32;
  86     int eventlength = 0; /* length after first 32 bytes for GenericEvents */
  87     void *buf;
  88     pending_reply *pend = 0;
  89     struct event_list *event;
  90
  91     /* Wait for there to be enough data for us to read a whole packet */
  92     if(c->in.queue_len < length)
  93         return 0;
  94
  95     /* Get the response type, length, and sequence number. */
  96     memcpy(&genrep, c->in.queue, sizeof(genrep));
  97
  98     /* Compute 32-bit sequence number of this packet. */
  99     if((genrep.response_type & 0x7f) != XCB_KEYMAP_NOTIFY)
 100     {
 101         uint64_t lastread = c->in.request_read;
 102         c->in.request_read = (lastread & UINT64_C(0xffffffffffff0000)) | genrep.sequence;
 103         if(XCB_SEQUENCE_COMPARE(c->in.request_read, <, lastread))
 104             c->in.request_read += 0x10000;
 105         if(XCB_SEQUENCE_COMPARE(c->in.request_read, >, c->in.request_expected))
 106             c->in.request_expected = c->in.request_read;
 107
 108         if(c->in.request_read != lastread)
 109         {
 110             if(c->in.current_reply)
 111             {
 112                 _xcb_map_put(c->in.replies, lastread, c->in.current_reply);
 113                 c->in.current_reply = 0;
 114                 c->in.current_reply_tail = &c->in.current_reply;
 115             }
 116             c->in.request_completed = c->in.request_read - 1;
 117         }
 118
 119         while(c->in.pending_replies &&
 120               c->in.pending_replies->workaround != WORKAROUND_EXTERNAL_SOCKET_OWNER &&
 121               XCB_SEQUENCE_COMPARE (c->in.pending_replies->last_request, <=, c->in.request_completed))
 122         {
 123             pending_reply *oldpend = c->in.pending_replies;
 124             c->in.pending_replies = oldpend->next;
 125             if(!oldpend->next)
 126                 c->in.pending_replies_tail = &c->in.pending_replies;
 127             free(oldpend);
 128         }
 129
 130         if(genrep.response_type == XCB_ERROR)
 131             c->in.request_completed = c->in.request_read;
 132     }
 133
 134     if(genrep.response_type == XCB_ERROR || genrep.response_type == XCB_REPLY)
 135     {
 136         pend = c->in.pending_replies;
 137         if(pend &&
 138            !(XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->in.request_read) &&
 139              (pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER ||
 140               XCB_SEQUENCE_COMPARE(c->in.request_read, <=, pend->last_request))))
 141             pend = 0;
 142     }
 143
 144     /* For reply packets, check that the entire packet is available. */
 145     if(genrep.response_type == XCB_REPLY)
 146     {
 147         if(pend && pend->workaround == WORKAROUND_GLX_GET_FB_CONFIGS_BUG)
 148         {
 149             uint32_t *p = (uint32_t *) c->in.queue;
 150             genrep.length = p[2] * p[3] * 2;
 151         }
 152         length += genrep.length * 4;
 153     }
 154
 155     /* XGE events may have sizes > 32 */
 156     if (genrep.response_type == XCB_XGE_EVENT)
 157         eventlength = genrep.length * 4;
 158
 159     buf = malloc(length + eventlength +
 160             (genrep.response_type == XCB_REPLY ? 0 : sizeof(uint32_t)));
 161     if(!buf)
 162     {
 163         _xcb_conn_shutdown(c);
 164         return 0;
 165     }
 166
 167     if(_xcb_in_read_block(c, buf, length) <= 0)
 168     {
 169         free(buf);
 170         return 0;
 171     }
 172
 173     /* pull in XGE event data if available, append after event struct */
 174     if (eventlength)
 175     {
 176         if(_xcb_in_read_block(c, &((xcb_generic_event_t*)buf)[1], eventlength) <= 0)
 177         {
 178             free(buf);
 179             return 0;
 180         }
 181     }
 182
 183     if(pend && (pend->flags & XCB_REQUEST_DISCARD_REPLY))
 184     {
 185         free(buf);
 186         return 1;
 187     }
 188
 189     if(genrep.response_type != XCB_REPLY)
 190         ((xcb_generic_event_t *) buf)->full_sequence = c->in.request_read;
 191
 192     /* reply, or checked error */
 193     if( genrep.response_type == XCB_REPLY ||
 194        (genrep.response_type == XCB_ERROR && pend && (pend->flags & XCB_REQUEST_CHECKED)))
 195     {
 196         reader_list *reader;
 197         struct reply_list *cur = malloc(sizeof(struct reply_list));
 198         if(!cur)
 199         {
 200             _xcb_conn_shutdown(c);
 201             free(buf);
 202             return 0;
 203         }
 204         cur->reply = buf;
 205         cur->next = 0;
 206         *c->in.current_reply_tail = cur;
 207         c->in.current_reply_tail = &cur->next;
 208         for(reader = c->in.readers;
 209             reader &&
 210             XCB_SEQUENCE_COMPARE_32(reader->request, <=, c->in.request_read);
 211             reader = reader->next)
 212         {
 213             if(XCB_SEQUENCE_COMPARE_32(reader->request, ==, c->in.request_read))
 214             {
 215                 pthread_cond_signal(reader->data);
 216                 break;
 217             }
 218         }
 219         return 1;
 220     }
 221
 222     /* event, or unchecked error */
 223     event = malloc(sizeof(struct event_list));
 224     if(!event)
 225     {
 226         _xcb_conn_shutdown(c);
 227         free(buf);
 228         return 0;
 229     }
 230     event->event = buf;
 231     event->next = 0;
 232     *c->in.events_tail = event;
 233     c->in.events_tail = &event->next;
 234     pthread_cond_signal(&c->in.event_cond);
 235     return 1; /* I have something for you... */
 236 }
 237
 238 static xcb_generic_event_t *get_event(xcb_connection_t *c)
 239 {
 240     struct event_list *cur = c->in.events;
 241     xcb_generic_event_t *ret;
 242     if(!c->in.events)
 243         return 0;
 244     ret = cur->event;
 245     c->in.events = cur->next;
 246     if(!cur->next)
 247         c->in.events_tail = &c->in.events;
 248     free(cur);
 249     return ret;
 250 }
 251
 252 static void free_reply_list(struct reply_list *head)
 253 {
 254     while(head)
 255     {
 256         struct reply_list *cur = head;
 257         head = cur->next;
 258         free(cur->reply);
 259         free(cur);
 260     }
 261 }
 262
 263 static int read_block(const int fd, void *buf, const ssize_t len)
 264 {
 265     int done = 0;
 266     while(done < len)
 267     {
 268         int ret = read(fd, ((char *) buf) + done, len - done);
 269         if(ret > 0)
 270             done += ret;
 271         if(ret < 0 && errno == EAGAIN)
 272         {
 273 #if USE_POLL
 274             struct pollfd pfd;
 275             pfd.fd = fd;
 276             pfd.events = POLLIN;
 277             pfd.revents = 0;
 278             do {
 279                 ret = poll(&pfd, 1, -1);
 280             } while (ret == -1 && errno == EINTR);
 281 #else
 282             fd_set fds;
 283             FD_ZERO(&fds);
 284             FD_SET(fd, &fds);
 285             do {
 286                 ret = select(fd + 1, &fds, 0, 0, 0);
 287             } while (ret == -1 && errno == EINTR);
 288 #endif
 289         }
 290         if(ret <= 0)
 291             return ret;
 292     }
 293     return len;
 294 }
 295
 296 static int poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply, xcb_generic_error_t **error)
 297 {
 298     struct reply_list *head;
 299
 300     /* If an error occurred when issuing the request, fail immediately. */
 301     if(!request)
 302         head = 0;
 303     /* We've read requests past the one we want, so if it has replies we have
 304      * them all and they're in the replies map. */
 305     else if(XCB_SEQUENCE_COMPARE_32(request, <, c->in.request_read))
 306     {
 307         head = _xcb_map_remove(c->in.replies, request);
 308         if(head && head->next)
 309             _xcb_map_put(c->in.replies, request, head->next);
 310     }
 311     /* We're currently processing the responses to the request we want, and we
 312      * have a reply ready to return. So just return it without blocking. */
 313     else if(XCB_SEQUENCE_COMPARE_32(request, ==, c->in.request_read) && c->in.current_reply)
 314     {
 315         head = c->in.current_reply;
 316         c->in.current_reply = head->next;
 317         if(!head->next)
 318             c->in.current_reply_tail = &c->in.current_reply;
 319     }
 320     /* We know this request can't have any more replies, and we've already
 321      * established it doesn't have a reply now. Don't bother blocking. */
 322     else if(XCB_SEQUENCE_COMPARE_32(request, ==, c->in.request_completed))
 323         head = 0;
 324     /* We may have more replies on the way for this request: block until we're
 325      * sure. */
 326     else
 327         return 0;
 328
 329     if(error)
 330         *error = 0;
 331     *reply = 0;
 332
 333     if(head)
 334     {
 335         if(((xcb_generic_reply_t *) head->reply)->response_type == XCB_ERROR)
 336         {
 337             if(error)
 338                 *error = head->reply;
 339             else
 340                 free(head->reply);
 341         }
 342         else
 343             *reply = head->reply;
 344
 345         free(head);
 346     }
 347
 348     return 1;
 349 }
 350
 351 /* Public interface */
 352
 353 void *xcb_wait_for_reply(xcb_connection_t *c, unsigned int request, xcb_generic_error_t **e)
 354 {
 355     uint64_t widened_request;
 356     void *ret = 0;
 357     if(e)
 358         *e = 0;
 359     if(c->has_error)
 360         return 0;
 361
 362     pthread_mutex_lock(&c->iolock);
 363
 364     widened_request = (c->out.request & UINT64_C(0xffffffff00000000)) | request;
 365     if(widened_request > c->out.request)
 366         widened_request -= UINT64_C(1) << 32;
 367
 368     /* If this request has not been written yet, write it. */
 369     if(c->out.return_socket || _xcb_out_flush_to(c, widened_request))
 370     {
 371         pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
 372         reader_list reader;
 373         reader_list **prev_reader;
 374
 375         for(prev_reader = &c->in.readers;
 376             *prev_reader &&
 377             XCB_SEQUENCE_COMPARE_32((*prev_reader)->request, <=, request);
 378             prev_reader = &(*prev_reader)->next)
 379         {
 380             /* empty */;
 381         }
 382         reader.request = request;
 383         reader.data = &cond;
 384         reader.next = *prev_reader;
 385         *prev_reader = &reader;
 386
 387         while(!poll_for_reply(c, request, &ret, e))
 388             if(!_xcb_conn_wait(c, &cond, 0, 0))
 389                 break;
 390
 391         for(prev_reader = &c->in.readers;
 392             *prev_reader &&
 393             XCB_SEQUENCE_COMPARE_32((*prev_reader)->request, <=, request);
 394             prev_reader = &(*prev_reader)->next)
 395         {
 396             if(*prev_reader == &reader)
 397             {
 398                 *prev_reader = (*prev_reader)->next;
 399                 break;
 400             }
 401         }
 402         pthread_cond_destroy(&cond);
 403     }
 404
 405     wake_up_next_reader(c);
 406     pthread_mutex_unlock(&c->iolock);
 407     return ret;
 408 }
 409
 410 static void insert_pending_discard(xcb_connection_t *c, pending_reply **prev_next, uint64_t seq)
 411 {
 412     pending_reply *pend;
 413     pend = malloc(sizeof(*pend));
 414     if(!pend)
 415     {
 416         _xcb_conn_shutdown(c);
 417         return;
 418     }
 419
 420     pend->first_request = seq;
 421     pend->last_request = seq;
 422     pend->workaround = 0;
 423     pend->flags = XCB_REQUEST_DISCARD_REPLY;
 424     pend->next = *prev_next;
 425     *prev_next = pend;
 426
 427     if(!pend->next)
 428         c->in.pending_replies_tail = &pend->next;
 429 }
 430
 431 static void discard_reply(xcb_connection_t *c, unsigned int request)
 432 {
 433     pending_reply *pend = 0;
 434     pending_reply **prev_pend;
 435     uint64_t widened_request;
 436
 437     /* We've read requests past the one we want, so if it has replies we have
 438      * them all and they're in the replies map. */
 439     if(XCB_SEQUENCE_COMPARE_32(request, <, c->in.request_read))
 440     {
 441         struct reply_list *head;
 442         head = _xcb_map_remove(c->in.replies, request);
 443         while (head)
 444         {
 445             struct reply_list *next = head->next;
 446             free(head->reply);
 447             free(head);
 448             head = next;
 449         }
 450         return;
 451     }
 452
 453     /* We're currently processing the responses to the request we want, and we
 454      * have a reply ready to return. Free it, and mark the pend to free any further
 455      * replies. */
 456     if(XCB_SEQUENCE_COMPARE_32(request, ==, c->in.request_read) && c->in.current_reply)
 457     {
 458         struct reply_list *head;
 459         head = c->in.current_reply;
 460         c->in.current_reply = NULL;
 461         c->in.current_reply_tail = &c->in.current_reply;
 462         while (head)
 463         {
 464             struct reply_list *next = head->next;
 465             free(head->reply);
 466             free(head);
 467             head = next;
 468         }
 469
 470         pend = c->in.pending_replies;
 471         if(pend &&
 472             !(XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->in.request_read) &&
 473              (pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER ||
 474               XCB_SEQUENCE_COMPARE(c->in.request_read, <=, pend->last_request))))
 475             pend = 0;
 476         if(pend)
 477             pend->flags |= XCB_REQUEST_DISCARD_REPLY;
 478         else
 479             insert_pending_discard(c, &c->in.pending_replies, c->in.request_read);
 480
 481         return;
 482     }
 483
 484     /* Walk the list of pending requests. Mark the first match for deletion. */
 485     for(prev_pend = &c->in.pending_replies; *prev_pend; prev_pend = &(*prev_pend)->next)
 486     {
 487         if(XCB_SEQUENCE_COMPARE_32((*prev_pend)->first_request, >, request))
 488             break;
 489
 490         if(XCB_SEQUENCE_COMPARE_32((*prev_pend)->first_request, ==, request))
 491         {
 492             /* Pending reply found. Mark for discard: */
 493             (*prev_pend)->flags |= XCB_REQUEST_DISCARD_REPLY;
 494             return;
 495         }
 496     }
 497
 498     /* Pending reply not found (likely due to _unchecked request). Create one: */
 499     widened_request = (c->out.request & UINT64_C(0xffffffff00000000)) | request;
 500     if(widened_request > c->out.request)
 501         widened_request -= UINT64_C(1) << 32;
 502
 503     insert_pending_discard(c, prev_pend, widened_request);
 504 }
 505
 506 void xcb_discard_reply(xcb_connection_t *c, unsigned int sequence)
 507 {
 508     if(c->has_error)
 509         return;
 510
 511     /* If an error occurred when issuing the request, fail immediately. */
 512     if(!sequence)
 513         return;
 514
 515     pthread_mutex_lock(&c->iolock);
 516     discard_reply(c, sequence);
 517     pthread_mutex_unlock(&c->iolock);
 518 }
 519
 520 int xcb_poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply, xcb_generic_error_t **error)
 521 {
 522     int ret;
 523     if(c->has_error)
 524     {
 525         *reply = 0;
 526         if(error)
 527             *error = 0;
 528         return 1; /* would not block */
 529     }
 530     assert(reply != 0);
 531     pthread_mutex_lock(&c->iolock);
 532     ret = poll_for_reply(c, request, reply, error);
 533     pthread_mutex_unlock(&c->iolock);
 534     return ret;
 535 }
 536
 537 xcb_generic_event_t *xcb_wait_for_event(xcb_connection_t *c)
 538 {
 539     xcb_generic_event_t *ret;
 540     if(c->has_error)
 541         return 0;
 542     pthread_mutex_lock(&c->iolock);
 543     /* get_event returns 0 on empty list. */
 544     while(!(ret = get_event(c)))
 545         if(!_xcb_conn_wait(c, &c->in.event_cond, 0, 0))
 546             break;
 547
 548     wake_up_next_reader(c);
 549     pthread_mutex_unlock(&c->iolock);
 550     return ret;
 551 }
 552
 553 xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c)
 554 {
 555     xcb_generic_event_t *ret = 0;
 556     if(!c->has_error)
 557     {
 558         pthread_mutex_lock(&c->iolock);
 559         /* FIXME: follow X meets Z architecture changes. */
 560         ret = get_event(c);
 561         if(!ret && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
 562             ret = get_event(c);
 563         pthread_mutex_unlock(&c->iolock);
 564     }
 565     return ret;
 566 }
 567
 568 xcb_generic_error_t *xcb_request_check(xcb_connection_t *c, xcb_void_cookie_t cookie)
 569 {
 570     /* FIXME: this could hold the lock to avoid syncing unnecessarily, but
 571      * that would require factoring the locking out of xcb_get_input_focus,
 572      * xcb_get_input_focus_reply, and xcb_wait_for_reply. */
 573     xcb_generic_error_t *ret;
 574     void *reply;
 575     if(c->has_error)
 576         return 0;
 577     if(XCB_SEQUENCE_COMPARE_32(cookie.sequence,>,c->in.request_expected)
 578        && XCB_SEQUENCE_COMPARE_32(cookie.sequence,>,c->in.request_completed))
 579     {
 580         free(xcb_get_input_focus_reply(c, xcb_get_input_focus(c), &ret));
 581         assert(!ret);
 582     }
 583     reply = xcb_wait_for_reply(c, cookie.sequence, &ret);
 584     assert(!reply);
 585     return ret;
 586 }
 587
 588 /* Private interface */
 589
 590 int _xcb_in_init(_xcb_in *in)
 591 {
 592     if(pthread_cond_init(&in->event_cond, 0))
 593         return 0;
 594     in->reading = 0;
 595
 596     in->queue_len = 0;
 597
 598     in->request_read = 0;
 599     in->request_completed = 0;
 600
 601     in->replies = _xcb_map_new();
 602     if(!in->replies)
 603         return 0;
 604
 605     in->current_reply_tail = &in->current_reply;
 606     in->events_tail = &in->events;
 607     in->pending_replies_tail = &in->pending_replies;
 608
 609     return 1;
 610 }
 611
 612 void _xcb_in_destroy(_xcb_in *in)
 613 {
 614     pthread_cond_destroy(&in->event_cond);
 615     free_reply_list(in->current_reply);
 616     _xcb_map_delete(in->replies, (void (*)(void *)) free_reply_list);
 617     while(in->events)
 618     {
 619         struct event_list *e = in->events;
 620         in->events = e->next;
 621         free(e->event);
 622         free(e);
 623     }
 624     while(in->pending_replies)
 625     {
 626         pending_reply *pend = in->pending_replies;
 627         in->pending_replies = pend->next;
 628         free(pend);
 629     }
 630 }
 631
 632 int _xcb_in_expect_reply(xcb_connection_t *c, uint64_t request, enum workarounds workaround, int flags)
 633 {
 634     pending_reply *pend = malloc(sizeof(pending_reply));
 635     assert(workaround != WORKAROUND_NONE || flags != 0);
 636     if(!pend)
 637     {
 638         _xcb_conn_shutdown(c);
 639         return 0;
 640     }
 641     pend->first_request = pend->last_request = request;
 642     pend->workaround = workaround;
 643     pend->flags = flags;
 644     pend->next = 0;
 645     *c->in.pending_replies_tail = pend;
 646     c->in.pending_replies_tail = &pend->next;
 647     return 1;
 648 }
 649
 650 void _xcb_in_replies_done(xcb_connection_t *c)
 651 {
 652     struct pending_reply *pend;
 653     if (c->in.pending_replies_tail != &c->in.pending_replies)
 654     {
 655         pend = container_of(c->in.pending_replies_tail, struct pending_reply, next);
 656         if(pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER)
 657         {
 658             pend->last_request = c->out.request;
 659             pend->workaround = WORKAROUND_NONE;
 660         }
 661     }
 662 }
 663
 664 int _xcb_in_read(xcb_connection_t *c)
 665 {
 666     int n = read(c->fd, c->in.queue + c->in.queue_len, sizeof(c->in.queue) - c->in.queue_len);
 667     if(n > 0)
 668         c->in.queue_len += n;
 669     while(read_packet(c))
 670         /* empty */;
 671     if((n > 0) || (n < 0 && errno == EAGAIN))
 672         return 1;
 673     _xcb_conn_shutdown(c);
 674     return 0;
 675 }
 676
 677 int _xcb_in_read_block(xcb_connection_t *c, void *buf, int len)
 678 {
 679     int done = c->in.queue_len;
 680     if(len < done)
 681         done = len;
 682
 683     memcpy(buf, c->in.queue, done);
 684     c->in.queue_len -= done;
 685     memmove(c->in.queue, c->in.queue + done, c->in.queue_len);
 686
 687     if(len > done)
 688     {
 689         int ret = read_block(c->fd, (char *) buf + done, len - done);
 690         if(ret <= 0)
 691         {
 692             _xcb_conn_shutdown(c);
 693             return ret;
 694         }
 695     }
 696
 697     return len;
 698 }