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   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 int read_packet(xcb_connection_t *c)
  73 {
  74     xcb_generic_reply_t genrep;
  75     int length = 32;
  76     int eventlength = 0; /* length after first 32 bytes for GenericEvents */
  77     void *buf;
  78     pending_reply *pend = 0;
  79     struct event_list *event;
  80
  81     /* Wait for there to be enough data for us to read a whole packet */
  82     if(c->in.queue_len < length)
  83         return 0;
  84
  85     /* Get the response type, length, and sequence number. */
  86     memcpy(&genrep, c->in.queue, sizeof(genrep));
  87
  88     /* Compute 32-bit sequence number of this packet. */
  89     if((genrep.response_type & 0x7f) != XCB_KEYMAP_NOTIFY)
  90     {
  91         uint64_t lastread = c->in.request_read;
  92         c->in.request_read = (lastread & UINT64_C(0xffffffffffff0000)) | genrep.sequence;
  93         if(XCB_SEQUENCE_COMPARE(c->in.request_read, <, lastread))
  94             c->in.request_read += 0x10000;
  95         if(XCB_SEQUENCE_COMPARE(c->in.request_read, >, c->in.request_expected))
  96             c->in.request_expected = c->in.request_read;
  97
  98         if(c->in.request_read != lastread)
  99         {
 100             if(c->in.current_reply)
 101             {
 102                 _xcb_map_put(c->in.replies, lastread, c->in.current_reply);
 103                 c->in.current_reply = 0;
 104                 c->in.current_reply_tail = &c->in.current_reply;
 105             }
 106             c->in.request_completed = c->in.request_read - 1;
 107         }
 108
 109         while(c->in.pending_replies &&
 110               c->in.pending_replies->workaround != WORKAROUND_EXTERNAL_SOCKET_OWNER &&
 111               XCB_SEQUENCE_COMPARE (c->in.pending_replies->last_request, <=, c->in.request_completed))
 112         {
 113             pending_reply *oldpend = c->in.pending_replies;
 114             c->in.pending_replies = oldpend->next;
 115             if(!oldpend->next)
 116                 c->in.pending_replies_tail = &c->in.pending_replies;
 117             free(oldpend);
 118         }
 119
 120         if(genrep.response_type == XCB_ERROR)
 121             c->in.request_completed = c->in.request_read;
 122     }
 123
 124     if(genrep.response_type == XCB_ERROR || genrep.response_type == XCB_REPLY)
 125     {
 126         pend = c->in.pending_replies;
 127         if(pend &&
 128            !(XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->in.request_read) &&
 129              (pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER ||
 130               XCB_SEQUENCE_COMPARE(c->in.request_read, <=, pend->last_request))))
 131             pend = 0;
 132     }
 133
 134     /* For reply packets, check that the entire packet is available. */
 135     if(genrep.response_type == XCB_REPLY)
 136     {
 137         if(pend && pend->workaround == WORKAROUND_GLX_GET_FB_CONFIGS_BUG)
 138         {
 139             uint32_t *p = (uint32_t *) c->in.queue;
 140             genrep.length = p[2] * p[3] * 2;
 141         }
 142         length += genrep.length * 4;
 143     }
 144
 145     /* XGE events may have sizes > 32 */
 146     if (genrep.response_type == XCB_XGE_EVENT)
 147         eventlength = genrep.length * 4;
 148
 149     buf = malloc(length + eventlength +
 150             (genrep.response_type == XCB_REPLY ? 0 : sizeof(uint32_t)));
 151     if(!buf)
 152     {
 153         _xcb_conn_shutdown(c);
 154         return 0;
 155     }
 156
 157     if(_xcb_in_read_block(c, buf, length) <= 0)
 158     {
 159         free(buf);
 160         return 0;
 161     }
 162
 163     /* pull in XGE event data if available, append after event struct */
 164     if (eventlength)
 165     {
 166         if(_xcb_in_read_block(c, &((xcb_generic_event_t*)buf)[1], eventlength) <= 0)
 167         {
 168             free(buf);
 169             return 0;
 170         }
 171     }
 172
 173     if(pend && (pend->flags & XCB_REQUEST_DISCARD_REPLY))
 174     {
 175         free(buf);
 176         return 1;
 177     }
 178
 179     if(genrep.response_type != XCB_REPLY)
 180         ((xcb_generic_event_t *) buf)->full_sequence = c->in.request_read;
 181
 182     /* reply, or checked error */
 183     if( genrep.response_type == XCB_REPLY ||
 184        (genrep.response_type == XCB_ERROR && pend && (pend->flags & XCB_REQUEST_CHECKED)))
 185     {
 186         reader_list *reader;
 187         struct reply_list *cur = malloc(sizeof(struct reply_list));
 188         if(!cur)
 189         {
 190             _xcb_conn_shutdown(c);
 191             free(buf);
 192             return 0;
 193         }
 194         cur->reply = buf;
 195         cur->next = 0;
 196         *c->in.current_reply_tail = cur;
 197         c->in.current_reply_tail = &cur->next;
 198         for(reader = c->in.readers;
 199             reader &&
 200             XCB_SEQUENCE_COMPARE_32(reader->request, <=, c->in.request_read);
 201             reader = reader->next)
 202         {
 203             if(XCB_SEQUENCE_COMPARE_32(reader->request, ==, c->in.request_read))
 204             {
 205                 pthread_cond_signal(reader->data);
 206                 break;
 207             }
 208         }
 209         return 1;
 210     }
 211
 212     /* event, or unchecked error */
 213     event = malloc(sizeof(struct event_list));
 214     if(!event)
 215     {
 216         _xcb_conn_shutdown(c);
 217         free(buf);
 218         return 0;
 219     }
 220     event->event = buf;
 221     event->next = 0;
 222     *c->in.events_tail = event;
 223     c->in.events_tail = &event->next;
 224     pthread_cond_signal(&c->in.event_cond);
 225     return 1; /* I have something for you... */
 226 }
 227
 228 static xcb_generic_event_t *get_event(xcb_connection_t *c)
 229 {
 230     struct event_list *cur = c->in.events;
 231     xcb_generic_event_t *ret;
 232     if(!c->in.events)
 233         return 0;
 234     ret = cur->event;
 235     c->in.events = cur->next;
 236     if(!cur->next)
 237         c->in.events_tail = &c->in.events;
 238     free(cur);
 239     return ret;
 240 }
 241
 242 static void free_reply_list(struct reply_list *head)
 243 {
 244     while(head)
 245     {
 246         struct reply_list *cur = head;
 247         head = cur->next;
 248         free(cur->reply);
 249         free(cur);
 250     }
 251 }
 252
 253 static int read_block(const int fd, void *buf, const ssize_t len)
 254 {
 255     int done = 0;
 256     while(done < len)
 257     {
 258         int ret = read(fd, ((char *) buf) + done, len - done);
 259         if(ret > 0)
 260             done += ret;
 261         if(ret < 0 && errno == EAGAIN)
 262         {
 263 #if USE_POLL
 264             struct pollfd pfd;
 265             pfd.fd = fd;
 266             pfd.events = POLLIN;
 267             pfd.revents = 0;
 268             do {
 269                 ret = poll(&pfd, 1, -1);
 270             } while (ret == -1 && errno == EINTR);
 271 #else
 272             fd_set fds;
 273             FD_ZERO(&fds);
 274             FD_SET(fd, &fds);
 275             do {
 276                 ret = select(fd + 1, &fds, 0, 0, 0);
 277             } while (ret == -1 && errno == EINTR);
 278 #endif
 279         }
 280         if(ret <= 0)
 281             return ret;
 282     }
 283     return len;
 284 }
 285
 286 static int poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply, xcb_generic_error_t **error)
 287 {
 288     struct reply_list *head;
 289
 290     /* If an error occurred when issuing the request, fail immediately. */
 291     if(!request)
 292         head = 0;
 293     /* We've read requests past the one we want, so if it has replies we have
 294      * them all and they're in the replies map. */
 295     else if(XCB_SEQUENCE_COMPARE_32(request, <, c->in.request_read))
 296     {
 297         head = _xcb_map_remove(c->in.replies, request);
 298         if(head && head->next)
 299             _xcb_map_put(c->in.replies, request, head->next);
 300     }
 301     /* We're currently processing the responses to the request we want, and we
 302      * have a reply ready to return. So just return it without blocking. */
 303     else if(XCB_SEQUENCE_COMPARE_32(request, ==, c->in.request_read) && c->in.current_reply)
 304     {
 305         head = c->in.current_reply;
 306         c->in.current_reply = head->next;
 307         if(!head->next)
 308             c->in.current_reply_tail = &c->in.current_reply;
 309     }
 310     /* We know this request can't have any more replies, and we've already
 311      * established it doesn't have a reply now. Don't bother blocking. */
 312     else if(XCB_SEQUENCE_COMPARE_32(request, ==, c->in.request_completed))
 313         head = 0;
 314     /* We may have more replies on the way for this request: block until we're
 315      * sure. */
 316     else
 317         return 0;
 318
 319     if(error)
 320         *error = 0;
 321     *reply = 0;
 322
 323     if(head)
 324     {
 325         if(((xcb_generic_reply_t *) head->reply)->response_type == XCB_ERROR)
 326         {
 327             if(error)
 328                 *error = head->reply;
 329             else
 330                 free(head->reply);
 331         }
 332         else
 333             *reply = head->reply;
 334
 335         free(head);
 336     }
 337
 338     return 1;
 339 }
 340
 341 /* Public interface */
 342
 343 void *xcb_wait_for_reply(xcb_connection_t *c, unsigned int request, xcb_generic_error_t **e)
 344 {
 345     uint64_t widened_request;
 346     void *ret = 0;
 347     if(e)
 348         *e = 0;
 349     if(c->has_error)
 350         return 0;
 351
 352     pthread_mutex_lock(&c->iolock);
 353
 354     widened_request = (c->out.request & UINT64_C(0xffffffff00000000)) | request;
 355     if(widened_request > c->out.request)
 356         widened_request -= UINT64_C(1) << 32;
 357
 358     /* If this request has not been written yet, write it. */
 359     if(c->out.return_socket || _xcb_out_flush_to(c, widened_request))
 360     {
 361         pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
 362         reader_list reader;
 363         reader_list **prev_reader;
 364
 365         for(prev_reader = &c->in.readers;
 366             *prev_reader &&
 367             XCB_SEQUENCE_COMPARE_32((*prev_reader)->request, <=, request);
 368             prev_reader = &(*prev_reader)->next)
 369         {
 370             /* empty */;
 371         }
 372         reader.request = request;
 373         reader.data = &cond;
 374         reader.next = *prev_reader;
 375         *prev_reader = &reader;
 376
 377         while(!poll_for_reply(c, request, &ret, e))
 378             if(!_xcb_conn_wait(c, &cond, 0, 0))
 379                 break;
 380
 381         for(prev_reader = &c->in.readers;
 382             *prev_reader &&
 383             XCB_SEQUENCE_COMPARE_32((*prev_reader)->request, <=, request);
 384             prev_reader = &(*prev_reader)->next)
 385         {
 386             if(*prev_reader == &reader)
 387             {
 388                 *prev_reader = (*prev_reader)->next;
 389                 break;
 390             }
 391         }
 392         pthread_cond_destroy(&cond);
 393     }
 394
 395     _xcb_in_wake_up_next_reader(c);
 396     pthread_mutex_unlock(&c->iolock);
 397     return ret;
 398 }
 399
 400 static void insert_pending_discard(xcb_connection_t *c, pending_reply **prev_next, uint64_t seq)
 401 {
 402     pending_reply *pend;
 403     pend = malloc(sizeof(*pend));
 404     if(!pend)
 405     {
 406         _xcb_conn_shutdown(c);
 407         return;
 408     }
 409
 410     pend->first_request = seq;
 411     pend->last_request = seq;
 412     pend->workaround = 0;
 413     pend->flags = XCB_REQUEST_DISCARD_REPLY;
 414     pend->next = *prev_next;
 415     *prev_next = pend;
 416
 417     if(!pend->next)
 418         c->in.pending_replies_tail = &pend->next;
 419 }
 420
 421 static void discard_reply(xcb_connection_t *c, unsigned int request)
 422 {
 423     pending_reply *pend = 0;
 424     pending_reply **prev_pend;
 425     uint64_t widened_request;
 426
 427     /* We've read requests past the one we want, so if it has replies we have
 428      * them all and they're in the replies map. */
 429     if(XCB_SEQUENCE_COMPARE_32(request, <, c->in.request_read))
 430     {
 431         struct reply_list *head;
 432         head = _xcb_map_remove(c->in.replies, request);
 433         while (head)
 434         {
 435             struct reply_list *next = head->next;
 436             free(head->reply);
 437             free(head);
 438             head = next;
 439         }
 440         return;
 441     }
 442
 443     /* We're currently processing the responses to the request we want, and we
 444      * have a reply ready to return. Free it, and mark the pend to free any further
 445      * replies. */
 446     if(XCB_SEQUENCE_COMPARE_32(request, ==, c->in.request_read) && c->in.current_reply)
 447     {
 448         struct reply_list *head;
 449         head = c->in.current_reply;
 450         c->in.current_reply = NULL;
 451         c->in.current_reply_tail = &c->in.current_reply;
 452         while (head)
 453         {
 454             struct reply_list *next = head->next;
 455             free(head->reply);
 456             free(head);
 457             head = next;
 458         }
 459
 460         pend = c->in.pending_replies;
 461         if(pend &&
 462             !(XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->in.request_read) &&
 463              (pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER ||
 464               XCB_SEQUENCE_COMPARE(c->in.request_read, <=, pend->last_request))))
 465             pend = 0;
 466         if(pend)
 467             pend->flags |= XCB_REQUEST_DISCARD_REPLY;
 468         else
 469             insert_pending_discard(c, &c->in.pending_replies, c->in.request_read);
 470
 471         return;
 472     }
 473
 474     /* Walk the list of pending requests. Mark the first match for deletion. */
 475     for(prev_pend = &c->in.pending_replies; *prev_pend; prev_pend = &(*prev_pend)->next)
 476     {
 477         if(XCB_SEQUENCE_COMPARE_32((*prev_pend)->first_request, >, request))
 478             break;
 479
 480         if(XCB_SEQUENCE_COMPARE_32((*prev_pend)->first_request, ==, request))
 481         {
 482             /* Pending reply found. Mark for discard: */
 483             (*prev_pend)->flags |= XCB_REQUEST_DISCARD_REPLY;
 484             return;
 485         }
 486     }
 487
 488     /* Pending reply not found (likely due to _unchecked request). Create one: */
 489     widened_request = (c->out.request & UINT64_C(0xffffffff00000000)) | request;
 490     if(widened_request > c->out.request)
 491         widened_request -= UINT64_C(1) << 32;
 492
 493     insert_pending_discard(c, prev_pend, widened_request);
 494 }
 495
 496 void xcb_discard_reply(xcb_connection_t *c, unsigned int sequence)
 497 {
 498     if(c->has_error)
 499         return;
 500
 501     /* If an error occurred when issuing the request, fail immediately. */
 502     if(!sequence)
 503         return;
 504
 505     pthread_mutex_lock(&c->iolock);
 506     discard_reply(c, sequence);
 507     pthread_mutex_unlock(&c->iolock);
 508 }
 509
 510 int xcb_poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply, xcb_generic_error_t **error)
 511 {
 512     int ret;
 513     if(c->has_error)
 514     {
 515         *reply = 0;
 516         if(error)
 517             *error = 0;
 518         return 1; /* would not block */
 519     }
 520     assert(reply != 0);
 521     pthread_mutex_lock(&c->iolock);
 522     ret = poll_for_reply(c, request, reply, error);
 523     pthread_mutex_unlock(&c->iolock);
 524     return ret;
 525 }
 526
 527 xcb_generic_event_t *xcb_wait_for_event(xcb_connection_t *c)
 528 {
 529     xcb_generic_event_t *ret;
 530     if(c->has_error)
 531         return 0;
 532     pthread_mutex_lock(&c->iolock);
 533     /* get_event returns 0 on empty list. */
 534     while(!(ret = get_event(c)))
 535         if(!_xcb_conn_wait(c, &c->in.event_cond, 0, 0))
 536             break;
 537
 538     _xcb_in_wake_up_next_reader(c);
 539     pthread_mutex_unlock(&c->iolock);
 540     return ret;
 541 }
 542
 543 xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c)
 544 {
 545     xcb_generic_event_t *ret = 0;
 546     if(!c->has_error)
 547     {
 548         pthread_mutex_lock(&c->iolock);
 549         /* FIXME: follow X meets Z architecture changes. */
 550         ret = get_event(c);
 551         if(!ret && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
 552             ret = get_event(c);
 553         pthread_mutex_unlock(&c->iolock);
 554     }
 555     return ret;
 556 }
 557
 558 xcb_generic_error_t *xcb_request_check(xcb_connection_t *c, xcb_void_cookie_t cookie)
 559 {
 560     /* FIXME: this could hold the lock to avoid syncing unnecessarily, but
 561      * that would require factoring the locking out of xcb_get_input_focus,
 562      * xcb_get_input_focus_reply, and xcb_wait_for_reply. */
 563     xcb_generic_error_t *ret;
 564     void *reply;
 565     if(c->has_error)
 566         return 0;
 567     if(XCB_SEQUENCE_COMPARE_32(cookie.sequence,>,c->in.request_expected)
 568        && XCB_SEQUENCE_COMPARE_32(cookie.sequence,>,c->in.request_completed))
 569     {
 570         free(xcb_get_input_focus_reply(c, xcb_get_input_focus(c), &ret));
 571         assert(!ret);
 572     }
 573     reply = xcb_wait_for_reply(c, cookie.sequence, &ret);
 574     assert(!reply);
 575     return ret;
 576 }
 577
 578 /* Private interface */
 579
 580 int _xcb_in_init(_xcb_in *in)
 581 {
 582     if(pthread_cond_init(&in->event_cond, 0))
 583         return 0;
 584     in->reading = 0;
 585
 586     in->queue_len = 0;
 587
 588     in->request_read = 0;
 589     in->request_completed = 0;
 590
 591     in->replies = _xcb_map_new();
 592     if(!in->replies)
 593         return 0;
 594
 595     in->current_reply_tail = &in->current_reply;
 596     in->events_tail = &in->events;
 597     in->pending_replies_tail = &in->pending_replies;
 598
 599     return 1;
 600 }
 601
 602 void _xcb_in_destroy(_xcb_in *in)
 603 {
 604     pthread_cond_destroy(&in->event_cond);
 605     free_reply_list(in->current_reply);
 606     _xcb_map_delete(in->replies, (void (*)(void *)) free_reply_list);
 607     while(in->events)
 608     {
 609         struct event_list *e = in->events;
 610         in->events = e->next;
 611         free(e->event);
 612         free(e);
 613     }
 614     while(in->pending_replies)
 615     {
 616         pending_reply *pend = in->pending_replies;
 617         in->pending_replies = pend->next;
 618         free(pend);
 619     }
 620 }
 621
 622 void _xcb_in_wake_up_next_reader(xcb_connection_t *c)
 623 {
 624     int pthreadret;
 625     if(c->in.readers)
 626         pthreadret = pthread_cond_signal(c->in.readers->data);
 627     else
 628         pthreadret = pthread_cond_signal(&c->in.event_cond);
 629     assert(pthreadret == 0);
 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 }