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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 #ifdef HAVE_CONFIG_H
  29 #include "config.h"
  30 #endif
  31
  32 #include <assert.h>
  33 #include <string.h>
  34 #include <stdlib.h>
  35 #include <unistd.h>
  36 #include <stdio.h>
  37 #include <errno.h>
  38
  39 #include "xcb.h"
  40 #include "xcbext.h"
  41 #include "xcbint.h"
  42 #if USE_POLL
  43 #include <poll.h>
  44 #endif
  45 #ifndef _WIN32
  46 #include <sys/select.h>
  47 #include <sys/socket.h>
  48 #endif
  49
  50 #ifdef _WIN32
  51 #include "xcb_windefs.h"
  52 #endif /* _WIN32 */
  53
  54 #define XCB_ERROR 0
  55 #define XCB_REPLY 1
  56 #define XCB_XGE_EVENT 35
  57
  58 struct event_list {
  59     xcb_generic_event_t *event;
  60     struct event_list *next;
  61 };
  62
  63 struct reply_list {
  64     void *reply;
  65     struct reply_list *next;
  66 };
  67
  68 typedef struct pending_reply {
  69     uint64_t first_request;
  70     uint64_t last_request;
  71     enum workarounds workaround;
  72     int flags;
  73     struct pending_reply *next;
  74 } pending_reply;
  75
  76 typedef struct reader_list {
  77     uint64_t request;
  78     pthread_cond_t *data;
  79     struct reader_list *next;
  80 } reader_list;
  81
  82 static void remove_finished_readers(reader_list **prev_reader, uint64_t completed)
  83 {
  84     while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, completed))
  85     {
  86         /* If you don't have what you're looking for now, you never
  87          * will. Wake up and leave me alone. */
  88         pthread_cond_signal((*prev_reader)->data);
  89         *prev_reader = (*prev_reader)->next;
  90     }
  91 }
  92
  93 static int read_packet(xcb_connection_t *c)
  94 {
  95     xcb_generic_reply_t genrep;
  96     int length = 32;
  97     int eventlength = 0; /* length after first 32 bytes for GenericEvents */
  98     void *buf;
  99     pending_reply *pend = 0;
 100     struct event_list *event;
 101
 102     /* Wait for there to be enough data for us to read a whole packet */
 103     if(c->in.queue_len < length)
 104         return 0;
 105
 106     /* Get the response type, length, and sequence number. */
 107     memcpy(&genrep, c->in.queue, sizeof(genrep));
 108
 109     /* Compute 32-bit sequence number of this packet. */
 110     if((genrep.response_type & 0x7f) != XCB_KEYMAP_NOTIFY)
 111     {
 112         uint64_t lastread = c->in.request_read;
 113         c->in.request_read = (lastread & UINT64_C(0xffffffffffff0000)) | genrep.sequence;
 114         if(XCB_SEQUENCE_COMPARE(c->in.request_read, <, lastread))
 115             c->in.request_read += 0x10000;
 116         if(XCB_SEQUENCE_COMPARE(c->in.request_read, >, c->in.request_expected))
 117             c->in.request_expected = c->in.request_read;
 118
 119         if(c->in.request_read != lastread)
 120         {
 121             if(c->in.current_reply)
 122             {
 123                 _xcb_map_put(c->in.replies, lastread, c->in.current_reply);
 124                 c->in.current_reply = 0;
 125                 c->in.current_reply_tail = &c->in.current_reply;
 126             }
 127             c->in.request_completed = c->in.request_read - 1;
 128         }
 129
 130         while(c->in.pending_replies &&
 131               c->in.pending_replies->workaround != WORKAROUND_EXTERNAL_SOCKET_OWNER &&
 132               XCB_SEQUENCE_COMPARE (c->in.pending_replies->last_request, <=, c->in.request_completed))
 133         {
 134             pending_reply *oldpend = c->in.pending_replies;
 135             c->in.pending_replies = oldpend->next;
 136             if(!oldpend->next)
 137                 c->in.pending_replies_tail = &c->in.pending_replies;
 138             free(oldpend);
 139         }
 140
 141         if(genrep.response_type == XCB_ERROR)
 142             c->in.request_completed = c->in.request_read;
 143
 144         remove_finished_readers(&c->in.readers, c->in.request_completed);
 145     }
 146
 147     if(genrep.response_type == XCB_ERROR || genrep.response_type == XCB_REPLY)
 148     {
 149         pend = c->in.pending_replies;
 150         if(pend &&
 151            !(XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->in.request_read) &&
 152              (pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER ||
 153               XCB_SEQUENCE_COMPARE(c->in.request_read, <=, pend->last_request))))
 154             pend = 0;
 155     }
 156
 157     /* For reply packets, check that the entire packet is available. */
 158     if(genrep.response_type == XCB_REPLY)
 159     {
 160         if(pend && pend->workaround == WORKAROUND_GLX_GET_FB_CONFIGS_BUG)
 161         {
 162             uint32_t *p = (uint32_t *) c->in.queue;
 163             genrep.length = p[2] * p[3] * 2;
 164         }
 165         length += genrep.length * 4;
 166     }
 167
 168     /* XGE events may have sizes > 32 */
 169     if ((genrep.response_type & 0x7f) == XCB_XGE_EVENT)
 170         eventlength = genrep.length * 4;
 171
 172     buf = malloc(length + eventlength +
 173             (genrep.response_type == XCB_REPLY ? 0 : sizeof(uint32_t)));
 174     if(!buf)
 175     {
 176         _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
 177         return 0;
 178     }
 179
 180     if(_xcb_in_read_block(c, buf, length) <= 0)
 181     {
 182         free(buf);
 183         return 0;
 184     }
 185
 186     /* pull in XGE event data if available, append after event struct */
 187     if (eventlength)
 188     {
 189         if(_xcb_in_read_block(c, &((xcb_generic_event_t*)buf)[1], eventlength) <= 0)
 190         {
 191             free(buf);
 192             return 0;
 193         }
 194     }
 195
 196     if(pend && (pend->flags & XCB_REQUEST_DISCARD_REPLY))
 197     {
 198         free(buf);
 199         return 1;
 200     }
 201
 202     if(genrep.response_type != XCB_REPLY)
 203         ((xcb_generic_event_t *) buf)->full_sequence = c->in.request_read;
 204
 205     /* reply, or checked error */
 206     if( genrep.response_type == XCB_REPLY ||
 207        (genrep.response_type == XCB_ERROR && pend && (pend->flags & XCB_REQUEST_CHECKED)))
 208     {
 209         struct reply_list *cur = malloc(sizeof(struct reply_list));
 210         if(!cur)
 211         {
 212             _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
 213             free(buf);
 214             return 0;
 215         }
 216         cur->reply = buf;
 217         cur->next = 0;
 218         *c->in.current_reply_tail = cur;
 219         c->in.current_reply_tail = &cur->next;
 220         if(c->in.readers && c->in.readers->request == c->in.request_read)
 221             pthread_cond_signal(c->in.readers->data);
 222         return 1;
 223     }
 224
 225     /* event, or unchecked error */
 226     event = malloc(sizeof(struct event_list));
 227     if(!event)
 228     {
 229         _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
 230         free(buf);
 231         return 0;
 232     }
 233     event->event = buf;
 234     event->next = 0;
 235     *c->in.events_tail = event;
 236     c->in.events_tail = &event->next;
 237     pthread_cond_signal(&c->in.event_cond);
 238     return 1; /* I have something for you... */
 239 }
 240
 241 static xcb_generic_event_t *get_event(xcb_connection_t *c)
 242 {
 243     struct event_list *cur = c->in.events;
 244     xcb_generic_event_t *ret;
 245     if(!c->in.events)
 246         return 0;
 247     ret = cur->event;
 248     c->in.events = cur->next;
 249     if(!cur->next)
 250         c->in.events_tail = &c->in.events;
 251     free(cur);
 252     return ret;
 253 }
 254
 255 static void free_reply_list(struct reply_list *head)
 256 {
 257     while(head)
 258     {
 259         struct reply_list *cur = head;
 260         head = cur->next;
 261         free(cur->reply);
 262         free(cur);
 263     }
 264 }
 265
 266 static int read_block(const int fd, void *buf, const ssize_t len)
 267 {
 268     int done = 0;
 269     while(done < len)
 270     {
 271         int ret = recv(fd, ((char *) buf) + done, len - done, 0);
 272         if(ret > 0)
 273             done += ret;
 274 #ifndef _WIN32
 275         if(ret < 0 && errno == EAGAIN)
 276 #else
 277         if(ret == SOCKET_ERROR && WSAGetLastError() == WSAEWOULDBLOCK)
 278 #endif /* !_Win32 */
 279         {
 280 #if USE_POLL
 281             struct pollfd pfd;
 282             pfd.fd = fd;
 283             pfd.events = POLLIN;
 284             pfd.revents = 0;
 285             do {
 286                 ret = poll(&pfd, 1, -1);
 287             } while (ret == -1 && errno == EINTR);
 288 #else
 289             fd_set fds;
 290             FD_ZERO(&fds);
 291             FD_SET(fd, &fds);
 292
 293             /* Initializing errno here makes sure that for Win32 this loop will execute only once */
 294             errno = 0;
 295             do {
 296                 ret = select(fd + 1, &fds, 0, 0, 0);
 297             } while (ret == -1 && errno == EINTR);
 298 #endif /* USE_POLL */
 299         }
 300         if(ret <= 0)
 301             return ret;
 302     }
 303     return len;
 304 }
 305
 306 static int poll_for_reply(xcb_connection_t *c, uint64_t request, void **reply, xcb_generic_error_t **error)
 307 {
 308     struct reply_list *head;
 309
 310     /* If an error occurred when issuing the request, fail immediately. */
 311     if(!request)
 312         head = 0;
 313     /* We've read requests past the one we want, so if it has replies we have
 314      * them all and they're in the replies map. */
 315     else if(XCB_SEQUENCE_COMPARE(request, <, c->in.request_read))
 316     {
 317         head = _xcb_map_remove(c->in.replies, request);
 318         if(head && head->next)
 319             _xcb_map_put(c->in.replies, request, head->next);
 320     }
 321     /* We're currently processing the responses to the request we want, and we
 322      * have a reply ready to return. So just return it without blocking. */
 323     else if(request == c->in.request_read && c->in.current_reply)
 324     {
 325         head = c->in.current_reply;
 326         c->in.current_reply = head->next;
 327         if(!head->next)
 328             c->in.current_reply_tail = &c->in.current_reply;
 329     }
 330     /* We know this request can't have any more replies, and we've already
 331      * established it doesn't have a reply now. Don't bother blocking. */
 332     else if(request == c->in.request_completed)
 333         head = 0;
 334     /* We may have more replies on the way for this request: block until we're
 335      * sure. */
 336     else
 337         return 0;
 338
 339     if(error)
 340         *error = 0;
 341     *reply = 0;
 342
 343     if(head)
 344     {
 345         if(((xcb_generic_reply_t *) head->reply)->response_type == XCB_ERROR)
 346         {
 347             if(error)
 348                 *error = head->reply;
 349             else
 350                 free(head->reply);
 351         }
 352         else
 353             *reply = head->reply;
 354
 355         free(head);
 356     }
 357
 358     return 1;
 359 }
 360
 361 static void insert_reader(reader_list **prev_reader, reader_list *reader, uint64_t request, pthread_cond_t *cond)
 362 {
 363     while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, request))
 364         prev_reader = &(*prev_reader)->next;
 365     reader->request = request;
 366     reader->data = cond;
 367     reader->next = *prev_reader;
 368     *prev_reader = reader;
 369 }
 370
 371 static void remove_reader(reader_list **prev_reader, reader_list *reader)
 372 {
 373     while(*prev_reader && XCB_SEQUENCE_COMPARE((*prev_reader)->request, <=, reader->request))
 374         if(*prev_reader == reader)
 375         {
 376             *prev_reader = (*prev_reader)->next;
 377             break;
 378         }
 379 }
 380
 381 static void *wait_for_reply(xcb_connection_t *c, uint64_t request, xcb_generic_error_t **e)
 382 {
 383     void *ret = 0;
 384
 385     /* If this request has not been written yet, write it. */
 386     if(c->out.return_socket || _xcb_out_flush_to(c, request))
 387     {
 388         pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
 389         reader_list reader;
 390
 391         insert_reader(&c->in.readers, &reader, request, &cond);
 392
 393         while(!poll_for_reply(c, request, &ret, e))
 394             if(!_xcb_conn_wait(c, &cond, 0, 0))
 395                 break;
 396
 397         remove_reader(&c->in.readers, &reader);
 398         pthread_cond_destroy(&cond);
 399     }
 400
 401     _xcb_in_wake_up_next_reader(c);
 402     return ret;
 403 }
 404
 405 static uint64_t widen(xcb_connection_t *c, unsigned int request)
 406 {
 407     uint64_t widened_request = (c->out.request & UINT64_C(0xffffffff00000000)) | request;
 408     if(widened_request > c->out.request)
 409         widened_request -= UINT64_C(1) << 32;
 410     return widened_request;
 411 }
 412
 413 /* Public interface */
 414
 415 void *xcb_wait_for_reply(xcb_connection_t *c, unsigned int request, xcb_generic_error_t **e)
 416 {
 417     void *ret;
 418     if(e)
 419         *e = 0;
 420     if(c->has_error)
 421         return 0;
 422
 423     pthread_mutex_lock(&c->iolock);
 424     ret = wait_for_reply(c, widen(c, request), e);
 425     pthread_mutex_unlock(&c->iolock);
 426     return ret;
 427 }
 428
 429 static void insert_pending_discard(xcb_connection_t *c, pending_reply **prev_next, uint64_t seq)
 430 {
 431     pending_reply *pend;
 432     pend = malloc(sizeof(*pend));
 433     if(!pend)
 434     {
 435         _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
 436         return;
 437     }
 438
 439     pend->first_request = seq;
 440     pend->last_request = seq;
 441     pend->workaround = 0;
 442     pend->flags = XCB_REQUEST_DISCARD_REPLY;
 443     pend->next = *prev_next;
 444     *prev_next = pend;
 445
 446     if(!pend->next)
 447         c->in.pending_replies_tail = &pend->next;
 448 }
 449
 450 static void discard_reply(xcb_connection_t *c, uint64_t request)
 451 {
 452     void *reply;
 453     pending_reply **prev_pend;
 454
 455     /* Free any replies or errors that we've already read. Stop if
 456      * xcb_wait_for_reply would block or we've run out of replies. */
 457     while(poll_for_reply(c, request, &reply, 0) && reply)
 458         free(reply);
 459
 460     /* If we've proven there are no more responses coming, we're done. */
 461     if(XCB_SEQUENCE_COMPARE(request, <=, c->in.request_completed))
 462         return;
 463
 464     /* Walk the list of pending requests. Mark the first match for deletion. */
 465     for(prev_pend = &c->in.pending_replies; *prev_pend; prev_pend = &(*prev_pend)->next)
 466     {
 467         if(XCB_SEQUENCE_COMPARE((*prev_pend)->first_request, >, request))
 468             break;
 469
 470         if((*prev_pend)->first_request == request)
 471         {
 472             /* Pending reply found. Mark for discard: */
 473             (*prev_pend)->flags |= XCB_REQUEST_DISCARD_REPLY;
 474             return;
 475         }
 476     }
 477
 478     /* Pending reply not found (likely due to _unchecked request). Create one: */
 479     insert_pending_discard(c, prev_pend, request);
 480 }
 481
 482 void xcb_discard_reply(xcb_connection_t *c, unsigned int sequence)
 483 {
 484     if(c->has_error)
 485         return;
 486
 487     /* If an error occurred when issuing the request, fail immediately. */
 488     if(!sequence)
 489         return;
 490
 491     pthread_mutex_lock(&c->iolock);
 492     discard_reply(c, widen(c, sequence));
 493     pthread_mutex_unlock(&c->iolock);
 494 }
 495
 496 int xcb_poll_for_reply(xcb_connection_t *c, unsigned int request, void **reply, xcb_generic_error_t **error)
 497 {
 498     int ret;
 499     if(c->has_error)
 500     {
 501         *reply = 0;
 502         if(error)
 503             *error = 0;
 504         return 1; /* would not block */
 505     }
 506     assert(reply != 0);
 507     pthread_mutex_lock(&c->iolock);
 508     ret = poll_for_reply(c, widen(c, request), reply, error);
 509     pthread_mutex_unlock(&c->iolock);
 510     return ret;
 511 }
 512
 513 xcb_generic_event_t *xcb_wait_for_event(xcb_connection_t *c)
 514 {
 515     xcb_generic_event_t *ret;
 516     if(c->has_error)
 517         return 0;
 518     pthread_mutex_lock(&c->iolock);
 519     /* get_event returns 0 on empty list. */
 520     while(!(ret = get_event(c)))
 521         if(!_xcb_conn_wait(c, &c->in.event_cond, 0, 0))
 522             break;
 523
 524     _xcb_in_wake_up_next_reader(c);
 525     pthread_mutex_unlock(&c->iolock);
 526     return ret;
 527 }
 528
 529 static xcb_generic_event_t *poll_for_next_event(xcb_connection_t *c, int queued)
 530 {
 531     xcb_generic_event_t *ret = 0;
 532     if(!c->has_error)
 533     {
 534         pthread_mutex_lock(&c->iolock);
 535         /* FIXME: follow X meets Z architecture changes. */
 536         ret = get_event(c);
 537         if(!ret && !queued && c->in.reading == 0 && _xcb_in_read(c)) /* _xcb_in_read shuts down the connection on error */
 538             ret = get_event(c);
 539         pthread_mutex_unlock(&c->iolock);
 540     }
 541     return ret;
 542 }
 543
 544 xcb_generic_event_t *xcb_poll_for_event(xcb_connection_t *c)
 545 {
 546     return poll_for_next_event(c, 0);
 547 }
 548
 549 xcb_generic_event_t *xcb_poll_for_queued_event(xcb_connection_t *c)
 550 {
 551     return poll_for_next_event(c, 1);
 552 }
 553
 554 xcb_generic_error_t *xcb_request_check(xcb_connection_t *c, xcb_void_cookie_t cookie)
 555 {
 556     uint64_t request;
 557     xcb_generic_error_t *ret = 0;
 558     void *reply;
 559     if(c->has_error)
 560         return 0;
 561     pthread_mutex_lock(&c->iolock);
 562     request = widen(c, cookie.sequence);
 563     if(XCB_SEQUENCE_COMPARE(request, >=, c->in.request_expected)
 564        && XCB_SEQUENCE_COMPARE(request, >, c->in.request_completed))
 565     {
 566         _xcb_out_send_sync(c);
 567         _xcb_out_flush_to(c, c->out.request);
 568     }
 569     reply = wait_for_reply(c, request, &ret);
 570     assert(!reply);
 571     pthread_mutex_unlock(&c->iolock);
 572     return ret;
 573 }
 574
 575 /* Private interface */
 576
 577 int _xcb_in_init(_xcb_in *in)
 578 {
 579     if(pthread_cond_init(&in->event_cond, 0))
 580         return 0;
 581     in->reading = 0;
 582
 583     in->queue_len = 0;
 584
 585     in->request_read = 0;
 586     in->request_completed = 0;
 587
 588     in->replies = _xcb_map_new();
 589     if(!in->replies)
 590         return 0;
 591
 592     in->current_reply_tail = &in->current_reply;
 593     in->events_tail = &in->events;
 594     in->pending_replies_tail = &in->pending_replies;
 595
 596     return 1;
 597 }
 598
 599 void _xcb_in_destroy(_xcb_in *in)
 600 {
 601     pthread_cond_destroy(&in->event_cond);
 602     free_reply_list(in->current_reply);
 603     _xcb_map_delete(in->replies, (void (*)(void *)) free_reply_list);
 604     while(in->events)
 605     {
 606         struct event_list *e = in->events;
 607         in->events = e->next;
 608         free(e->event);
 609         free(e);
 610     }
 611     while(in->pending_replies)
 612     {
 613         pending_reply *pend = in->pending_replies;
 614         in->pending_replies = pend->next;
 615         free(pend);
 616     }
 617 }
 618
 619 void _xcb_in_wake_up_next_reader(xcb_connection_t *c)
 620 {
 621     int pthreadret;
 622     if(c->in.readers)
 623         pthreadret = pthread_cond_signal(c->in.readers->data);
 624     else
 625         pthreadret = pthread_cond_signal(&c->in.event_cond);
 626     assert(pthreadret == 0);
 627 }
 628
 629 int _xcb_in_expect_reply(xcb_connection_t *c, uint64_t request, enum workarounds workaround, int flags)
 630 {
 631     pending_reply *pend = malloc(sizeof(pending_reply));
 632     assert(workaround != WORKAROUND_NONE || flags != 0);
 633     if(!pend)
 634     {
 635         _xcb_conn_shutdown(c, XCB_CONN_CLOSED_MEM_INSUFFICIENT);
 636         return 0;
 637     }
 638     pend->first_request = pend->last_request = request;
 639     pend->workaround = workaround;
 640     pend->flags = flags;
 641     pend->next = 0;
 642     *c->in.pending_replies_tail = pend;
 643     c->in.pending_replies_tail = &pend->next;
 644     return 1;
 645 }
 646
 647 void _xcb_in_replies_done(xcb_connection_t *c)
 648 {
 649     struct pending_reply *pend;
 650     if (c->in.pending_replies_tail != &c->in.pending_replies)
 651     {
 652         pend = container_of(c->in.pending_replies_tail, struct pending_reply, next);
 653         if(pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER)
 654         {
 655             pend->last_request = c->out.request;
 656             pend->workaround = WORKAROUND_NONE;
 657         }
 658     }
 659 }
 660
 661 int _xcb_in_read(xcb_connection_t *c)
 662 {
 663     int n = recv(c->fd, c->in.queue + c->in.queue_len, sizeof(c->in.queue) - c->in.queue_len, 0);
 664     if(n > 0)
 665         c->in.queue_len += n;
 666     while(read_packet(c))
 667         /* empty */;
 668 #ifndef _WIN32
 669     if((n > 0) || (n < 0 && errno == EAGAIN))
 670 #else
 671     if((n > 0) || (n < 0 && WSAGetLastError() == WSAEWOULDBLOCK))
 672 #endif /* !_WIN32 */
 673         return 1;
 674     _xcb_conn_shutdown(c, XCB_CONN_ERROR);
 675     return 0;
 676 }
 677
 678 int _xcb_in_read_block(xcb_connection_t *c, void *buf, int len)
 679 {
 680     int done = c->in.queue_len;
 681     if(len < done)
 682         done = len;
 683
 684     memcpy(buf, c->in.queue, done);
 685     c->in.queue_len -= done;
 686     memmove(c->in.queue, c->in.queue + done, c->in.queue_len);
 687
 688     if(len > done)
 689     {
 690         int ret = read_block(c->fd, (char *) buf + done, len - done);
 691         if(ret <= 0)
 692         {
 693             _xcb_conn_shutdown(c, XCB_CONN_ERROR);
 694             return ret;
 695         }
 696     }
 697
 698     return len;
 699 }