glib/gpoll.c

   1 /* GLIB - Library of useful routines for C programming
   2  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
   3  *
   4  * gpoll.c: poll(2) abstraction
   5  * Copyright 1998 Owen Taylor
   6  * Copyright 2008 Red Hat, Inc.
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2 of the License, or (at your option) any later version.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  20  */
  21
  22 /*
  23  * Modified by the GLib Team and others 1997-2000.  See the AUTHORS
  24  * file for a list of people on the GLib Team.  See the ChangeLog
  25  * files for a list of changes.  These files are distributed with
  26  * GLib at ftp://ftp.gtk.org/pub/gtk/.
  27  */
  28
  29 /*
  30  * MT safe
  31  */
  32
  33 #include "config.h"
  34 #include "glibconfig.h"
  35 #include "giochannel.h"
  36
  37 /* Uncomment the next line (and the corresponding line in gmain.c) to
  38  * enable debugging printouts if the environment variable
  39  * G_MAIN_POLL_DEBUG is set to some value.
  40  */
  41 /* #define G_MAIN_POLL_DEBUG */
  42
  43 #ifdef _WIN32
  44 /* Always enable debugging printout on Windows, as it is more often
  45  * needed there...
  46  */
  47 #define G_MAIN_POLL_DEBUG
  48 #endif
  49
  50 #include <sys/types.h>
  51 #include <time.h>
  52 #include <stdlib.h>
  53 #ifdef HAVE_SYS_TIME_H
  54 #include <sys/time.h>
  55 #endif /* HAVE_SYS_TIME_H */
  56 #ifdef HAVE_POLL
  57 #  include <poll.h>
  58
  59 /* The poll() emulation on OS/X doesn't handle fds=NULL, nfds=0,
  60  * so we prefer our own poll emulation.
  61  */
  62 #if defined(_POLL_EMUL_H_) || defined(BROKEN_POLL)
  63 #undef HAVE_POLL
  64 #endif
  65
  66 #endif /* GLIB_HAVE_SYS_POLL_H */
  67 #ifdef G_OS_UNIX
  68 #include <unistd.h>
  69 #endif /* G_OS_UNIX */
  70 #include <errno.h>
  71
  72 #ifdef G_OS_WIN32
  73 #define STRICT
  74 #include <windows.h>
  75 #endif /* G_OS_WIN32 */
  76
  77 #include "gpoll.h"
  78
  79 #ifdef G_OS_WIN32
  80 #include "gprintf.h"
  81 #endif
  82
  83 #ifdef G_MAIN_POLL_DEBUG
  84 extern gboolean _g_main_poll_debug;
  85 #endif
  86
  87 #ifdef HAVE_POLL
  88
  89 /**
  90  * g_poll:
  91  * @fds: file descriptors to poll
  92  * @nfds: the number of file descriptors in @fds
  93  * @timeout: amount of time to wait, in milliseconds, or -1 to wait forever
  94  *
  95  * Polls @fds, as with the poll() system call, but portably. (On
  96  * systems that don't have poll(), it is emulated using select().)
  97  * This is used internally by #GMainContext, but it can be called
  98  * directly if you need to block until a file descriptor is ready, but
  99  * don't want to run the full main loop.
 100  *
 101  * Each element of @fds is a #GPollFD describing a single file
 102  * descriptor to poll. The %fd field indicates the file descriptor,
 103  * and the %events field indicates the events to poll for. On return,
 104  * the %revents fields will be filled with the events that actually
 105  * occurred.
 106  *
 107  * On POSIX systems, the file descriptors in @fds can be any sort of
 108  * file descriptor, but the situation is much more complicated on
 109  * Windows. If you need to use g_poll() in code that has to run on
 110  * Windows, the easiest solution is to construct all of your
 111  * #GPollFDs with g_io_channel_win32_make_pollfd().
 112  *
 113  * Returns: the number of entries in @fds whose %revents fields
 114  * were filled in, or 0 if the operation timed out, or -1 on error or
 115  * if the call was interrupted.
 116  *
 117  * Since: 2.20
 118  **/
 119 gint
 120 g_poll (GPollFD *fds,
 121         guint    nfds,
 122         gint     timeout)
 123 {
 124   return poll ((struct pollfd *)fds, nfds, timeout);
 125 }
 126
 127 #else   /* !HAVE_POLL */
 128
 129 #ifdef G_OS_WIN32
 130
 131 static int
 132 poll_rest (gboolean  poll_msgs,
 133            HANDLE   *handles,
 134            gint      nhandles,
 135            GPollFD  *fds,
 136            guint     nfds,
 137            gint      timeout)
 138 {
 139   DWORD ready;
 140   GPollFD *f;
 141   int recursed_result;
 142
 143   if (poll_msgs)
 144     {
 145       /* Wait for either messages or handles
 146        * -> Use MsgWaitForMultipleObjectsEx
 147        */
 148       if (_g_main_poll_debug)
 149         g_print ("  MsgWaitForMultipleObjectsEx(%d, %d)\n", nhandles, timeout);
 150
 151       ready = MsgWaitForMultipleObjectsEx (nhandles, handles, timeout,
 152                                            QS_ALLINPUT, MWMO_ALERTABLE);
 153
 154       if (ready == WAIT_FAILED)
 155         {
 156           gchar *emsg = g_win32_error_message (GetLastError ());
 157           g_warning ("MsgWaitForMultipleObjectsEx failed: %s", emsg);
 158           g_free (emsg);
 159         }
 160     }
 161   else if (nhandles == 0)
 162     {
 163       /* No handles to wait for, just the timeout */
 164       if (timeout == INFINITE)
 165         ready = WAIT_FAILED;
 166       else
 167         {
 168           SleepEx (timeout, TRUE);
 169           ready = WAIT_TIMEOUT;
 170         }
 171     }
 172   else
 173     {
 174       /* Wait for just handles
 175        * -> Use WaitForMultipleObjectsEx
 176        */
 177       if (_g_main_poll_debug)
 178         g_print ("  WaitForMultipleObjectsEx(%d, %d)\n", nhandles, timeout);
 179
 180       ready = WaitForMultipleObjectsEx (nhandles, handles, FALSE, timeout, TRUE);
 181       if (ready == WAIT_FAILED)
 182         {
 183           gchar *emsg = g_win32_error_message (GetLastError ());
 184           g_warning ("WaitForMultipleObjectsEx failed: %s", emsg);
 185           g_free (emsg);
 186         }
 187     }
 188
 189   if (_g_main_poll_debug)
 190     g_print ("  wait returns %ld%s\n",
 191              ready,
 192              (ready == WAIT_FAILED ? " (WAIT_FAILED)" :
 193               (ready == WAIT_TIMEOUT ? " (WAIT_TIMEOUT)" :
 194                (poll_msgs && ready == WAIT_OBJECT_0 + nhandles ? " (msg)" : ""))));
 195
 196   if (ready == WAIT_FAILED)
 197     return -1;
 198   else if (ready == WAIT_TIMEOUT ||
 199            ready == WAIT_IO_COMPLETION)
 200     return 0;
 201   else if (poll_msgs && ready == WAIT_OBJECT_0 + nhandles)
 202     {
 203       for (f = fds; f < &fds[nfds]; ++f)
 204         if (f->fd == G_WIN32_MSG_HANDLE && f->events & G_IO_IN)
 205           f->revents |= G_IO_IN;
 206
 207       /* If we have a timeout, or no handles to poll, be satisfied
 208        * with just noticing we have messages waiting.
 209        */
 210       if (timeout != 0 || nhandles == 0)
 211         return 1;
 212
 213       /* If no timeout and handles to poll, recurse to poll them,
 214        * too.
 215        */
 216       recursed_result = poll_rest (FALSE, handles, nhandles, fds, nfds, 0);
 217       return (recursed_result == -1) ? -1 : 1 + recursed_result;
 218     }
 219   else if (ready >= WAIT_OBJECT_0 && ready < WAIT_OBJECT_0 + nhandles)
 220     {
 221       for (f = fds; f < &fds[nfds]; ++f)
 222         {
 223           if ((HANDLE) f->fd == handles[ready - WAIT_OBJECT_0])
 224             {
 225               f->revents = f->events;
 226               if (_g_main_poll_debug)
 227                 g_print ("  got event %p\n", (HANDLE) f->fd);
 228             }
 229         }
 230
 231       /* If no timeout and polling several handles, recurse to poll
 232        * the rest of them.
 233        */
 234       if (timeout == 0 && nhandles > 1)
 235         {
 236           /* Remove the handle that fired */
 237           int i;
 238           if (ready < nhandles - 1)
 239             for (i = ready - WAIT_OBJECT_0 + 1; i < nhandles; i++)
 240               handles[i-1] = handles[i];
 241           nhandles--;
 242           recursed_result = poll_rest (FALSE, handles, nhandles, fds, nfds, 0);
 243           return (recursed_result == -1) ? -1 : 1 + recursed_result;
 244         }
 245       return 1;
 246     }
 247
 248   return 0;
 249 }
 250
 251 gint
 252 g_poll (GPollFD *fds,
 253         guint    nfds,
 254         gint     timeout)
 255 {
 256   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
 257   gboolean poll_msgs = FALSE;
 258   GPollFD *f;
 259   gint nhandles = 0;
 260   int retval;
 261
 262   if (_g_main_poll_debug)
 263     g_print ("g_poll: waiting for");
 264
 265   for (f = fds; f < &fds[nfds]; ++f)
 266     if (f->fd == G_WIN32_MSG_HANDLE && (f->events & G_IO_IN))
 267       {
 268         if (_g_main_poll_debug && !poll_msgs)
 269           g_print (" MSG");
 270         poll_msgs = TRUE;
 271       }
 272     else if (f->fd > 0)
 273       {
 274         if (nhandles == MAXIMUM_WAIT_OBJECTS)
 275           {
 276             g_warning ("Too many handles to wait for!\n");
 277             break;
 278           }
 279         else
 280           {
 281             if (_g_main_poll_debug)
 282               g_print (" %p", (HANDLE) f->fd);
 283             handles[nhandles++] = (HANDLE) f->fd;
 284           }
 285       }
 286
 287   if (_g_main_poll_debug)
 288     g_print ("\n");
 289
 290   for (f = fds; f < &fds[nfds]; ++f)
 291     f->revents = 0;
 292
 293   if (timeout == -1)
 294     timeout = INFINITE;
 295
 296   /* Polling for several things? */
 297   if (nhandles > 1 || (nhandles > 0 && poll_msgs))
 298     {
 299       /* First check if one or several of them are immediately
 300        * available
 301        */
 302       retval = poll_rest (poll_msgs, handles, nhandles, fds, nfds, 0);
 303
 304       /* If not, and we have a significant timeout, poll again with
 305        * timeout then. Note that this will return indication for only
 306        * one event, or only for messages.
 307        */
 308       if (retval == 0 && (timeout == INFINITE || timeout > 0))
 309         retval = poll_rest (poll_msgs, handles, nhandles, fds, nfds, timeout);
 310     }
 311   else
 312     {
 313       /* Just polling for one thing, so no need to check first if
 314        * available immediately
 315        */
 316       retval = poll_rest (poll_msgs, handles, nhandles, fds, nfds, timeout);
 317     }
 318
 319   if (retval == -1)
 320     for (f = fds; f < &fds[nfds]; ++f)
 321       f->revents = 0;
 322
 323   return retval;
 324 }
 325
 326 #else  /* !G_OS_WIN32 */
 327
 328 /* The following implementation of poll() comes from the GNU C Library.
 329  * Copyright (C) 1994, 1996, 1997 Free Software Foundation, Inc.
 330  */
 331
 332 #include <string.h> /* for bzero on BSD systems */
 333
 334 #ifdef HAVE_SYS_SELECT_H
 335 #include <sys/select.h>
 336 #endif /* HAVE_SYS_SELECT_H */
 337
 338 #ifndef NO_FD_SET
 339 #  define SELECT_MASK fd_set
 340 #else /* !NO_FD_SET */
 341 #  ifndef _AIX
 342 typedef long fd_mask;
 343 #  endif /* _AIX */
 344 #  ifdef _IBMR2
 345 #    define SELECT_MASK void
 346 #  else /* !_IBMR2 */
 347 #    define SELECT_MASK int
 348 #  endif /* !_IBMR2 */
 349 #endif /* !NO_FD_SET */
 350
 351 gint
 352 g_poll (GPollFD *fds,
 353         guint    nfds,
 354         gint     timeout)
 355 {
 356   struct timeval tv;
 357   SELECT_MASK rset, wset, xset;
 358   GPollFD *f;
 359   int ready;
 360   int maxfd = 0;
 361
 362   FD_ZERO (&rset);
 363   FD_ZERO (&wset);
 364   FD_ZERO (&xset);
 365
 366   for (f = fds; f < &fds[nfds]; ++f)
 367     if (f->fd >= 0)
 368       {
 369         if (f->events & G_IO_IN)
 370           FD_SET (f->fd, &rset);
 371         if (f->events & G_IO_OUT)
 372           FD_SET (f->fd, &wset);
 373         if (f->events & G_IO_PRI)
 374           FD_SET (f->fd, &xset);
 375         if (f->fd > maxfd && (f->events & (G_IO_IN|G_IO_OUT|G_IO_PRI)))
 376           maxfd = f->fd;
 377       }
 378
 379   tv.tv_sec = timeout / 1000;
 380   tv.tv_usec = (timeout % 1000) * 1000;
 381
 382   ready = select (maxfd + 1, &rset, &wset, &xset,
 383                   timeout == -1 ? NULL : &tv);
 384   if (ready > 0)
 385     for (f = fds; f < &fds[nfds]; ++f)
 386       {
 387         f->revents = 0;
 388         if (f->fd >= 0)
 389           {
 390             if (FD_ISSET (f->fd, &rset))
 391               f->revents |= G_IO_IN;
 392             if (FD_ISSET (f->fd, &wset))
 393               f->revents |= G_IO_OUT;
 394             if (FD_ISSET (f->fd, &xset))
 395               f->revents |= G_IO_PRI;
 396           }
 397       }
 398
 399   return ready;
 400 }
 401
 402 #endif /* !G_OS_WIN32 */
 403
 404 #endif  /* !HAVE_POLL */