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 2.1 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 (GPollFD *msg_fd,
 133            HANDLE  *handles,
 134            GPollFD *handle_to_fd[],
 135            gint     nhandles,
 136            gint     timeout)
 137 {
 138   DWORD ready;
 139   GPollFD *f;
 140   int recursed_result;
 141
 142   if (msg_fd != NULL)
 143     {
 144       /* Wait for either messages or handles
 145        * -> Use MsgWaitForMultipleObjectsEx
 146        */
 147       if (_g_main_poll_debug)
 148         g_print ("  MsgWaitForMultipleObjectsEx(%d, %d)\n", nhandles, timeout);
 149
 150       ready = MsgWaitForMultipleObjectsEx (nhandles, handles, timeout,
 151                                            QS_ALLINPUT, MWMO_ALERTABLE);
 152
 153       if (ready == WAIT_FAILED)
 154         {
 155           gchar *emsg = g_win32_error_message (GetLastError ());
 156           g_warning ("MsgWaitForMultipleObjectsEx failed: %s", emsg);
 157           g_free (emsg);
 158         }
 159     }
 160   else if (nhandles == 0)
 161     {
 162       /* No handles to wait for, just the timeout */
 163       if (timeout == INFINITE)
 164         ready = WAIT_FAILED;
 165       else
 166         {
 167           /* Wait for the current process to die, more efficient than SleepEx(). */
 168           WaitForSingleObjectEx (GetCurrentProcess (), 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                (msg_fd != NULL && 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 (msg_fd != NULL && ready == WAIT_OBJECT_0 + nhandles)
 202     {
 203       msg_fd->revents |= G_IO_IN;
 204
 205       /* If we have a timeout, or no handles to poll, be satisfied
 206        * with just noticing we have messages waiting.
 207        */
 208       if (timeout != 0 || nhandles == 0)
 209         return 1;
 210
 211       /* If no timeout and handles to poll, recurse to poll them,
 212        * too.
 213        */
 214       recursed_result = poll_rest (NULL, handles, handle_to_fd, nhandles, 0);
 215       return (recursed_result == -1) ? -1 : 1 + recursed_result;
 216     }
 217   else if (ready >= WAIT_OBJECT_0 && ready < WAIT_OBJECT_0 + nhandles)
 218     {
 219       f = handle_to_fd[ready - WAIT_OBJECT_0];
 220       f->revents = f->events;
 221       if (_g_main_poll_debug)
 222         g_print ("  got event %p\n", (HANDLE) f->fd);
 223
 224       /* If no timeout and polling several handles, recurse to poll
 225        * the rest of them.
 226        */
 227       if (timeout == 0 && nhandles > 1)
 228         {
 229           /* Poll the handles with index > ready */
 230           HANDLE  *shorter_handles;
 231           GPollFD **shorter_handle_to_fd;
 232           gint     shorter_nhandles;
 233
 234           shorter_handles = &handles[ready - WAIT_OBJECT_0 + 1];
 235           shorter_handle_to_fd = &handle_to_fd[ready - WAIT_OBJECT_0 + 1];
 236           shorter_nhandles = nhandles - (ready - WAIT_OBJECT_0 + 1);
 237
 238           recursed_result = poll_rest (NULL, shorter_handles, shorter_handle_to_fd, shorter_nhandles, 0);
 239           return (recursed_result == -1) ? -1 : 1 + recursed_result;
 240         }
 241       return 1;
 242     }
 243
 244   return 0;
 245 }
 246
 247 gint
 248 g_poll (GPollFD *fds,
 249         guint    nfds,
 250         gint     timeout)
 251 {
 252   HANDLE handles[MAXIMUM_WAIT_OBJECTS];
 253   GPollFD *handle_to_fd[MAXIMUM_WAIT_OBJECTS];
 254   GPollFD *msg_fd = NULL;
 255   GPollFD *f;
 256   gint nhandles = 0;
 257   int retval;
 258
 259   if (_g_main_poll_debug)
 260     g_print ("g_poll: waiting for");
 261
 262   for (f = fds; f < &fds[nfds]; ++f)
 263     {
 264       if (f->fd == G_WIN32_MSG_HANDLE && (f->events & G_IO_IN))
 265         {
 266           if (_g_main_poll_debug && msg_fd == NULL)
 267             g_print (" MSG");
 268           msg_fd = f;
 269         }
 270       else if (f->fd > 0)
 271         {
 272           if (nhandles == MAXIMUM_WAIT_OBJECTS)
 273             {
 274               g_warning ("Too many handles to wait for!");
 275               break;
 276             }
 277           else
 278             {
 279               if (_g_main_poll_debug)
 280                 g_print (" %p", (HANDLE) f->fd);
 281               handle_to_fd[nhandles] = f;
 282               handles[nhandles++] = (HANDLE) f->fd;
 283             }
 284         }
 285       f->revents = 0;
 286     }
 287
 288   if (_g_main_poll_debug)
 289     g_print ("\n");
 290
 291   if (timeout == -1)
 292     timeout = INFINITE;
 293
 294   /* Polling for several things? */
 295   if (nhandles > 1 || (nhandles > 0 && msg_fd != NULL))
 296     {
 297       /* First check if one or several of them are immediately
 298        * available
 299        */
 300       retval = poll_rest (msg_fd, handles, handle_to_fd, nhandles, 0);
 301
 302       /* If not, and we have a significant timeout, poll again with
 303        * timeout then. Note that this will return indication for only
 304        * one event, or only for messages.
 305        */
 306       if (retval == 0 && (timeout == INFINITE || timeout > 0))
 307         retval = poll_rest (msg_fd, handles, handle_to_fd, nhandles, timeout);
 308     }
 309   else
 310     {
 311       /* Just polling for one thing, so no need to check first if
 312        * available immediately
 313        */
 314       retval = poll_rest (msg_fd, handles, handle_to_fd, nhandles, timeout);
 315     }
 316
 317   if (retval == -1)
 318     for (f = fds; f < &fds[nfds]; ++f)
 319       f->revents = 0;
 320
 321   return retval;
 322 }
 323
 324 #else  /* !G_OS_WIN32 */
 325
 326 /* The following implementation of poll() comes from the GNU C Library.
 327  * Copyright (C) 1994, 1996, 1997 Free Software Foundation, Inc.
 328  */
 329
 330 #include <string.h> /* for bzero on BSD systems */
 331
 332 #ifdef HAVE_SYS_SELECT_H
 333 #include <sys/select.h>
 334 #endif /* HAVE_SYS_SELECT_H */
 335
 336 gint
 337 g_poll (GPollFD *fds,
 338         guint    nfds,
 339         gint     timeout)
 340 {
 341   struct timeval tv;
 342   fd_set rset, wset, xset;
 343   GPollFD *f;
 344   int ready;
 345   int maxfd = 0;
 346
 347   FD_ZERO (&rset);
 348   FD_ZERO (&wset);
 349   FD_ZERO (&xset);
 350
 351   for (f = fds; f < &fds[nfds]; ++f)
 352     if (f->fd >= 0)
 353       {
 354         if (f->events & G_IO_IN)
 355           FD_SET (f->fd, &rset);
 356         if (f->events & G_IO_OUT)
 357           FD_SET (f->fd, &wset);
 358         if (f->events & G_IO_PRI)
 359           FD_SET (f->fd, &xset);
 360         if (f->fd > maxfd && (f->events & (G_IO_IN|G_IO_OUT|G_IO_PRI)))
 361           maxfd = f->fd;
 362       }
 363
 364   tv.tv_sec = timeout / 1000;
 365   tv.tv_usec = (timeout % 1000) * 1000;
 366
 367   ready = select (maxfd + 1, &rset, &wset, &xset,
 368                   timeout == -1 ? NULL : &tv);
 369   if (ready > 0)
 370     for (f = fds; f < &fds[nfds]; ++f)
 371       {
 372         f->revents = 0;
 373         if (f->fd >= 0)
 374           {
 375             if (FD_ISSET (f->fd, &rset))
 376               f->revents |= G_IO_IN;
 377             if (FD_ISSET (f->fd, &wset))
 378               f->revents |= G_IO_OUT;
 379             if (FD_ISSET (f->fd, &xset))
 380               f->revents |= G_IO_PRI;
 381           }
 382       }
 383
 384   return ready;
 385 }
 386
 387 #endif /* !G_OS_WIN32 */
 388
 389 #endif  /* !HAVE_POLL */