gio/gunixoutputstream.c

   1 /* GIO - GLib Input, Output and Streaming Library
   2  *
   3  * Copyright (C) 2006-2007 Red Hat, Inc.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General
  16  * Public License along with this library; if not, write to the
  17  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  18  * Boston, MA 02111-1307, USA.
  19  *
  20  * Author: Alexander Larsson <alexl@redhat.com>
  21  */
  22
  23 #include "config.h"
  24
  25 #include <sys/types.h>
  26 #include <sys/stat.h>
  27 #include <unistd.h>
  28 #include <errno.h>
  29 #include <stdio.h>
  30 #include <fcntl.h>
  31
  32 #include <glib.h>
  33 #include <glib/gstdio.h>
  34 #include "gioerror.h"
  35 #include "gunixoutputstream.h"
  36 #include "gcancellable.h"
  37 #include "gsimpleasyncresult.h"
  38 #include "gasynchelper.h"
  39 #include "gfiledescriptorbased.h"
  40 #include "glibintl.h"
  41
  42
  43 /**
  44  * SECTION:gunixoutputstream
  45  * @short_description: Streaming output operations for UNIX file descriptors
  46  * @include: gio/gunixoutputstream.h
  47  * @see_also: #GOutputStream
  48  *
  49  * #GUnixOutputStream implements #GOutputStream for writing to a UNIX
  50  * file descriptor, including asynchronous operations. (If the file
  51  * descriptor refers to a socket or pipe, this will use poll() to do
  52  * asynchronous I/O. If it refers to a regular file, it will fall back
  53  * to doing asynchronous I/O in another thread.)
  54  *
  55  * Note that <filename>&lt;gio/gunixoutputstream.h&gt;</filename> belongs
  56  * to the UNIX-specific GIO interfaces, thus you have to use the
  57  * <filename>gio-unix-2.0.pc</filename> pkg-config file when using it.
  58  */
  59
  60 enum {
  61   PROP_0,
  62   PROP_FD,
  63   PROP_CLOSE_FD
  64 };
  65
  66 static void g_unix_output_stream_pollable_iface_init (GPollableOutputStreamInterface *iface);
  67 static void g_unix_output_stream_file_descriptor_based_iface_init (GFileDescriptorBasedIface *iface);
  68
  69 G_DEFINE_TYPE_WITH_CODE (GUnixOutputStream, g_unix_output_stream, G_TYPE_OUTPUT_STREAM,
  70                          G_IMPLEMENT_INTERFACE (G_TYPE_POLLABLE_OUTPUT_STREAM,
  71                                                 g_unix_output_stream_pollable_iface_init)
  72                          G_IMPLEMENT_INTERFACE (G_TYPE_FILE_DESCRIPTOR_BASED,
  73                                                 g_unix_output_stream_file_descriptor_based_iface_init)
  74                          )
  75
  76 struct _GUnixOutputStreamPrivate {
  77   int fd;
  78   guint close_fd : 1;
  79   guint is_pipe_or_socket : 1;
  80 };
  81
  82 static void     g_unix_output_stream_set_property (GObject              *object,
  83                                                    guint                 prop_id,
  84                                                    const GValue         *value,
  85                                                    GParamSpec           *pspec);
  86 static void     g_unix_output_stream_get_property (GObject              *object,
  87                                                    guint                 prop_id,
  88                                                    GValue               *value,
  89                                                    GParamSpec           *pspec);
  90 static gssize   g_unix_output_stream_write        (GOutputStream        *stream,
  91                                                    const void           *buffer,
  92                                                    gsize                 count,
  93                                                    GCancellable         *cancellable,
  94                                                    GError              **error);
  95 static gboolean g_unix_output_stream_close        (GOutputStream        *stream,
  96                                                    GCancellable         *cancellable,
  97                                                    GError              **error);
  98 static void     g_unix_output_stream_write_async  (GOutputStream        *stream,
  99                                                    const void           *buffer,
 100                                                    gsize                 count,
 101                                                    int                   io_priority,
 102                                                    GCancellable         *cancellable,
 103                                                    GAsyncReadyCallback   callback,
 104                                                    gpointer              data);
 105 static gssize   g_unix_output_stream_write_finish (GOutputStream        *stream,
 106                                                    GAsyncResult         *result,
 107                                                    GError              **error);
 108 static void     g_unix_output_stream_close_async  (GOutputStream        *stream,
 109                                                    int                   io_priority,
 110                                                    GCancellable         *cancellable,
 111                                                    GAsyncReadyCallback   callback,
 112                                                    gpointer              data);
 113 static gboolean g_unix_output_stream_close_finish (GOutputStream        *stream,
 114                                                    GAsyncResult         *result,
 115                                                    GError              **error);
 116
 117 static gboolean g_unix_output_stream_pollable_is_writable   (GPollableOutputStream *stream);
 118 static GSource *g_unix_output_stream_pollable_create_source (GPollableOutputStream *stream,
 119                                                              GCancellable         *cancellable);
 120
 121 static void
 122 g_unix_output_stream_finalize (GObject *object)
 123 {
 124   G_OBJECT_CLASS (g_unix_output_stream_parent_class)->finalize (object);
 125 }
 126
 127 static void
 128 g_unix_output_stream_class_init (GUnixOutputStreamClass *klass)
 129 {
 130   GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
 131   GOutputStreamClass *stream_class = G_OUTPUT_STREAM_CLASS (klass);
 132
 133   g_type_class_add_private (klass, sizeof (GUnixOutputStreamPrivate));
 134
 135   gobject_class->get_property = g_unix_output_stream_get_property;
 136   gobject_class->set_property = g_unix_output_stream_set_property;
 137   gobject_class->finalize = g_unix_output_stream_finalize;
 138
 139   stream_class->write_fn = g_unix_output_stream_write;
 140   stream_class->close_fn = g_unix_output_stream_close;
 141   stream_class->write_async = g_unix_output_stream_write_async;
 142   stream_class->write_finish = g_unix_output_stream_write_finish;
 143   stream_class->close_async = g_unix_output_stream_close_async;
 144   stream_class->close_finish = g_unix_output_stream_close_finish;
 145
 146    /**
 147    * GUnixOutputStream:fd:
 148    *
 149    * The file descriptor that the stream writes to.
 150    *
 151    * Since: 2.20
 152    */
 153   g_object_class_install_property (gobject_class,
 154                                    PROP_FD,
 155                                    g_param_spec_int ("fd",
 156                                                      P_("File descriptor"),
 157                                                      P_("The file descriptor to write to"),
 158                                                      G_MININT, G_MAXINT, -1,
 159                                                      G_PARAM_READABLE | G_PARAM_WRITABLE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_STATIC_NAME | G_PARAM_STATIC_NICK | G_PARAM_STATIC_BLURB));
 160
 161   /**
 162    * GUnixOutputStream:close-fd:
 163    *
 164    * Whether to close the file descriptor when the stream is closed.
 165    *
 166    * Since: 2.20
 167    */
 168   g_object_class_install_property (gobject_class,
 169                                    PROP_CLOSE_FD,
 170                                    g_param_spec_boolean ("close-fd",
 171                                                          P_("Close file descriptor"),
 172                                                          P_("Whether to close the file descriptor when the stream is closed"),
 173                                                          TRUE,
 174                                                          G_PARAM_READABLE | G_PARAM_WRITABLE | G_PARAM_STATIC_NAME | G_PARAM_STATIC_NICK | G_PARAM_STATIC_BLURB));
 175 }
 176
 177 static void
 178 g_unix_output_stream_pollable_iface_init (GPollableOutputStreamInterface *iface)
 179 {
 180   iface->is_writable = g_unix_output_stream_pollable_is_writable;
 181   iface->create_source = g_unix_output_stream_pollable_create_source;
 182 }
 183
 184 static void
 185 g_unix_output_stream_file_descriptor_based_iface_init (GFileDescriptorBasedIface *iface)
 186 {
 187   iface->get_fd = (int (*) (GFileDescriptorBased *))g_unix_output_stream_get_fd;
 188 }
 189
 190 static void
 191 g_unix_output_stream_set_property (GObject         *object,
 192                                    guint            prop_id,
 193                                    const GValue    *value,
 194                                    GParamSpec      *pspec)
 195 {
 196   GUnixOutputStream *unix_stream;
 197
 198   unix_stream = G_UNIX_OUTPUT_STREAM (object);
 199
 200   switch (prop_id)
 201     {
 202     case PROP_FD:
 203       unix_stream->priv->fd = g_value_get_int (value);
 204       if (lseek (unix_stream->priv->fd, 0, SEEK_CUR) == -1 && errno == ESPIPE)
 205         unix_stream->priv->is_pipe_or_socket = TRUE;
 206       else
 207         unix_stream->priv->is_pipe_or_socket = FALSE;
 208       break;
 209     case PROP_CLOSE_FD:
 210       unix_stream->priv->close_fd = g_value_get_boolean (value);
 211       break;
 212     default:
 213       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 214       break;
 215     }
 216 }
 217
 218 static void
 219 g_unix_output_stream_get_property (GObject    *object,
 220                                    guint       prop_id,
 221                                    GValue     *value,
 222                                    GParamSpec *pspec)
 223 {
 224   GUnixOutputStream *unix_stream;
 225
 226   unix_stream = G_UNIX_OUTPUT_STREAM (object);
 227
 228   switch (prop_id)
 229     {
 230     case PROP_FD:
 231       g_value_set_int (value, unix_stream->priv->fd);
 232       break;
 233     case PROP_CLOSE_FD:
 234       g_value_set_boolean (value, unix_stream->priv->close_fd);
 235       break;
 236     default:
 237       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 238     }
 239 }
 240
 241 static void
 242 g_unix_output_stream_init (GUnixOutputStream *unix_stream)
 243 {
 244   unix_stream->priv = G_TYPE_INSTANCE_GET_PRIVATE (unix_stream,
 245                                                    G_TYPE_UNIX_OUTPUT_STREAM,
 246                                                    GUnixOutputStreamPrivate);
 247
 248   unix_stream->priv->fd = -1;
 249   unix_stream->priv->close_fd = TRUE;
 250 }
 251
 252 /**
 253  * g_unix_output_stream_new:
 254  * @fd: a UNIX file descriptor
 255  * @close_fd: %TRUE to close the file descriptor when done
 256  *
 257  * Creates a new #GUnixOutputStream for the given @fd.
 258  *
 259  * If @close_fd, is %TRUE, the file descriptor will be closed when
 260  * the output stream is destroyed.
 261  *
 262  * Returns: a new #GOutputStream
 263  **/
 264 GOutputStream *
 265 g_unix_output_stream_new (gint     fd,
 266                           gboolean close_fd)
 267 {
 268   GUnixOutputStream *stream;
 269
 270   g_return_val_if_fail (fd != -1, NULL);
 271
 272   stream = g_object_new (G_TYPE_UNIX_OUTPUT_STREAM,
 273                          "fd", fd,
 274                          "close-fd", close_fd,
 275                          NULL);
 276
 277   return G_OUTPUT_STREAM (stream);
 278 }
 279
 280 /**
 281  * g_unix_output_stream_set_close_fd:
 282  * @stream: a #GUnixOutputStream
 283  * @close_fd: %TRUE to close the file descriptor when done
 284  *
 285  * Sets whether the file descriptor of @stream shall be closed
 286  * when the stream is closed.
 287  *
 288  * Since: 2.20
 289  */
 290 void
 291 g_unix_output_stream_set_close_fd (GUnixOutputStream *stream,
 292                                    gboolean           close_fd)
 293 {
 294   g_return_if_fail (G_IS_UNIX_OUTPUT_STREAM (stream));
 295
 296   close_fd = close_fd != FALSE;
 297   if (stream->priv->close_fd != close_fd)
 298     {
 299       stream->priv->close_fd = close_fd;
 300       g_object_notify (G_OBJECT (stream), "close-fd");
 301     }
 302 }
 303
 304 /**
 305  * g_unix_output_stream_get_close_fd:
 306  * @stream: a #GUnixOutputStream
 307  *
 308  * Returns whether the file descriptor of @stream will be
 309  * closed when the stream is closed.
 310  *
 311  * Return value: %TRUE if the file descriptor is closed when done
 312  *
 313  * Since: 2.20
 314  */
 315 gboolean
 316 g_unix_output_stream_get_close_fd (GUnixOutputStream *stream)
 317 {
 318   g_return_val_if_fail (G_IS_UNIX_OUTPUT_STREAM (stream), FALSE);
 319
 320   return stream->priv->close_fd;
 321 }
 322
 323 /**
 324  * g_unix_output_stream_get_fd:
 325  * @stream: a #GUnixOutputStream
 326  *
 327  * Return the UNIX file descriptor that the stream writes to.
 328  *
 329  * Return value: The file descriptor of @stream
 330  *
 331  * Since: 2.20
 332  */
 333 gint
 334 g_unix_output_stream_get_fd (GUnixOutputStream *stream)
 335 {
 336   g_return_val_if_fail (G_IS_UNIX_OUTPUT_STREAM (stream), -1);
 337
 338   return stream->priv->fd;
 339 }
 340
 341 static gssize
 342 g_unix_output_stream_write (GOutputStream  *stream,
 343                             const void     *buffer,
 344                             gsize           count,
 345                             GCancellable   *cancellable,
 346                             GError        **error)
 347 {
 348   GUnixOutputStream *unix_stream;
 349   gssize res = -1;
 350   GPollFD poll_fds[2];
 351   int nfds;
 352   int poll_ret;
 353
 354   unix_stream = G_UNIX_OUTPUT_STREAM (stream);
 355
 356   poll_fds[0].fd = unix_stream->priv->fd;
 357   poll_fds[0].events = G_IO_OUT;
 358
 359   if (unix_stream->priv->is_pipe_or_socket &&
 360       g_cancellable_make_pollfd (cancellable, &poll_fds[1]))
 361     nfds = 2;
 362   else
 363     nfds = 1;
 364
 365   while (1)
 366     {
 367       poll_fds[0].revents = poll_fds[1].revents = 0;
 368       do
 369         poll_ret = g_poll (poll_fds, nfds, -1);
 370       while (poll_ret == -1 && errno == EINTR);
 371
 372       if (poll_ret == -1)
 373         {
 374           int errsv = errno;
 375
 376           g_set_error (error, G_IO_ERROR,
 377                        g_io_error_from_errno (errsv),
 378                        _("Error writing to file descriptor: %s"),
 379                        g_strerror (errsv));
 380           break;
 381         }
 382
 383       if (g_cancellable_set_error_if_cancelled (cancellable, error))
 384         break;
 385
 386       if (!poll_fds[0].revents)
 387         continue;
 388
 389       res = write (unix_stream->priv->fd, buffer, count);
 390       if (res == -1)
 391         {
 392           int errsv = errno;
 393
 394           if (errsv == EINTR || errsv == EAGAIN)
 395             continue;
 396
 397           g_set_error (error, G_IO_ERROR,
 398                        g_io_error_from_errno (errsv),
 399                        _("Error writing to file descriptor: %s"),
 400                        g_strerror (errsv));
 401         }
 402
 403       break;
 404     }
 405
 406   g_cancellable_release_fd (cancellable);
 407   return res;
 408 }
 409
 410 static gboolean
 411 g_unix_output_stream_close (GOutputStream  *stream,
 412                             GCancellable   *cancellable,
 413                             GError        **error)
 414 {
 415   GUnixOutputStream *unix_stream;
 416   int res;
 417
 418   unix_stream = G_UNIX_OUTPUT_STREAM (stream);
 419
 420   if (!unix_stream->priv->close_fd)
 421     return TRUE;
 422
 423   while (1)
 424     {
 425       /* This might block during the close. Doesn't seem to be a way to avoid it though. */
 426       res = close (unix_stream->priv->fd);
 427       if (res == -1)
 428         {
 429           int errsv = errno;
 430
 431           g_set_error (error, G_IO_ERROR,
 432                        g_io_error_from_errno (errsv),
 433                        _("Error closing file descriptor: %s"),
 434                        g_strerror (errsv));
 435         }
 436       break;
 437     }
 438
 439   return res != -1;
 440 }
 441
 442 typedef struct {
 443   gsize count;
 444   const void *buffer;
 445   GAsyncReadyCallback callback;
 446   gpointer user_data;
 447   GCancellable *cancellable;
 448   GUnixOutputStream *stream;
 449 } WriteAsyncData;
 450
 451 static gboolean
 452 write_async_cb (int             fd,
 453                 GIOCondition    condition,
 454                 WriteAsyncData *data)
 455 {
 456   GSimpleAsyncResult *simple;
 457   GError *error = NULL;
 458   gssize count_written;
 459
 460   while (1)
 461     {
 462       if (g_cancellable_set_error_if_cancelled (data->cancellable, &error))
 463         {
 464           count_written = -1;
 465           break;
 466         }
 467
 468       count_written = write (data->stream->priv->fd, data->buffer, data->count);
 469       if (count_written == -1)
 470         {
 471           int errsv = errno;
 472
 473           if (errsv == EINTR || errsv == EAGAIN)
 474             return TRUE;
 475
 476           g_set_error (&error, G_IO_ERROR,
 477                        g_io_error_from_errno (errsv),
 478                        _("Error writing to file descriptor: %s"),
 479                        g_strerror (errsv));
 480         }
 481       break;
 482     }
 483
 484   simple = g_simple_async_result_new (G_OBJECT (data->stream),
 485                                       data->callback,
 486                                       data->user_data,
 487                                       g_unix_output_stream_write_async);
 488
 489   g_simple_async_result_set_op_res_gssize (simple, count_written);
 490
 491   if (count_written == -1)
 492     g_simple_async_result_take_error (simple, error);
 493
 494   /* Complete immediately, not in idle, since we're already in a mainloop callout */
 495   g_simple_async_result_complete (simple);
 496   g_object_unref (simple);
 497
 498   return FALSE;
 499 }
 500
 501 static void
 502 g_unix_output_stream_write_async (GOutputStream       *stream,
 503                                   const void          *buffer,
 504                                   gsize                count,
 505                                   int                  io_priority,
 506                                   GCancellable        *cancellable,
 507                                   GAsyncReadyCallback  callback,
 508                                   gpointer             user_data)
 509 {
 510   GSource *source;
 511   GUnixOutputStream *unix_stream;
 512   WriteAsyncData *data;
 513
 514   unix_stream = G_UNIX_OUTPUT_STREAM (stream);
 515
 516   if (!unix_stream->priv->is_pipe_or_socket)
 517     {
 518       G_OUTPUT_STREAM_CLASS (g_unix_output_stream_parent_class)->
 519         write_async (stream, buffer, count, io_priority,
 520                      cancellable, callback, user_data);
 521       return;
 522     }
 523
 524   data = g_new0 (WriteAsyncData, 1);
 525   data->count = count;
 526   data->buffer = buffer;
 527   data->callback = callback;
 528   data->user_data = user_data;
 529   data->cancellable = cancellable;
 530   data->stream = unix_stream;
 531
 532   source = _g_fd_source_new (unix_stream->priv->fd,
 533                              G_IO_OUT,
 534                              cancellable);
 535   g_source_set_name (source, "GUnixOutputStream");
 536
 537   g_source_set_callback (source, (GSourceFunc)write_async_cb, data, g_free);
 538   g_source_attach (source, g_main_context_get_thread_default ());
 539
 540   g_source_unref (source);
 541 }
 542
 543 static gssize
 544 g_unix_output_stream_write_finish (GOutputStream  *stream,
 545                                    GAsyncResult   *result,
 546                                    GError        **error)
 547 {
 548   GUnixOutputStream *unix_stream = G_UNIX_OUTPUT_STREAM (stream);
 549   GSimpleAsyncResult *simple;
 550   gssize nwritten;
 551
 552   if (!unix_stream->priv->is_pipe_or_socket)
 553     {
 554       return G_OUTPUT_STREAM_CLASS (g_unix_output_stream_parent_class)->
 555         write_finish (stream, result, error);
 556     }
 557
 558   simple = G_SIMPLE_ASYNC_RESULT (result);
 559   g_warn_if_fail (g_simple_async_result_get_source_tag (simple) == g_unix_output_stream_write_async);
 560
 561   nwritten = g_simple_async_result_get_op_res_gssize (simple);
 562   return nwritten;
 563 }
 564
 565 typedef struct {
 566   GOutputStream *stream;
 567   GAsyncReadyCallback callback;
 568   gpointer user_data;
 569 } CloseAsyncData;
 570
 571 static gboolean
 572 close_async_cb (CloseAsyncData *data)
 573 {
 574   GUnixOutputStream *unix_stream;
 575   GSimpleAsyncResult *simple;
 576   GError *error = NULL;
 577   gboolean result;
 578   int res;
 579
 580   unix_stream = G_UNIX_OUTPUT_STREAM (data->stream);
 581
 582   if (!unix_stream->priv->close_fd)
 583     {
 584       result = TRUE;
 585       goto out;
 586     }
 587
 588   while (1)
 589     {
 590       res = close (unix_stream->priv->fd);
 591       if (res == -1)
 592         {
 593           int errsv = errno;
 594
 595           g_set_error (&error, G_IO_ERROR,
 596                        g_io_error_from_errno (errsv),
 597                        _("Error closing file descriptor: %s"),
 598                        g_strerror (errsv));
 599         }
 600       break;
 601     }
 602
 603   result = res != -1;
 604
 605  out:
 606   simple = g_simple_async_result_new (G_OBJECT (data->stream),
 607                                       data->callback,
 608                                       data->user_data,
 609                                       g_unix_output_stream_close_async);
 610
 611   if (!result)
 612     g_simple_async_result_take_error (simple, error);
 613
 614   /* Complete immediately, not in idle, since we're already in a mainloop callout */
 615   g_simple_async_result_complete (simple);
 616   g_object_unref (simple);
 617
 618   return FALSE;
 619 }
 620
 621 static void
 622 g_unix_output_stream_close_async (GOutputStream        *stream,
 623                                   int                  io_priority,
 624                                   GCancellable        *cancellable,
 625                                   GAsyncReadyCallback  callback,
 626                                   gpointer             user_data)
 627 {
 628   GSource *idle;
 629   CloseAsyncData *data;
 630
 631   data = g_new0 (CloseAsyncData, 1);
 632
 633   data->stream = stream;
 634   data->callback = callback;
 635   data->user_data = user_data;
 636
 637   idle = g_idle_source_new ();
 638   g_source_set_callback (idle, (GSourceFunc)close_async_cb, data, g_free);
 639   g_source_attach (idle, g_main_context_get_thread_default ());
 640   g_source_unref (idle);
 641 }
 642
 643 static gboolean
 644 g_unix_output_stream_close_finish (GOutputStream  *stream,
 645                                    GAsyncResult   *result,
 646                                    GError        **error)
 647 {
 648   /* Failures handled in generic close_finish code */
 649   return TRUE;
 650 }
 651
 652 static gboolean
 653 g_unix_output_stream_pollable_is_writable (GPollableOutputStream *stream)
 654 {
 655   GUnixOutputStream *unix_stream = G_UNIX_OUTPUT_STREAM (stream);
 656   GPollFD poll_fd;
 657   gint result;
 658
 659   poll_fd.fd = unix_stream->priv->fd;
 660   poll_fd.events = G_IO_OUT;
 661
 662   do
 663     result = g_poll (&poll_fd, 1, 0);
 664   while (result == -1 && errno == EINTR);
 665
 666   return poll_fd.revents != 0;
 667 }
 668
 669 static GSource *
 670 g_unix_output_stream_pollable_create_source (GPollableOutputStream *stream,
 671                                              GCancellable          *cancellable)
 672 {
 673   GUnixOutputStream *unix_stream = G_UNIX_OUTPUT_STREAM (stream);
 674   GSource *inner_source, *pollable_source;
 675
 676   pollable_source = g_pollable_source_new (G_OBJECT (stream));
 677
 678   inner_source = _g_fd_source_new (unix_stream->priv->fd, G_IO_OUT, cancellable);
 679   g_source_set_dummy_callback (inner_source);
 680   g_source_add_child_source (pollable_source, inner_source);
 681   g_source_unref (inner_source);
 682
 683   return pollable_source;
 684 }