gstreamer/gst/gstpoll.c
Matthew Waters 3d887c7f07 gst: don't use volatile to mean atomic
volatile is not sufficient to provide atomic guarantees and real atomics
should be used instead.  GCC 11 has started warning about using volatile
with atomic operations.

https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1719

Discovered in https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/issues/868

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/775>
2021-03-19 04:15:19 +00:00

1789 lines
43 KiB
C

/* GStreamer
* Copyright (C) 1999 Erik Walthinsen <omega@cse.ogi.edu>
* Copyright (C) 2004 Wim Taymans <wim.taymans@gmail.com>
* Copyright (C) 2007 Peter Kjellerstedt <pkj@axis.com>
* Copyright (C) 2008 Ole André Vadla Ravnås <ole.andre.ravnas@tandberg.com>
*
* gstpoll.c: File descriptor set
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/**
* SECTION:gstpoll
* @title: GstPoll
* @short_description: Keep track of file descriptors and make it possible
* to wait on them in a cancellable way
*
* A #GstPoll keeps track of file descriptors much like fd_set (used with
* select ()) or a struct pollfd array (used with poll ()). Once created with
* gst_poll_new(), the set can be used to wait for file descriptors to be
* readable and/or writable. It is possible to make this wait be controlled
* by specifying %TRUE for the @controllable flag when creating the set (or
* later calling gst_poll_set_controllable()).
*
* New file descriptors are added to the set using gst_poll_add_fd(), and
* removed using gst_poll_remove_fd(). Controlling which file descriptors
* should be waited for to become readable and/or writable are done using
* gst_poll_fd_ctl_read(), gst_poll_fd_ctl_write() and gst_poll_fd_ctl_pri().
*
* Use gst_poll_wait() to wait for the file descriptors to actually become
* readable and/or writable, or to timeout if no file descriptor is available
* in time. The wait can be controlled by calling gst_poll_restart() and
* gst_poll_set_flushing().
*
* Once the file descriptor set has been waited for, one can use
* gst_poll_fd_has_closed() to see if the file descriptor has been closed,
* gst_poll_fd_has_error() to see if it has generated an error,
* gst_poll_fd_can_read() to see if it is possible to read from the file
* descriptor, and gst_poll_fd_can_write() to see if it is possible to
* write to it.
*
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "gst_private.h"
#include "glib-compat-private.h"
#include <sys/types.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <errno.h>
#include <fcntl.h>
#include <glib.h>
#ifdef G_OS_WIN32
#include <winsock2.h>
#else
#define _GNU_SOURCE 1
#ifdef HAVE_SYS_POLL_H
#include <sys/poll.h>
#endif
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#include <sys/time.h>
#include <sys/socket.h>
#endif
#ifdef G_OS_WIN32
# ifndef EWOULDBLOCK
# define EWOULDBLOCK EAGAIN /* This is just to placate gcc */
# endif
#endif /* G_OS_WIN32 */
/* OS/X needs this because of bad headers */
#include <string.h>
/* The poll() emulation on OS/X doesn't handle fds=NULL, nfds=0,
* so we prefer our own poll emulation.
*/
#if defined(BROKEN_POLL)
#undef HAVE_POLL
#endif
#include "gstpoll.h"
#define GST_CAT_DEFAULT GST_CAT_POLL
#ifdef G_OS_WIN32
typedef struct _WinsockFd WinsockFd;
struct _WinsockFd
{
gint fd;
glong event_mask;
WSANETWORKEVENTS events;
glong ignored_event_mask;
};
#endif
typedef enum
{
GST_POLL_MODE_AUTO,
GST_POLL_MODE_SELECT,
GST_POLL_MODE_PSELECT,
GST_POLL_MODE_POLL,
GST_POLL_MODE_PPOLL,
GST_POLL_MODE_WINDOWS
} GstPollMode;
struct _GstPoll
{
GstPollMode mode;
GMutex lock;
/* array of fds, always written to and read from with lock */
GArray *fds;
/* array of active fds, only written to from the waiting thread with the
* lock and read from with the lock or without the lock from the waiting
* thread */
GArray *active_fds;
#ifndef G_OS_WIN32
GstPollFD control_read_fd;
GstPollFD control_write_fd;
#else
GArray *active_fds_ignored;
GArray *events;
GArray *active_events;
HANDLE wakeup_event;
#endif
gboolean controllable;
gint waiting;
gint control_pending;
gint flushing;
gboolean timer;
gint rebuild;
};
static gboolean gst_poll_fd_ctl_read_unlocked (GstPoll * set, GstPollFD * fd,
gboolean active);
static gboolean gst_poll_add_fd_unlocked (GstPoll * set, GstPollFD * fd);
#define IS_FLUSHING(s) (g_atomic_int_get(&(s)->flushing))
#define SET_FLUSHING(s,val) (g_atomic_int_set(&(s)->flushing, (val)))
#define INC_WAITING(s) (g_atomic_int_add(&(s)->waiting, 1))
#define DEC_WAITING(s) (g_atomic_int_add(&(s)->waiting, -1))
#define GET_WAITING(s) (g_atomic_int_get(&(s)->waiting))
#define TEST_REBUILD(s) (g_atomic_int_compare_and_exchange(&(s)->rebuild, 1, 0))
#define MARK_REBUILD(s) (g_atomic_int_set(&(s)->rebuild, 1))
#ifndef G_OS_WIN32
static gboolean
wake_event (GstPoll * set)
{
ssize_t num_written;
while ((num_written = write (set->control_write_fd.fd, "W", 1)) != 1) {
if (num_written == -1 && errno != EAGAIN && errno != EINTR) {
g_critical ("%p: failed to wake event: %s", set, strerror (errno));
return FALSE;
}
}
return TRUE;
}
static gboolean
release_event (GstPoll * set)
{
gchar buf[1] = { '\0' };
ssize_t num_read;
while ((num_read = read (set->control_read_fd.fd, buf, 1)) != 1) {
if (num_read == -1 && errno != EAGAIN && errno != EINTR) {
g_critical ("%p: failed to release event: %s", set, strerror (errno));
return FALSE;
}
}
return TRUE;
}
#else
static void
format_last_error (gchar * buf, size_t buf_len)
{
DWORD flags = FORMAT_MESSAGE_FROM_SYSTEM;
LPCVOID src = NULL;
DWORD lang = 0;
DWORD id;
id = GetLastError ();
FormatMessage (flags, src, id, lang, buf, (DWORD) buf_len, NULL);
SetLastError (id);
}
static gboolean
wake_event (GstPoll * set)
{
SetLastError (0);
errno = 0;
if (!SetEvent (set->wakeup_event)) {
gchar msg[1024] = "<unknown>";
format_last_error (msg, sizeof (msg));
g_critical ("%p: failed to set wakup_event: %s", set, msg);
errno = EBADF;
return FALSE;
}
return TRUE;
}
static gboolean
release_event (GstPoll * set)
{
DWORD status;
SetLastError (0);
errno = 0;
status = WaitForSingleObject (set->wakeup_event, INFINITE);
if (status) {
const gchar *reason = "unknown";
gchar msg[1024] = "<unknown>";
switch (status) {
case WAIT_ABANDONED:
reason = "WAIT_ABANDONED";
break;
case WAIT_TIMEOUT:
reason = "WAIT_TIMEOUT";
break;
case WAIT_FAILED:
format_last_error (msg, sizeof (msg));
reason = msg;
break;
default:
reason = "other";
break;
}
g_critical ("%p: failed to block on wakup_event: %s", set, reason);
errno = EBADF;
return FALSE;
}
if (!ResetEvent (set->wakeup_event)) {
gchar msg[1024] = "<unknown>";
format_last_error (msg, sizeof (msg));
g_critical ("%p: failed to reset wakup_event: %s", set, msg);
errno = EBADF;
return FALSE;
}
return TRUE;
}
#endif
/* the poll/select call is also performed on a control socket, that way
* we can send special commands to control it */
static inline gboolean
raise_wakeup (GstPoll * set)
{
gboolean result = TRUE;
/* makes testing control_pending and WAKE_EVENT() atomic. */
g_mutex_lock (&set->lock);
if (set->control_pending == 0) {
/* raise when nothing pending */
GST_LOG ("%p: raise", set);
result = wake_event (set);
}
if (result) {
set->control_pending++;
}
g_mutex_unlock (&set->lock);
return result;
}
static inline gboolean
release_wakeup (GstPoll * set)
{
gboolean result = FALSE;
/* makes testing/modifying control_pending and RELEASE_EVENT() atomic. */
g_mutex_lock (&set->lock);
if (set->control_pending > 0) {
/* release, only if this was the last pending. */
if (set->control_pending == 1) {
GST_LOG ("%p: release", set);
result = release_event (set);
} else {
result = TRUE;
}
if (result) {
set->control_pending--;
}
} else {
errno = EWOULDBLOCK;
}
g_mutex_unlock (&set->lock);
return result;
}
static inline gint
release_all_wakeup (GstPoll * set)
{
gint old;
/* makes testing control_pending and RELEASE_EVENT() atomic. */
g_mutex_lock (&set->lock);
if ((old = set->control_pending) > 0) {
GST_LOG ("%p: releasing %d", set, old);
if (release_event (set)) {
set->control_pending = 0;
} else {
old = 0;
}
}
g_mutex_unlock (&set->lock);
return old;
}
static gint
find_index (GArray * array, GstPollFD * fd)
{
#ifndef G_OS_WIN32
struct pollfd *ifd;
#else
WinsockFd *ifd;
#endif
guint i;
/* start by assuming the index found in the fd is still valid */
if (fd->idx >= 0 && fd->idx < array->len) {
#ifndef G_OS_WIN32
ifd = &g_array_index (array, struct pollfd, fd->idx);
#else
ifd = &g_array_index (array, WinsockFd, fd->idx);
#endif
if (ifd->fd == fd->fd) {
return fd->idx;
}
}
/* the pollfd array has changed and we need to lookup the fd again */
for (i = 0; i < array->len; i++) {
#ifndef G_OS_WIN32
ifd = &g_array_index (array, struct pollfd, i);
#else
ifd = &g_array_index (array, WinsockFd, i);
#endif
if (ifd->fd == fd->fd) {
fd->idx = (gint) i;
return fd->idx;
}
}
fd->idx = -1;
return fd->idx;
}
#if !defined(HAVE_PPOLL) && defined(HAVE_POLL)
/* check if all file descriptors will fit in an fd_set */
static gboolean
selectable_fds (GstPoll * set)
{
guint i;
g_mutex_lock (&set->lock);
for (i = 0; i < set->fds->len; i++) {
struct pollfd *pfd = &g_array_index (set->fds, struct pollfd, i);
if (pfd->fd >= FD_SETSIZE)
goto too_many;
}
g_mutex_unlock (&set->lock);
return TRUE;
too_many:
{
g_mutex_unlock (&set->lock);
return FALSE;
}
}
/* check if the timeout will convert to a timeout value used for poll()
* without a loss of precision
*/
static gboolean
pollable_timeout (GstClockTime timeout)
{
if (timeout == GST_CLOCK_TIME_NONE)
return TRUE;
/* not a nice multiple of milliseconds */
if (timeout % 1000000)
return FALSE;
return TRUE;
}
#endif
static GstPollMode
choose_mode (GstPoll * set, GstClockTime timeout)
{
GstPollMode mode;
if (set->mode == GST_POLL_MODE_AUTO) {
#ifdef HAVE_PPOLL
mode = GST_POLL_MODE_PPOLL;
#elif defined(HAVE_POLL)
if (!selectable_fds (set) || pollable_timeout (timeout)) {
mode = GST_POLL_MODE_POLL;
} else {
#ifdef HAVE_PSELECT
mode = GST_POLL_MODE_PSELECT;
#else
mode = GST_POLL_MODE_SELECT;
#endif
}
#elif defined(HAVE_PSELECT)
mode = GST_POLL_MODE_PSELECT;
#else
mode = GST_POLL_MODE_SELECT;
#endif
} else {
mode = set->mode;
}
return mode;
}
#ifndef G_OS_WIN32
static gint
pollfd_to_fd_set (GstPoll * set, fd_set * readfds, fd_set * writefds,
fd_set * errorfds)
{
gint max_fd = -1;
guint i;
FD_ZERO (readfds);
FD_ZERO (writefds);
FD_ZERO (errorfds);
g_mutex_lock (&set->lock);
for (i = 0; i < set->active_fds->len; i++) {
struct pollfd *pfd = &g_array_index (set->fds, struct pollfd, i);
if (pfd->fd < FD_SETSIZE) {
if (pfd->events & POLLIN)
FD_SET (pfd->fd, readfds);
if (pfd->events & POLLOUT)
FD_SET (pfd->fd, writefds);
if (pfd->events)
FD_SET (pfd->fd, errorfds);
if (pfd->fd > max_fd && (pfd->events & (POLLIN | POLLOUT)))
max_fd = pfd->fd;
}
}
g_mutex_unlock (&set->lock);
return max_fd;
}
static void
fd_set_to_pollfd (GstPoll * set, fd_set * readfds, fd_set * writefds,
fd_set * errorfds)
{
guint i;
g_mutex_lock (&set->lock);
for (i = 0; i < set->active_fds->len; i++) {
struct pollfd *pfd = &g_array_index (set->active_fds, struct pollfd, i);
if (pfd->fd < FD_SETSIZE) {
pfd->revents = 0;
if (FD_ISSET (pfd->fd, readfds))
pfd->revents |= POLLIN;
if (FD_ISSET (pfd->fd, writefds))
pfd->revents |= POLLOUT;
if (FD_ISSET (pfd->fd, errorfds))
pfd->revents |= POLLERR;
}
}
g_mutex_unlock (&set->lock);
}
#else /* G_OS_WIN32 */
/*
* Translate errors thrown by the Winsock API used by GstPoll:
* WSAEventSelect, WSAWaitForMultipleEvents and WSAEnumNetworkEvents
*/
static gint
gst_poll_winsock_error_to_errno (DWORD last_error)
{
switch (last_error) {
case WSA_INVALID_HANDLE:
case WSAEINVAL:
case WSAENOTSOCK:
return EBADF;
case WSA_NOT_ENOUGH_MEMORY:
return ENOMEM;
/*
* Anything else, including:
* WSA_INVALID_PARAMETER, WSAEFAULT, WSAEINPROGRESS, WSAENETDOWN,
* WSANOTINITIALISED
*/
default:
return EINVAL;
}
}
static void
gst_poll_free_winsock_event (GstPoll * set, gint idx)
{
WinsockFd *wfd = &g_array_index (set->fds, WinsockFd, idx);
HANDLE event = g_array_index (set->events, HANDLE, idx);
WSAEventSelect (wfd->fd, event, 0);
CloseHandle (event);
}
static void
gst_poll_update_winsock_event_mask (GstPoll * set, gint idx, glong flags,
gboolean active)
{
WinsockFd *wfd;
wfd = &g_array_index (set->fds, WinsockFd, idx);
if (active)
wfd->event_mask |= flags;
else
wfd->event_mask &= ~flags;
/* reset ignored state if the new mask doesn't overlap at all */
if ((wfd->ignored_event_mask & wfd->event_mask) == 0)
wfd->ignored_event_mask = 0;
}
static gboolean
gst_poll_prepare_winsock_active_sets (GstPoll * set)
{
guint i;
g_array_set_size (set->active_fds, 0);
g_array_set_size (set->active_fds_ignored, 0);
g_array_set_size (set->active_events, 0);
g_array_append_val (set->active_events, set->wakeup_event);
for (i = 0; i < set->fds->len; i++) {
WinsockFd *wfd = &g_array_index (set->fds, WinsockFd, i);
HANDLE event = g_array_index (set->events, HANDLE, i);
if (wfd->ignored_event_mask == 0) {
gint ret;
g_array_append_val (set->active_fds, *wfd);
g_array_append_val (set->active_events, event);
ret = WSAEventSelect (wfd->fd, event, wfd->event_mask);
if (G_UNLIKELY (ret != 0)) {
errno = gst_poll_winsock_error_to_errno (WSAGetLastError ());
return FALSE;
}
} else {
g_array_append_val (set->active_fds_ignored, wfd);
}
}
return TRUE;
}
static gint
gst_poll_collect_winsock_events (GstPoll * set)
{
gint res, i;
/*
* We need to check which events are signaled, and call
* WSAEnumNetworkEvents for those that are, which resets
* the event and clears the internal network event records.
*/
res = 0;
for (i = 0; i < set->active_fds->len; i++) {
WinsockFd *wfd = &g_array_index (set->active_fds, WinsockFd, i);
HANDLE event = g_array_index (set->active_events, HANDLE, i + 1);
DWORD wait_ret;
wait_ret = WaitForSingleObject (event, 0);
if (wait_ret == WAIT_OBJECT_0) {
gint enum_ret = WSAEnumNetworkEvents (wfd->fd, event, &wfd->events);
if (G_UNLIKELY (enum_ret != 0)) {
res = -1;
errno = gst_poll_winsock_error_to_errno (WSAGetLastError ());
break;
}
res++;
} else {
/* clear any previously stored result */
memset (&wfd->events, 0, sizeof (wfd->events));
}
}
/* If all went well we also need to reset the ignored fds. */
if (res >= 0) {
res += set->active_fds_ignored->len;
for (i = 0; i < set->active_fds_ignored->len; i++) {
WinsockFd *wfd = g_array_index (set->active_fds_ignored, WinsockFd *, i);
wfd->ignored_event_mask = 0;
}
g_array_set_size (set->active_fds_ignored, 0);
}
return res;
}
#endif
/**
* gst_poll_new: (skip)
* @controllable: whether it should be possible to control a wait.
*
* Create a new file descriptor set. If @controllable, it
* is possible to restart or flush a call to gst_poll_wait() with
* gst_poll_restart() and gst_poll_set_flushing() respectively.
*
* Free-function: gst_poll_free
*
* Returns: (transfer full) (nullable): a new #GstPoll, or %NULL in
* case of an error. Free with gst_poll_free().
*/
GstPoll *
gst_poll_new (gboolean controllable)
{
GstPoll *nset;
nset = g_slice_new0 (GstPoll);
GST_DEBUG ("%p: new controllable : %d", nset, controllable);
g_mutex_init (&nset->lock);
#ifndef G_OS_WIN32
nset->mode = GST_POLL_MODE_AUTO;
nset->fds = g_array_new (FALSE, FALSE, sizeof (struct pollfd));
nset->active_fds = g_array_new (FALSE, FALSE, sizeof (struct pollfd));
nset->control_read_fd.fd = -1;
nset->control_write_fd.fd = -1;
{
gint control_sock[2];
if (socketpair (PF_UNIX, SOCK_STREAM, 0, control_sock) < 0)
goto no_socket_pair;
nset->control_read_fd.fd = control_sock[0];
nset->control_write_fd.fd = control_sock[1];
gst_poll_add_fd_unlocked (nset, &nset->control_read_fd);
gst_poll_fd_ctl_read_unlocked (nset, &nset->control_read_fd, TRUE);
}
#else
nset->mode = GST_POLL_MODE_WINDOWS;
nset->fds = g_array_new (FALSE, FALSE, sizeof (WinsockFd));
nset->active_fds = g_array_new (FALSE, FALSE, sizeof (WinsockFd));
nset->active_fds_ignored = g_array_new (FALSE, FALSE, sizeof (WinsockFd *));
nset->events = g_array_new (FALSE, FALSE, sizeof (HANDLE));
nset->active_events = g_array_new (FALSE, FALSE, sizeof (HANDLE));
nset->wakeup_event = CreateEvent (NULL, TRUE, FALSE, NULL);
#endif
/* ensure (re)build, though already sneakily set in non-windows case */
MARK_REBUILD (nset);
nset->controllable = controllable;
nset->control_pending = 0;
return nset;
/* ERRORS */
#ifndef G_OS_WIN32
no_socket_pair:
{
GST_WARNING ("%p: can't create socket pair !", nset);
gst_poll_free (nset);
return NULL;
}
#endif
}
/**
* gst_poll_new_timer: (skip)
*
* Create a new poll object that can be used for scheduling cancellable
* timeouts.
*
* A timeout is performed with gst_poll_wait(). Multiple timeouts can be
* performed from different threads.
*
* Free-function: gst_poll_free
*
* Returns: (transfer full) (nullable): a new #GstPoll, or %NULL in
* case of an error. Free with gst_poll_free().
*/
GstPoll *
gst_poll_new_timer (void)
{
GstPoll *poll;
/* make a new controllable poll set */
if (!(poll = gst_poll_new (TRUE)))
goto done;
/* we are a timer */
poll->timer = TRUE;
done:
return poll;
}
/**
* gst_poll_free:
* @set: (transfer full): a file descriptor set.
*
* Free a file descriptor set.
*/
void
gst_poll_free (GstPoll * set)
{
g_return_if_fail (set != NULL);
GST_DEBUG ("%p: freeing", set);
#ifndef G_OS_WIN32
if (set->control_write_fd.fd >= 0)
close (set->control_write_fd.fd);
if (set->control_read_fd.fd >= 0)
close (set->control_read_fd.fd);
#else
CloseHandle (set->wakeup_event);
{
guint i;
for (i = 0; i < set->events->len; i++)
gst_poll_free_winsock_event (set, i);
}
g_array_free (set->active_events, TRUE);
g_array_free (set->events, TRUE);
g_array_free (set->active_fds_ignored, TRUE);
#endif
g_array_free (set->active_fds, TRUE);
g_array_free (set->fds, TRUE);
g_mutex_clear (&set->lock);
g_slice_free (GstPoll, set);
}
/**
* gst_poll_get_read_gpollfd:
* @set: a #GstPoll
* @fd: a #GPollFD
*
* Get a GPollFD for the reading part of the control socket. This is useful when
* integrating with a GSource and GMainLoop.
*/
void
gst_poll_get_read_gpollfd (GstPoll * set, GPollFD * fd)
{
g_return_if_fail (set != NULL);
g_return_if_fail (fd != NULL);
#ifndef G_OS_WIN32
fd->fd = set->control_read_fd.fd;
#else
#if GLIB_SIZEOF_VOID_P == 8
fd->fd = (gint64) set->wakeup_event;
#else
fd->fd = (gint) set->wakeup_event;
#endif
#endif
fd->events = G_IO_IN | G_IO_HUP | G_IO_ERR;
fd->revents = 0;
}
/**
* gst_poll_fd_init:
* @fd: a #GstPollFD
*
* Initializes @fd. Alternatively you can initialize it with
* #GST_POLL_FD_INIT.
*/
void
gst_poll_fd_init (GstPollFD * fd)
{
g_return_if_fail (fd != NULL);
fd->fd = -1;
fd->idx = -1;
}
static gboolean
gst_poll_add_fd_unlocked (GstPoll * set, GstPollFD * fd)
{
gint idx;
GST_DEBUG ("%p: fd (fd:%d, idx:%d)", set, fd->fd, fd->idx);
idx = find_index (set->fds, fd);
if (idx < 0) {
#ifndef G_OS_WIN32
struct pollfd nfd;
nfd.fd = fd->fd;
nfd.events = POLLERR | POLLNVAL | POLLHUP;
nfd.revents = 0;
g_array_append_val (set->fds, nfd);
fd->idx = set->fds->len - 1;
#else
WinsockFd wfd;
HANDLE event;
wfd.fd = fd->fd;
wfd.event_mask = FD_CLOSE;
memset (&wfd.events, 0, sizeof (wfd.events));
wfd.ignored_event_mask = 0;
event = WSACreateEvent ();
g_array_append_val (set->fds, wfd);
g_array_append_val (set->events, event);
fd->idx = set->fds->len - 1;
#endif
MARK_REBUILD (set);
} else {
GST_WARNING ("%p: fd already added !", set);
}
return TRUE;
}
/**
* gst_poll_add_fd:
* @set: a file descriptor set.
* @fd: a file descriptor.
*
* Add a file descriptor to the file descriptor set.
*
* Returns: %TRUE if the file descriptor was successfully added to the set.
*/
gboolean
gst_poll_add_fd (GstPoll * set, GstPollFD * fd)
{
gboolean ret;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
g_mutex_lock (&set->lock);
ret = gst_poll_add_fd_unlocked (set, fd);
g_mutex_unlock (&set->lock);
return ret;
}
/**
* gst_poll_remove_fd:
* @set: a file descriptor set.
* @fd: a file descriptor.
*
* Remove a file descriptor from the file descriptor set.
*
* Returns: %TRUE if the file descriptor was successfully removed from the set.
*/
gboolean
gst_poll_remove_fd (GstPoll * set, GstPollFD * fd)
{
gint idx;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
GST_DEBUG ("%p: fd (fd:%d, idx:%d)", set, fd->fd, fd->idx);
g_mutex_lock (&set->lock);
/* get the index, -1 is an fd that is not added */
idx = find_index (set->fds, fd);
if (idx >= 0) {
#ifdef G_OS_WIN32
gst_poll_free_winsock_event (set, idx);
g_array_remove_index_fast (set->events, idx);
#endif
/* remove the fd at index, we use _remove_index_fast, which copies the last
* element of the array to the freed index */
g_array_remove_index_fast (set->fds, idx);
/* mark fd as removed by setting the index to -1 */
fd->idx = -1;
MARK_REBUILD (set);
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
g_mutex_unlock (&set->lock);
return idx >= 0;
}
/**
* gst_poll_fd_ctl_write:
* @set: a file descriptor set.
* @fd: a file descriptor.
* @active: a new status.
*
* Control whether the descriptor @fd in @set will be monitored for
* writability.
*
* Returns: %TRUE if the descriptor was successfully updated.
*/
gboolean
gst_poll_fd_ctl_write (GstPoll * set, GstPollFD * fd, gboolean active)
{
gint idx;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
GST_DEBUG ("%p: fd (fd:%d, idx:%d), active : %d", set,
fd->fd, fd->idx, active);
g_mutex_lock (&set->lock);
idx = find_index (set->fds, fd);
if (idx >= 0) {
#ifndef G_OS_WIN32
struct pollfd *pfd = &g_array_index (set->fds, struct pollfd, idx);
if (active)
pfd->events |= POLLOUT;
else
pfd->events &= ~POLLOUT;
GST_LOG ("%p: pfd->events now %d (POLLOUT:%d)", set, pfd->events, POLLOUT);
#else
gst_poll_update_winsock_event_mask (set, idx, FD_WRITE | FD_CONNECT,
active);
#endif
MARK_REBUILD (set);
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
g_mutex_unlock (&set->lock);
return idx >= 0;
}
static gboolean
gst_poll_fd_ctl_read_unlocked (GstPoll * set, GstPollFD * fd, gboolean active)
{
gint idx;
GST_DEBUG ("%p: fd (fd:%d, idx:%d), active : %d", set,
fd->fd, fd->idx, active);
idx = find_index (set->fds, fd);
if (idx >= 0) {
#ifndef G_OS_WIN32
struct pollfd *pfd = &g_array_index (set->fds, struct pollfd, idx);
if (active)
pfd->events |= POLLIN;
else
pfd->events &= ~POLLIN;
#else
gst_poll_update_winsock_event_mask (set, idx, FD_READ | FD_ACCEPT, active);
#endif
MARK_REBUILD (set);
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
return idx >= 0;
}
/**
* gst_poll_fd_ctl_read:
* @set: a file descriptor set.
* @fd: a file descriptor.
* @active: a new status.
*
* Control whether the descriptor @fd in @set will be monitored for
* readability.
*
* Returns: %TRUE if the descriptor was successfully updated.
*/
gboolean
gst_poll_fd_ctl_read (GstPoll * set, GstPollFD * fd, gboolean active)
{
gboolean ret;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
g_mutex_lock (&set->lock);
ret = gst_poll_fd_ctl_read_unlocked (set, fd, active);
g_mutex_unlock (&set->lock);
return ret;
}
/**
* gst_poll_fd_ctl_pri:
* @set: a file descriptor set.
* @fd: a file descriptor.
* @active: a new status.
*
* Control whether the descriptor @fd in @set will be monitored for
* exceptional conditions (POLLPRI).
*
* Not implemented on Windows (will just return %FALSE there).
*
* Returns: %TRUE if the descriptor was successfully updated.
*
* Since: 1.16
*/
gboolean
gst_poll_fd_ctl_pri (GstPoll * set, GstPollFD * fd, gboolean active)
{
#ifdef G_OS_WIN32
return FALSE;
#else
gint idx;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
GST_DEBUG ("%p: fd (fd:%d, idx:%d), active : %d", set,
fd->fd, fd->idx, active);
g_mutex_lock (&set->lock);
idx = find_index (set->fds, fd);
if (idx >= 0) {
struct pollfd *pfd = &g_array_index (set->fds, struct pollfd, idx);
if (active)
pfd->events |= POLLPRI;
else
pfd->events &= ~POLLPRI;
GST_LOG ("%p: pfd->events now %d (POLLPRI:%d)", set, pfd->events, POLLOUT);
MARK_REBUILD (set);
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
g_mutex_unlock (&set->lock);
return idx >= 0;
#endif
}
/**
* gst_poll_fd_ignored:
* @set: a file descriptor set.
* @fd: a file descriptor.
*
* Mark @fd as ignored so that the next call to gst_poll_wait() will yield
* the same result for @fd as last time. This function must be called if no
* operation (read/write/recv/send/etc.) will be performed on @fd before
* the next call to gst_poll_wait().
*
* The reason why this is needed is because the underlying implementation
* might not allow querying the fd more than once between calls to one of
* the re-enabling operations.
*/
void
gst_poll_fd_ignored (GstPoll * set, GstPollFD * fd)
{
#ifdef G_OS_WIN32
gint idx;
g_return_if_fail (set != NULL);
g_return_if_fail (fd != NULL);
g_return_if_fail (fd->fd >= 0);
g_mutex_lock (&set->lock);
idx = find_index (set->fds, fd);
if (idx >= 0) {
WinsockFd *wfd = &g_array_index (set->fds, WinsockFd, idx);
wfd->ignored_event_mask = wfd->event_mask & (FD_READ | FD_WRITE);
MARK_REBUILD (set);
}
g_mutex_unlock (&set->lock);
#endif
}
/**
* gst_poll_fd_has_closed:
* @set: a file descriptor set.
* @fd: a file descriptor.
*
* Check if @fd in @set has closed the connection.
*
* Returns: %TRUE if the connection was closed.
*/
gboolean
gst_poll_fd_has_closed (const GstPoll * set, GstPollFD * fd)
{
gboolean res = FALSE;
gint idx;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
g_mutex_lock (&((GstPoll *) set)->lock);
idx = find_index (set->active_fds, fd);
if (idx >= 0) {
#ifndef G_OS_WIN32
struct pollfd *pfd = &g_array_index (set->active_fds, struct pollfd, idx);
res = (pfd->revents & POLLHUP) != 0;
#else
WinsockFd *wfd = &g_array_index (set->active_fds, WinsockFd, idx);
res = (wfd->events.lNetworkEvents & FD_CLOSE) != 0;
#endif
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
g_mutex_unlock (&((GstPoll *) set)->lock);
GST_DEBUG ("%p: fd (fd:%d, idx:%d) %d", set, fd->fd, fd->idx, res);
return res;
}
/**
* gst_poll_fd_has_error:
* @set: a file descriptor set.
* @fd: a file descriptor.
*
* Check if @fd in @set has an error.
*
* Returns: %TRUE if the descriptor has an error.
*/
gboolean
gst_poll_fd_has_error (const GstPoll * set, GstPollFD * fd)
{
gboolean res = FALSE;
gint idx;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
g_mutex_lock (&((GstPoll *) set)->lock);
idx = find_index (set->active_fds, fd);
if (idx >= 0) {
#ifndef G_OS_WIN32
struct pollfd *pfd = &g_array_index (set->active_fds, struct pollfd, idx);
res = (pfd->revents & (POLLERR | POLLNVAL)) != 0;
#else
WinsockFd *wfd = &g_array_index (set->active_fds, WinsockFd, idx);
res = (wfd->events.iErrorCode[FD_CLOSE_BIT] != 0) ||
(wfd->events.iErrorCode[FD_READ_BIT] != 0) ||
(wfd->events.iErrorCode[FD_WRITE_BIT] != 0) ||
(wfd->events.iErrorCode[FD_ACCEPT_BIT] != 0) ||
(wfd->events.iErrorCode[FD_CONNECT_BIT] != 0);
#endif
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
g_mutex_unlock (&((GstPoll *) set)->lock);
GST_DEBUG ("%p: fd (fd:%d, idx:%d) %d", set, fd->fd, fd->idx, res);
return res;
}
static gboolean
gst_poll_fd_can_read_unlocked (const GstPoll * set, GstPollFD * fd)
{
gboolean res = FALSE;
gint idx;
idx = find_index (set->active_fds, fd);
if (idx >= 0) {
#ifndef G_OS_WIN32
struct pollfd *pfd = &g_array_index (set->active_fds, struct pollfd, idx);
res = (pfd->revents & POLLIN) != 0;
#else
WinsockFd *wfd = &g_array_index (set->active_fds, WinsockFd, idx);
res = (wfd->events.lNetworkEvents & (FD_READ | FD_ACCEPT)) != 0;
#endif
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
GST_DEBUG ("%p: fd (fd:%d, idx:%d) %d", set, fd->fd, fd->idx, res);
return res;
}
/**
* gst_poll_fd_can_read:
* @set: a file descriptor set.
* @fd: a file descriptor.
*
* Check if @fd in @set has data to be read.
*
* Returns: %TRUE if the descriptor has data to be read.
*/
gboolean
gst_poll_fd_can_read (const GstPoll * set, GstPollFD * fd)
{
gboolean res = FALSE;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
g_mutex_lock (&((GstPoll *) set)->lock);
res = gst_poll_fd_can_read_unlocked (set, fd);
g_mutex_unlock (&((GstPoll *) set)->lock);
return res;
}
/**
* gst_poll_fd_can_write:
* @set: a file descriptor set.
* @fd: a file descriptor.
*
* Check if @fd in @set can be used for writing.
*
* Returns: %TRUE if the descriptor can be used for writing.
*/
gboolean
gst_poll_fd_can_write (const GstPoll * set, GstPollFD * fd)
{
gboolean res = FALSE;
gint idx;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
g_mutex_lock (&((GstPoll *) set)->lock);
idx = find_index (set->active_fds, fd);
if (idx >= 0) {
#ifndef G_OS_WIN32
struct pollfd *pfd = &g_array_index (set->active_fds, struct pollfd, idx);
res = (pfd->revents & POLLOUT) != 0;
#else
WinsockFd *wfd = &g_array_index (set->active_fds, WinsockFd, idx);
res = (wfd->events.lNetworkEvents & FD_WRITE) != 0;
#endif
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
g_mutex_unlock (&((GstPoll *) set)->lock);
GST_DEBUG ("%p: fd (fd:%d, idx:%d) %d", set, fd->fd, fd->idx, res);
return res;
}
/**
* gst_poll_fd_has_pri:
* @set: a file descriptor set.
* @fd: a file descriptor.
*
* Check if @fd in @set has an exceptional condition (POLLPRI).
*
* Not implemented on Windows (will just return %FALSE there).
*
* Returns: %TRUE if the descriptor has an exceptional condition.
*
* Since: 1.16
*/
gboolean
gst_poll_fd_has_pri (const GstPoll * set, GstPollFD * fd)
{
#ifdef G_OS_WIN32
return FALSE;
#else
gboolean res = FALSE;
gint idx;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (fd != NULL, FALSE);
g_return_val_if_fail (fd->fd >= 0, FALSE);
g_mutex_lock (&((GstPoll *) set)->lock);
idx = find_index (set->active_fds, fd);
if (idx >= 0) {
struct pollfd *pfd = &g_array_index (set->active_fds, struct pollfd, idx);
res = (pfd->revents & POLLPRI) != 0;
} else {
GST_WARNING ("%p: couldn't find fd !", set);
}
g_mutex_unlock (&((GstPoll *) set)->lock);
GST_DEBUG ("%p: fd (fd:%d, idx:%d) %d", set, fd->fd, fd->idx, res);
return res;
#endif
}
/**
* gst_poll_wait:
* @set: a #GstPoll.
* @timeout: a timeout in nanoseconds.
*
* Wait for activity on the file descriptors in @set. This function waits up to
* the specified @timeout. A timeout of #GST_CLOCK_TIME_NONE waits forever.
*
* For #GstPoll objects created with gst_poll_new(), this function can only be
* called from a single thread at a time. If called from multiple threads,
* -1 will be returned with errno set to EPERM.
*
* This is not true for timer #GstPoll objects created with
* gst_poll_new_timer(), where it is allowed to have multiple threads waiting
* simultaneously.
*
* Returns: The number of #GstPollFD in @set that have activity or 0 when no
* activity was detected after @timeout. If an error occurs, -1 is returned
* and errno is set.
*/
gint
gst_poll_wait (GstPoll * set, GstClockTime timeout)
{
gboolean restarting;
gboolean is_timer;
int res;
gint old_waiting;
g_return_val_if_fail (set != NULL, -1);
GST_DEBUG ("%p: timeout :%" GST_TIME_FORMAT, set, GST_TIME_ARGS (timeout));
is_timer = set->timer;
/* add one more waiter */
old_waiting = INC_WAITING (set);
/* we cannot wait from multiple threads unless we are a timer */
if (G_UNLIKELY (old_waiting > 0 && !is_timer))
goto already_waiting;
/* flushing, exit immediately */
if (G_UNLIKELY (IS_FLUSHING (set)))
goto flushing;
do {
GstPollMode mode;
res = -1;
restarting = FALSE;
mode = choose_mode (set, timeout);
if (TEST_REBUILD (set)) {
g_mutex_lock (&set->lock);
#ifndef G_OS_WIN32
g_array_set_size (set->active_fds, set->fds->len);
memcpy (set->active_fds->data, set->fds->data,
set->fds->len * sizeof (struct pollfd));
#else
if (!gst_poll_prepare_winsock_active_sets (set))
goto winsock_error;
#endif
g_mutex_unlock (&set->lock);
}
switch (mode) {
case GST_POLL_MODE_AUTO:
g_assert_not_reached ();
break;
case GST_POLL_MODE_PPOLL:
{
#ifdef HAVE_PPOLL
struct timespec ts;
struct timespec *tsptr;
if (timeout != GST_CLOCK_TIME_NONE) {
GST_TIME_TO_TIMESPEC (timeout, ts);
tsptr = &ts;
} else {
tsptr = NULL;
}
res =
ppoll ((struct pollfd *) set->active_fds->data,
set->active_fds->len, tsptr, NULL);
#else
g_assert_not_reached ();
errno = ENOSYS;
#endif
break;
}
case GST_POLL_MODE_POLL:
{
#ifdef HAVE_POLL
gint t;
if (timeout != GST_CLOCK_TIME_NONE) {
t = GST_TIME_AS_MSECONDS (timeout);
} else {
t = -1;
}
res =
poll ((struct pollfd *) set->active_fds->data,
set->active_fds->len, t);
#else
g_assert_not_reached ();
errno = ENOSYS;
#endif
break;
}
case GST_POLL_MODE_PSELECT:
#ifndef HAVE_PSELECT
{
g_assert_not_reached ();
errno = ENOSYS;
break;
}
#endif
case GST_POLL_MODE_SELECT:
{
#ifndef G_OS_WIN32
fd_set readfds;
fd_set writefds;
fd_set errorfds;
gint max_fd;
max_fd = pollfd_to_fd_set (set, &readfds, &writefds, &errorfds);
if (mode == GST_POLL_MODE_SELECT) {
struct timeval tv;
struct timeval *tvptr;
if (timeout != GST_CLOCK_TIME_NONE) {
GST_TIME_TO_TIMEVAL (timeout, tv);
tvptr = &tv;
} else {
tvptr = NULL;
}
GST_DEBUG ("%p: Calling select", set);
res = select (max_fd + 1, &readfds, &writefds, &errorfds, tvptr);
GST_DEBUG ("%p: After select, res:%d", set, res);
} else {
#ifdef HAVE_PSELECT
struct timespec ts;
struct timespec *tsptr;
if (timeout != GST_CLOCK_TIME_NONE) {
GST_TIME_TO_TIMESPEC (timeout, ts);
tsptr = &ts;
} else {
tsptr = NULL;
}
GST_DEBUG ("%p: Calling pselect", set);
res =
pselect (max_fd + 1, &readfds, &writefds, &errorfds, tsptr, NULL);
GST_DEBUG ("%p: After pselect, res:%d", set, res);
#endif
}
if (res >= 0) {
fd_set_to_pollfd (set, &readfds, &writefds, &errorfds);
}
#else /* G_OS_WIN32 */
g_assert_not_reached ();
errno = ENOSYS;
#endif
break;
}
case GST_POLL_MODE_WINDOWS:
{
#ifdef G_OS_WIN32
gint ignore_count = set->active_fds_ignored->len;
DWORD t, wait_ret;
if (G_LIKELY (ignore_count == 0)) {
if (timeout != GST_CLOCK_TIME_NONE)
t = GST_TIME_AS_MSECONDS (timeout);
else
t = INFINITE;
} else {
/* already one or more ignored fds, so we quickly sweep the others */
t = 0;
}
if (set->active_events->len != 0) {
wait_ret = WSAWaitForMultipleEvents (set->active_events->len,
(HANDLE *) set->active_events->data, FALSE, t, FALSE);
} else {
wait_ret = WSA_WAIT_FAILED;
WSASetLastError (WSA_INVALID_PARAMETER);
}
if (ignore_count == 0 && wait_ret == WSA_WAIT_TIMEOUT) {
res = 0;
} else if (wait_ret == WSA_WAIT_FAILED) {
res = -1;
errno = gst_poll_winsock_error_to_errno (WSAGetLastError ());
} else {
/* the first entry is the wakeup event */
if (wait_ret - WSA_WAIT_EVENT_0 >= 1) {
res = gst_poll_collect_winsock_events (set);
} else {
res = 1; /* wakeup event */
}
}
#else
g_assert_not_reached ();
errno = ENOSYS;
#endif
break;
}
}
if (!is_timer) {
/* Applications needs to clear the control socket themselves for timer
* polls.
* For other polls, we need to clear the control socket. If there was only
* one socket with activity and it was the control socket, we need to
* restart */
if (release_all_wakeup (set) > 0 && res == 1)
restarting = TRUE;
}
/* we got woken up and we are flushing, we need to stop */
if (G_UNLIKELY (IS_FLUSHING (set)))
goto flushing;
} while (G_UNLIKELY (restarting));
DEC_WAITING (set);
return res;
/* ERRORS */
already_waiting:
{
GST_LOG ("%p: we are already waiting", set);
DEC_WAITING (set);
errno = EPERM;
return -1;
}
flushing:
{
GST_LOG ("%p: we are flushing", set);
DEC_WAITING (set);
errno = EBUSY;
return -1;
}
#ifdef G_OS_WIN32
winsock_error:
{
GST_LOG ("%p: winsock error", set);
g_mutex_unlock (&set->lock);
DEC_WAITING (set);
return -1;
}
#endif
}
/**
* gst_poll_set_controllable:
* @set: a #GstPoll.
* @controllable: new controllable state.
*
* When @controllable is %TRUE, this function ensures that future calls to
* gst_poll_wait() will be affected by gst_poll_restart() and
* gst_poll_set_flushing().
*
* This function only works for non-timer #GstPoll objects created with
* gst_poll_new().
*
* Returns: %TRUE if the controllability of @set could be updated.
*/
gboolean
gst_poll_set_controllable (GstPoll * set, gboolean controllable)
{
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (!set->timer, FALSE);
GST_LOG ("%p: controllable : %d", set, controllable);
set->controllable = controllable;
return TRUE;
}
/**
* gst_poll_restart:
* @set: a #GstPoll.
*
* Restart any gst_poll_wait() that is in progress. This function is typically
* used after adding or removing descriptors to @set.
*
* If @set is not controllable, then this call will have no effect.
*
* This function only works for non-timer #GstPoll objects created with
* gst_poll_new().
*/
void
gst_poll_restart (GstPoll * set)
{
g_return_if_fail (set != NULL);
g_return_if_fail (!set->timer);
if (set->controllable && GET_WAITING (set) > 0) {
/* we are controllable and waiting, wake up the waiter. The socket will be
* cleared by the _wait() thread and the poll will be restarted */
raise_wakeup (set);
}
}
/**
* gst_poll_set_flushing:
* @set: a #GstPoll.
* @flushing: new flushing state.
*
* When @flushing is %TRUE, this function ensures that current and future calls
* to gst_poll_wait() will return -1, with errno set to EBUSY.
*
* Unsetting the flushing state will restore normal operation of @set.
*
* This function only works for non-timer #GstPoll objects created with
* gst_poll_new().
*/
void
gst_poll_set_flushing (GstPoll * set, gboolean flushing)
{
g_return_if_fail (set != NULL);
g_return_if_fail (!set->timer);
GST_LOG ("%p: flushing: %d", set, flushing);
/* update the new state first */
SET_FLUSHING (set, flushing);
if (flushing && set->controllable && GET_WAITING (set) > 0) {
/* we are flushing, controllable and waiting, wake up the waiter. When we
* stop the flushing operation we don't clear the wakeup fd here, this will
* happen in the _wait() thread. */
raise_wakeup (set);
}
}
/**
* gst_poll_write_control:
* @set: a #GstPoll.
*
* Write a byte to the control socket of the controllable @set.
* This function is mostly useful for timer #GstPoll objects created with
* gst_poll_new_timer().
*
* It will make any current and future gst_poll_wait() function return with
* 1, meaning the control socket is set. After an equal amount of calls to
* gst_poll_read_control() have been performed, calls to gst_poll_wait() will
* block again until their timeout expired.
*
* This function only works for timer #GstPoll objects created with
* gst_poll_new_timer().
*
* Returns: %TRUE on success. %FALSE when when the byte could not be written.
* errno contains the detailed error code but will never be EAGAIN, EINTR or
* EWOULDBLOCK. %FALSE always signals a critical error.
*/
gboolean
gst_poll_write_control (GstPoll * set)
{
gboolean res;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (set->timer, FALSE);
res = raise_wakeup (set);
return res;
}
/**
* gst_poll_read_control:
* @set: a #GstPoll.
*
* Read a byte from the control socket of the controllable @set.
*
* This function only works for timer #GstPoll objects created with
* gst_poll_new_timer().
*
* Returns: %TRUE on success. %FALSE when when there was no byte to read or
* reading the byte failed. If there was no byte to read, and only then, errno
* will contain EWOULDBLOCK or EAGAIN. For all other values of errno this always signals a
* critical error.
*/
gboolean
gst_poll_read_control (GstPoll * set)
{
gboolean res;
g_return_val_if_fail (set != NULL, FALSE);
g_return_val_if_fail (set->timer, FALSE);
res = release_wakeup (set);
return res;
}