[aravis/wip/emmanuel/wakeup: 1/2] wakeup: import wakeup API from glib

[Emmanuel Pacaud <emmanuel src gnome org>]

commit 65296116873c4d253442bd491e78ad78c6697907
Author: Emmanuel Pacaud <emmanuel gnome org>
Date:   Mon May 4 20:55:19 2015 +0200

    wakeup: import wakeup API from glib
    
    To be used for cancellation of stream reception.

 docs/reference/aravis/Makefile.am |    1 +
 src/Makefile.am                   |    6 +-
 src/arvwakeup.c                   |  258 +++++++++++++++++++++++++++++++++++++
 src/arvwakeupprivate.h            |   35 +++++
 4 files changed, 298 insertions(+), 2 deletions(-)
---
diff --git a/docs/reference/aravis/Makefile.am b/docs/reference/aravis/Makefile.am
index cdaa864..e26a175 100644
--- a/docs/reference/aravis/Makefile.am
+++ b/docs/reference/aravis/Makefile.am
@@ -68,6 +68,7 @@ IGNORE_HFILES=\
        arvdeviceprivate.h              \
        arvstreamprivate.h              \
        arvrealtimeprivate.h            \
+       arvwakeupprivate.h              \
        arv.h
 
 # Images to copy into HTML directory.
diff --git a/src/Makefile.am b/src/Makefile.am
index c6626a9..7a3105a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -83,7 +83,8 @@ ARAVIS_SRCS_NO_INTRO =                                \
        arvzip.c                                \
        arvstr.c                                \
        arvgvcp.c                               \
-       arvgvsp.c
+       arvgvsp.c                               \
+       arvwakeup.c
 
 ARAVIS_HDRS =                                  \
        arv.h                                   \
@@ -154,7 +155,8 @@ noinst_HEADERS =                            \
        arvchunkparserprivate.h                 \
        arvdeviceprivate.h                      \
        arvstreamprivate.h                      \
-       arvrealtimeprivate.h
+       arvrealtimeprivate.h                    \
+       arvwakeupprivate.h
 
 arv_fake_cameradir = $(aravis_datadir)
 arv_fake_camera_DATA = arv-fake-camera.xml
diff --git a/src/arvwakeup.c b/src/arvwakeup.c
new file mode 100644
index 0000000..efa2913
--- /dev/null
+++ b/src/arvwakeup.c
@@ -0,0 +1,258 @@
+/*
+ * Copyright © 2011 Canonical Limited
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the licence, 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Ryan Lortie <desrt desrt ca>
+ */
+
+/* arvwakeup.c is special -- GIO and some test cases include it.  As such,
+ * it cannot include other glib headers without triggering the single
+ * includes warnings.  We have to manually include its dependencies here
+ * (and at all other use sites).
+ */
+
+#include <arvwakeupprivate.h>
+
+/*< private >
+ * SECTION:arvwakeup
+ * @title: ArvWakeup
+ * @short_description: portable cross-thread event signal mechanism
+ *
+ * #ArvWakeup is a simple and portable way of signaling events between
+ * different threads in a way that integrates nicely with g_poll().
+ *
+ * You first create a #ArvWakeup with arv_wakeup_new() and initialise a
+ * #GPollFD from it using arv_wakeup_get_pollfd().  Polling on the created
+ * #GPollFD will block until arv_wakeup_signal() is called, at which point
+ * it will immediately return.  Future attempts to poll will continue to
+ * return until arv_wakeup_acknowledge() is called.  arv_wakeup_free() is
+ * used to free a #ArvWakeup.
+ *
+ * On sufficiently modern Linux, this is implemented using eventfd.  On
+ * Windows it is implemented using an event handle.  On other systems it
+ * is implemented with a pair of pipes.
+ *
+ * Since: 0.3.8
+ **/
+#ifdef _WIN32
+
+#include <windows.h>
+
+ArvWakeup *
+arv_wakeup_new (void)
+{
+  HANDLE wakeup;
+
+  wakeup = CreateEvent (NULL, TRUE, FALSE, NULL);
+
+  if (wakeup == NULL)
+    g_error ("Cannot create event for ArvWakeup: %s",
+             g_win32_error_message (GetLastError ()));
+
+  return (ArvWakeup *) wakeup;
+}
+
+void
+arv_wakeup_get_pollfd (ArvWakeup *wakeup,
+                     GPollFD *poll_fd)
+{
+  poll_fd->fd = (gintptr) wakeup;
+  poll_fd->events = G_IO_IN;
+}
+
+void
+arv_wakeup_acknowledge (ArvWakeup *wakeup)
+{
+  ResetEvent ((HANDLE) wakeup);
+}
+
+void
+arv_wakeup_signal (ArvWakeup *wakeup)
+{
+  SetEvent ((HANDLE) wakeup);
+}
+
+void
+arv_wakeup_free (ArvWakeup *wakeup)
+{
+  CloseHandle ((HANDLE) wakeup);
+}
+
+#else
+
+#include "glib-unix.h"
+#include <fcntl.h>
+
+#if defined (HAVE_EVENTFD)
+#include <sys/eventfd.h>
+#endif
+
+struct _ArvWakeup
+{
+  gint fds[2];
+};
+
+/**
+ * arv_wakeup_new:
+ *
+ * Creates a new #ArvWakeup.
+ *
+ * You should use arv_wakeup_free() to free it when you are done.
+ *
+ * Returns: a new #ArvWakeup
+ *
+ * Since: 0.3.8
+ **/
+
+ArvWakeup *
+arv_wakeup_new (void)
+{
+  GError *error = NULL;
+  ArvWakeup *wakeup;
+
+  wakeup = g_slice_new (ArvWakeup);
+
+  /* try eventfd first, if we think we can */
+#if defined (HAVE_EVENTFD)
+#ifndef TEST_EVENTFD_FALLBACK
+  wakeup->fds[0] = eventfd (0, EFD_CLOEXEC | EFD_NONBLOCK);
+#else
+  wakeup->fds[0] = -1;
+#endif
+
+  if (wakeup->fds[0] != -1)
+    {
+      wakeup->fds[1] = -1;
+      return wakeup;
+    }
+
+  /* for any failure, try a pipe instead */
+#endif
+
+  if (!g_unix_open_pipe (wakeup->fds, FD_CLOEXEC, &error))
+    g_error ("Creating pipes for ArvWakeup: %s\n", error->message);
+
+  if (!g_unix_set_fd_nonblocking (wakeup->fds[0], TRUE, &error) ||
+      !g_unix_set_fd_nonblocking (wakeup->fds[1], TRUE, &error))
+    g_error ("Set pipes non-blocking for ArvWakeup: %s\n", error->message);
+
+  return wakeup;
+}
+
+/**
+ * arv_wakeup_get_pollfd:
+ * @wakeup: a #ArvWakeup
+ * @poll_fd: a #GPollFD
+ *
+ * Prepares a @poll_fd such that polling on it will succeed when
+ * arv_wakeup_signal() has been called on @wakeup.
+ *
+ * @poll_fd is valid until @wakeup is freed.
+ *
+ * Since: 0.3.8
+ **/
+void
+arv_wakeup_get_pollfd (ArvWakeup *wakeup,
+                     GPollFD *poll_fd)
+{
+  poll_fd->fd = wakeup->fds[0];
+  poll_fd->events = G_IO_IN;
+}
+
+/**
+ * arv_wakeup_acknowledge:
+ * @wakeup: a #ArvWakeup
+ *
+ * Acknowledges receipt of a wakeup signal on @wakeup.
+ *
+ * You must call this after @wakeup polls as ready.  If not, it will
+ * continue to poll as ready until you do so.
+ *
+ * If you call this function and @wakeup is not signaled, nothing
+ * happens.
+ *
+ * Since: 0.3.8
+ **/
+void
+arv_wakeup_acknowledge (ArvWakeup *wakeup)
+{
+  char buffer[16];
+
+  /* read until it is empty */
+  while (read (wakeup->fds[0], buffer, sizeof buffer) == sizeof buffer);
+}
+
+/**
+ * arv_wakeup_signal:
+ * @wakeup: a #ArvWakeup
+ *
+ * Signals @wakeup.
+ *
+ * Any future (or present) polling on the #GPollFD returned by
+ * arv_wakeup_get_pollfd() will immediately succeed until such a time as
+ * arv_wakeup_acknowledge() is called.
+ *
+ * This function is safe to call from a UNIX signal handler.
+ *
+ * Since: 0.3.8
+ **/
+void
+arv_wakeup_signal (ArvWakeup *wakeup)
+{
+  int res;
+
+  if (wakeup->fds[1] == -1)
+    {
+      guint64 one = 1;
+
+      /* eventfd() case. It requires a 64-bit counter increment value to be
+       * written. */
+      do
+        res = write (wakeup->fds[0], &one, sizeof one);
+      while (G_UNLIKELY (res == -1 && errno == EINTR));
+    }
+  else
+    {
+      guint8 one = 1;
+
+      /* Non-eventfd() case. Only a single byte needs to be written, and it can
+       * have an arbitrary value. */
+      do
+        res = write (wakeup->fds[1], &one, sizeof one);
+      while (G_UNLIKELY (res == -1 && errno == EINTR));
+    }
+}
+
+/**
+ * arv_wakeup_free:
+ * @wakeup: a #ArvWakeup
+ *
+ * Frees @wakeup.
+ *
+ * You must not currently be polling on the #GPollFD returned by
+ * arv_wakeup_get_pollfd(), or the result is undefined.
+ **/
+void
+arv_wakeup_free (ArvWakeup *wakeup)
+{
+  close (wakeup->fds[0]);
+
+  if (wakeup->fds[1] != -1)
+    close (wakeup->fds[1]);
+
+  g_slice_free (ArvWakeup, wakeup);
+}
+
+#endif /* !_WIN32 */
diff --git a/src/arvwakeupprivate.h b/src/arvwakeupprivate.h
new file mode 100644
index 0000000..c0e9910
--- /dev/null
+++ b/src/arvwakeupprivate.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright © 2011 Canonical Limited
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the licence, 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Ryan Lortie <desrt desrt ca>
+ */
+
+#ifndef ARV_WAKEUP_H
+#define ARV_WAKEUP_H
+
+#include <arvtypes.h>
+
+typedef struct _ArvWakeup ArvWakeup;
+
+ArvWakeup *    arv_wakeup_new            (void);
+void            arv_wakeup_free           (ArvWakeup *wakeup);
+
+void            arv_wakeup_get_pollfd     (ArvWakeup *wakeup,
+                                          GPollFD *poll_fd);
+void            arv_wakeup_signal         (ArvWakeup *wakeup);
+void            arv_wakeup_acknowledge    (ArvWakeup *wakeup);
+
+#endif