[at-spi2-atk] Add a class for taking leased references of GObjects.

[Mark Doffman <markdoffman src gnome org>]

commit 1dd7a3f08c3ac54abca261ae5aa539371f77ccc9
Author: Mark Doffman <mark doffman codethink co uk>
Date:   Sat Jan 2 08:34:45 2010 -0800

    Add a class for taking leased references of GObjects.

 atk-adaptor/Makefile.am          |    2 +
 atk-adaptor/accessible-leasing.c |  196 ++++++++++++++++++++++++++++++++++++++
 atk-adaptor/accessible-leasing.h |   59 ++++++++++++
 3 files changed, 257 insertions(+), 0 deletions(-)
---
diff --git a/atk-adaptor/Makefile.am b/atk-adaptor/Makefile.am
index 8538c4c..fea7091 100644
--- a/atk-adaptor/Makefile.am
+++ b/atk-adaptor/Makefile.am
@@ -27,6 +27,8 @@ libatk_bridge_la_LIBADD = $(DBUS_GLIB_LIBS) \
 			  $(top_builddir)/atk-adaptor/adaptors/libatk-bridge-adaptors.la
 
 libatk_bridge_la_SOURCES =	\
+        accessible-leasing.c    \
+        accessible-leasing.h    \
 	accessible-register.c	\
 	accessible-register.h	\
 	bridge.c		\
diff --git a/atk-adaptor/accessible-leasing.c b/atk-adaptor/accessible-leasing.c
new file mode 100644
index 0000000..0bfd496
--- /dev/null
+++ b/atk-adaptor/accessible-leasing.c
@@ -0,0 +1,196 @@
+/*
+ * AT-SPI - Assistive Technology Service Provider Interface
+ * (Gnome Accessibility Project; http://developer.gnome.org/projects/gap)
+ *
+ * Copyright 2009, 2010 Codethink Ltd.
+ *
+ * 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., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <accessible-leasing.h>
+
+/*---------------------------------------------------------------------------*/
+
+typedef struct _ExpiryElement
+{
+  guint expiry_s;
+  GObject *object;
+} ExpiryElement;
+
+static void spi_leasing_dispose (GObject * object);
+
+static void spi_leasing_finalize (GObject * object);
+
+static void add_expiry_timeout (SpiLeasing * leasing);
+
+/*---------------------------------------------------------------------------*/
+
+G_DEFINE_TYPE (SpiLeasing, spi_leasing, G_TYPE_OBJECT)
+
+static void spi_leasing_class_init (SpiLeasingClass * klass)
+{
+  GObjectClass *object_class = (GObjectClass *) klass;
+
+  spi_leasing_parent_class = g_type_class_ref (G_TYPE_OBJECT);
+
+  object_class->finalize = spi_leasing_finalize;
+  object_class->dispose = spi_leasing_dispose;
+}
+
+static void
+spi_leasing_init (SpiLeasing * leasing)
+{
+  leasing->expiry_queue = g_queue_new ();
+  leasing->expiry_func_id = 0;
+}
+
+static void
+spi_leasing_finalize (GObject * object)
+{
+  SpiLeasing *leasing = SPI_LEASING (object);
+
+  g_free (leasing->expiry_queue);
+  G_OBJECT_CLASS (spi_leasing_parent_class)->finalize (object);
+}
+
+static void
+spi_leasing_dispose (GObject * object)
+{
+  SpiLeasing *leasing = SPI_LEASING (object);
+
+  ExpiryElement *head;
+  while (head = g_queue_pop_head (leasing->expiry_queue))
+    {
+      g_object_unref (head->object);
+      g_slice_free (ExpiryElement, head);
+    }
+  G_OBJECT_CLASS (spi_leasing_parent_class)->dispose (object);
+}
+
+/*---------------------------------------------------------------------------*/
+
+/*
+  End the lease on all objects whose expiry time has passed.
+ 
+  Check when the next event is and set the next expiry func.
+*/
+static gboolean
+expiry_func (gpointer data)
+{
+  SpiLeasing *leasing = SPI_LEASING (data);
+
+  ExpiryElement *head, *current;
+  GTimeVal t;
+
+  g_get_current_time (&t);
+
+  head = g_queue_peek_head (leasing->expiry_queue);
+  while (head != NULL && head->expiry_s <= t.tv_sec)
+    {
+      current = g_queue_pop_head (leasing->expiry_queue);
+
+      g_object_unref (current->object);
+      g_slice_free (ExpiryElement, current);
+
+      head = g_queue_peek_head (leasing->expiry_queue);
+    }
+
+  leasing->expiry_func_id = 0;
+  add_expiry_timeout (leasing);
+
+  return FALSE;
+}
+
+/*---------------------------------------------------------------------------*/
+
+/*
+  Checks if an expiry timeout is already scheduled, if so returns.
+  This is becasue events will always be added to the end of the queue.
+  Events are always later in time to previoulsy added events.
+
+  Otherwise calculate the next wake time using the top of the queue
+  and add the next expiry function.
+
+  This function is called when a lease is added or at the end of the
+  expiry function to add the next expiry timeout.
+*/
+static void
+add_expiry_timeout (SpiLeasing * leasing)
+{
+  ExpiryElement *elem;
+  GTimeVal t;
+  guint next_expiry;
+
+  if (leasing->expiry_func_id != 0)
+    return;
+
+  elem = (ExpiryElement *) g_queue_peek_head (leasing->expiry_queue);
+  if (elem == NULL)
+    return;
+
+  /* The current time is implicitly rounded down here by ignoring the us */
+  g_get_current_time (&t);
+  next_expiry = elem->expiry_s - t.tv_sec;
+  leasing->expiry_func_id = g_timeout_add_seconds (next_expiry,
+                                                   expiry_func, leasing);
+}
+
+/*---------------------------------------------------------------------------*/
+
+/*
+  The lease time is expected to be in seconds, the rounding is going to be to
+  intervals of 1 second.
+
+  The lease time is going to be rounded up, as the lease time should be
+  considered a MINIMUM that the object will be leased for.
+*/
+#define LEASE_TIME_S 3
+#define EXPIRY_TIME_S (LEASE_TIME_S + 1)
+
+GObject *
+spi_leasing_take (SpiLeasing * leasing, GObject * object)
+{
+  /*
+     Get the current time.
+     Quantize the time.
+     Add the release event to the queue.
+     Check the next expiry.
+   */
+
+  GTimeVal t;
+  guint expiry_s;
+
+  ExpiryElement *elem;
+
+  g_get_current_time (&t);
+  expiry_s = t.tv_sec + EXPIRY_TIME_S;
+
+  elem = g_slice_new (ExpiryElement);
+  elem->expiry_s = expiry_s;
+  elem->object = g_object_ref (object);
+
+  g_queue_push_tail (leasing->expiry_queue, elem);
+
+  add_expiry_timeout (leasing);
+
+  return object;
+}
+
+/*END------------------------------------------------------------------------*/
diff --git a/atk-adaptor/accessible-leasing.h b/atk-adaptor/accessible-leasing.h
new file mode 100644
index 0000000..50f1f3c
--- /dev/null
+++ b/atk-adaptor/accessible-leasing.h
@@ -0,0 +1,59 @@
+/*
+ * AT-SPI - Assistive Technology Service Provider Interface
+ * (Gnome Accessibility Project; http://developer.gnome.org/projects/gap)
+ *
+ * Copyright 2008 Novell, Inc.
+ * Copyright 2008, 2009 Codethink Ltd.
+ *
+ * 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., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef ACCESSIBLE_LEASING
+#define ACCESSIBLE_LEASING
+
+#include <glib.h>
+#include <glib-object.h>
+
+typedef struct _SpiLeasing SpiLeasing;
+typedef struct _SpiLeasingClass SpiLeasingClass;
+
+G_BEGIN_DECLS
+
+#define SPI_LEASING_TYPE        (spi_leasing_get_type ())
+#define SPI_LEASING(o)          (G_TYPE_CHECK_INSTANCE_CAST ((o), SPI_LEASING_TYPE, SpiLeasing))
+#define SPI_LEASING_CLASS(k)    (G_TYPE_CHECK_CLASS_CAST((k), SPI_LEASING_TYPE, SpiLeasingClass))
+#define SPI_IS_LEASING(o)       (G_TYPE_CHECK__INSTANCE_TYPE ((o), SPI_LEASING_TYPE))
+#define SPI_IS_LEASING_CLASS(k) (G_TYPE_CHECK_CLASS_TYPE ((k), SPI_LEASING_TYPE))
+
+struct _SpiLeasing
+{
+  GObject parent;
+
+  GQueue *expiry_queue;
+  guint expiry_func_id;
+};
+
+struct _SpiLeasingClass
+{
+  GObjectClass parent_class;
+};
+
+GType spi_leasing_get_type (void);
+
+GObject *spi_leasing_take (SpiLeasing * leasing, GObject * object);
+
+G_END_DECLS
+#endif /* ACCESSIBLE_LEASING */