Import Upstream version 2.72.4

gio/gmemorymonitor.c

@@ -0,0 +1,158 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright 2019 Red Hat, Inc
+ *
+ * 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 2.1 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
+ * 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/>.
+ */
+
+#include "config.h"
+#include "glib.h"
+#include "glibintl.h"
+
+#include "gmemorymonitor.h"
+#include "ginetaddress.h"
+#include "ginetsocketaddress.h"
+#include "ginitable.h"
+#include "gioenumtypes.h"
+#include "giomodule-priv.h"
+#include "gtask.h"
+
+/**
+ * SECTION:gmemorymonitor
+ * @title: GMemoryMonitor
+ * @short_description: Memory usage monitor
+ * @include: gio/gio.h
+ *
+ * #GMemoryMonitor will monitor system memory and suggest to the application
+ * when to free memory so as to leave more room for other applications.
+ * It is implemented on Linux using the [Low Memory Monitor](https://gitlab.freedesktop.org/hadess/low-memory-monitor/)
+ * ([API documentation](https://hadess.pages.freedesktop.org/low-memory-monitor/)).
+ *
+ * There is also an implementation for use inside Flatpak sandboxes.
+ *
+ * Possible actions to take when the signal is received are:
+ *
+ *  - Free caches
+ *  - Save files that haven't been looked at in a while to disk, ready to be reopened when needed
+ *  - Run a garbage collection cycle
+ *  - Try and compress fragmented allocations
+ *  - Exit on idle if the process has no reason to stay around
+ *  - Call [`malloc_trim(3)`](man:malloc_trim) to return cached heap pages to
+ *    the kernel (if supported by your libc)
+ *
+ * Note that some actions may not always improve system performance, and so
+ * should be profiled for your application. `malloc_trim()`, for example, may
+ * make future heap allocations slower (due to releasing cached heap pages back
+ * to the kernel).
+ *
+ * See #GMemoryMonitorWarningLevel for details on the various warning levels.
+ *
+ * |[<!-- language="C" -->
+ * static void
+ * warning_cb (GMemoryMonitor *m, GMemoryMonitorWarningLevel level)
+ * {
+ *   g_debug ("Warning level: %d", level);
+ *   if (warning_level > G_MEMORY_MONITOR_WARNING_LEVEL_LOW)
+ *     drop_caches ();
+ * }
+ *
+ * static GMemoryMonitor *
+ * monitor_low_memory (void)
+ * {
+ *   GMemoryMonitor *m;
+ *   m = g_memory_monitor_dup_default ();
+ *   g_signal_connect (G_OBJECT (m), "low-memory-warning",
+ *                     G_CALLBACK (warning_cb), NULL);
+ *   return m;
+ * }
+ * ]|
+ *
+ * Don't forget to disconnect the #GMemoryMonitor::low-memory-warning
+ * signal, and unref the #GMemoryMonitor itself when exiting.
+ *
+ * Since: 2.64
+ */
+
+/**
+ * GMemoryMonitor:
+ *
+ * #GMemoryMonitor monitors system memory and indicates when
+ * the system is low on memory.
+ *
+ * Since: 2.64
+ */
+
+/**
+ * GMemoryMonitorInterface:
+ * @g_iface: The parent interface.
+ * @low_memory_warning: the virtual function pointer for the
+ *  #GMemoryMonitor::low-memory-warning signal.
+ *
+ * The virtual function table for #GMemoryMonitor.
+ *
+ * Since: 2.64
+ */
+
+G_DEFINE_INTERFACE_WITH_CODE (GMemoryMonitor, g_memory_monitor, G_TYPE_OBJECT,
+                              g_type_interface_add_prerequisite (g_define_type_id, G_TYPE_INITABLE))
+
+enum {
+  LOW_MEMORY_WARNING,
+  LAST_SIGNAL
+};
+
+static guint signals[LAST_SIGNAL] = { 0 };
+
+/**
+ * g_memory_monitor_dup_default:
+ *
+ * Gets a reference to the default #GMemoryMonitor for the system.
+ *
+ * Returns: (not nullable) (transfer full): a new reference to the default #GMemoryMonitor
+ *
+ * Since: 2.64
+ */
+GMemoryMonitor *
+g_memory_monitor_dup_default (void)
+{
+  return g_object_ref (_g_io_module_get_default (G_MEMORY_MONITOR_EXTENSION_POINT_NAME,
+                                                 "GIO_USE_MEMORY_MONITOR",
+                                                 NULL));
+}
+
+static void
+g_memory_monitor_default_init (GMemoryMonitorInterface *iface)
+{
+  /**
+   * GMemoryMonitor::low-memory-warning:
+   * @monitor: a #GMemoryMonitor
+   * @level: the #GMemoryMonitorWarningLevel warning level
+   *
+   * Emitted when the system is running low on free memory. The signal
+   * handler should then take the appropriate action depending on the
+   * warning level. See the #GMemoryMonitorWarningLevel documentation for
+   * details.
+   *
+   * Since: 2.64
+   */
+  signals[LOW_MEMORY_WARNING] =
+    g_signal_new (I_("low-memory-warning"),
+                  G_TYPE_MEMORY_MONITOR,
+                  G_SIGNAL_RUN_LAST,
+                  G_STRUCT_OFFSET (GMemoryMonitorInterface, low_memory_warning),
+                  NULL, NULL,
+                  NULL,
+                  G_TYPE_NONE, 1,
+                  G_TYPE_MEMORY_MONITOR_WARNING_LEVEL);
+}