1  /*
       2   * Copyright © 2010 Codethink Limited
       3   *
       4   * SPDX-License-Identifier: LGPL-2.1-or-later
       5   *
       6   * This library is free software; you can redistribute it and/or
       7   * modify it under the terms of the GNU Lesser General Public
       8   * License as published by the Free Software Foundation; either
       9   * version 2.1 of the License, or (at your option) any later version.
      10   *
      11   * This library is distributed in the hope that it will be useful,
      12   * but WITHOUT ANY WARRANTY; without even the implied warranty of
      13   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      14   * Lesser General Public License for more details.
      15   *
      16   * You should have received a copy of the GNU Lesser General Public
      17   * License along with this library; if not, see <http://www.gnu.org/licenses/>.
      18   *
      19   * Author: Ryan Lortie <desrt@desrt.ca>
      20   */
      21  
      22  #include "config.h"
      23  
      24  #include "gsettingsbackendinternal.h"
      25  #include "giomodule-priv.h"
      26  #include "gsimplepermission.h"
      27  
      28  
      29  #define G_TYPE_NULL_SETTINGS_BACKEND    (g_null_settings_backend_get_type ())
      30  #define G_NULL_SETTINGS_BACKEND(inst)   (G_TYPE_CHECK_INSTANCE_CAST ((inst), \
      31                                           G_TYPE_NULL_SETTINGS_BACKEND,       \
      32                                           GNullSettingsBackend))
      33  
      34  
      35  typedef GSettingsBackendClass GNullSettingsBackendClass;
      36  typedef GSettingsBackend      GNullSettingsBackend;
      37  
      38  G_DEFINE_TYPE_WITH_CODE (GNullSettingsBackend,
      39                           g_null_settings_backend,
      40                           G_TYPE_SETTINGS_BACKEND,
      41                           _g_io_modules_ensure_extension_points_registered ();
      42                           g_io_extension_point_implement (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME,
      43                                                           g_define_type_id, "null", 10))
      44  
      45  static GVariant *
      46  g_null_settings_backend_read (GSettingsBackend   *backend,
      47                                const gchar        *key,
      48                                const GVariantType *expected_type,
      49                                gboolean            default_value)
      50  {
      51    return NULL;
      52  }
      53  
      54  static gboolean
      55  g_null_settings_backend_write (GSettingsBackend *backend,
      56                                 const gchar      *key,
      57                                 GVariant         *value,
      58                                 gpointer          origin_tag)
      59  {
      60    if (value)
      61      g_variant_unref (g_variant_ref_sink (value));
      62    return FALSE;
      63  }
      64  
      65  static gboolean
      66  g_null_settings_backend_write_one (gpointer key,
      67                                     gpointer value,
      68                                     gpointer data)
      69  {
      70    if (value)
      71      g_variant_unref (g_variant_ref_sink (value));
      72    return FALSE;
      73  }
      74  
      75  static gboolean
      76  g_null_settings_backend_write_tree (GSettingsBackend *backend,
      77                                      GTree            *tree,
      78                                      gpointer          origin_tag)
      79  {
      80    g_tree_foreach (tree, g_null_settings_backend_write_one, backend);
      81    return FALSE;
      82  }
      83  
      84  static void
      85  g_null_settings_backend_reset (GSettingsBackend *backend,
      86                                 const gchar      *key,
      87                                 gpointer          origin_tag)
      88  {
      89  }
      90  
      91  static gboolean
      92  g_null_settings_backend_get_writable (GSettingsBackend *backend,
      93                                        const gchar      *name)
      94  {
      95    return FALSE;
      96  }
      97  
      98  static GPermission *
      99  g_null_settings_backend_get_permission (GSettingsBackend *backend,
     100                                          const gchar      *path)
     101  {
     102    return g_simple_permission_new (FALSE);
     103  }
     104  
     105  static void
     106  g_null_settings_backend_init (GNullSettingsBackend *memory)
     107  {
     108  }
     109  
     110  static void
     111  g_null_settings_backend_class_init (GNullSettingsBackendClass *class)
     112  {
     113    GSettingsBackendClass *backend_class = G_SETTINGS_BACKEND_CLASS (class);
     114  
     115    backend_class->read = g_null_settings_backend_read;
     116    backend_class->write = g_null_settings_backend_write;
     117    backend_class->write_tree = g_null_settings_backend_write_tree;
     118    backend_class->reset = g_null_settings_backend_reset;
     119    backend_class->get_writable = g_null_settings_backend_get_writable;
     120    backend_class->get_permission = g_null_settings_backend_get_permission;
     121  }
     122  
     123  /**
     124   * g_null_settings_backend_new:
     125   *
     126   *
     127   * Creates a readonly #GSettingsBackend.
     128   *
     129   * This backend does not allow changes to settings, so all settings
     130   * will always have their default values.
     131   *
     132   * Returns: (transfer full): a newly created #GSettingsBackend
     133   *
     134   * Since: 2.28
     135   */
     136  GSettingsBackend *
     137  g_null_settings_backend_new (void)
     138  {
     139    return g_object_new (G_TYPE_NULL_SETTINGS_BACKEND, NULL);
     140  }