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glib2.0/gio/gsettingsbackend.c

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/*
* Copyright © 2009, 2010 Codethink Limited
* Copyright © 2010 Red Hat, Inc.
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* 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/>.
*
* Authors: Ryan Lortie <desrt@desrt.ca>
* Matthias Clasen <mclasen@redhat.com>
*/
#include "config.h"
#include "gsettingsbackendinternal.h"
#include "gsimplepermission.h"
#include "giomodule-priv.h"
#include <string.h>
#include <stdlib.h>
#include <glib.h>
#include <glibintl.h>
typedef struct _GSettingsBackendClosure GSettingsBackendClosure;
typedef struct _GSettingsBackendWatch GSettingsBackendWatch;
struct _GSettingsBackendPrivate
{
GSettingsBackendWatch *watches;
GMutex lock;
};
G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE (GSettingsBackend, g_settings_backend, G_TYPE_OBJECT)
/* For g_settings_backend_sync_default(), we only want to actually do
* the sync if the backend already exists. This avoids us creating an
* entire GSettingsBackend in order to call a do-nothing sync()
* operation on it. This variable lets us avoid that.
*/
static gboolean g_settings_has_backend;
/**
* SECTION:gsettingsbackend
* @title: GSettingsBackend
* @short_description: Interface for settings backend implementations
* @include: gio/gsettingsbackend.h
* @see_also: #GSettings, #GIOExtensionPoint
*
* The #GSettingsBackend interface defines a generic interface for
* non-strictly-typed data that is stored in a hierarchy. To implement
* an alternative storage backend for #GSettings, you need to implement
* the #GSettingsBackend interface and then make it implement the
* extension point %G_SETTINGS_BACKEND_EXTENSION_POINT_NAME.
*
* The interface defines methods for reading and writing values, a
* method for determining if writing of certain values will fail
* (lockdown) and a change notification mechanism.
*
* The semantics of the interface are very precisely defined and
* implementations must carefully adhere to the expectations of
* callers that are documented on each of the interface methods.
*
* Some of the #GSettingsBackend functions accept or return a #GTree.
* These trees always have strings as keys and #GVariant as values.
* g_settings_backend_create_tree() is a convenience function to create
* suitable trees.
*
* The #GSettingsBackend API is exported to allow third-party
* implementations, but does not carry the same stability guarantees
* as the public GIO API. For this reason, you have to define the
* C preprocessor symbol %G_SETTINGS_ENABLE_BACKEND before including
* `gio/gsettingsbackend.h`.
**/
static gboolean
is_key (const gchar *key)
{
gint length;
gint i;
g_return_val_if_fail (key != NULL, FALSE);
g_return_val_if_fail (key[0] == '/', FALSE);
for (i = 1; key[i]; i++)
g_return_val_if_fail (key[i] != '/' || key[i + 1] != '/', FALSE);
length = i;
g_return_val_if_fail (key[length - 1] != '/', FALSE);
return TRUE;
}
static gboolean
is_path (const gchar *path)
{
gint length;
gint i;
g_return_val_if_fail (path != NULL, FALSE);
g_return_val_if_fail (path[0] == '/', FALSE);
for (i = 1; path[i]; i++)
g_return_val_if_fail (path[i] != '/' || path[i + 1] != '/', FALSE);
length = i;
g_return_val_if_fail (path[length - 1] == '/', FALSE);
return TRUE;
}
struct _GSettingsBackendWatch
{
/* Always access the target via the weak reference */
GWeakRef target;
/* The pointer is only for comparison from the weak notify,
* at which point the target might already be close to
* destroyed. It's not safe to use it for anything anymore
* at that point */
GObject *target_ptr;
const GSettingsListenerVTable *vtable;
GMainContext *context;
GSettingsBackendWatch *next;
};
struct _GSettingsBackendClosure
{
void (*function) (GObject *target,
GSettingsBackend *backend,
const gchar *name,
gpointer origin_tag,
gchar **names);
GMainContext *context;
GObject *target;
GSettingsBackend *backend;
gchar *name;
gpointer origin_tag;
gchar **names;
};
static void
g_settings_backend_watch_weak_notify (gpointer data,
GObject *where_the_object_was)
{
GSettingsBackend *backend = data;
GSettingsBackendWatch **ptr;
/* search and remove */
g_mutex_lock (&backend->priv->lock);
for (ptr = &backend->priv->watches; *ptr; ptr = &(*ptr)->next)
if ((*ptr)->target_ptr == where_the_object_was)
{
GSettingsBackendWatch *tmp = *ptr;
*ptr = tmp->next;
g_weak_ref_clear (&tmp->target);
g_slice_free (GSettingsBackendWatch, tmp);
g_mutex_unlock (&backend->priv->lock);
return;
}
/* we didn't find it. that shouldn't happen. */
g_assert_not_reached ();
}
/*< private >
* g_settings_backend_watch:
* @backend: a #GSettingsBackend
* @target: the GObject (typically GSettings instance) to call back to
* @context: (nullable): a #GMainContext, or %NULL
* ...: callbacks...
*
* Registers a new watch on a #GSettingsBackend.
*
* note: %NULL @context does not mean "default main context" but rather,
* "it is okay to dispatch in any context". If the default main context
* is specifically desired then it must be given.
*
* note also: if you want to get meaningful values for the @origin_tag
* that appears as an argument to some of the callbacks, you *must* have
* @context as %NULL. Otherwise, you are subject to cross-thread
* dispatching and whatever owned @origin_tag at the time that the event
* occurred may no longer own it. This is a problem if you consider that
* you may now be the new owner of that address and mistakenly think
* that the event in question originated from yourself.
*
* tl;dr: If you give a non-%NULL @context then you must ignore the
* value of @origin_tag given to any callbacks.
**/
void
g_settings_backend_watch (GSettingsBackend *backend,
const GSettingsListenerVTable *vtable,
GObject *target,
GMainContext *context)
{
GSettingsBackendWatch *watch;
/* For purposes of discussion, we assume that our target is a
* GSettings instance.
*
* Our strategy to defend against the final reference dropping on the
* GSettings object in a thread other than the one that is doing the
* dispatching is as follows:
*
* 1) hold a strong reference on the GSettings during an outstanding
* dispatch. This ensures that the delivery is always possible while
* the GSettings object is alive, and if this was the last reference
* then it will be dropped from the dispatch thread.
*
* 2) hold a weak reference on the GSettings at other times. This
* allows us to receive early notification of pending destruction
* of the object. At this point, it is still safe to obtain a
* reference on the GObject to keep it alive, so #1 will work up
* to that point. After that point, we'll have been able to drop
* the watch from the list.
*
* Note, in particular, that it's not possible to simply have an
* "unwatch" function that gets called from the finalize function of
* the GSettings instance because, by that point it is no longer
* possible to keep the object alive using g_object_ref() and we would
* have no way of knowing this.
*
* Note also that we need to hold a reference on the main context here
* since the GSettings instance may be finalized before the closure runs.
*
* All access to the list holds a mutex. We have some strategies to
* avoid some of the pain that would be associated with that.
*/
watch = g_slice_new (GSettingsBackendWatch);
watch->context = context;
watch->vtable = vtable;
g_weak_ref_init (&watch->target, target);
watch->target_ptr = target;
g_object_weak_ref (target, g_settings_backend_watch_weak_notify, backend);
/* linked list prepend */
g_mutex_lock (&backend->priv->lock);
watch->next = backend->priv->watches;
backend->priv->watches = watch;
g_mutex_unlock (&backend->priv->lock);
}
void
g_settings_backend_unwatch (GSettingsBackend *backend,
GObject *target)
{
/* Our caller surely owns a reference on 'target', so the order of
* these two calls is unimportant.
*/
g_object_weak_unref (target, g_settings_backend_watch_weak_notify, backend);
g_settings_backend_watch_weak_notify (backend, target);
}
static gboolean
g_settings_backend_invoke_closure (gpointer user_data)
{
GSettingsBackendClosure *closure = user_data;
closure->function (closure->target, closure->backend, closure->name,
closure->origin_tag, closure->names);
if (closure->context)
g_main_context_unref (closure->context);
g_object_unref (closure->backend);
g_object_unref (closure->target);
g_strfreev (closure->names);
g_free (closure->name);
g_slice_free (GSettingsBackendClosure, closure);
return FALSE;
}
static void
g_settings_backend_dispatch_signal (GSettingsBackend *backend,
gsize function_offset,
const gchar *name,
gpointer origin_tag,
const gchar * const *names)
{
GSettingsBackendWatch *watch;
GSList *closures = NULL;
/* We're in a little bit of a tricky situation here. We need to hold
* a lock while traversing the list, but we don't want to hold the
* lock while calling back into user code.
*
* We work around this by creating a bunch of GSettingsBackendClosure
* objects while holding the lock and dispatching them after. We
* never touch the list without holding the lock.
*/
g_mutex_lock (&backend->priv->lock);
for (watch = backend->priv->watches; watch; watch = watch->next)
{
GSettingsBackendClosure *closure;
GObject *target = g_weak_ref_get (&watch->target);
/* If the target was destroyed in the meantime, just skip it here */
if (!target)
continue;
closure = g_slice_new (GSettingsBackendClosure);
closure->context = watch->context;
if (closure->context)
g_main_context_ref (closure->context);
closure->backend = g_object_ref (backend);
closure->target = g_steal_pointer (&target);
closure->function = G_STRUCT_MEMBER (void *, watch->vtable,
function_offset);
closure->name = g_strdup (name);
closure->origin_tag = origin_tag;
closure->names = g_strdupv ((gchar **) names);
closures = g_slist_prepend (closures, closure);
}
g_mutex_unlock (&backend->priv->lock);
while (closures)
{
GSettingsBackendClosure *closure = closures->data;
if (closure->context)
g_main_context_invoke (closure->context,
g_settings_backend_invoke_closure,
closure);
else
g_settings_backend_invoke_closure (closure);
closures = g_slist_delete_link (closures, closures);
}
}
/**
* g_settings_backend_changed:
* @backend: a #GSettingsBackend implementation
* @key: the name of the key
* @origin_tag: the origin tag
*
* Signals that a single key has possibly changed. Backend
* implementations should call this if a key has possibly changed its
* value.
*
* @key must be a valid key (ie starting with a slash, not containing
* '//', and not ending with a slash).
*
* The implementation must call this function during any call to
* g_settings_backend_write(), before the call returns (except in the
* case that no keys are actually changed and it cares to detect this
* fact). It may not rely on the existence of a mainloop for
* dispatching the signal later.
*
* The implementation may call this function at any other time it likes
* in response to other events (such as changes occurring outside of the
* program). These calls may originate from a mainloop or may originate
* in response to any other action (including from calls to
* g_settings_backend_write()).
*
* In the case that this call is in response to a call to
* g_settings_backend_write() then @origin_tag must be set to the same
* value that was passed to that call.
*
* Since: 2.26
**/
void
g_settings_backend_changed (GSettingsBackend *backend,
const gchar *key,
gpointer origin_tag)
{
g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
g_return_if_fail (is_key (key));
g_settings_backend_dispatch_signal (backend,
G_STRUCT_OFFSET (GSettingsListenerVTable,
changed),
key, origin_tag, NULL);
}
/**
* g_settings_backend_keys_changed:
* @backend: a #GSettingsBackend implementation
* @path: the path containing the changes
* @items: (array zero-terminated=1): the %NULL-terminated list of changed keys
* @origin_tag: the origin tag
*
* Signals that a list of keys have possibly changed. Backend
* implementations should call this if keys have possibly changed their
* values.
*
* @path must be a valid path (ie starting and ending with a slash and
* not containing '//'). Each string in @items must form a valid key
* name when @path is prefixed to it (ie: each item must not start or
* end with '/' and must not contain '//').
*
* The meaning of this signal is that any of the key names resulting
* from the contatenation of @path with each item in @items may have
* changed.
*
* The same rules for when notifications must occur apply as per
* g_settings_backend_changed(). These two calls can be used
* interchangeably if exactly one item has changed (although in that
* case g_settings_backend_changed() is definitely preferred).
*
* For efficiency reasons, the implementation should strive for @path to
* be as long as possible (ie: the longest common prefix of all of the
* keys that were changed) but this is not strictly required.
*
* Since: 2.26
*/
void
g_settings_backend_keys_changed (GSettingsBackend *backend,
const gchar *path,
gchar const * const *items,
gpointer origin_tag)
{
g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
g_return_if_fail (is_path (path));
/* XXX: should do stricter checking (ie: inspect each item) */
g_return_if_fail (items != NULL);
g_settings_backend_dispatch_signal (backend,
G_STRUCT_OFFSET (GSettingsListenerVTable,
keys_changed),
path, origin_tag, items);
}
/**
* g_settings_backend_path_changed:
* @backend: a #GSettingsBackend implementation
* @path: the path containing the changes
* @origin_tag: the origin tag
*
* Signals that all keys below a given path may have possibly changed.
* Backend implementations should call this if an entire path of keys
* have possibly changed their values.
*
* @path must be a valid path (ie starting and ending with a slash and
* not containing '//').
*
* The meaning of this signal is that any of the key which has a name
* starting with @path may have changed.
*
* The same rules for when notifications must occur apply as per
* g_settings_backend_changed(). This call might be an appropriate
* reasponse to a 'reset' call but implementations are also free to
* explicitly list the keys that were affected by that call if they can
* easily do so.
*
* For efficiency reasons, the implementation should strive for @path to
* be as long as possible (ie: the longest common prefix of all of the
* keys that were changed) but this is not strictly required. As an
* example, if this function is called with the path of "/" then every
* single key in the application will be notified of a possible change.
*
* Since: 2.26
*/
void
g_settings_backend_path_changed (GSettingsBackend *backend,
const gchar *path,
gpointer origin_tag)
{
g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
g_return_if_fail (is_path (path));
g_settings_backend_dispatch_signal (backend,
G_STRUCT_OFFSET (GSettingsListenerVTable,
path_changed),
path, origin_tag, NULL);
}
/**
* g_settings_backend_writable_changed:
* @backend: a #GSettingsBackend implementation
* @key: the name of the key
*
* Signals that the writability of a single key has possibly changed.
*
* Since GSettings performs no locking operations for itself, this call
* will always be made in response to external events.
*
* Since: 2.26
**/
void
g_settings_backend_writable_changed (GSettingsBackend *backend,
const gchar *key)
{
g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
g_return_if_fail (is_key (key));
g_settings_backend_dispatch_signal (backend,
G_STRUCT_OFFSET (GSettingsListenerVTable,
writable_changed),
key, NULL, NULL);
}
/**
* g_settings_backend_path_writable_changed:
* @backend: a #GSettingsBackend implementation
* @path: the name of the path
*
* Signals that the writability of all keys below a given path may have
* changed.
*
* Since GSettings performs no locking operations for itself, this call
* will always be made in response to external events.
*
* Since: 2.26
**/
void
g_settings_backend_path_writable_changed (GSettingsBackend *backend,
const gchar *path)
{
g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
g_return_if_fail (is_path (path));
g_settings_backend_dispatch_signal (backend,
G_STRUCT_OFFSET (GSettingsListenerVTable,
path_writable_changed),
path, NULL, NULL);
}
typedef struct
{
const gchar **keys;
GVariant **values;
gint prefix_len;
gchar *prefix;
} FlattenState;
static gboolean
g_settings_backend_flatten_one (gpointer key,
gpointer value,
gpointer user_data)
{
FlattenState *state = user_data;
const gchar *skey = key;
gint i;
g_return_val_if_fail (is_key (key), TRUE);
/* calculate longest common prefix */
if (state->prefix == NULL)
{
gchar *last_byte;
/* first key? just take the prefix up to the last '/' */
state->prefix = g_strdup (skey);
last_byte = strrchr (state->prefix, '/') + 1;
state->prefix_len = last_byte - state->prefix;
*last_byte = '\0';
}
else
{
/* find the first character that does not match. we will
* definitely find one because the prefix ends in '/' and the key
* does not. also: no two keys in the tree are the same.
*/
for (i = 0; state->prefix[i] == skey[i]; i++);
/* check if we need to shorten the prefix */
if (state->prefix[i] != '\0')
{
/* find the nearest '/', terminate after it */
while (state->prefix[i - 1] != '/')
i--;
state->prefix[i] = '\0';
state->prefix_len = i;
}
}
/* save the entire item into the array.
* the prefixes will be removed later.
*/
*state->keys++ = key;
if (state->values)
*state->values++ = value;
return FALSE;
}
/**
* g_settings_backend_flatten_tree:
* @tree: a #GTree containing the changes
* @path: (out): the location to save the path
* @keys: (out) (transfer container) (array zero-terminated=1): the
* location to save the relative keys
* @values: (out) (optional) (transfer container) (array zero-terminated=1):
* the location to save the values, or %NULL
*
* Calculate the longest common prefix of all keys in a tree and write
* out an array of the key names relative to that prefix and,
* optionally, the value to store at each of those keys.
*
* You must free the value returned in @path, @keys and @values using
* g_free(). You should not attempt to free or unref the contents of
* @keys or @values.
*
* Since: 2.26
**/
void
g_settings_backend_flatten_tree (GTree *tree,
gchar **path,
const gchar ***keys,
GVariant ***values)
{
FlattenState state = { 0, };
gsize nnodes;
nnodes = g_tree_nnodes (tree);
*keys = state.keys = g_new (const gchar *, nnodes + 1);
state.keys[nnodes] = NULL;
if (values != NULL)
{
*values = state.values = g_new (GVariant *, nnodes + 1);
state.values[nnodes] = NULL;
}
g_tree_foreach (tree, g_settings_backend_flatten_one, &state);
g_return_if_fail (*keys + nnodes == state.keys);
*path = state.prefix;
while (nnodes--)
*--state.keys += state.prefix_len;
}
/**
* g_settings_backend_changed_tree:
* @backend: a #GSettingsBackend implementation
* @tree: a #GTree containing the changes
* @origin_tag: the origin tag
*
* This call is a convenience wrapper. It gets the list of changes from
* @tree, computes the longest common prefix and calls
* g_settings_backend_changed().
*
* Since: 2.26
**/
void
g_settings_backend_changed_tree (GSettingsBackend *backend,
GTree *tree,
gpointer origin_tag)
{
const gchar **keys;
gchar *path;
g_return_if_fail (G_IS_SETTINGS_BACKEND (backend));
g_settings_backend_flatten_tree (tree, &path, &keys, NULL);
#ifdef DEBUG_CHANGES
{
gint i;
g_print ("----\n");
g_print ("changed_tree(): prefix %s\n", path);
for (i = 0; keys[i]; i++)
g_print (" %s\n", keys[i]);
g_print ("----\n");
}
#endif
g_settings_backend_keys_changed (backend, path, keys, origin_tag);
g_free (path);
g_free (keys);
}
/*< private >
* g_settings_backend_read:
* @backend: a #GSettingsBackend implementation
* @key: the key to read
* @expected_type: a #GVariantType
* @default_value: if the default value should be returned
*
* Reads a key. This call will never block.
*
* If the key exists, the value associated with it will be returned.
* If the key does not exist, %NULL will be returned.
*
* The returned value will be of the type given in @expected_type. If
* the backend stored a value of a different type then %NULL will be
* returned.
*
* If @default_value is %TRUE then this gets the default value from the
* backend (ie: the one that the backend would contain if
* g_settings_reset() were called).
*
* Returns: (nullable) (transfer full): the value that was read, or %NULL
*/
GVariant *
g_settings_backend_read (GSettingsBackend *backend,
const gchar *key,
const GVariantType *expected_type,
gboolean default_value)
{
GVariant *value;
value = G_SETTINGS_BACKEND_GET_CLASS (backend)
->read (backend, key, expected_type, default_value);
if (value != NULL)
value = g_variant_take_ref (value);
if G_UNLIKELY (value && !g_variant_is_of_type (value, expected_type))
{
g_variant_unref (value);
value = NULL;
}
return value;
}
/*< private >
* g_settings_backend_read_user_value:
* @backend: a #GSettingsBackend implementation
* @key: the key to read
* @expected_type: a #GVariantType
*
* Reads the 'user value' of a key.
*
* This is the value of the key that the user has control over and has
* set for themselves. Put another way: if the user did not set the
* value for themselves, then this will return %NULL (even if the
* sysadmin has provided a default value).
*
* Returns: (nullable) (transfer full): the value that was read, or %NULL
*/
GVariant *
g_settings_backend_read_user_value (GSettingsBackend *backend,
const gchar *key,
const GVariantType *expected_type)
{
GVariant *value;
value = G_SETTINGS_BACKEND_GET_CLASS (backend)
->read_user_value (backend, key, expected_type);
if (value != NULL)
value = g_variant_take_ref (value);
if G_UNLIKELY (value && !g_variant_is_of_type (value, expected_type))
{
g_variant_unref (value);
value = NULL;
}
return value;
}
/*< private >
* g_settings_backend_write:
* @backend: a #GSettingsBackend implementation
* @key: the name of the key
* @value: a #GVariant value to write to this key
* @origin_tag: the origin tag
*
* Writes exactly one key.
*
* This call does not fail. During this call a
* #GSettingsBackend::changed signal will be emitted if the value of the
* key has changed. The updated key value will be visible to any signal
* callbacks.
*
* One possible method that an implementation might deal with failures is
* to emit a second "changed" signal (either during this call, or later)
* to indicate that the affected keys have suddenly "changed back" to their
* old values.
*
* If @value has a floating reference, it will be sunk.
*
* Returns: %TRUE if the write succeeded, %FALSE if the key was not writable
*/
gboolean
g_settings_backend_write (GSettingsBackend *backend,
const gchar *key,
GVariant *value,
gpointer origin_tag)
{
gboolean success;
g_variant_ref_sink (value);
success = G_SETTINGS_BACKEND_GET_CLASS (backend)
->write (backend, key, value, origin_tag);
g_variant_unref (value);
return success;
}
/*< private >
* g_settings_backend_write_tree:
* @backend: a #GSettingsBackend implementation
* @tree: a #GTree containing key-value pairs to write
* @origin_tag: the origin tag
*
* Writes one or more keys. This call will never block.
*
* The key of each item in the tree is the key name to write to and the
* value is a #GVariant to write. The proper type of #GTree for this
* call can be created with g_settings_backend_create_tree(). This call
* might take a reference to the tree; you must not modified the #GTree
* after passing it to this call.
*
* This call does not fail. During this call a #GSettingsBackend::changed
* signal will be emitted if any keys have been changed. The new values of
* all updated keys will be visible to any signal callbacks.
*
* One possible method that an implementation might deal with failures is
* to emit a second "changed" signal (either during this call, or later)
* to indicate that the affected keys have suddenly "changed back" to their
* old values.
*/
gboolean
g_settings_backend_write_tree (GSettingsBackend *backend,
GTree *tree,
gpointer origin_tag)
{
return G_SETTINGS_BACKEND_GET_CLASS (backend)
->write_tree (backend, tree, origin_tag);
}
/*< private >
* g_settings_backend_reset:
* @backend: a #GSettingsBackend implementation
* @key: the name of a key
* @origin_tag: the origin tag
*
* "Resets" the named key to its "default" value (ie: after system-wide
* defaults, mandatory keys, etc. have been taken into account) or possibly
* unsets it.
*/
void
g_settings_backend_reset (GSettingsBackend *backend,
const gchar *key,
gpointer origin_tag)
{
G_SETTINGS_BACKEND_GET_CLASS (backend)
->reset (backend, key, origin_tag);
}
/*< private >
* g_settings_backend_get_writable:
* @backend: a #GSettingsBackend implementation
* @key: the name of a key
*
* Finds out if a key is available for writing to. This is the
* interface through which 'lockdown' is implemented. Locked down
* keys will have %FALSE returned by this call.
*
* You should not write to locked-down keys, but if you do, the
* implementation will deal with it.
*
* Returns: %TRUE if the key is writable
*/
gboolean
g_settings_backend_get_writable (GSettingsBackend *backend,
const gchar *key)
{
return G_SETTINGS_BACKEND_GET_CLASS (backend)
->get_writable (backend, key);
}
/*< private >
* g_settings_backend_unsubscribe:
* @backend: a #GSettingsBackend
* @name: a key or path to subscribe to
*
* Reverses the effect of a previous call to
* g_settings_backend_subscribe().
*/
void
g_settings_backend_unsubscribe (GSettingsBackend *backend,
const char *name)
{
G_SETTINGS_BACKEND_GET_CLASS (backend)
->unsubscribe (backend, name);
}
/*< private >
* g_settings_backend_subscribe:
* @backend: a #GSettingsBackend
* @name: a key or path to subscribe to
*
* Requests that change signals be emitted for events on @name.
*/
void
g_settings_backend_subscribe (GSettingsBackend *backend,
const gchar *name)
{
G_SETTINGS_BACKEND_GET_CLASS (backend)
->subscribe (backend, name);
}
static void
g_settings_backend_finalize (GObject *object)
{
GSettingsBackend *backend = G_SETTINGS_BACKEND (object);
g_mutex_clear (&backend->priv->lock);
G_OBJECT_CLASS (g_settings_backend_parent_class)
->finalize (object);
}
static void
ignore_subscription (GSettingsBackend *backend,
const gchar *key)
{
}
static GVariant *
g_settings_backend_real_read_user_value (GSettingsBackend *backend,
const gchar *key,
const GVariantType *expected_type)
{
return g_settings_backend_read (backend, key, expected_type, FALSE);
}
static void
g_settings_backend_init (GSettingsBackend *backend)
{
backend->priv = g_settings_backend_get_instance_private (backend);
g_mutex_init (&backend->priv->lock);
}
static void
g_settings_backend_class_init (GSettingsBackendClass *class)
{
GObjectClass *gobject_class = G_OBJECT_CLASS (class);
class->subscribe = ignore_subscription;
class->unsubscribe = ignore_subscription;
class->read_user_value = g_settings_backend_real_read_user_value;
gobject_class->finalize = g_settings_backend_finalize;
}
static void
g_settings_backend_variant_unref0 (gpointer data)
{
if (data != NULL)
g_variant_unref (data);
}
/*< private >
* g_settings_backend_create_tree:
*
* This is a convenience function for creating a tree that is compatible
* with g_settings_backend_write(). It merely calls g_tree_new_full()
* with strcmp(), g_free() and g_variant_unref().
*
* Returns: a new #GTree
*/
GTree *
g_settings_backend_create_tree (void)
{
return g_tree_new_full ((GCompareDataFunc) strcmp, NULL,
g_free, g_settings_backend_variant_unref0);
}
static gboolean
g_settings_backend_verify (gpointer impl)
{
GSettingsBackend *backend = impl;
if (strcmp (G_OBJECT_TYPE_NAME (backend), "GMemorySettingsBackend") == 0 &&
g_strcmp0 (g_getenv ("GSETTINGS_BACKEND"), "memory") != 0)
{
g_message ("Using the 'memory' GSettings backend. Your settings "
"will not be saved or shared with other applications.");
}
g_settings_has_backend = TRUE;
return TRUE;
}
/* We need to cache the default #GSettingsBackend for the entire process
* lifetime, especially if the backend is #GMemorySettingsBackend: it needs to
* keep the in-memory settings around even while there are no #GSettings
* instances alive. */
static GSettingsBackend *settings_backend_default_singleton = NULL; /* (owned) (atomic) */
/**
* g_settings_backend_get_default:
*
* Returns the default #GSettingsBackend. It is possible to override
* the default by setting the `GSETTINGS_BACKEND` environment variable
* to the name of a settings backend.
*
* The user gets a reference to the backend.
*
* Returns: (not nullable) (transfer full): the default #GSettingsBackend,
* which will be a dummy (memory) settings backend if no other settings
* backend is available.
*
* Since: 2.28
*/
GSettingsBackend *
g_settings_backend_get_default (void)
{
if (g_once_init_enter (&settings_backend_default_singleton))
{
GSettingsBackend *singleton;
singleton = _g_io_module_get_default (G_SETTINGS_BACKEND_EXTENSION_POINT_NAME,
"GSETTINGS_BACKEND",
g_settings_backend_verify);
g_once_init_leave (&settings_backend_default_singleton, singleton);
}
return g_object_ref (settings_backend_default_singleton);
}
/*< private >
* g_settings_backend_get_permission:
* @backend: a #GSettingsBackend
* @path: a path
*
* Gets the permission object associated with writing to keys below
* @path on @backend.
*
* If this is not implemented in the backend, then a %TRUE
* #GSimplePermission is returned.
*
* Returns: (not nullable) (transfer full): a non-%NULL #GPermission.
* Free with g_object_unref()
*/
GPermission *
g_settings_backend_get_permission (GSettingsBackend *backend,
const gchar *path)
{
GSettingsBackendClass *class = G_SETTINGS_BACKEND_GET_CLASS (backend);
if (class->get_permission)
return class->get_permission (backend, path);
return g_simple_permission_new (TRUE);
}
/*< private >
* g_settings_backend_sync_default:
*
* Syncs the default backend.
*/
void
g_settings_backend_sync_default (void)
{
if (g_settings_has_backend)
{
GSettingsBackendClass *class;
GSettingsBackend *backend;
backend = g_settings_backend_get_default ();
class = G_SETTINGS_BACKEND_GET_CLASS (backend);
if (class->sync)
class->sync (backend);
g_object_unref (backend);
}
}
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