path: root/src/libtracker-sparql/tracker-namespace-manager.c

/*
 * Copyright (C) 2016, Sam Thursfield <sam@afuera.me.uk>
 *
 * 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, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA  02110-1301, USA.
 */

#include "config.h"

#include <string.h>
#include <stdlib.h>

#include <glib.h>

#include "tracker-namespace-manager.h"
#include "tracker-ontologies.h"

#define MAX_PREFIX_LENGTH 100

struct _TrackerNamespaceManager {
	GObject parent;
};

typedef struct {
	GHashTable *prefix_to_namespace;
	GHashTable *namespace_to_prefix;
} TrackerNamespaceManagerPrivate;

G_DEFINE_TYPE_WITH_PRIVATE (TrackerNamespaceManager, tracker_namespace_manager, G_TYPE_OBJECT);
#define GET_PRIVATE(object)  (tracker_namespace_manager_get_instance_private (object))

/**
 * SECTION: tracker-namespace-manager
 * @short_description: A set of well-known namespaces, and known abbreviations for them
 * @title: TrackerNamespaceManager
 * @stability: Stable
 * @include: tracker-namespace-manager.h
 *
 * <para>
 * #TrackerNamespaceManager keeps track of namespaces. It allows you to assign
 * short prefixes for them to avoid typing full URLs all the time.
 *
 * The syntax used is that of Compact URIs (CURIEs) as defined here:
 * (https://www.w3.org/TR/2010/NOTE-curie-20101216)
 *
 * Usually you will want to use the default namespace manager, as returned by
 * tracker_namespace_manager_get_default(). This has a set of well-known
 * prefixes predefined.
 * </para>
 */

static void finalize     (GObject *object);

static void
tracker_namespace_manager_class_init (TrackerNamespaceManagerClass *klass)
{
	GObjectClass *object_class = G_OBJECT_CLASS (klass);

	object_class->finalize     = finalize;
}

static void
tracker_namespace_manager_init (TrackerNamespaceManager *self)
{
	TrackerNamespaceManagerPrivate *priv = GET_PRIVATE (self);

	priv->prefix_to_namespace = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_free);
	priv->namespace_to_prefix = g_hash_table_new_full (g_str_hash, g_str_equal, g_free, g_free);
}

static void
finalize (GObject *object)
{
	TrackerNamespaceManagerPrivate *priv;

	priv = GET_PRIVATE (TRACKER_NAMESPACE_MANAGER (object));

	g_hash_table_unref (priv->prefix_to_namespace);
	g_hash_table_unref (priv->namespace_to_prefix);

	(G_OBJECT_CLASS (tracker_namespace_manager_parent_class)->finalize)(object);
}

/**
 * tracker_namespace_manager_new:
 *
 * Creates a new #TrackerNamespaceManager instance.
 *
 * Returns: a new #TrackerNamespaceManager instance
 *
 * Since: 1.10
 */
TrackerNamespaceManager *
tracker_namespace_manager_new ()
{
	TrackerNamespaceManager *namespace_manager;

	namespace_manager = g_object_new (TRACKER_TYPE_NAMESPACE_MANAGER, NULL);

	return namespace_manager;
}

/**
 * tracker_namespace_manager_get_default:
 *
 * Returns the global #TrackerNamespaceManager that contains a set of well-known
 * namespaces and prefixes, such as rdf:, rdfs:, nie:, tracker:, etc.
 *
 * Note that the list of prefixes and namespaces is hardcoded in
 * libtracker-sparql. It may not correspond with the installed set of
 * ontologies, if they have been modified since they were installed.
 *
 * Returns: (transfer none): a global, shared #TrackerNamespaceManager instance
 *
 * Since: 1.10
 */
TrackerNamespaceManager *
tracker_namespace_manager_get_default ()
{
	static TrackerNamespaceManager * volatile default_namespace_manager__volatile = NULL;

	if (g_once_init_enter (&default_namespace_manager__volatile)) {
		TrackerNamespaceManager *manager = tracker_namespace_manager_new();

		tracker_namespace_manager_add_prefix (manager, "rdf", TRACKER_PREFIX_RDF);
		tracker_namespace_manager_add_prefix (manager, "rdfs", TRACKER_PREFIX_RDFS);
		tracker_namespace_manager_add_prefix (manager, "xsd", TRACKER_PREFIX_XSD);
		tracker_namespace_manager_add_prefix (manager, "tracker", TRACKER_PREFIX_TRACKER);
		tracker_namespace_manager_add_prefix (manager, "dc", TRACKER_PREFIX_DC);

		tracker_namespace_manager_add_prefix (manager, "nrl", TRACKER_PREFIX_NRL);
		tracker_namespace_manager_add_prefix (manager, "nmo", TRACKER_PREFIX_NMO);
		tracker_namespace_manager_add_prefix (manager, "nie", TRACKER_PREFIX_NIE);
		tracker_namespace_manager_add_prefix (manager, "nco", TRACKER_PREFIX_NCO);
		tracker_namespace_manager_add_prefix (manager, "nao", TRACKER_PREFIX_NAO);
		tracker_namespace_manager_add_prefix (manager, "nid3", TRACKER_PREFIX_NID3);
		tracker_namespace_manager_add_prefix (manager, "nfo", TRACKER_PREFIX_NFO);

		tracker_namespace_manager_add_prefix (manager, "slo", TRACKER_PREFIX_SLO);
		tracker_namespace_manager_add_prefix (manager, "nmm", TRACKER_PREFIX_NMM);
		tracker_namespace_manager_add_prefix (manager, "mlo", TRACKER_PREFIX_MLO);
		tracker_namespace_manager_add_prefix (manager, "mfo", TRACKER_PREFIX_MFO);
		tracker_namespace_manager_add_prefix (manager, "osinfo", TRACKER_PREFIX_OSINFO);

		g_once_init_leave (&default_namespace_manager__volatile, manager);
	}

	return default_namespace_manager__volatile;
}

/**
 * tracker_namespace_manager_has_prefix:
 * @self: a #TrackerNamespaceManager
 * @prefix: a string
 *
 * Returns: %TRUE if the #TrackerNamespaceManager knows about @prefix, %FALSE otherwise
 *
 * Since: 1.10
 */
gboolean
tracker_namespace_manager_has_prefix (TrackerNamespaceManager *self,
                                      const char              *prefix)
{
	TrackerNamespaceManagerPrivate *priv;

	g_return_val_if_fail (TRACKER_IS_NAMESPACE_MANAGER (self), FALSE);

	priv = GET_PRIVATE (self);

	return g_hash_table_contains (priv->prefix_to_namespace, prefix);
}

/**
 * tracker_namespace_manager_lookup_prefix:
 * @self: a #TrackerNamespaceManager
 * @prefix: a string
 *
 * Looks up the namespace URI corresponding to @prefix, or %NULL if the prefix
 * is not known.
 *
 * Returns: a string owned by the #TrackerNamespaceManager, or %NULL
 *
 * Since: 1.10
 */
const char *
tracker_namespace_manager_lookup_prefix (TrackerNamespaceManager *self,
                                         const char              *prefix)
{
	TrackerNamespaceManagerPrivate *priv;

	g_return_val_if_fail (TRACKER_IS_NAMESPACE_MANAGER (self), NULL);

	priv = GET_PRIVATE (self);

	return g_hash_table_lookup (priv->prefix_to_namespace, prefix);
}

/**
 * tracker_namespace_manager_add_prefix:
 * @self: a #TrackerNamespaceManager
 * @prefix: a short, unique prefix to identify @namespace
 * @namespace: the URL of the given namespace
 *
 * Adds @prefix as the recognised abbreviaton of @namespace.
 *
 * Only one prefix is allowed for a given namespace, and all prefixes must
 * be unique.
 *
 * Since: 1.10
 */
void
tracker_namespace_manager_add_prefix (TrackerNamespaceManager *self,
                                      const char              *prefix,
                                      const char              *namespace)
{
	TrackerNamespaceManagerPrivate *priv;
	const char *str;

	g_return_if_fail (TRACKER_IS_NAMESPACE_MANAGER (self));
	g_return_if_fail (prefix != NULL);
	g_return_if_fail (namespace != NULL);

	priv = GET_PRIVATE (TRACKER_NAMESPACE_MANAGER (self));

	if (strlen (prefix) > MAX_PREFIX_LENGTH) {
		g_error ("Prefix is too long: max %i characters.", MAX_PREFIX_LENGTH);
		return;
	}

	str = g_hash_table_lookup (priv->prefix_to_namespace, prefix);
	if (str) {
		g_error ("Prefix %s already points to %s", prefix, str);
		return;
	}

	str = g_hash_table_lookup (priv->namespace_to_prefix, namespace);
	if (str) {
		g_error ("Namespace %s already has prefix %s", namespace, str);
		return;
	}

	g_hash_table_insert (priv->prefix_to_namespace, g_strdup (prefix), g_strdup (namespace));
	g_hash_table_insert (priv->namespace_to_prefix, g_strdup (namespace), g_strdup (prefix));
}

/**
 * tracker_namespace_manager_expand_uri:
 * @self: a #TrackerNamespaceManager
 * @compact_uri: a URI or compact URI
 *
 * If @compact_uri begins with one of the prefixes known to this
 * #TrackerNamespaceManager, then the return value will be the
 * expanded URI. Otherwise, a copy of @compact_uri will be returned.
 *
 * Returns: a newly-allocated string
 *
 * Since: 1.10
 */
char *
tracker_namespace_manager_expand_uri (TrackerNamespaceManager *self,
                                      const char              *compact_uri)
{
	TrackerNamespaceManagerPrivate *priv;

	char prefix[MAX_PREFIX_LENGTH + 1] = { 0 };
	char *colon;
	char *namespace = NULL;

	g_return_val_if_fail (TRACKER_IS_NAMESPACE_MANAGER (self), NULL);
	g_return_val_if_fail (compact_uri != NULL, NULL);

	priv = GET_PRIVATE (self);

	colon = strchr (compact_uri, ':');
	if (colon != NULL) {
		int colon_pos = colon - compact_uri;
		if (colon_pos < MAX_PREFIX_LENGTH) {
			strncpy (prefix, compact_uri, colon_pos - 1);
			prefix[colon_pos] = 0;

			namespace = g_hash_table_lookup (priv->prefix_to_namespace, prefix);
		}
	}

	if (namespace) {
		return g_strconcat (namespace, colon, NULL);
	} else {
		return g_strdup (compact_uri);
	}
}

/**
 * tracker_namespace_manager_print_turtle:
 * @self: a #TrackerNamespaceManager
 *
 * Writes out all namespaces as Turtle @prefix statements.
 *
 * Returns: a newly-allocated string
 *
 * Since: 1.10
 */
char *
tracker_namespace_manager_print_turtle (TrackerNamespaceManager *self)
{
	TrackerNamespaceManagerPrivate *priv;
	GString *result = g_string_new ("");
	GHashTableIter iter;
	const char *prefix;
	const char *namespace;

	g_return_val_if_fail (TRACKER_IS_NAMESPACE_MANAGER (self), NULL);

	priv = GET_PRIVATE (self);

	g_hash_table_iter_init (&iter, priv->prefix_to_namespace);
	while (g_hash_table_iter_next (&iter, (gpointer *)&prefix, (gpointer *)&namespace)) {
		g_string_append_printf (result, "@prefix %s: <%s> .\n", prefix, namespace);
	}

	return g_string_free (result, FALSE);
}

/**
 * tracker_namespace_manager_foreach:
 * @self: a #TrackerNamespaceManager
 * @func: the function to call for each prefix / URI pair
 * @user_data: user data to pass to the function
 *
 * Calls @func for each known prefix / URI pair.
 *
 * Since: 1.10
 */
void
tracker_namespace_manager_foreach (TrackerNamespaceManager *self,
                                   GHFunc                   func,
                                   gpointer                 user_data)
{
	TrackerNamespaceManagerPrivate *priv = GET_PRIVATE (self);

	g_hash_table_foreach (priv->prefix_to_namespace, func, user_data);
};