bluez5: add abstraction for remote DBus objects

Add framework for enumerating remote objects via DBus object manager
interfaces.

spa/plugins/bluez5/dbus-monitor.h

@@ -0,0 +1,139 @@
+/* Spa dbus
+ *
+ * Copyright © 2022 Pauli Virtanen
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef SPA_DBUS_MONITOR_H_
+#define SPA_DBUS_MONITOR_H_
+
+#include <dbus/dbus.h>
+
+#include <spa/utils/list.h>
+#include <spa/support/log.h>
+
+struct spa_dbus_object;
+
+/**
+ * DBus interface specification.
+ */
+struct spa_dbus_interface {
+	/** DBus interface name. */
+	const char *name;
+
+	/** Size of object struct. Must be at least sizeof(struct spa_dbus_object). */
+	const size_t object_size;
+
+	/** Property value updated. */
+	void (*property) (struct spa_dbus_object *object, const char *key, DBusMessageIter *value);
+
+	/** Interface at the object path added, or property updates complete. */
+	void (*update) (struct spa_dbus_object *object);
+
+	/**
+	 * Interface at the object path removed.
+	 * The object will be deallocated after this, so any associated data,
+	 * for example in a custom object struct, can be freed in this hook.
+	 */
+	void (*remove) (struct spa_dbus_object *object);
+};
+
+/**
+ * DBus object instance, for one interface.
+ *
+ * A custom object struct can be also used for each interface, specified
+ * as
+ *
+ *     struct my_dbus_object {
+ *         struct spa_dbus_object object;
+ *         int some_extra_value;
+ *     }
+ *
+ * The struct will be zero-initialized when first allocated. The object
+ * instances are owned by spa_dbus_monitor and allocated and freed by it.
+ */
+struct spa_dbus_object
+{
+	struct spa_list link;	/**< Link in interface's object list */
+	const char *path;	/**< DBus object path */
+	const struct spa_dbus_interface *interface;	/**< The interface of the object */
+	void *user_data;	/**< Pointer passed in spa_dbus_monitor_new */
+};
+
+/** DBus object monitor */
+struct spa_dbus_monitor
+{
+	const char *service;	/**< Service name */
+	const char *path;	/**< Object path */
+	const struct spa_dbus_interface *interfaces;	/**< Monitored interfaces
+							 * (zero-terminated) */
+	void *user_data;	/**< Pointer passed in spa_dbus_monitor_new */
+};
+
+/**
+ * Non-DBus interface type representing the monitored service itself.
+ * Can be used to track NameOwner events.
+ */
+#define SPA_DBUS_MONITOR_NAME_OWNER_INTERFACE	"org.freedesktop.pipewire.spa.dbus.monitor.owner"
+
+/**
+ * Create new object monitor.
+ *
+ * \param conn DBus connection
+ * \param service DBus service name to monitor
+ * \param path Object path to monitor
+ * \param interfaces Zero-terminated array of interfaces to monitor. Corresponding objects
+ *                   will be created.
+ * \param log Log to output to
+ * \param user_data User data to set in object instances.
+ */
+struct spa_dbus_monitor *spa_dbus_monitor_new(DBusConnection *conn,
+		const char *service,
+		const char *path,
+		const struct spa_dbus_interface *interfaces,
+		struct spa_log *log,
+		void *user_data);
+
+/**
+ * Destroy object monitor and all interface objects owned by it.
+ */
+void spa_dbus_monitor_destroy(struct spa_dbus_monitor *monitor);
+
+/** Find interface object by name */
+struct spa_dbus_object *spa_dbus_monitor_find(struct spa_dbus_monitor *monitor,
+		const char *path, const char *interface);
+
+/** Destroy an object, and don't receive further updates concerning it. */
+void spa_dbus_monitor_ignore_object(struct spa_dbus_monitor *monitor,
+		struct spa_dbus_object *object);
+
+/**
+ * Get the object list for the named interface.
+ *
+ * The returned list is not mutable.
+ *
+ * \param monitor The DBus monitor.
+ * \param interface Interface name. Must be one of those monitored.
+ */
+struct spa_list *spa_dbus_monitor_object_list(struct spa_dbus_monitor *monitor,
+		const char *interface);
+
+#endif