自学教程：C++ x_check_conn函数代码示例

/** * Request the current id broadcast. This will be called then the * current playing id is changed. New song for example. */xmmsc_result_t *xmmsc_broadcast_playback_current_id (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_broadcast_msg (c, XMMS_IPC_SIGNAL_PLAYBACK_CURRENTID);}

xmmsc_result_t *xmmsc_visualization_init (xmmsc_connection_t *c){	xmmsc_result_t *res = NULL;	x_check_conn (c, 0);	c->visc++;	c->visv = realloc (c->visv, sizeof (xmmsc_visualization_t*) * c->visc);	if (!c->visv) {		x_oom ();		c->visc = 0;	}	if (c->visc > 0) {		int vv = c->visc-1;		if (!(c->visv[vv] = x_new0 (xmmsc_visualization_t, 1))) {			x_oom ();		} else {			c->visv[vv]->idx = vv;			c->visv[vv]->state = VIS_NEW;			res = xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_VISUALIZATION, XMMS_IPC_CMD_VISUALIZATION_REGISTER);			if (res) {				xmmsc_result_visc_set (res, c->visv[vv]);			}		}	}	return res;}

/** * Requests the playback status broadcast. This will be called when * events like play, stop and pause is triggered. */xmmsc_result_t *xmmsc_broadcast_playback_status (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_broadcast_msg (c, XMMS_IPC_SIGNAL_PLAYBACK_STATUS);}

xmmsc_result_t *xmmsc_visualization_start (xmmsc_connection_t *c, int vv){	xmmsc_result_t *res;	xmmsc_visualization_t *v;	x_check_conn (c, 0);	v = get_dataset (c, vv);	x_api_error_if (!v, "with unregistered/unconnected visualization dataset", 0);	switch (v->state) {	case VIS_WORKING:	case VIS_ERRORED:		break;	case VIS_NEW:#ifdef HAVE_SEMTIMEDOP		/* first try unixshm */		v->type = VIS_UNIXSHM;		res = setup_shm_prepare (c, vv);		v->state = VIS_TRYING_UNIXSHM;		break;#endif	case VIS_TO_TRY_UDP:		v->type = VIS_UDP;		res = setup_udp_prepare (c, vv);		v->state = VIS_TRYING_UDP;		break;	default:		v->state = VIS_ERRORED;		x_api_warning ("out of sequence");		break;	}	return res;}

/** * Request the playlist current pos broadcast. When the position * in the playlist is changed this will be called. */xmmsc_result_t *xmmsc_broadcast_playlist_current_pos (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_broadcast_msg (c, XMMS_IPC_SIGNAL_PLAYLIST_CURRENT_POS);}

xmmsc_result_t *xmmsc_playback_pause (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_PLAYBACK, XMMS_IPC_CMD_PAUSE);}

/** * Stop decoding of current song. This will start decoding of the song * set with xmmsc_playlist_set_next, or the current song again if no * xmmsc_playlist_set_next was executed. */xmmsc_result_t *xmmsc_playback_tickle (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_PLAYBACK, XMMS_IPC_CMD_DECODER_KILL);}

/** * Request the playlist_loaded broadcast. This will be called * if a playlist is loaded server-side. The argument will be a string * with the playlist name. */xmmsc_result_t *xmmsc_broadcast_playlist_loaded (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_broadcast_msg (c, XMMS_IPC_SIGNAL_PLAYLIST_LOADED);}

/** * Queries the medialib for media and inserts the matching ones to * the current playlist at the given position. * * @param c The connection structure. * @param playlist The playlist in which to insert the media. * @param pos A position in the playlist * @param coll The collection to find media in the medialib. * @param order The list of properties by which to order the matching *              media, passed as an #xmmsv_t list of strings. */xmmsc_result_t *xmmsc_playlist_insert_collection (xmmsc_connection_t *c, const char *playlist,                                  int pos, xmmsv_coll_t *coll,                                  xmmsv_t *order){	xmms_ipc_msg_t *msg;	x_check_conn (c, NULL);	/* default to the active playlist */	if (playlist == NULL) {		playlist = XMMS_ACTIVE_PLAYLIST;	}	/* default to empty ordering */	msg = xmms_ipc_msg_new (XMMS_IPC_OBJECT_PLAYLIST, XMMS_IPC_CMD_INSERT_COLL);	xmms_ipc_msg_put_string (msg, playlist);	xmms_ipc_msg_put_int32 (msg, pos);	xmms_ipc_msg_put_collection (msg, coll);	xmms_ipc_msg_put_value_list (msg, order); /* purposedly skip typing */	return xmmsc_send_msg (c, msg);}

/** * Request the collection changed broadcast from the server. Everytime someone * manipulates a collection this will be emitted. */xmmsc_result_t*xmmsc_broadcast_collection_changed (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_broadcast_msg (c, XMMS_IPC_SIGNAL_COLLECTION_CHANGED);}

/** * Search for a entry (URL) in the medialib db and return its ID number * * Same as #xmmsc_medialib_get_id but expects a encoded URL instead * * @param conn The #xmmsc_connection_t * @param url The URL to search for */xmmsc_result_t *xmmsc_medialib_get_id_encoded (xmmsc_connection_t *conn, const char *url){	x_check_conn (conn, NULL);	return do_methodcall (conn, XMMS_IPC_CMD_GET_ID, url);}

/** * List the ids of all media matched by the given collection. * A list of ordering properties can be specified, as well as offsets * to only retrieve part of the result set. * * @param conn  The connection to the server. * @param coll  The collection used to query. * @param order  The list of properties to order by, passed as an #xmmsv_t list of strings. * @param limit_start  The offset at which to start retrieving results (0 to disable). * @param limit_len  The maximum number of entries to retrieve (0 to disable). */xmmsc_result_t*xmmsc_coll_query_ids (xmmsc_connection_t *conn, xmmsv_coll_t *coll,                      xmmsv_t *order, int limit_start,                      int limit_len){	xmms_ipc_msg_t *msg;	x_check_conn (conn, NULL);	x_api_error_if (!coll, "with a NULL collection", NULL);	/* default to empty ordering */	if (!order) {		order = xmmsv_new_list ();	} else {		xmmsv_ref (order);	}	msg = xmms_ipc_msg_new (XMMS_IPC_OBJECT_COLLECTION, XMMS_IPC_CMD_QUERY_IDS);	xmms_ipc_msg_put_collection (msg, coll);	xmms_ipc_msg_put_int32 (msg, limit_start);	xmms_ipc_msg_put_int32 (msg, limit_len);	xmms_ipc_msg_put_value_list (msg, order); /* purposedly skip typing */	xmmsv_unref (order);	return xmmsc_send_msg (conn, msg);}

/** * Request the playback_playtime signal. Will update the * time we have played the current entry. */xmmsc_result_t *xmmsc_signal_playback_playtime (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_signal_msg (c, XMMS_IPC_SIGNAL_PLAYBACK_PLAYTIME);}

/** * Request the medialib_entry_changed broadcast. This will be called * if a entry changes on the serverside. The argument will be an medialib * id. */xmmsc_result_t *xmmsc_broadcast_medialib_entry_changed (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_broadcast_msg (c, XMMS_IPC_SIGNAL_MEDIALIB_ENTRY_UPDATE);}

/** * Retrive the name of the active playlist */xmmsc_result_t *xmmsc_playlist_current_active (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_PLAYLIST, XMMS_IPC_CMD_CURRENT_ACTIVE);}

xmmsc_result_t *xmmsc_broadcast_playback_volume_changed (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_broadcast_msg (c, XMMS_IPC_SIGNAL_PLAYBACK_VOLUME_CHANGED);}

xmmsc_result_t *xmmsc_visualization_version (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_VISUALIZATION, XMMS_IPC_CMD_VISUALIZATION_QUERY_VERSION);}

/** * Request number of unindexed entries in medialib. */xmmsc_result_t *xmmsc_signal_mediainfo_reader_unindexed (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_signal_msg (c, XMMS_IPC_SIGNAL_MEDIAINFO_READER_UNINDEXED);}

/** * Request status for the mediainfo reader. It can be idle or working */xmmsc_result_t *xmmsc_broadcast_mediainfo_reader_status (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_broadcast_msg (c, XMMS_IPC_SIGNAL_MEDIAINFO_READER_STATUS);}

/** * Get a list of statistics from the server */xmmsc_result_t *xmmsc_main_stats (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_MAIN, XMMS_IPC_CMD_STATS);}

/** * Make server emit the playback status. */xmmsc_result_t *xmmsc_playback_status (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_PLAYBACK,	                              XMMS_IPC_CMD_PLAYBACK_STATUS);}

/** * List all bindata hashes stored on the server */xmmsc_result_t *xmmsc_bindata_list (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_cmd (c, XMMS_IPC_OBJECT_BINDATA, XMMS_IPC_CMD_LIST_DATA,	                       XMMSV_LIST_END);}

/** * Remove a file with associated with the hash from the server */xmmsc_result_t *xmmsc_bindata_remove (xmmsc_connection_t *c, const char *hash){	x_check_conn (c, NULL);	return xmmsc_send_cmd (c, XMMS_IPC_OBJECT_BINDATA, XMMS_IPC_CMD_REMOVE_DATA,	                       XMMSV_LIST_ENTRY_STR (hash), XMMSV_LIST_END);}

/** * Get a list of loaded plugins from the server */xmmsc_result_t *xmmsc_main_list_plugins (xmmsc_connection_t *c, xmms_plugin_type_t type){	x_check_conn (c, NULL);	return xmmsc_send_cmd (c, XMMS_IPC_OBJECT_MAIN, XMMS_IPC_CMD_PLUGIN_LIST,	                       XMMSV_LIST_ENTRY_INT (type), XMMSV_LIST_END);}

/** * Retrieve information about a entry from the medialib. */xmmsc_result_t *xmmsc_medialib_get_info (xmmsc_connection_t *c, int id){	x_check_conn (c, NULL);	return xmmsc_send_cmd (c, XMMS_IPC_OBJECT_MEDIALIB, XMMS_IPC_CMD_INFO,	                       XMMSV_LIST_ENTRY_INT (id), XMMSV_LIST_END);}

xmmsc_result_t *xmmsc_playback_volume_get (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_PLAYBACK,	                              XMMS_IPC_CMD_VOLUME_GET);}

/** * Make server emit the current id. */xmmsc_result_t *xmmsc_playback_current_id (xmmsc_connection_t *c){	x_check_conn (c, NULL);	return xmmsc_send_msg_no_arg (c, XMMS_IPC_OBJECT_PLAYBACK,	                              XMMS_IPC_CMD_CURRENTID);}

/** * Remove a entry from the medialib * @param conn The #xmmsc_connection_t * @param entry The entry id you want to remove */xmmsc_result_t *xmmsc_medialib_remove_entry (xmmsc_connection_t *conn, int entry){	x_check_conn (conn, NULL);	return xmmsc_send_cmd (conn, XMMS_IPC_OBJECT_MEDIALIB,	                       XMMS_IPC_CMD_REMOVE_ID,	                       XMMSV_LIST_ENTRY_INT (entry),	                       XMMSV_LIST_END);}

/** * Rehash the medialib, this will check data in the medialib * still is the same as the data in files. * * @param conn #xmmsc_connection_t * @param id The id to rehash. Set it to 0 if you want to rehash * the whole medialib. */xmmsc_result_t *xmmsc_medialib_rehash (xmmsc_connection_t *conn, int id){	x_check_conn (conn, NULL);	return xmmsc_send_cmd (conn, XMMS_IPC_OBJECT_MEDIALIB,	                       XMMS_IPC_CMD_REHASH,	                       XMMSV_LIST_ENTRY_INT (id),	                       XMMSV_LIST_END);}

/** * Add a URL to the medialib. If you want to add mutiple files * you should call #xmmsc_medialib_import_path * * same as #xmmsc_medialib_add_entry but expects a encoded URL * instead * * @param conn The #xmmsc_connection_t * @param url URL to add to the medialib. */xmmsc_result_t *xmmsc_medialib_add_entry_encoded (xmmsc_connection_t *conn, const char *url){	x_check_conn (conn, NULL);	if (!_xmmsc_medialib_verify_url (url))		x_api_error ("with a non encoded url", NULL);	return do_methodcall (conn, XMMS_IPC_CMD_MLIB_ADD_URL, url);}