libnjb: The playlist manipulation API

int NJB_Delete_Playlist	(	njb_t *	njb,
		u_int32_t	plid
	)

This deletes a playlist from the device.

Parameters:

	njb	a pointer to the `njb_t` object to delete the playlist from
	plid	the playlist ID as reported from `NJB_Get_Playlist()`.

Returns:: 0 on success, -1 on failure.

Examples:: pl.c.

njb_playlist_t* NJB_Get_Playlist ( njb_t * njb )

This gets a playlist from the device. The device should first be rewound using the NJB_Reset_Get_Playlist() function. The playlists are newly allocated and should be destroyed with NJB_Playlist_Destroy() after use.

Parameters:

njb a pointer to the njb_t object to get playlists from

Returns:: a playlist or NULL if the last playlist has already been returned

See also:: NJB_Reset_Get_Playlist()
NJB_Playlist_Destroy()

Examples:: pl.c, and playlists.c.

void NJB_Playlist_Addtrack	(	njb_playlist_t *	pl,
		njb_playlist_track_t *	track,
		unsigned int	pos
	)

This function adds a playlist track (a data structure representing a track that is part of a playlist) to a playlist data structure.

Parameters:

	pl	the playlist that the track shall be added to
	track	the track to add
	pos	the position in the playlist where this track should be added

See also:: NJB_Playlist_Deltrack()

Examples:: pl.c.

void NJB_Playlist_Deltrack	(	njb_playlist_t *	pl,
		unsigned int	pos
	)

This function deletes a track from a playlist.

Parameters:

	pl	the playlist that the track shall be removed from
	pos	the position in the playlist to be deleted

See also:: NJB_Playlist_Addtrack()
NJB_Playlist_Deltrack_TrackID()

void NJB_Playlist_Deltrack_TrackID	(	njb_playlist_t *	pl,
		u_int32_t	trackid
	)

This function removes a track from a playlist by way of the track ID (as opposed to the position in the playlist). This function can be called even on playlists that don't have this track in them - this is useful for e.g. looping through all playlists and removing a certain track before deleting the track itself from the device.

You need to call the NJB_Update_Playlist() function for each playlist that has been manipulated by this function, to assure that any changes are written back to the playlist on the device.

Typical use to remove a track with ID id from all playlists on a device:

 njb_playlist_t *playlist;

 NJB_Reset_Get_Playlist(njb);
 while (playlist = NJB_Get_Playlist(njb)) {
    NJB_Playlist_Deltrack_TrackID(playlist, id);
    // If the playlist changed, update it
    if (NJB_Update_Playlist(njb, playlist) == -1)
        NJB_Error_Dump(njb, stderr);
    }
    NJB_Playlist_Destroy(playlist);
 }
 if (NJB_Error_Pending(njb)) {
    NJB_Error_Dump(njb, stderr);
 }

Parameters:

	pl	the playlist that the track shall be removed from, if present.
	trackid	the track ID to remove from this playlist

See also:: NJB_Playlist_Deltrack()
NJB_Update_Playlist()

void NJB_Playlist_Destroy ( njb_playlist_t * pl )

This function destroys a playlist and frees up the memory used by it. All tracks that are part of the playlist will also be destroyed.

Parameters:

pl

the playlist to destroy

Examples:: pl.c.

njb_playlist_track_t* NJB_Playlist_Gettrack ( njb_playlist_t * pl )

Returns a track from a playlist. The playlist has an internal structure to keep track of the constituent tracks, so the tracks will be retrieved in order. This function should typically be called repeatedly after an initial NJB_Playlist_Reset_Gettrack() call.

Parameters:

pl

the playlist to get tracks from.

Returns:: a track or NULL of the last track from a playlist has already been returned

See also:: NJB_Playlist_Reset_Gettrack()

Examples:: pl.c, and playlists.c.

njb_playlist_t* NJB_Playlist_New ( void )

This function creates a new playlist data structure to hold a name and a number of tracks.

Returns:: a new playlist structure

Examples:: pl.c.

void NJB_Playlist_Reset_Gettrack ( njb_playlist_t * pl )

Resets the internal counter used when retrieveing tracks from a playlist. Should typically be called first, before any subsequent calls to NJB_Playlist_Gettrack().

Parameters:

pl

the playlist to be reset

See also:: NJB_Playlist_Gettrack()

Examples:: pl.c, and playlists.c.

int NJB_Playlist_Set_Name	(	njb_playlist_t *	pl,
		const char *	name
	)

This function sets the name of the playlist. The name will be duplicated and stored internally, so the string is only needed during the function call.

Parameters:

	pl	the playlist to set the name for
	name	the name to set for the playlist

Examples:: pl.c.

void NJB_Playlist_Track_Destroy ( njb_playlist_track_t * track )

This destroys a playlist track entry and frees any memory used by it.

Parameters:

track

the track entry to destroy.

njb_playlist_track_t* NJB_Playlist_Track_New ( u_int32_t trackid )

This creates a new track entry for playlists. The trackid used should be the same as retrieved from libnjb track reading functions.

Parameters:

trackid

the ID of the new track

Returns:: the new playlist track entry

Examples:: pl.c.

void NJB_Reset_Get_Playlist ( njb_t * njb )

This resets the playlist retrieveal function. The playlists can then be retrieved one by one using the NJB_Get_Playlist() function.

Typical usage:

 njb_t *njb;
 njb_playlist_t *pl;

 NJB_Reset_Get_Playlist(njb);
 while ( (pl = NJB_Get_Playlist(njb)) != NULL ) {
    // Do something with all the playlists...
    NJB_Playlist_Destroy(pl);
 }

Parameters:

njb a pointer to the njb_t object to reset the playlist retrieveal pointer for

See also:: NJB_Get_Playlist()

Examples:: pl.c, and playlists.c.

int NJB_Update_Playlist	(	njb_t *	njb,
		njb_playlist_t *	pl
	)

This writes back an updated (modified) or new playlist to the device.

This function may modify the playlist ID, i.e. the plid member of the njb_playlist_t struct, which means that if your program has cached this number anywhere, you need to update it using the value from pl->plid afterwards. This stems from the fact that playlists are sometimes updated by deleting the old playlist and creating a new one.

Parameters:

	njb	a pointer to the `njb_t` object to update the playlist on
	pl	the playlist to update.

Returns:: 0 on success, -1 on failure.

Examples:: pl.c.


Defines
#define	NJB_PL_END 0
#define	NJB_PL_START 1
Functions
void	NJB_Reset_Get_Playlist (njb_t *njb)
njb_playlist_t *	NJB_Get_Playlist (njb_t *njb)
int	NJB_Delete_Playlist (njb_t *njb, u_int32_t plid)
int	NJB_Update_Playlist (njb_t njb, njb_playlist_t pl)
njb_playlist_t *	NJB_Playlist_New (void)
void	NJB_Playlist_Destroy (njb_playlist_t *pl)
void	NJB_Playlist_Addtrack (njb_playlist_t pl, njb_playlist_track_t track, unsigned int pos)
void	NJB_Playlist_Reset_Gettrack (njb_playlist_t *pl)
njb_playlist_track_t *	NJB_Playlist_Gettrack (njb_playlist_t *pl)
int	NJB_Playlist_Set_Name (njb_playlist_t pl, const char name)
void	NJB_Playlist_Deltrack (njb_playlist_t *pl, unsigned int pos)
void	NJB_Playlist_Deltrack_TrackID (njb_playlist_t *pl, u_int32_t trackid)
njb_playlist_track_t *	NJB_Playlist_Track_New (u_int32_t trackid)
void	NJB_Playlist_Track_Destroy (njb_playlist_track_t *track)

The playlist manipulation API

Defines

Functions

Function Documentation