libnjb: The track and tag (song ID metadata) manipulation API

int NJB_Delete_Track	(	njb_t *	njb,
		u_int32_t	trackid
	)

This deletes a track from the device.

Parameters:

	njb	a pointer to the `njb_t` jukebox object to use
	trackid	the track ID for the track to delete

Returns:: 0 on success, -1 on failure

Examples:: deltr.c.

void NJB_Get_Extended_Tags	(	njb_t *	njb,
		int	extended
	)

This configures libnjb to retrieve extended tags from the device. For the NJB1 this is the default behaviour anyway so it need not be set, but for the series 3 devices, retrieving the extended tag information is a costly operation that will slow down the initial track scanning by orders of magnitude and irritate the user. Make sure end-users can configure whether they want to use this or not.

The extended tags will include things like the filename and folder that the file used on the host before it was transfered to the device.

Parameters:

	njb	a pointer to the `njb_t` object to set this mode for
	extended	use 0 for non-exetended tags (default), 1 for extended tags

Examples:: tracks.c.

int NJB_Get_Track	(	njb_t *	njb,
		u_int32_t	fileid,
		u_int32_t	size,
		const char *	path,
		NJB_Xfer_Callback *	callback,
		void *	data
	)

This retrieves ("uploads") a track from the device to the host computer.

Parameters:

	njb	a pointer to the `njb_t` object to get the track from
	fileid	the unique trackid (also known as file ID, they are the same things) as reported by the device from e.g. `NJB_Get_Track_Tag()`.
	size	the size of the track in bytes. You know this size from previous calls to `NJB_Get_Track_Tag()` and it is needed among other things for displaying a progress bar and for determining that all bytes have been correctly retrieved.
	path	the path where the resulting file should be written. If this parameter is null, the blocks are delivered via the callback's buf parameter.
	callback	a function that will be called repeatedly to report progress during transfer, used for e.g. displaying progress bars
	data	a voluntary parameter that can associate some user-supplied data with each callback call. It is OK to set this to NULL of course.

Returns:: 0 on success, -1 on failure

See also:: NJB_Get_Track_fd()

Examples:: gettr.c.

int NJB_Get_Track_fd	(	njb_t *	njb,
		u_int32_t	fileid,
		u_int32_t	size,
		int	fd,
		NJB_Xfer_Callback *	callback,
		void *	data
	)

This retrieves ("uploads") a track from the device to the host computer by way of a file descriptor, which is good for e.g. streaming stuff. The daring type can start playing back audio from the file descriptor before it is finished. This is also good for fetching to temporary files, which are often only given as file descriptors.

Parameters:

	njb	a pointer to the `njb_t` object to get the track from
	fileid	the unique trackid (also known as file ID, they are the same things) as reported by the device from e.g. `NJB_Get_Track_Tag()`.
	size	the size of the track in bytes. You know this size from previous calls to `NJB_Get_Track_Tag()` and it is needed among other things for displaying a progress bar and for determining that all bytes have been correctly retrieved.
	fd	the file descriptor that shall be fed with the track contents. The file descriptor must be writable. On win32 make sure it is a binary descriptor and not textual.
	callback	a function that will be called repeatedly to report progress during transfer, used for e.g. displaying progress bars
	data	a voluntary parameter that can associate some user-supplied data with each callback call. It is OK to set this to NULL of course.

Returns:: 0 on success, -1 on failure

See also:: NJB_Get_Track()

njb_songid_t* NJB_Get_Track_Tag ( njb_t * njb )

This gets a track tag (song ID) from the device. The device should first be rewound using the NJB_Reset_Get_Track_Tag() function.

Notice that there is no function for getting the tag for a single track, there is just this function that dumps out the entire database in one big go. The recommended approach is to keep an internal track cache of all tracks and use this for getting metadata for single tracks. There is as far as we know no function in the Creative firmwares for getting the metadata of a single track, so access through this function is the only option.

Parameters:

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

Returns:: a track tag (song ID) or NULL if the last track tag has already been retrieved

See also:: NJB_Reset_Get_Track_Tag()

Examples:: gettr.c, and tracks.c.

int NJB_Replace_Track_Tag	(	njb_t *	njb,
		u_int32_t	trackid,
		njb_songid_t *	songid
	)

This routine will replace the track tag or parts of a track tag for a track that already exist on the device. On the NJB1 the whole metadata set must be specified for this routine to work properly, but on the series 3 devices you can specify incremental updates (only parts of the metadata set). Be sure to either specify the full set all the time, or check if we are handling an NJB1 before submitting an incremental update (see example below).

Parameters:

	njb	a pointer to the jukebox object to use
	trackid	the track ID to replace the tag for
	songid	the new tag

Typical usage:

 njb_t *njb;
 njb_songid_t *songid;
 njb_songid_frame_t *frame;

 songid = NJB_Songid_New();
 // On NJB1 incremental update is not possible, so a full
 // metadata set must always be specified.
 if (njb->device_type == NJB_DEVICE_NJB1) {
   frame = NJB_Songid_Frame_New_Codec(meta->codec);
   NJB_Songid_Addframe(songid, frame);
   frame = NJB_Songid_Frame_New_Filesize(meta->size);
   NJB_Songid_Addframe(songid, frame);
 }
 frame = NJB_Songid_Frame_New_Codec(NJB_CODEC_MP3);
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Title("MyTitle");
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Album("MyAlbum");
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Artist("MyArtist");
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Genre("MyGenre");
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Year(2004);
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Tracknum(1);
 NJB_Songid_Addframe(songid, frame);
 // The length of the track should typically be given, or such things
 // as progress indicators will stop working. If you absolutely want to
 // upload a file of unknown length and break progress indicators, set
 // length to 1 second.
 frame = NJB_Songid_Frame_New_Length(123);
 NJB_Songid_Addframe(songid, frame);
 // This one is optional, the track will survive without it.
 frame = NJB_Songid_Frame_New_Filename("Foo.mp3");
 NJB_Songid_Addframe(songid, frame);
 if (NJB_Replace_Track_Tag(njb, 123456, songid) == -1) {
    NJB_Error_Dump(stderr);
 }
 NJB_Songid_Destroy(songid);

Examples:: tagtr.c.

void NJB_Reset_Get_Track_Tag ( njb_t * njb )

This resets the track tag (song ID) retrieveal function. The track tags can then be retrieved one by one using the NJB_Get_Track_Tag() function.

Typical usage:

 njb_t *njb;
 njb_songid_t *song;

 NJB_Songid_Reset_Get_Track_Tag(njb);
 while ( (song = NJB_Get_Track_Tag(njb)) != NULL ) {
    // Do something with all the songs...
 }

Parameters:

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

See also:: NJB_Get_Track_Tag()

Examples:: gettr.c, and tracks.c.

int NJB_Send_Track	(	njb_t *	njb,
		const char *	path,
		njb_songid_t *	songid,
		NJB_Xfer_Callback *	callback,
		void *	data,
		u_int32_t *	trackid
	)

This sends ("downloads") a track (playable music file) to the device.

Typical usage:

 njb_t *njb;
 njb_songid_t *songid;
 njb_songid_frame_t *frame;
 u_int32_t id;

 songid = NJB_Songid_New();
 frame = NJB_Songid_Frame_New_Codec(NJB_CODEC_MP3);
 NJB_Songid_Addframe(songid, frame);
 // This one is optional - libnjb will fill it in if not specified
 frame = NJB_Songid_Frame_New_Filesize(12345678);
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Title("MyTitle");
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Album("MyAlbum");
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Artist("MyArtist");
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Genre("MyGenre");
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Year(2004);
 NJB_Songid_Addframe(songid, frame);
 frame = NJB_Songid_Frame_New_Tracknum(1);
 NJB_Songid_Addframe(songid, frame);
 // The length of the track should typically be given, or such things
 // as progress indicators will stop working. If you absolutely want to
 // upload a file of unknown length and break progress indicators, set
 // length to 1 second.
 frame = NJB_Songid_Frame_New_Length(123);
 NJB_Songid_Addframe(songid, frame);
 // This one is optional - libnjb will fill it in if not specified
 frame = NJB_Songid_Frame_New_Filename("Foo.mp3");
 NJB_Songid_Addframe(songid, frame);
 if (NJB_Send_Track (njb, "foo.mp3", songid, NULL, NULL, &id) == -1) {
     NJB_Error_Dump(stderr);
 }
 NJB_Songid_Destroy(songid);

Parameters:

	njb	a pointer to the `njb_t` object to send the track file to.
	path	the filesystem path on the local host to use as indata
	songid	the tag for this track, which has to be built separately before the transfer is started with a call to this function.
	callback	a function that will be called repeatedly to report progress during transfer, used for e.g. displaying progress bars. This may be NULL if you don't want any callbacks.
	data	a voluntary parameter that can associate some user-supplied data with each callback call. It is OK to set this to NULL of course.
	trackid	a pointer to an integer that will hold the resulting track ID after this transfer has commenced successfully.

Returns:: 0 on success, -1 on failure

See also:: NJB_Send_File()

Examples:: sendtr.c.

void NJB_Songid_Addframe	(	njb_songid_t *	song,
		njb_songid_frame_t *	frame
	)

This adds a song ID frame to a song ID.

Parameters:

	song	the song ID to add the frame to
	frame	the frame to add to this song ID

Examples:: sendtr.c, and tagtr.c.

void NJB_Songid_Destroy ( njb_songid_t * songid )

This destroys an entire song ID structure and free the memory used by it.

Parameters:

songid

the song ID structure to destroy

Examples:: gettr.c, sendtr.c, tagtr.c, and tracks.c.

njb_songid_frame_t* NJB_Songid_Findframe	(	njb_songid_t *	song,
		const char *	label
	)

This locates a particular song ID frame inside a song ID, by using the textual label given.

Parameters:

	song	the song ID to look in
	label	the textual label of the frame to look for

Returns:: the song ID frame if found, else NULL

Examples:: gettr.c.

void NJB_Songid_Frame_Destroy ( njb_songid_frame_t * frame )

This destroys a song ID frame and free any memory used by it.

Parameters:

frame

the song ID frame to destroy

njb_songid_frame_t* NJB_Songid_Frame_New_Codec ( const char * value )

This is a wrapper function to fix a common mistake made when creating codec frames: lowercase codec names and other strange mistakes.

Examples:: sendtr.c, and tagtr.c.

njb_songid_frame_t* NJB_Songid_Frame_New_String	(	const char *	label,
		const char *	value
	)

Creates a new string frame.

Parameters:

	label	the label of this string frame
	value	the string contained in this string frame

Returns:: valid string frame on success, NULL on failure

njb_songid_frame_t* NJB_Songid_Frame_New_Uint16	(	const char *	label,
		u_int16_t	value
	)

Creates a new unsigned 16-bit integer frame.

Parameters:

	label	the label of this unsigned 16-bit integer frame
	value	the unsigned 16-bit integer contained in this frame

Returns:: valid unsigned 16-bit integer frame on success, NULL on failure

njb_songid_frame_t* NJB_Songid_Frame_New_Uint32	(	const char *	label,
		u_int32_t	value
	)

Creates a new unsigned 32-bit integer frame.

Parameters:

	label	the label of this unsigned 32-bit integer frame
	value	the unsigned 32-bit integer contained in this frame

Returns:: valid unsigned 32-bit integer frame on success, NULL on failure

njb_songid_frame_t* NJB_Songid_Getframe ( njb_songid_t * song )

This gets the next song ID frame from a song ID structure.

Parameters:

song

the song ID to get frames from

Returns:: a song ID frame, or NULL if the last frame has already been returned.

See also:: NJB_Songid_Reset_Getframe()

Examples:: tracks.c.

njb_songid_t* NJB_Songid_New ( void )

This creates a new song ID holder structure. (A songid in turn contains several frames represening different metadata.)

Returns:: a new song ID structure

Examples:: sendtr.c, and tagtr.c.

void NJB_Songid_Reset_Getframe ( njb_songid_t * song )

This resets the internal pointer in the song ID so that it points to the first frame of the song ID. It should typically be called before subsequent calls to NJB_Songid_Getframe().

Typical usage:

 njb_songid_t *song;
 njb_songid_frame_t *frame;

 // Get a song ID into "song"...
 NJB_Songid_Reset_Getframe(song);
 while ( (frame = NJB_Songid_Getframe(song)) != NULL ) {
    // Do something with all the frames...
 }

Parameters:

song

the song ID structure whose internal frame pointer shall be reset.

See also:: NJB_Songid_Getframe()

Examples:: tracks.c.


Defines
#define	NJB_Songid_Frame_New_Title(a) NJB_Songid_Frame_New_String(FR_TITLE, a)
#define	NJB_Songid_Frame_New_Album(a) NJB_Songid_Frame_New_String(FR_ALBUM, a)
#define	NJB_Songid_Frame_New_Genre(a) NJB_Songid_Frame_New_String(FR_GENRE, a)
#define	NJB_Songid_Frame_New_Artist(a) NJB_Songid_Frame_New_String(FR_ARTIST, a)
#define	NJB_Songid_Frame_New_Length(a) NJB_Songid_Frame_New_Uint16(FR_LENGTH, a)
#define	NJB_Songid_Frame_New_Filesize(a) NJB_Songid_Frame_New_Uint32(FR_SIZE, a)
#define	NJB_Songid_Frame_New_Tracknum(a) NJB_Songid_Frame_New_Uint16(FR_TRACK, a)
#define	NJB_Songid_Frame_New_Year(a) NJB_Songid_Frame_New_Uint16(FR_YEAR, a)
#define	NJB_Songid_Frame_New_Filename(a) NJB_Songid_Frame_New_String(FR_FNAME, a)
#define	NJB_Songid_Frame_New_Protected(a) NJB_Songid_Frame_New_Uint16(FR_PROTECTED, a)
#define	NJB_Songid_Frame_New_Bitrate(a) NJB_Songid_Frame_New_Uint32(FR_BITRATE, a)
#define	NJB_Songid_Frame_New_Comment(a) NJB_Songid_Frame_New_String(FR_COMMENT, a)
#define	NJB_Songid_Frame_New_Folder(a) NJB_Songid_Frame_New_String(FR_FOLDER, a)
Functions
njb_songid_t *	NJB_Songid_New (void)
void	NJB_Songid_Destroy (njb_songid_t *song)
void	NJB_Songid_Addframe (njb_songid_t song, njb_songid_frame_t frame)
void	NJB_Songid_Reset_Getframe (njb_songid_t *song)
njb_songid_frame_t *	NJB_Songid_Getframe (njb_songid_t *song)
njb_songid_frame_t *	NJB_Songid_Findframe (njb_songid_t song, const char label)
njb_songid_frame_t *	NJB_Songid_Frame_New_String (const char label, const char value)
njb_songid_frame_t *	NJB_Songid_Frame_New_Uint16 (const char *label, u_int16_t value)
njb_songid_frame_t *	NJB_Songid_Frame_New_Uint32 (const char *label, u_int32_t value)
njb_songid_frame_t *	NJB_Songid_Frame_New_Codec (const char *value)
void	NJB_Songid_Frame_Destroy (njb_songid_frame_t *frame)
void	NJB_Get_Extended_Tags (njb_t *njb, int extended)
void	NJB_Reset_Get_Track_Tag (njb_t *njb)
njb_songid_t *	NJB_Get_Track_Tag (njb_t *njb)
int	NJB_Replace_Track_Tag (njb_t njb, u_int32_t trackid, njb_songid_t songid)
int	NJB_Get_Track (njb_t njb, u_int32_t trackid, u_int32_t size, const char path, NJB_Xfer_Callback callback, void data)
int	NJB_Get_Track_fd (njb_t njb, u_int32_t trackid, u_int32_t size, int fd, NJB_Xfer_Callback callback, void *data)
int	NJB_Send_Track (njb_t njb, const char path, njb_songid_t songid, NJB_Xfer_Callback callback, void data, u_int32_t trackid)
int	NJB_Delete_Track (njb_t *njb, u_int32_t trackid)

The track and tag (song ID metadata) manipulation API

Defines

Functions

Function Documentation