control/: don't show warnings about unused exceptions
[vlc.git] / src / control / media_descriptor.c
1 /*****************************************************************************
2  * media_descriptor.c: Libvlc API media descripor management
3  *****************************************************************************
4  * Copyright (C) 2007 the VideoLAN team
5  * $Id$
6  *
7  * Authors: Pierre d'Herbemont <pdherbemont@videolan.org>
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17  * GNU General Public License for more details.
18  *
19  * You should have received a copy of the GNU General Public License
20  * along with this program; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
22  *****************************************************************************/
23
24 #include "libvlc_internal.h"
25
26 #include <vlc/libvlc.h>
27 #include <vlc_input.h>
28 #include <vlc_meta.h>
29
30 /* For the preparser */
31 #include <vlc_playlist.h>
32
33 static const vlc_meta_type_t libvlc_to_vlc_meta[] =
34 {
35     [libvlc_meta_Title]        = vlc_meta_Title,
36     [libvlc_meta_Artist]       = vlc_meta_Artist,
37     [libvlc_meta_Genre]        = vlc_meta_Genre,
38     [libvlc_meta_Copyright]    = vlc_meta_Copyright,
39     [libvlc_meta_Album]        = vlc_meta_Album,
40     [libvlc_meta_TrackNumber]  = vlc_meta_TrackNumber,
41     [libvlc_meta_Description]  = vlc_meta_Description,
42     [libvlc_meta_Rating]       = vlc_meta_Rating,
43     [libvlc_meta_Date]         = vlc_meta_Date,
44     [libvlc_meta_Setting]      = vlc_meta_Setting,
45     [libvlc_meta_URL]          = vlc_meta_URL,
46     [libvlc_meta_Language]     = vlc_meta_Language,
47     [libvlc_meta_NowPlaying]   = vlc_meta_NowPlaying,
48     [libvlc_meta_Publisher]    = vlc_meta_Publisher,
49     [libvlc_meta_EncodedBy]    = vlc_meta_EncodedBy,
50     [libvlc_meta_ArtworkURL]   = vlc_meta_ArtworkURL,
51     [libvlc_meta_TrackID]      = vlc_meta_TrackID
52 };
53
54 static const libvlc_meta_t vlc_to_libvlc_meta[] =
55 {
56     [vlc_meta_Title]        = libvlc_meta_Title,
57     [vlc_meta_Artist]       = libvlc_meta_Artist,
58     [vlc_meta_Genre]        = libvlc_meta_Genre,
59     [vlc_meta_Copyright]    = libvlc_meta_Copyright,
60     [vlc_meta_Album]        = libvlc_meta_Album,
61     [vlc_meta_TrackNumber]  = libvlc_meta_TrackNumber,
62     [vlc_meta_Description]  = libvlc_meta_Description,
63     [vlc_meta_Rating]       = libvlc_meta_Rating,
64     [vlc_meta_Date]         = libvlc_meta_Date,
65     [vlc_meta_Setting]      = libvlc_meta_Setting,
66     [vlc_meta_URL]          = libvlc_meta_URL,
67     [vlc_meta_Language]     = libvlc_meta_Language,
68     [vlc_meta_NowPlaying]   = libvlc_meta_NowPlaying,
69     [vlc_meta_Publisher]    = libvlc_meta_Publisher,
70     [vlc_meta_EncodedBy]    = libvlc_meta_EncodedBy,
71     [vlc_meta_ArtworkURL]   = libvlc_meta_ArtworkURL,
72     [vlc_meta_TrackID]      = libvlc_meta_TrackID
73 };
74
75 /**************************************************************************
76  * input_item_subitem_added (Private) (vlc event Callback)
77  **************************************************************************/
78 static void input_item_subitem_added( const vlc_event_t *p_event,
79                                        void * user_data )
80 {
81     libvlc_media_descriptor_t * p_md = user_data;
82     libvlc_media_descriptor_t * p_md_child;
83     libvlc_event_t event;
84
85     p_md_child = libvlc_media_descriptor_new_from_input_item(
86                 p_md->p_libvlc_instance,
87                 p_event->u.input_item_subitem_added.p_new_child, NULL );
88
89     /* Add this to our media list */
90     if( !p_md->p_subitems )
91     {
92         p_md->p_subitems = libvlc_media_list_new( p_md->p_libvlc_instance, NULL );
93         libvlc_media_list_set_media_descriptor( p_md->p_subitems, p_md, NULL );
94     }
95     if( p_md->p_subitems )
96     {
97         libvlc_media_list_add_media_descriptor( p_md->p_subitems, p_md_child, NULL );
98     }
99
100     /* Construct the event */
101     event.type = libvlc_MediaDescriptorSubItemAdded;
102     event.u.media_descriptor_subitem_added.new_child = p_md_child;
103
104     /* Send the event */
105     libvlc_event_send( p_md->p_event_manager, &event );
106     libvlc_media_descriptor_release( p_md_child );
107 }
108
109 /**************************************************************************
110  * input_item_meta_changed (Private) (vlc event Callback)
111  **************************************************************************/
112 static void input_item_meta_changed( const vlc_event_t *p_event,
113                                      void * user_data )
114 {
115     libvlc_media_descriptor_t * p_md = user_data;
116     libvlc_event_t event;
117
118     /* Construct the event */
119     event.type = libvlc_MediaDescriptorMetaChanged;
120     event.u.media_descriptor_meta_changed.meta_type =
121         vlc_to_libvlc_meta[p_event->u.input_item_meta_changed.meta_type];
122
123     /* Send the event */
124     libvlc_event_send( p_md->p_event_manager, &event );
125 }
126
127 /**************************************************************************
128  * input_item_duration_changed (Private) (vlc event Callback)
129  **************************************************************************/
130 static void input_item_duration_changed( const vlc_event_t *p_event,
131                                          void * user_data )
132 {
133     libvlc_media_descriptor_t * p_md = user_data;
134     libvlc_event_t event;
135
136     /* Construct the event */
137     event.type = libvlc_MediaDescriptorDurationChanged;
138     event.u.media_descriptor_duration_changed.new_duration = 
139         p_event->u.input_item_duration_changed.new_duration;
140
141     /* Send the event */
142     libvlc_event_send( p_md->p_event_manager, &event );
143 }
144
145 /**************************************************************************
146  * input_item_preparsed_changed (Private) (vlc event Callback)
147  **************************************************************************/
148 static void input_item_preparsed_changed( const vlc_event_t *p_event,
149                                           void * user_data )
150 {
151     libvlc_media_descriptor_t * p_md = user_data;
152     libvlc_event_t event;
153
154     /* Construct the event */
155     event.type = libvlc_MediaDescriptorPreparsedChanged;
156     event.u.media_descriptor_preparsed_changed.new_status = 
157         p_event->u.input_item_preparsed_changed.new_status;
158
159     /* Send the event */
160     libvlc_event_send( p_md->p_event_manager, &event );
161 }
162
163 /**************************************************************************
164  * Install event handler (Private)
165  **************************************************************************/
166 static void install_input_item_observer( libvlc_media_descriptor_t *p_md )
167 {
168     vlc_event_attach( &p_md->p_input_item->event_manager,
169                       vlc_InputItemSubItemAdded,
170                       input_item_subitem_added,
171                       p_md );
172     vlc_event_attach( &p_md->p_input_item->event_manager,
173                       vlc_InputItemMetaChanged,
174                       input_item_meta_changed,
175                       p_md );
176     vlc_event_attach( &p_md->p_input_item->event_manager,
177                       vlc_InputItemDurationChanged,
178                       input_item_duration_changed,
179                       p_md );
180     vlc_event_attach( &p_md->p_input_item->event_manager,
181                       vlc_InputItemPreparsedChanged,
182                       input_item_preparsed_changed,
183                       p_md );
184 }
185
186 /**************************************************************************
187  * Uninstall event handler (Private)
188  **************************************************************************/
189 static void uninstall_input_item_observer( libvlc_media_descriptor_t *p_md )
190 {
191     vlc_event_detach( &p_md->p_input_item->event_manager,
192                       vlc_InputItemSubItemAdded,
193                       input_item_subitem_added,
194                       p_md );
195     vlc_event_detach( &p_md->p_input_item->event_manager,
196                       vlc_InputItemMetaChanged,
197                       input_item_meta_changed,
198                       p_md );
199     vlc_event_detach( &p_md->p_input_item->event_manager,
200                       vlc_InputItemDurationChanged,
201                       input_item_duration_changed,
202                       p_md );
203     vlc_event_detach( &p_md->p_input_item->event_manager,
204                       vlc_InputItemPreparsedChanged,
205                       input_item_preparsed_changed,
206                       p_md );
207 }
208
209 /**************************************************************************
210  * Preparse if not already done (Private)
211  **************************************************************************/
212 static void preparse_if_needed( libvlc_media_descriptor_t *p_md )
213 {
214     /* XXX: need some locking here */
215     if (!p_md->b_preparsed)
216     {
217         playlist_PreparseEnqueue(
218                 p_md->p_libvlc_instance->p_libvlc_int->p_playlist,
219                 p_md->p_input_item );
220         playlist_AskForArtEnqueue(
221                 p_md->p_libvlc_instance->p_libvlc_int->p_playlist,
222                 p_md->p_input_item );
223
224         p_md->b_preparsed = VLC_TRUE;
225     }
226 }
227
228 /**************************************************************************
229  * Create a new media descriptor object from an input_item
230  * (libvlc internal)
231  * That's the generic constructor
232  **************************************************************************/
233 libvlc_media_descriptor_t * libvlc_media_descriptor_new_from_input_item(
234                                    libvlc_instance_t *p_instance,
235                                    input_item_t *p_input_item,
236                                    libvlc_exception_t *p_e )
237 {
238     libvlc_media_descriptor_t * p_md;
239
240     if (!p_input_item)
241     {
242         libvlc_exception_raise( p_e, "No input item given" );
243         return NULL;
244     }
245
246     p_md = malloc( sizeof(libvlc_media_descriptor_t) );
247     p_md->p_libvlc_instance = p_instance;
248     p_md->p_input_item      = p_input_item;
249     p_md->b_preparsed       = VLC_FALSE;
250     p_md->i_refcount        = 1;
251     p_md->p_user_data       = NULL;
252
253     p_md->state = libvlc_NothingSpecial;
254
255     /* A media descriptor can be a playlist. When you open a playlist
256      * It can give a bunch of item to read. */
257     p_md->p_subitems        = NULL;
258
259     vlc_dictionary_init( &p_md->tags, 1 );
260
261     p_md->p_event_manager = libvlc_event_manager_new( p_md, p_instance, p_e );
262     libvlc_event_manager_register_event_type( p_md->p_event_manager,
263         libvlc_MediaDescriptorMetaChanged, p_e );
264     libvlc_event_manager_register_event_type( p_md->p_event_manager,
265         libvlc_MediaDescriptorSubItemAdded, p_e );
266     libvlc_event_manager_register_event_type( p_md->p_event_manager,
267         libvlc_MediaDescriptorFreed, p_e );
268     libvlc_event_manager_register_event_type( p_md->p_event_manager,
269         libvlc_MediaDescriptorDurationChanged, p_e );
270     libvlc_event_manager_register_event_type( p_md->p_event_manager,
271         libvlc_MediaDescriptorStateChanged, p_e );
272
273     vlc_gc_incref( p_md->p_input_item );
274
275     install_input_item_observer( p_md );
276
277     return p_md;
278 }
279
280 /**************************************************************************
281  * Create a new media descriptor object
282  **************************************************************************/
283 libvlc_media_descriptor_t * libvlc_media_descriptor_new(
284                                    libvlc_instance_t *p_instance,
285                                    const char * psz_mrl,
286                                    libvlc_exception_t *p_e )
287 {
288     input_item_t * p_input_item;
289     libvlc_media_descriptor_t * p_md;
290
291     p_input_item = input_ItemNew( p_instance->p_libvlc_int, psz_mrl, NULL );
292
293     if (!p_input_item)
294     {
295         libvlc_exception_raise( p_e, "Can't create md's input_item" );
296         return NULL;
297     }
298
299     p_md = libvlc_media_descriptor_new_from_input_item( p_instance,
300                 p_input_item, p_e );
301
302     /* The p_input_item is retained in libvlc_media_descriptor_new_from_input_item */
303     vlc_gc_decref( p_input_item );
304     
305     return p_md;
306 }
307
308 /**************************************************************************
309  * Create a new media descriptor object
310  **************************************************************************/
311 libvlc_media_descriptor_t * libvlc_media_descriptor_new_as_node(
312                                    libvlc_instance_t *p_instance,
313                                    const char * psz_name,
314                                    libvlc_exception_t *p_e )
315 {
316     input_item_t * p_input_item;
317     libvlc_media_descriptor_t * p_md;
318
319     p_input_item = input_ItemNew( p_instance->p_libvlc_int, "vlc:nop", psz_name );
320
321     if (!p_input_item)
322     {
323         libvlc_exception_raise( p_e, "Can't create md's input_item" );
324         return NULL;
325     }
326
327     p_md = libvlc_media_descriptor_new_from_input_item( p_instance,
328                 p_input_item, p_e );
329
330     p_md->p_subitems = libvlc_media_list_new( p_md->p_libvlc_instance, NULL );
331
332     return p_md;
333 }
334
335 /**************************************************************************
336  * Add an option to the media descriptor,
337  * that will be used to determine how the media_instance will read the
338  * media_descriptor. This allow to use VLC advanced reading/streaming
339  * options in a per-media basis
340  *
341  * The options are detailled in vlc --long-help, for instance "--sout-all"
342  **************************************************************************/
343 void libvlc_media_descriptor_add_option(
344                                    libvlc_media_descriptor_t * p_md,
345                                    const char * ppsz_option,
346                                    libvlc_exception_t *p_e )
347 {
348     (void)p_e;
349     input_ItemAddOptionNoDup( p_md->p_input_item, ppsz_option );
350 }
351
352 /**************************************************************************
353  * Delete a media descriptor object
354  **************************************************************************/
355 void libvlc_media_descriptor_release( libvlc_media_descriptor_t *p_md )
356 {
357     int i;
358     if (!p_md)
359         return;
360
361     p_md->i_refcount--;
362
363     if( p_md->i_refcount > 0 )
364         return;
365
366     if( p_md->p_subitems )
367         libvlc_media_list_release( p_md->p_subitems );
368
369     uninstall_input_item_observer( p_md );
370     vlc_gc_decref( p_md->p_input_item );
371
372     /* Construct the event */
373     libvlc_event_t event;
374     event.type = libvlc_MediaDescriptorFreed;
375     event.u.media_descriptor_freed.md = p_md;
376
377     /* Send the event */
378     libvlc_event_send( p_md->p_event_manager, &event );
379
380     libvlc_event_manager_release( p_md->p_event_manager );
381
382     char ** all_keys = vlc_dictionary_all_keys( &p_md->tags );
383     for( i = 0; all_keys[i]; i++ )
384     {
385         int j;
386         struct libvlc_tags_storage_t * p_ts = vlc_dictionary_value_for_key( &p_md->tags, all_keys[i] );
387         for( j = 0; j < p_ts->i_count; j++ )
388         {
389             free( p_ts->ppsz_tags[j] );
390             free( p_ts->ppsz_tags );
391         }
392         free( p_ts );
393     }
394     vlc_dictionary_clear( &p_md->tags );
395     free( p_md );
396 }
397
398 /**************************************************************************
399  * Retain a media descriptor object
400  **************************************************************************/
401 void libvlc_media_descriptor_retain( libvlc_media_descriptor_t *p_md )
402 {
403     if (!p_md)
404         return;
405
406     p_md->i_refcount++;
407 }
408
409 /**************************************************************************
410  * Duplicate a media descriptor object
411  **************************************************************************/
412 libvlc_media_descriptor_t *
413 libvlc_media_descriptor_duplicate( libvlc_media_descriptor_t *p_md_orig )
414 {
415     return libvlc_media_descriptor_new_from_input_item(
416         p_md_orig->p_libvlc_instance, p_md_orig->p_input_item, NULL );
417 }
418
419 /**************************************************************************
420  * Retain a media descriptor object
421  **************************************************************************/
422 char *
423 libvlc_media_descriptor_get_mrl( libvlc_media_descriptor_t * p_md,
424                                  libvlc_exception_t * p_e )
425 {
426     (void)p_e;
427     return input_item_GetURI( p_md->p_input_item );
428 }
429
430 /**************************************************************************
431  * Getter for meta information
432  **************************************************************************/
433
434 char * libvlc_media_descriptor_get_meta( libvlc_media_descriptor_t *p_md,
435                                          libvlc_meta_t e_meta,
436                                          libvlc_exception_t *p_e )
437 {
438     VLC_UNUSED(p_e);
439
440     char * psz_meta;
441
442     /* XXX: locking */
443
444     preparse_if_needed( p_md );
445
446     psz_meta = input_item_GetMeta( p_md->p_input_item,
447                                    libvlc_to_vlc_meta[e_meta] );
448
449     /* Should be integrated in core */
450     if( !psz_meta && e_meta == libvlc_meta_Title && p_md->p_input_item->psz_name )
451     {
452         free( psz_meta );
453         return strdup( p_md->p_input_item->psz_name );
454     }
455
456     return psz_meta;
457 }
458
459 /**************************************************************************
460  * Getter for state information
461  * Can be error, playing, buffering, NothingSpecial.
462  **************************************************************************/
463
464 libvlc_state_t
465 libvlc_media_descriptor_get_state( libvlc_media_descriptor_t *p_md,
466                                    libvlc_exception_t *p_e )
467 {
468     (void)p_e;
469     return p_md->state;
470 }
471
472 /**************************************************************************
473  * Setter for state information (LibVLC Internal)
474  **************************************************************************/
475
476 void
477 libvlc_media_descriptor_set_state( libvlc_media_descriptor_t *p_md,
478                                    libvlc_state_t state,
479                                    libvlc_exception_t *p_e )
480 {
481     (void)p_e;
482     libvlc_event_t event;
483
484     p_md->state = state;
485
486     /* Construct the event */
487     event.type = libvlc_MediaDescriptorStateChanged;
488     event.u.media_descriptor_state_changed.new_state = state;
489
490     /* Send the event */
491     libvlc_event_send( p_md->p_event_manager, &event );
492 }
493
494 /**************************************************************************
495  * Add a tag
496  **************************************************************************/
497 void libvlc_media_descriptor_add_tag( libvlc_media_descriptor_t *p_md,
498                                       const char * key,
499                                       const libvlc_tag_t tag,
500                                       libvlc_exception_t *p_e )
501 {
502     VLC_UNUSED(p_e);
503
504     struct libvlc_tags_storage_t * p_ts;
505
506     if( !tag || !key )
507         return;
508  
509     p_ts = vlc_dictionary_value_for_key( &p_md->tags, key );
510
511     if( !p_ts )
512     {
513         p_ts = malloc(sizeof(struct libvlc_tags_storage_t));
514         memset( p_ts, 0, sizeof(struct libvlc_tags_storage_t) );
515     }
516     p_ts->i_count++;
517
518     if( !p_ts->ppsz_tags )
519         p_ts->ppsz_tags = malloc(sizeof(char*)*(p_ts->i_count));
520     else
521         p_ts->ppsz_tags = realloc(p_ts->ppsz_tags, sizeof(char*)*(p_ts->i_count));
522  
523     p_ts->ppsz_tags[p_ts->i_count-1] = strdup( tag );
524 }
525
526
527 /**************************************************************************
528  * Remove a tag
529  **************************************************************************/
530 void libvlc_media_descriptor_remove_tag( libvlc_media_descriptor_t *p_md,
531                                          const char * key,
532                                          const libvlc_tag_t tag,
533                                          libvlc_exception_t *p_e )
534 {
535     VLC_UNUSED(p_e);
536
537     struct libvlc_tags_storage_t * p_ts;
538     int i;
539
540     if( !tag || !key )
541         return;
542  
543     p_ts = vlc_dictionary_value_for_key( &p_md->tags, key );
544
545     if( !p_ts )
546         return;
547
548     for( i = 0; i < p_ts->i_count; i++ )
549     {
550         if( !strcmp( p_ts->ppsz_tags[i], tag ) )
551         {
552             free( p_ts->ppsz_tags[i] );
553             memcpy( p_ts->ppsz_tags + i + 1, p_ts->ppsz_tags + i, (p_ts->i_count - i - 2)*sizeof(char*) );
554             /* Don't dealloc, the memory will be regain if we add a new tag */
555             p_ts->i_count--;
556             return;
557         }
558     }
559 }
560
561 /**************************************************************************
562  * Get tags count
563  **************************************************************************/
564 int libvlc_media_descriptor_tags_count_for_key( libvlc_media_descriptor_t *p_md,
565                                                  const char * key,
566                                                  libvlc_exception_t *p_e )
567 {
568     VLC_UNUSED(p_e);
569
570     struct libvlc_tags_storage_t * p_ts;
571
572     if( !key )
573         return 0;
574  
575     p_ts = vlc_dictionary_value_for_key( &p_md->tags, key );
576
577     if( !p_ts )
578         return 0;
579     return p_ts->i_count;
580 }
581
582 /**************************************************************************
583  * Get a tag
584  **************************************************************************/
585 libvlc_tag_t
586 libvlc_media_descriptor_tag_at_index_for_key( libvlc_media_descriptor_t *p_md,
587                                               int i,
588                                               const char * key,
589                                               libvlc_exception_t *p_e )
590 {
591     VLC_UNUSED(p_e);
592
593     struct libvlc_tags_storage_t * p_ts;
594
595     if( !key )
596         return NULL;
597  
598     p_ts = vlc_dictionary_value_for_key( &p_md->tags, key );
599
600     if( !p_ts )
601         return NULL;
602  
603     return strdup( p_ts->ppsz_tags[i] );
604 }
605
606 /**************************************************************************
607  * subitems
608  **************************************************************************/
609 libvlc_media_list_t *
610 libvlc_media_descriptor_subitems( libvlc_media_descriptor_t * p_md,
611                                   libvlc_exception_t * p_e )
612 {
613     VLC_UNUSED(p_e);
614
615     if( p_md->p_subitems )
616         libvlc_media_list_retain( p_md->p_subitems );
617     return p_md->p_subitems;
618 }
619
620 /**************************************************************************
621  * event_manager
622  **************************************************************************/
623 libvlc_event_manager_t *
624 libvlc_media_descriptor_event_manager( libvlc_media_descriptor_t * p_md,
625                                        libvlc_exception_t * p_e )
626 {
627     VLC_UNUSED(p_e);
628
629     return p_md->p_event_manager;
630 }
631
632 /**************************************************************************
633  * Get duration of media_descriptor object.
634  **************************************************************************/
635 vlc_int64_t
636 libvlc_media_descriptor_get_duration( libvlc_media_descriptor_t * p_md,
637                                       libvlc_exception_t * p_e )
638 {
639     VLC_UNUSED(p_e);
640
641     if( p_md && p_md->p_input_item)
642     {
643         return input_item_GetDuration( p_md->p_input_item );
644     }
645     else
646     {
647         return -1;
648     }
649 }
650
651 /**************************************************************************
652  * Get preparsed status for media_descriptor object.
653  **************************************************************************/
654 vlc_bool_t
655 libvlc_media_descriptor_is_preparsed( libvlc_media_descriptor_t * p_md,
656                                        libvlc_exception_t * p_e )
657 {
658     VLC_UNUSED(p_e);
659
660     if( p_md && p_md->p_input_item)
661     {
662         return input_item_IsPreparsed( p_md->p_input_item );
663     }
664     else
665     {
666         return VLC_FALSE;
667     }
668 }
669
670 /**************************************************************************
671  * Sets media descriptor's user_data. user_data is specialized data 
672  * accessed by the host application, VLC.framework uses it as a pointer to 
673  * an native object that references a libvlc_media_descriptor_t pointer
674  **************************************************************************/
675 void 
676 libvlc_media_descriptor_set_user_data( libvlc_media_descriptor_t * p_md,
677                                        void * p_new_user_data,
678                                        libvlc_exception_t * p_e )
679 {
680     VLC_UNUSED(p_e);
681
682     if( p_md )
683     {
684         p_md->p_user_data = p_new_user_data;
685     }
686 }
687
688 /**************************************************************************
689  * Get media descriptor's user_data. user_data is specialized data 
690  * accessed by the host application, VLC.framework uses it as a pointer to 
691  * an native object that references a libvlc_media_descriptor_t pointer
692  **************************************************************************/
693 void *
694 libvlc_media_descriptor_get_user_data( libvlc_media_descriptor_t * p_md,
695                                        libvlc_exception_t * p_e )
696 {
697     VLC_UNUSED(p_e);
698
699     if( p_md )
700     {
701         return p_md->p_user_data;
702     }
703     else
704     {
705         return NULL;
706     }
707 }
708