libextractor

ogg_extractor.c (5731B)

---

 /*
      This file is part of libextractor.
      Copyright (C) 2002, 2003, 2009, 2012 Vidyut Samanta and Christian Grothoff
 
      libextractor is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
      by the Free Software Foundation; either version 3, or (at your
      option) any later version.
 
      libextractor is distributed in the hope that it will be useful, but
      WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      General Public License for more details.
 
      You should have received a copy of the GNU General Public License
      along with libextractor; see the file COPYING.  If not, write to the
      Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
      Boston, MA 02110-1301, USA.
  */
 /**
  * @file plugins/ogg_extractor.c
  * @brief plugin to support OGG files
  * @author Christian Grothoff
  */
 #include "platform.h"
 #include "extractor.h"
 #include <vorbis/vorbisfile.h>
 
 /**
  * Bytes each ogg file must begin with (not used, but we might
  * choose to add this back in the future to improve performance
  * for non-ogg files).
  */
 #define OGG_HEADER 0x4f676753
 
 
 /**
  * Custom read function for ogg.
  *
  * @param ptr where to write the data
  * @param size number of bytes to read per member
  * @param nmemb number of members to read
  * @param datasource the 'struct EXTRACTOR_ExtractContext'
  * @return 0 on end-of-data, 0 with errno set to indicate read error
  */
 static size_t
 read_ogg (void *ptr, size_t size, size_t nmemb, void *datasource)
 {
   struct EXTRACTOR_ExtractContext *ec = datasource;
   void *data;
   ssize_t ret;
 
   data = NULL;
   ret = ec->read (ec->cls,
                   &data,
                   size * nmemb);
   if (-1 == ret)
     return 0;
   if (0 == ret)
   {
     errno = 0;
     return 0;
   }
   memcpy (ptr, data, ret);
   errno = 0;
   return ret;
 }
 
 
 /**
  * Seek to a particular position in the file.
  *
  * @param datasource  the 'struct EXTRACTOR_ExtractContext'
  * @param offset where to seek
  * @param whence how to seek
  * @return -1 on error, new position on success
  */
 static int
 seek_ogg (void *datasource,
           ogg_int64_t offset,
           int whence)
 {
   struct EXTRACTOR_ExtractContext *ec = datasource;
   int64_t new_position;
 
   new_position = ec->seek (ec->cls,
                            (int64_t) offset,
                            whence);
   return (long) new_position;
 }
 
 
 /**
  * Tell ogg where we are in the file
  *
  * @param datasource  the 'struct EXTRACTOR_ExtractContext'
  * @return
  */
 static long
 tell_ogg (void *datasource)
 {
   struct EXTRACTOR_ExtractContext *ec = datasource;
 
   return (long) ec->seek (ec->cls,
                           0,
                           SEEK_CUR);
 }
 
 
 /**
  * Extract the associated meta data for a given label from vorbis.
  *
  * @param vc vorbis comment data
  * @param label label marking the desired entry
  * @return NULL on error, otherwise the meta data
  */
 static char *
 get_comment (vorbis_comment *vc,
              const char *label)
 {
   if (NULL == vc)
     return NULL;
   return vorbis_comment_query (vc, label, 0);
 }
 
 
 /**
  * Extract meta data from vorbis using the given LE type and value.
  *
  * @param t LE meta data type
  * @param s meta data to add
  */
 #define ADD(t,s) do { if (0 != (ret = ec->proc (ec->cls, "ogg", t, \
                                                 EXTRACTOR_METAFORMAT_UTF8, \
                                                 "text/plain", s, strlen (s) \
                                                 + 1))) goto FINISH; \
 } while (0)
 
 
 /**
  * Extract meta data from vorbis using the given LE type and label.
  *
  * @param t LE meta data type
  * @param d vorbis meta data label
  */
 #define ADDG(t,d) do { m = get_comment (comments, d); if (NULL != m) ADD (t,m); \
 } while (0)
 
 
 /**
  * Main entry method for the 'application/ogg' extraction plugin.
  *
  * @param ec extraction context provided to the plugin
  */
 void
 EXTRACTOR_ogg_extract_method (struct EXTRACTOR_ExtractContext *ec)
 {
   uint64_t fsize;
   ov_callbacks callbacks;
   OggVorbis_File vf;
   vorbis_comment *comments;
   int ret;
   const char *m;
 
   fsize = ec->get_size (ec->cls);
   if (fsize < 8)
     return;
 
   callbacks.read_func = &read_ogg;
   callbacks.seek_func = &seek_ogg;
   callbacks.close_func = NULL;
   callbacks.tell_func = &tell_ogg;
   ret = ov_open_callbacks (ec, &vf, NULL, 0, callbacks);
   if (0 != ret)
   {
     ov_clear (&vf);
     return;
   }
   comments = ov_comment (&vf, -1);
   if (NULL == comments)
   {
     ov_clear (&vf);
     return;
   }
   ADD (EXTRACTOR_METATYPE_MIMETYPE, "application/ogg");
   if ((comments->vendor != NULL) && (strlen (comments->vendor) > 0))
     ADD (EXTRACTOR_METATYPE_VENDOR, comments->vendor);
   ADDG (EXTRACTOR_METATYPE_TITLE, "title");
   ADDG (EXTRACTOR_METATYPE_ARTIST, "artist");
   ADDG (EXTRACTOR_METATYPE_PERFORMER, "performer");
   ADDG (EXTRACTOR_METATYPE_ALBUM, "album");
   ADDG (EXTRACTOR_METATYPE_TRACK_NUMBER, "tracknumber");
   ADDG (EXTRACTOR_METATYPE_DISC_NUMBER, "discnumber");
   ADDG (EXTRACTOR_METATYPE_CONTACT_INFORMATION, "contact");
   ADDG (EXTRACTOR_METATYPE_GENRE, "genre");
   ADDG (EXTRACTOR_METATYPE_CREATION_DATE, "date");
   ADDG (EXTRACTOR_METATYPE_COMMENT, "");
   ADDG (EXTRACTOR_METATYPE_LOCATION_SUBLOCATION, "location");
   ADDG (EXTRACTOR_METATYPE_DESCRIPTION, "description");
   ADDG (EXTRACTOR_METATYPE_ISRC, "isrc");
   ADDG (EXTRACTOR_METATYPE_ORGANIZATION, "organization");
   ADDG (EXTRACTOR_METATYPE_COPYRIGHT, "copyright");
   ADDG (EXTRACTOR_METATYPE_LICENSE, "license");
   ADDG (EXTRACTOR_METATYPE_SONG_VERSION, "version");
 FINISH:
   ov_clear (&vf);
 }
 
 
 /* end of ogg_extractor.c */