vorbisfile.c

在x86平台上运行不可信任代码的sandbox。

    ogg_stream_reset(&work_os); /* eliminate the spurious OV_HOLE
                                   return from not necessarily
                                   starting from the beginning */

    while(1){
      if(vf->ready_state>=STREAMSET){
	/* snarf/scan a packet if we can */
	int result=ogg_stream_packetout(&work_os,&op);
      
	if(result>0){

	  if(vf->vi[vf->current_link].codec_setup){
	    thisblock=vorbis_packet_blocksize(vf->vi+vf->current_link,&op);
	    if(thisblock<0){
	      ogg_stream_packetout(&vf->os,NULL);
	      thisblock=0;
	    }else{
	      
	      if(eosflag)
	      ogg_stream_packetout(&vf->os,NULL);
	      else
		if(lastblock)accblock+=(lastblock+thisblock)>>2;
	    }	    

	    if(op.granulepos!=-1){
	      int i,link=vf->current_link;
	      ogg_int64_t granulepos=op.granulepos-vf->pcmlengths[link*2];
	      if(granulepos<0)granulepos=0;
	      
	      for(i=0;i<link;i++)
		granulepos+=vf->pcmlengths[i*2+1];
	      vf->pcm_offset=granulepos-accblock;
	      break;
	    }
	    lastblock=thisblock;
	    continue;
	  }else
	    ogg_stream_packetout(&vf->os,NULL);
	}
      }
      
      if(!lastblock){
	if(_get_next_page(vf,&og,-1)<0){
	  vf->pcm_offset=ov_pcm_total(vf,-1);
	  break;
	}
      }else{
	/* huh?  Bogus stream with packets but no granulepos */
	vf->pcm_offset=-1;
	break;
      }
      
      /* has our decoding just traversed a bitstream boundary? */
      if(vf->ready_state>=STREAMSET)
	if(vf->current_serialno!=ogg_page_serialno(&og)){
	  _decode_clear(vf); /* clear out stream state */
	  ogg_stream_clear(&work_os);
	}

      if(vf->ready_state<STREAMSET){
	int link;
	
	vf->current_serialno=ogg_page_serialno(&og);
	for(link=0;link<vf->links;link++)
	  if(vf->serialnos[link]==vf->current_serialno)break;
	if(link==vf->links)goto seek_error; /* sign of a bogus stream.
					       error out, leave
					       machine uninitialized */
	vf->current_link=link;
	
	ogg_stream_reset_serialno(&vf->os,vf->current_serialno);
	ogg_stream_reset_serialno(&work_os,vf->current_serialno); 
	vf->ready_state=STREAMSET;
	
      }
    
      ogg_stream_pagein(&vf->os,&og);
      ogg_stream_pagein(&work_os,&og);
      eosflag=ogg_page_eos(&og);
    }
  }

  ogg_stream_clear(&work_os);
  vf->bittrack=0.f;
  vf->samptrack=0.f;
  return(0);

 seek_error:
  /* dump the machine so we're in a known state */
  vf->pcm_offset=-1;
  ogg_stream_clear(&work_os);
  _decode_clear(vf);
  return OV_EBADLINK;
}

/* Page granularity seek (faster than sample granularity because we
   don't do the last bit of decode to find a specific sample).

   Seek to the last [granule marked] page preceeding the specified pos
   location, such that decoding past the returned point will quickly
   arrive at the requested position. */
int ov_pcm_seek_page(OggVorbis_File *vf,ogg_int64_t pos){
  int link=-1;
  ogg_int64_t result=0;
  ogg_int64_t total=ov_pcm_total(vf,-1);

  if(vf->ready_state<OPENED)return(OV_EINVAL);
  if(!vf->seekable)return(OV_ENOSEEK);

  if(pos<0 || pos>total)return(OV_EINVAL);
 
  /* which bitstream section does this pcm offset occur in? */
  for(link=vf->links-1;link>=0;link--){
    total-=vf->pcmlengths[link*2+1];
    if(pos>=total)break;
  }

  /* search within the logical bitstream for the page with the highest
     pcm_pos preceeding (or equal to) pos.  There is a danger here;
     missing pages or incorrect frame number information in the
     bitstream could make our task impossible.  Account for that (it
     would be an error condition) */

  /* new search algorithm by HB (Nicholas Vinen) */
  {
    ogg_int64_t end=vf->offsets[link+1];
    ogg_int64_t begin=vf->offsets[link];
    ogg_int64_t begintime = vf->pcmlengths[link*2];
    ogg_int64_t endtime = vf->pcmlengths[link*2+1]+begintime;
    ogg_int64_t target=pos-total+begintime;
    ogg_int64_t best=begin;
    
    ogg_page og;
    while(begin<end){
      ogg_int64_t bisect;
      
      if(end-begin<CHUNKSIZE){
	bisect=begin;
      }else{
	/* take a (pretty decent) guess. */
	bisect=begin + 
	  (target-begintime)*(end-begin)/(endtime-begintime) - CHUNKSIZE;
	if(bisect<=begin)
	  bisect=begin+1;
      }
      
      _seek_helper(vf,bisect);
    
      while(begin<end){
	result=_get_next_page(vf,&og,end-vf->offset);
	if(result==OV_EREAD) goto seek_error;
	if(result<0){
	  if(bisect<=begin+1)
	    end=begin; /* found it */
	  else{
	    if(bisect==0) goto seek_error;
	    bisect-=CHUNKSIZE;
	    if(bisect<=begin)bisect=begin+1;
	    _seek_helper(vf,bisect);
	  }
	}else{
	  ogg_int64_t granulepos=ogg_page_granulepos(&og);
	  if(granulepos==-1)continue;
	  if(granulepos<target){
	    best=result;  /* raw offset of packet with granulepos */ 
	    begin=vf->offset; /* raw offset of next page */
	    begintime=granulepos;
	    
	    if(target-begintime>44100)break;
	    bisect=begin; /* *not* begin + 1 */
	  }else{
	    if(bisect<=begin+1)
	      end=begin;  /* found it */
	    else{
	      if(end==vf->offset){ /* we're pretty close - we'd be stuck in */
		end=result;
		bisect-=CHUNKSIZE; /* an endless loop otherwise. */
		if(bisect<=begin)bisect=begin+1;
		_seek_helper(vf,bisect);
	      }else{
		end=result;
		endtime=granulepos;
		break;
	      }
	    }
	  }
	}
      }
    }

    /* found our page. seek to it, update pcm offset. Easier case than
       raw_seek, don't keep packets preceeding granulepos. */
    {
      ogg_page og;
      ogg_packet op;
      
      /* seek */
      _seek_helper(vf,best);
      vf->pcm_offset=-1;
      
      if(_get_next_page(vf,&og,-1)<0)return(OV_EOF); /* shouldn't happen */
      
      if(link!=vf->current_link){
	/* Different link; dump entire decode machine */
	_decode_clear(vf);  
	
	vf->current_link=link;
	vf->current_serialno=ogg_page_serialno(&og);
	vf->ready_state=STREAMSET;
	
      }else{
	vorbis_synthesis_restart(&vf->vd);
      }

      ogg_stream_reset_serialno(&vf->os,vf->current_serialno);
      ogg_stream_pagein(&vf->os,&og);

      /* pull out all but last packet; the one with granulepos */
      while(1){
	result=ogg_stream_packetpeek(&vf->os,&op);
	if(result==0){
	  /* !!! the packet finishing this page originated on a
             preceeding page. Keep fetching previous pages until we
             get one with a granulepos or without the 'continued' flag
             set.  Then just use raw_seek for simplicity. */
	  
	  _seek_helper(vf,best);
	  
	  while(1){
	    result=_get_prev_page(vf,&og);
	    if(result<0) goto seek_error;
	    if(ogg_page_granulepos(&og)>-1 ||
	       !ogg_page_continued(&og)){
	      return ov_raw_seek(vf,result);
	    }
	    vf->offset=result;
	  }
	}
	if(result<0){
	  result = OV_EBADPACKET; 
	  goto seek_error;
	}
	if(op.granulepos!=-1){
	  vf->pcm_offset=op.granulepos-vf->pcmlengths[vf->current_link*2];
	  if(vf->pcm_offset<0)vf->pcm_offset=0;
	  vf->pcm_offset+=total;
	  break;
	}else
	  result=ogg_stream_packetout(&vf->os,NULL);
      }
    }
  }
  
  /* verify result */
  if(vf->pcm_offset>pos || pos>ov_pcm_total(vf,-1)){
    result=OV_EFAULT;
    goto seek_error;
  }
  vf->bittrack=0.f;
  vf->samptrack=0.f;
  return(0);
  
 seek_error:
  /* dump machine so we're in a known state */
  vf->pcm_offset=-1;
  _decode_clear(vf);
  return (int)result;
}

/* seek to a sample offset relative to the decompressed pcm stream 
   returns zero on success, nonzero on failure */

int ov_pcm_seek(OggVorbis_File *vf,ogg_int64_t pos){
  int thisblock,lastblock=0;
  int ret=ov_pcm_seek_page(vf,pos);
  if(ret<0)return(ret);
  if((ret=_make_decode_ready(vf)))return ret;

  /* discard leading packets we don't need for the lapping of the
     position we want; don't decode them */

  while(1){
    ogg_packet op;
    ogg_page og;

    int ret=ogg_stream_packetpeek(&vf->os,&op);
    if(ret>0){
      thisblock=vorbis_packet_blocksize(vf->vi+vf->current_link,&op);
      if(thisblock<0){
	ogg_stream_packetout(&vf->os,NULL);
	continue; /* non audio packet */
      }
      if(lastblock)vf->pcm_offset+=(lastblock+thisblock)>>2;
      
      if(vf->pcm_offset+((thisblock+
			  vorbis_info_blocksize(vf->vi,1))>>2)>=pos)break;
      
      /* remove the packet from packet queue and track its granulepos */
      ogg_stream_packetout(&vf->os,NULL);
      vorbis_synthesis_trackonly(&vf->vb,&op);  /* set up a vb with
                                                   only tracking, no
                                                   pcm_decode */
      vorbis_synthesis_blockin(&vf->vd,&vf->vb); 
      
      /* end of logical stream case is hard, especially with exact
	 length positioning. */
      
      if(op.granulepos>-1){
	int i;
	/* always believe the stream markers */
	vf->pcm_offset=op.granulepos-vf->pcmlengths[vf->current_link*2];
	if(vf->pcm_offset<0)vf->pcm_offset=0;
	for(i=0;i<vf->current_link;i++)
	  vf->pcm_offset+=vf->pcmlengths[i*2+1];
      }
	
      lastblock=thisblock;
      
    }else{
      if(ret<0 && ret!=OV_HOLE)break;
      
      /* suck in a new page */
      if(_get_next_page(vf,&og,-1)<0)break;
      if(vf->current_serialno!=ogg_page_serialno(&og))_decode_clear(vf);
      
      if(vf->ready_state<STREAMSET){
	int link;
	
	vf->current_serialno=ogg_page_serialno(&og);
	for(link=0;link<vf->links;link++)
	  if(vf->serialnos[link]==vf->current_serialno)break;
	if(link==vf->links)return(OV_EBADLINK);
	vf->current_link=link;
	
	ogg_stream_reset_serialno(&vf->os,vf->current_serialno); 
	vf->ready_state=STREAMSET;      
	ret=_make_decode_ready(vf);
	if(ret)return ret;
	lastblock=0;
      }

      ogg_stream_pagein(&vf->os,&og);
    }
  }

  vf->bittrack=0.f;
  vf->samptrack=0.f;
  /* discard samples until we reach the desired position. Crossing a
     logical bitstream boundary with abandon is OK. */
  while(vf->pcm_offset<pos){
    ogg_int64_t target=pos-vf->pcm_offset;
    long samples=vorbis_synthesis_pcmout(&vf->vd,NULL);

    if(samples>target)samples=target;
    vorbis_synthesis_read(&vf->vd,samples);
    vf->pcm_offset+=samples;
    
    if(samples<target)
      if(_fetch_and_process_packet(vf,NULL,1,1)<=0)
	vf->pcm_offset=ov_pcm_total(vf,-1); /* eof */
  }
  return 0;
}

/* seek to a playback time relative to the decompressed pcm stream 
   returns zero on success, nonzero on failure */
int ov_time_seek(OggVorbis_File *vf,double seconds){
  /* translate time to PCM position and call ov_pcm_seek */

  int link=-1;
  ogg_int64_t pcm_total=ov_pcm_total(vf,-1);
  double time_total=ov_time_total(vf,-1);

  if(vf->ready_state<OPENED)return(OV_EINVAL);
  if(!vf->seekable)return(OV_ENOSEEK);
  if(seconds<0 || seconds>time_total)return(OV_EINVAL);
  
  /* which bitstream section does this time offset occur in? */
  for(link=vf->links-1;link>=0;link--){
    pcm_total-=vf->pcmlengths[link*2+1];
    time_total-=ov_time_total(vf,link);
    if(seconds>=time_total)break;
  }

  /* enough information to convert time offset to pcm offset */
  {
    ogg_int64_t target=pcm_total+(seconds-time_total)*vf->vi[link].rate;
    return(ov_pcm_seek(vf,target));
  }
}

/* page-granularity version of ov_time_seek 
   returns zero on success, nonzero on failure */
int ov_time_seek_page(OggVorbis_File *vf,double seconds){
  /* translate time to PCM position and call ov_pcm_seek */

  int link=-1;
  ogg_int64_t pcm_total=ov_pcm_total(vf,-1);
  double time_total=ov_time_total(vf,-1);

  if(vf->ready_state<OPENED)return(OV_EINVAL);
  if(!vf->seekable)return(OV_ENOSEEK);
  if(seconds<0 || seconds>time_total)return(OV_EINVAL);
  
  /* which bitstream section does this time offset occur in? */
  for(link=vf->links-1;link>=0;link--){
    pcm_total-=vf->pcmlengths[link*2+1];
    time_total-=ov_time_total(vf,link);
    if(seconds>=time_total)break;
  }

  /* enough information to convert time offset to pcm offset */
  {
    ogg_int64_t target=pcm_total+(seconds-time_total)*vf->vi[link].rate;
    return(ov_pcm_seek_page(vf,target));
  }
}

/* tell the current stream offset cursor.  Note that seek followed by
   tell will likely not give the set offset due to caching */
ogg_int64_t ov_raw_tell(OggVorbis_File *vf){
  if(vf->ready_state<OPENED)return(OV_EINVAL);
  return(vf->offset);
}

/* return PCM offset (sample) of next PCM sample to be read */
ogg_int64_t ov_pcm_tell(OggVorbis_File *vf){
  if(vf->ready_state<OPENED)return(OV_EINVAL);
  return(vf->pcm_offset);
}

/* return time offset (seconds) of next PCM sample to be read */
double ov_time_tell(OggVorbis_File *vf){
  int link=0;
  ogg_int64_t pcm_total=0;
  double time_total=0.f;
  
  if(vf->ready_state<OPENED)return(OV_EINVAL);
  if(vf->seekable){
    pcm_total=ov_pcm_total(vf,-1);
    time_total=ov_time_total(vf,-1);
  
    /* which bitstream section does this time offset occur in? */
    for(link=vf->links-1;link>=0;link--){
      pcm_total-=vf->pcmlengths[link*2+1];
      time_total-=ov_time_total(vf,link);
      if(vf->pcm_offset>=pcm_total)break;
    }
  }

  return((double)time_total+(double)(vf->pcm_offset-pcm_total)/vf->vi[link].rate);
}

/*  link:   -1) return the vorbis_info struct for the bitstream section
                currently being decoded
           0-n) to request information for a specific bitstream section
    
    In the case of a non-seekable bitstream, any call returns the
    current bitstream.  NULL in the case that the machine is not
    initialized */

vorbis_info *ov_info(OggVorbis_File *vf,int link){
  if(vf->seekable){
    if(link<0)
      if(vf->ready_state>=STREAMSET)
	return vf->vi+vf->current_link;
      else
      return vf->vi;
    else
      if(link>=vf->links)
	return NULL;
      else
	return vf->vi+link;
  }else{
    return vf->vi;
  }
}

/* grr, strong typing, grr, no templates/inheritence, grr */
vorbis_comment *ov_comment(OggVorbis_File *vf,int link){
  if(vf->seekable){
    if(link<0)
      if(vf->ready_state>=STREAMSET)
	return vf->vc+vf->current_link;
      else
	return vf->vc;
    else
      if(link>=vf->links)
	return NULL;
      else
	return vf->vc+link;
  }else{
    return vf->vc;
  }
}