static ogg_int64_t _get_prev_page(OggVorbis_File *vf,ogg_page *og){
ogg_int64_t begin=vf->offset;
ogg_int64_t end=begin;
ogg_int64_t ret;
ogg_int64_t offset=-1;
while(offset==-1){
begin-=CHUNKSIZE;
if(begin<0)
begin=0;
_seek_helper(vf,begin);
while(vf->offset<end){
ret=_get_next_page(vf,og,end-vf->offset);
if(ret==OV_EREAD)return(OV_EREAD);
if(ret<0){
break;
}else{
offset=ret;
}
}
}
/* we have the offset. Actually snork and hold the page now */
_seek_helper(vf,offset);
ret=_get_next_page(vf,og,CHUNKSIZE);
if(ret<0)
/* this shouldn't be possible */
return(OV_EFAULT);
return(offset);
}
/* finds each bitstream link one at a time using a bisection search
(has to begin by knowing the offset of the lb's initial page).
Recurses for each link so it can alloc the link storage after
finding them all, then unroll and fill the cache at the same time */
static int _bisect_forward_serialno(OggVorbis_File *vf,
ogg_int64_t begin,
ogg_int64_t searched,
ogg_int64_t end,
ogg_uint32_t currentno,
long m){
ogg_int64_t endsearched=end;
ogg_int64_t next=end;
ogg_page og={0,0,0,0};
ogg_int64_t ret;
/* the below guards against garbage seperating the last and
first pages of two links. */
while(searched<endsearched){
ogg_int64_t bisect;
if(endsearched-searched<CHUNKSIZE){
bisect=searched;
}else{
bisect=(searched+endsearched)/2;
}
_seek_helper(vf,bisect);
ret=_get_next_page(vf,&og,-1);
if(ret==OV_EREAD)return(OV_EREAD);
if(ret<0 || ogg_page_serialno(&og)!=currentno){
endsearched=bisect;
if(ret>=0)next=ret;
}else{
searched=ret+og.header_len+og.body_len;
}
ogg_page_release(&og);
}
_seek_helper(vf,next);
ret=_get_next_page(vf,&og,-1);
if(ret==OV_EREAD)return(OV_EREAD);
if(searched>=end || ret<0){
ogg_page_release(&og);
vf->links=m+1;
vf->offsets=_ogg_malloc((vf->links+1)*sizeof(*vf->offsets));
vf->serialnos=_ogg_malloc(vf->links*sizeof(*vf->serialnos));
vf->offsets[m+1]=searched;
}else{
ret=_bisect_forward_serialno(vf,next,vf->offset,
end,ogg_page_serialno(&og),m+1);
ogg_page_release(&og);
if(ret==OV_EREAD)return(OV_EREAD);
}
vf->offsets[m]=begin;
vf->serialnos[m]=currentno;
return(0);
}
/* this is void and does not propogate errors up because we want to be
able to open and use damaged bitstreams as well as we can. Just
watch out for missing information for links in the OggVorbis_File
struct */
static void _prefetch_all_headers(OggVorbis_File *vf, long dataoffset){
ogg_page og;
int i,ret;
vf->vi=(vorbis_info *)_ogg_realloc(vf->vi,vf->links*sizeof(*vf->vi));
vf->vc=(vorbis_comment *)_ogg_realloc(vf->vc,vf->links*sizeof(*vf->vc));
vf->dataoffsets=(ogg_int64_t *)_ogg_malloc(vf->links*sizeof(*vf->dataoffsets));
vf->pcmlengths=(ogg_int64_t *)_ogg_malloc(vf->links*sizeof(*vf->pcmlengths));
vf->serialnos=(long *)_ogg_malloc(vf->links*sizeof(*vf->serialnos));
for(i=0;i<vf->links;i++){
if(i==0){
/* we already grabbed the initial header earlier. Just set the offset */
vf->dataoffsets[i]=dataoffset;
}else{
/* seek to the location of the initial header */
_seek_helper(vf,vf->offsets[i]);
if(_fetch_headers(vf,vf->vi+i,vf->vc+i,NULL,NULL)<0){
vf->dataoffsets[i]=-1;
}else{
vf->dataoffsets[i]=vf->offset;
ogg_stream_clear(&vf->os);
}
}
/* get the serial number and PCM length of this link. To do this,
get the last page of the stream */
{
long end=vf->offsets[i+1];
_seek_helper(vf,end);
while(1){
ret=_get_prev_page(vf,&og);
if(ret<0){
/* this should not be possible */
vorbis_info_clear(vf->vi+i);
vorbis_comment_clear(vf->vc+i);
break;
}
if(ogg_page_granulepos(&og)!=-1){
vf->serialnos[i]=ogg_page_serialno(&og);
vf->pcmlengths[i]=ogg_page_granulepos(&og);
break;
}
vf->offset=ret;
}
}
}
}
static int _set_link_number_preserve_pos(OggVorbis_File *vf,int link){
ogg_int64_t pos=vf->offset;
int ret=_set_link_number(vf,link);
if(ret)return ret;
_seek_helper(vf,pos);
if(pos<vf->offsets[link] || pos>=vf->offsets[link+1])
vf->ready_state=STREAMSET;
return 0;
}
/* we no longer preload all vorbis_info (and the associated
codec_setup) structs. Call this to seek and fetch the info from
the bitstream, if needed */
static int _set_link_number(OggVorbis_File *vf,int link){
if(link != vf->current_link) _decode_clear(vf);
if(vf->ready_state<STREAMSET){
_seek_helper(vf,vf->offsets[link]);
ogg_stream_reset_serialno(vf->os,vf->serialnos[link]);
vf->current_serialno=vf->serialnos[link];
vf->current_link=link;
return _fetch_headers(vf,&vf->vi,&vf->vc,&vf->current_serialno,NULL);
}
return 0;
}
/* this is void and does not propogate errors up because we want to be
able to open and use damaged bitstreams as well as we can. Just
watch out for missing information for links in the OggVorbis_File
struct */
static void _prefetch_all_headers(OggVorbis_File *vf, ogg_int64_t dataoffset){
ogg_page og={0,0,0,0};
int i;
ogg_int64_t ret;
vf->vi=_ogg_realloc(vf->vi,vf->links*sizeof(*vf->vi));
vf->vc=_ogg_realloc(vf->vc,vf->links*sizeof(*vf->vc));
vf->dataoffsets=_ogg_malloc(vf->links*sizeof(*vf->dataoffsets));
vf->pcmlengths=_ogg_malloc(vf->links*2*sizeof(*vf->pcmlengths));
for(i=0;i<vf->links;i++){
if(i==0){
/* we already grabbed the initial header earlier. Just set the offset */
vf->dataoffsets[i]=dataoffset;
_seek_helper(vf,dataoffset);
}else{
/* seek to the location of the initial header */
_seek_helper(vf,vf->offsets[i]);
if(_fetch_headers(vf,vf->vi+i,vf->vc+i,NULL,NULL)<0){
vf->dataoffsets[i]=-1;
}else{
vf->dataoffsets[i]=vf->offset;
}
}
/* fetch beginning PCM offset */
if(vf->dataoffsets[i]!=-1){
ogg_int64_t accumulated=0,pos;
long lastblock=-1;
int result;
ogg_stream_reset_serialno(vf->os,vf->serialnos[i]);
while(1){
ogg_packet op={0,0,0,0,0,0};
ret=_get_next_page(vf,&og,-1);
if(ret<0)
/* this should not be possible unless the file is
truncated/mangled */
break;
if(ogg_page_serialno(&og)!=vf->serialnos[i])
break;
pos=ogg_page_granulepos(&og);
/* count blocksizes of all frames in the page */
ogg_stream_pagein(vf->os,&og);
while((result=ogg_stream_packetout(vf->os,&op))){
if(result>0){ /* ignore holes */
long thisblock=vorbis_packet_blocksize(vf->vi+i,&op);
if(lastblock!=-1)
accumulated+=(lastblock+thisblock)>>2;
lastblock=thisblock;
}
}
ogg_packet_release(&op);
if(pos!=-1){
/* pcm offset of last packet on the first audio page */
accumulated= pos-accumulated;
break;
}
}
/* less than zero? This is a stream with samples trimmed off
the beginning, a normal occurrence; set the offset to zero */
if(accumulated<0)accumulated=0;
vf->pcmlengths[i*2]=accumulated;
}
int ov_raw_seek(OggVorbis_File *vf,long pos){
ogg_stream_state work_os;
if(vf->ready_state<OPENED)return(OV_EINVAL);
if(!vf->seekable)
return(OV_ENOSEEK); /* don't dump machine if we can't seek */
if(pos<0 || pos>vf->offsets[vf->links])return(OV_EINVAL);
/* clear out decoding machine state */
vf->pcm_offset=-1;
_decode_clear(vf);
_seek_helper(vf,pos);
/* we need to make sure the pcm_offset is set, but we don't want to
advance the raw cursor past good packets just to get to the first
with a granulepos. That's not equivalent behavior to beginning
decoding as immediately after the seek position as possible.
So, a hack. We use two stream states; a local scratch state and
a the shared vf->os stream state. We use the local state to
scan, and the shared state as a buffer for later decode.
Unfortuantely, on the last page we still advance to last packet
because the granulepos on the last page is not necessarily on a
packet boundary, and we need to make sure the granpos is
correct.
*/
{
ogg_page og;
ogg_packet op;
int lastblock=0;
int accblock=0;
int thisblock=-1;
int eosflag=0;
memset(&work_os,0,sizeof(work_os));/* so that it's safe to clear
it later even if we don't
init it */
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(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;
for(i=0;i<link;i++)
granulepos+=vf->pcmlengths[i];
vf->pcm_offset=granulepos-accblock;
break;
}
lastblock=thisblock;
continue;
}
}
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_init(&vf->os,vf->current_serialno);
ogg_stream_reset(&vf->os);
ogg_stream_init(&work_os,vf->current_serialno);
ogg_stream_reset(&work_os);
vf->ready_state=STREAMSET;
}
ogg_stream_pagein(&vf->os,&og);
ogg_stream_pagein(&work_os,&og);
eosflag=ogg_page_eos(&og);
}
}