/********************************************************************

 *                                                                  *

 * THIS FILE IS PART OF THE OggVorbis 'TREMOR' CODEC SOURCE CODE.   *

 *                                                                  *

 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *

 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *

 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *

 *                                                                  *

 * THE OggVorbis 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2003    *

 * BY THE Xiph.Org FOUNDATION http://www.xiph.org/                  *

 *                                                                  *

 ********************************************************************

 function: stdio-based convenience library for opening/seeking/decoding

 ********************************************************************/

#include <stdlib.h>

#include <stdio.h>

#include <errno.h>

#include <string.h>

#include <math.h>

#include "ivorbisfile.h"

#include "misc.h"

/* A 'chained bitstream' is a Vorbis bitstream that contains more than

   one logical bitstream arranged end to end (the only form of Ogg

   multiplexing allowed in a Vorbis bitstream; grouping [parallel

   multiplexing] is not allowed in Vorbis) */

/* A Vorbis file can be played beginning to end (streamed) without

   worrying ahead of time about chaining (see decoder_example.c).  If

   we have the whole file, however, and want random access

   (seeking/scrubbing) or desire to know the total length/time of a

   file, we need to account for the possibility of chaining. */

/* We can handle things a number of ways; we can determine the entire

   bitstream structure right off the bat, or find pieces on demand.

   This example determines and caches structure for the entire

   bitstream, but builds a virtual decoder on the fly when moving

   between links in the chain. */

/* There are also different ways to implement seeking.  Enough

   information exists in an Ogg bitstream to seek to

   sample-granularity positions in the output.  Or, one can seek by

   picking some portion of the stream roughly in the desired area if

   we only want coarse navigation through the stream. */

/*************************************************************************

 * Many, many internal helpers.  The intention is not to be confusing; 

 * rampant duplication and monolithic function implementation would be 

 * harder to understand anyway.  The high level functions are last.  Begin

 * grokking near the end of the file */

/* read a little more data from the file/pipe into the ogg_sync framer */

static long _get_data(OggVorbis_File *vf){

  errno=0;

  if(vf->datasource){

    unsigned char *buffer=ogg_sync_bufferin(vf->oy,CHUNKSIZE);

    long bytes=(vf->callbacks.read_func)(buffer,1,CHUNKSIZE,vf->datasource);

    if(bytes>0)ogg_sync_wrote(vf->oy,bytes);

  }else

}

/* save a tiny smidge of verbosity to make the code more readable */

static void _seek_helper(OggVorbis_File *vf,ogg_int64_t offset){

  if(vf->datasource){ 

    (vf->callbacks.seek_func)(vf->datasource, offset, SEEK_SET);

    vf->offset=offset;

    ogg_sync_reset(vf->oy);

  }else{

    /* shouldn't happen unless someone writes a broken callback */

    return;

  }

}

/* The read/seek functions track absolute position within the stream */

/* from the head of the stream, get the next page.  boundary specifies

   if the function is allowed to fetch more data from the stream (and

   how much) or only use internally buffered data.

   boundary: -1) unbounded search

              0) read no additional data; use cached only

	      n) search for a new page beginning for n bytes

   return:   <0) did not find a page (OV_FALSE, OV_EOF, OV_EREAD)

              n) found a page at absolute offset n 

              produces a refcounted page */

static ogg_int64_t _get_next_page(OggVorbis_File *vf,ogg_page *og,

				  ogg_int64_t boundary){

  if(boundary>0)boundary+=vf->offset;

  while(1){

    long more;

    more=ogg_sync_pageseek(vf->oy,og);

    if(more<0){

      /* skipped n bytes */

      vf->offset-=more;

    }else{

      if(more==0){

	/* send more paramedics */

	{

	  long ret=_get_data(vf);

	}

      }else{

	/* got a page.  Return the offset at the page beginning,

           advance the internal offset past the page end */

	ogg_int64_t ret=vf->offset;

	vf->offset+=more;

      }

    }

  }

}

/* find the latest page beginning before the current stream cursor

   position. Much dirtier than the above as Ogg doesn't have any

   backward search linkage.  no 'readp' as it will certainly have to

   read. */

/* returns offset or OV_EREAD, OV_FAULT and produces a refcounted page */

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<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 */

}

/* 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<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(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);

  }

  vf->offsets[m]=begin;

  vf->serialnos[m]=currentno;

}

/* uses the local ogg_stream storage in vf; this is important for

   non-streaming input sources */

/* consumes the page that's passed in (if any) */

static int _fetch_headers(OggVorbis_File *vf,

			  vorbis_info *vi,

			  vorbis_comment *vc,

			  ogg_uint32_t *serialno,

			  ogg_page *og_ptr){

  ogg_page og={0,0,0,0};

  ogg_packet op={0,0,0,0,0,0};

  int i,ret;

  if(!og_ptr){

    ogg_int64_t llret=_get_next_page(vf,&og,CHUNKSIZE);

    if(llret<0)return OV_ENOTVORBIS;

    og_ptr=&og;

  }

  ogg_stream_reset_serialno(vf->os,ogg_page_serialno(og_ptr));

  if(serialno)*serialno=vf->os->serialno;

  /* extract the initial header from the first page and verify that the

     Ogg bitstream is in fact Vorbis data */

  vorbis_info_init(vi);

  vorbis_comment_init(vc);

  i=0;

  while(i<3){

    ogg_stream_pagein(vf->os,og_ptr);

    while(i<3){

      int result=ogg_stream_packetout(vf->os,&op);

      if(result==0)break;

      if(result==-1){

	ret=OV_EBADHEADER;

	goto bail_header;

      }

	goto bail_header;

      }

      i++;

    }

    if(i<3)

      if(_get_next_page(vf,og_ptr,CHUNKSIZE)<0){

	ret=OV_EBADHEADER;

	goto bail_header;

      }

  }

  ogg_packet_release(&op);

  ogg_page_release(&og);

  return 0; 

 bail_header:

  ogg_packet_release(&op);

  ogg_page_release(&og);

  vorbis_info_clear(vi);

  vorbis_comment_clear(vc);

  vf->ready_state=OPENED;

  return ret;

}

/* 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 */

  ogg_page og={0,0,0,0};

  int i;

  ogg_int64_t ret;

  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]);

    	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 */

	    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;

    }

    /* get the PCM length of this link. To do this,

       get the last page of the stream */

    {

      ogg_int64_t 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 */

	  break;

	}

	if(ogg_page_granulepos(&og)!=-1){

	  vf->pcmlengths[i*2+1]=ogg_page_granulepos(&og)-vf->pcmlengths[i*2];

	  break;

	}

	vf->offset=ret;

      }

    }

  }

  ogg_page_release(&og);

}

}

static int _open_seekable2(OggVorbis_File *vf){

  ogg_uint32_t serialno=vf->current_serialno;

  ogg_uint32_t tempserialno;

  ogg_int64_t dataoffset=vf->offset, end;

  ogg_page og={0,0,0,0};

  /* we're partially open and have a first link header state in

     storage in vf */

  /* we can seek, so set out learning all about this file */

  (vf->callbacks.seek_func)(vf->datasource,0,SEEK_END);

  vf->offset=vf->end=(vf->callbacks.tell_func)(vf->datasource);

  /* We get the offset for the last page of the physical bitstream.

     Most OggVorbis files will contain a single logical bitstream */

  end=_get_prev_page(vf,&og);

  /* more than one logical bitstream? */

  tempserialno=ogg_page_serialno(&og);

  ogg_page_release(&og);

  if(tempserialno!=serialno){

    /* Chained bitstream. Bisect-search each logical bitstream

       section.  Do so based on serial number only */

  }else{

    /* Only one logical bitstream */

  }

  /* the initial header memory is referenced by vf after; don't free it */