framing.c

这是一个和OGGPLAY的播放程序的附代码

    if(next){
      /* possible capture in this segment */
      long bytes=next-now;
      oy->fifo_tail=ogg_buffer_pretruncate(oy->fifo_tail,bytes);
      ret-=bytes;
      break;
    }else{
      /* no capture.  advance to next segment */
      long bytes=oy->fifo_tail->length;
      ret-=bytes;
      oy->fifo_tail=ogg_buffer_pretruncate(oy->fifo_tail,bytes);
    }
  }
  if(!oy->fifo_tail)oy->fifo_head=0;
  oy->fifo_fill+=ret;

 sync_out:
  return ret;
}

/* sync the stream and get a page.  Keep trying until we find a page.
   Supress 'sync errors' after reporting the first.

   return values:
   OGG_HOLE) recapture (hole in data)
          0) need more data
          1) page returned

   Returns pointers into buffered data; invalidated by next call to
   _stream, _clear, _init, or _buffer */

int ogg_sync_pageout(ogg_sync_state *oy, ogg_page *og){

  /* all we need to do is verify a page at the head of the stream
     buffer.  If it doesn't verify, we look for the next potential
     frame */

  while(1){
    long ret=ogg_sync_pageseek(oy,og);
    if(ret>0){
      /* have a page */
      return 1;
    }
    if(ret==0){
      /* need more data */
      return 0;
    }
    
    /* head did not start a synced page... skipped some bytes */
    if(!oy->unsynced){
      oy->unsynced=1;
      return OGG_HOLE;
    }

    /* loop. keep looking */

  }
}

/* clear things to an initial state.  Good to call, eg, before seeking */
int ogg_sync_reset(ogg_sync_state *oy){
  ogg_buffer_release(oy->fifo_tail);
  oy->fifo_tail=0;
  oy->fifo_head=0;
  oy->fifo_fill=0;

  oy->unsynced=0;
  oy->headerbytes=0;
  oy->bodybytes=0;
  return OGG_SUCCESS;
}

ogg_stream_state *ogg_stream_create(int serialno){
  ogg_stream_state *os=_ogg_calloc(1,sizeof(*os));
  os->serialno=serialno;
  os->pageno=-1;
  return os;
} 

int ogg_stream_destroy(ogg_stream_state *os){
  if(os){
    ogg_buffer_release(os->header_tail);
    ogg_buffer_release(os->body_tail);
    memset(os,0,sizeof(*os));    
    _ogg_free(os);
  }
  return OGG_SUCCESS;
} 


#define FINFLAG 0x80000000UL
#define FINMASK 0x7fffffffUL

static void _next_lace(oggbyte_buffer *ob,ogg_stream_state *os){
  /* search ahead one lace */
  os->body_fill_next=0;
  while(os->laceptr<os->lacing_fill){
    int val=oggbyte_read1(ob,27+os->laceptr++);
    os->body_fill_next+=val;
    if(val<255){
      os->body_fill_next|=FINFLAG;
      os->clearflag=1;
      break;
    }
  }
}

static void _span_queued_page(ogg_stream_state *os){ 
  while( !(os->body_fill&FINFLAG) ){
    
    if(!os->header_tail)break;

    /* first flush out preceeding page header (if any).  Body is
       flushed as it's consumed, so that's not done here. */

    if(os->lacing_fill>=0)
      os->header_tail=ogg_buffer_pretruncate(os->header_tail,
                                             os->lacing_fill+27);
    os->lacing_fill=0;
    os->laceptr=0;
    os->clearflag=0;

    if(!os->header_tail){
      os->header_head=0;
      break;
    }else{
      
      /* process/prepare next page, if any */

      long pageno;
      oggbyte_buffer ob;
      ogg_page og;               /* only for parsing header values */
      og.header=os->header_tail; /* only for parsing header values */
      pageno=ogg_page_pageno(&og);

      oggbyte_init(&ob,os->header_tail);
      os->lacing_fill=oggbyte_read1(&ob,26);
      
      /* are we in sequence? */
      if(pageno!=os->pageno){
        if(os->pageno==-1) /* indicates seek or reset */
          os->holeflag=1;  /* set for internal use */
        else
          os->holeflag=2;  /* set for external reporting */

        os->body_tail=ogg_buffer_pretruncate(os->body_tail,
                                             os->body_fill);
        if(os->body_tail==0)os->body_head=0;
        os->body_fill=0;

      }
    
      if(ogg_page_continued(&og)){
        if(os->body_fill==0){
          /* continued packet, but no preceeding data to continue */
          /* dump the first partial packet on the page */
          _next_lace(&ob,os);   
          os->body_tail=
            ogg_buffer_pretruncate(os->body_tail,os->body_fill_next&FINMASK);
          if(os->body_tail==0)os->body_head=0;
          /* set span flag */
          if(!os->spanflag && !os->holeflag)os->spanflag=2;
        }
      }else{
        if(os->body_fill>0){
          /* preceeding data to continue, but not a continued page */
          /* dump body_fill */
          os->body_tail=ogg_buffer_pretruncate(os->body_tail,
                                               os->body_fill);
          if(os->body_tail==0)os->body_head=0;
          os->body_fill=0;

          /* set espan flag */
          if(!os->spanflag && !os->holeflag)os->spanflag=2;
        }
      }

      if(os->laceptr<os->lacing_fill){
        os->granulepos=ogg_page_granulepos(&og);

        /* get current packet size & flag */
        _next_lace(&ob,os);
        os->body_fill+=os->body_fill_next; /* addition handles the flag fine;
                                             unsigned on purpose */
        /* ...and next packet size & flag */
        _next_lace(&ob,os);

      }
      
      os->pageno=pageno+1;
      os->e_o_s=ogg_page_eos(&og);
      os->b_o_s=ogg_page_bos(&og);
    
    }
  }
}

/* add the incoming page to the stream state; we decompose the page
   into packet segments here as well. */

int ogg_stream_pagein(ogg_stream_state *os, ogg_page *og){

  int serialno=ogg_page_serialno(og);
  int version=ogg_page_version(og);

  /* check the serial number */
  if(serialno!=os->serialno){
    ogg_page_release(og);
    return OGG_ESERIAL;
  }
  if(version>0){
    ogg_page_release(og);
    return OGG_EVERSION;
  }

  /* add to fifos */
  if(!os->body_tail){
    os->body_tail=og->body;
    os->body_head=ogg_buffer_walk(og->body);
  }else{
    os->body_head=ogg_buffer_cat(os->body_head,og->body);
  }
  if(!os->header_tail){
    os->header_tail=og->header;
    os->header_head=ogg_buffer_walk(og->header);
    os->lacing_fill=-27;
  }else{
    os->header_head=ogg_buffer_cat(os->header_head,og->header);
  }

  memset(og,0,sizeof(*og));
  return OGG_SUCCESS;
}

int ogg_stream_reset(ogg_stream_state *os){

  ogg_buffer_release(os->header_tail);
  ogg_buffer_release(os->body_tail);
  os->header_tail=os->header_head=0;
  os->body_tail=os->body_head=0;

  os->e_o_s=0;
  os->b_o_s=0;
  os->pageno=-1;
  os->packetno=0;
  os->granulepos=0;

  os->body_fill=0;
  os->lacing_fill=0;

  os->holeflag=0;
  os->spanflag=0;
  os->clearflag=0;
  os->laceptr=0;
  os->body_fill_next=0;

  return OGG_SUCCESS;
}

int ogg_stream_reset_serialno(ogg_stream_state *os,int serialno){
  ogg_stream_reset(os);
  os->serialno=serialno;
  return OGG_SUCCESS;
}

static int _packetout(ogg_stream_state *os,ogg_packet *op,int adv){

  ogg_packet_release(op);
  _span_queued_page(os);

  if(os->holeflag){
    int temp=os->holeflag;
    if(os->clearflag)
      os->holeflag=0;
    else
      os->holeflag=1;
    if(temp==2){
      os->packetno++;
      return OGG_HOLE;
    }
  }
  if(os->spanflag){
    int temp=os->spanflag;
    if(os->clearflag)
      os->spanflag=0;
    else
      os->spanflag=1;
    if(temp==2){
      os->packetno++;
      return OGG_SPAN;
    }
  }

  if(!(os->body_fill&FINFLAG)) return 0;
  if(!op && !adv)return 1; /* just using peek as an inexpensive way
                               to ask if there's a whole packet
                               waiting */
  if(op){
    op->b_o_s=os->b_o_s;
    if(os->e_o_s && os->body_fill_next==0)
      op->e_o_s=os->e_o_s;
    else
      op->e_o_s=0;
    if( (os->body_fill&FINFLAG) && !(os->body_fill_next&FINFLAG) )
      op->granulepos=os->granulepos;
    else
      op->granulepos=-1;
    op->packetno=os->packetno;
  }

  if(adv){
    oggbyte_buffer ob;
    oggbyte_init(&ob,os->header_tail);

    /* split the body contents off */
    if(op){
      op->packet=ogg_buffer_split(&os->body_tail,&os->body_head,
				  os->body_fill&FINMASK);
      op->bytes=os->body_fill&FINMASK;
    }else{
      os->body_tail=ogg_buffer_pretruncate(os->body_tail,
					   os->body_fill&FINMASK);
      if(os->body_tail==0)os->body_head=0;
    }

    /* update lacing pointers */
    os->body_fill=os->body_fill_next;
    _next_lace(&ob,os);
  }else{
    if(op){
      op->packet=ogg_buffer_sub(os->body_tail,0,os->body_fill&FINMASK);
      op->bytes=os->body_fill&FINMASK;
    }
  }
  
  if(adv){
    os->packetno++;
    os->b_o_s=0;
  }

  return 1;
}

int ogg_stream_packetout(ogg_stream_state *os,ogg_packet *op){
  return _packetout(os,op,1);
}

int ogg_stream_packetpeek(ogg_stream_state *os,ogg_packet *op){
  return _packetout(os,op,0);
}

int ogg_packet_release(ogg_packet *op) {
  if(op){
    ogg_buffer_release(op->packet);
    memset(op, 0, sizeof(*op));
  }
  return OGG_SUCCESS;
}

int ogg_page_release(ogg_page *og) {
  if(og){
    ogg_buffer_release(og->header);
    ogg_buffer_release(og->body);
    memset(og, 0, sizeof(*og));
  }
  return OGG_SUCCESS;
}

void ogg_page_dup(ogg_page *dup,ogg_page *orig){
  dup->header_len=orig->header_len;
  dup->body_len=orig->body_len;
  dup->header=ogg_buffer_dup(orig->header);
  dup->body=ogg_buffer_dup(orig->body);
}