framing.c

这是一个和OGGPLAY的播放程序的附代码

static void oggbyte_set4(oggbyte_buffer *b,ogg_uint32_t val,int pos){
  int i;
  _positionB(b,pos);
  for(i=0;i<4;i++){
    _positionF(b,pos);
    b->ptr[pos-b->pos]=val;
    val>>=8;
    ++pos;
  }
}
 
static unsigned char oggbyte_read1(oggbyte_buffer *b,int pos){
  _positionB(b,pos);
  _positionF(b,pos);
  return b->ptr[pos-b->pos];
}

static ogg_uint32_t oggbyte_read4(oggbyte_buffer *b,int pos){
  ogg_uint32_t ret;
  _positionB(b,pos);
  _positionF(b,pos);
  ret=b->ptr[pos-b->pos];
  _positionF(b,++pos);
  ret|=b->ptr[pos-b->pos]<<8;
  _positionF(b,++pos);
  ret|=b->ptr[pos-b->pos]<<16;
  _positionF(b,++pos);
  ret|=b->ptr[pos-b->pos]<<24;
  return ret;
}

static ogg_int64_t oggbyte_read8(oggbyte_buffer *b,int pos){
  ogg_int64_t ret;
  unsigned char t[7];
  int i;
  _positionB(b,pos);
  for(i=0;i<7;i++){
    _positionF(b,pos);
    t[i]=b->ptr[pos++ -b->pos];
  }

  _positionF(b,pos);
  ret=b->ptr[pos-b->pos];

  for(i=6;i>=0;--i)
    ret= ret<<8 | t[i];

  return ret;
}

/* Now we get to the actual framing code */

int ogg_page_version(ogg_page *og){
  oggbyte_buffer ob;
  oggbyte_init(&ob,og->header);
  return oggbyte_read1(&ob,4);
}

int ogg_page_continued(ogg_page *og){
  oggbyte_buffer ob;
  oggbyte_init(&ob,og->header);
  return oggbyte_read1(&ob,5)&0x01;
}

int ogg_page_bos(ogg_page *og){
  oggbyte_buffer ob;
  oggbyte_init(&ob,og->header);
  return oggbyte_read1(&ob,5)&0x02;
}

int ogg_page_eos(ogg_page *og){
  oggbyte_buffer ob;
  oggbyte_init(&ob,og->header);
  return oggbyte_read1(&ob,5)&0x04;
}

ogg_int64_t ogg_page_granulepos(ogg_page *og){
  oggbyte_buffer ob;
  oggbyte_init(&ob,og->header);
  return oggbyte_read8(&ob,6);
}

ogg_uint32_t ogg_page_serialno(ogg_page *og){
  oggbyte_buffer ob;
  oggbyte_init(&ob,og->header);
  return oggbyte_read4(&ob,14);
}
 
ogg_uint32_t ogg_page_pageno(ogg_page *og){
  oggbyte_buffer ob;
  oggbyte_init(&ob,og->header);
  return oggbyte_read4(&ob,18);
}

/* returns the number of packets that are completed on this page (if
   the leading packet is begun on a previous page, but ends on this
   page, it's counted */

/* NOTE:
If a page consists of a packet begun on a previous page, and a new
packet begun (but not completed) on this page, the return will be:
  ogg_page_packets(page)   ==1, 
  ogg_page_continued(page) !=0

If a page happens to be a single packet that was begun on a
previous page, and spans to the next page (in the case of a three or
more page packet), the return will be: 
  ogg_page_packets(page)   ==0, 
  ogg_page_continued(page) !=0
*/

int ogg_page_packets(ogg_page *og){
  int i;
  int n;
  int count=0;
  oggbyte_buffer ob;
  oggbyte_init(&ob,og->header);

  n=oggbyte_read1(&ob,26);
  for(i=0;i<n;i++)
    if(oggbyte_read1(&ob,27+i)<255)count++;
  return(count);
}

/* Static CRC calculation table.  See older code in CVS for dead
   run-time initialization code. */

static ogg_uint32_t const crc_lookup[256]={
  0x00000000,0x04c11db7,0x09823b6e,0x0d4326d9,
  0x130476dc,0x17c56b6b,0x1a864db2,0x1e475005,
  0x2608edb8,0x22c9f00f,0x2f8ad6d6,0x2b4bcb61,
  0x350c9b64,0x31cd86d3,0x3c8ea00a,0x384fbdbd,
  0x4c11db70,0x48d0c6c7,0x4593e01e,0x4152fda9,
  0x5f15adac,0x5bd4b01b,0x569796c2,0x52568b75,
  0x6a1936c8,0x6ed82b7f,0x639b0da6,0x675a1011,
  0x791d4014,0x7ddc5da3,0x709f7b7a,0x745e66cd,
  0x9823b6e0,0x9ce2ab57,0x91a18d8e,0x95609039,
  0x8b27c03c,0x8fe6dd8b,0x82a5fb52,0x8664e6e5,
  0xbe2b5b58,0xbaea46ef,0xb7a96036,0xb3687d81,
  0xad2f2d84,0xa9ee3033,0xa4ad16ea,0xa06c0b5d,
  0xd4326d90,0xd0f37027,0xddb056fe,0xd9714b49,
  0xc7361b4c,0xc3f706fb,0xceb42022,0xca753d95,
  0xf23a8028,0xf6fb9d9f,0xfbb8bb46,0xff79a6f1,
  0xe13ef6f4,0xe5ffeb43,0xe8bccd9a,0xec7dd02d,
  0x34867077,0x30476dc0,0x3d044b19,0x39c556ae,
  0x278206ab,0x23431b1c,0x2e003dc5,0x2ac12072,
  0x128e9dcf,0x164f8078,0x1b0ca6a1,0x1fcdbb16,
  0x018aeb13,0x054bf6a4,0x0808d07d,0x0cc9cdca,
  0x7897ab07,0x7c56b6b0,0x71159069,0x75d48dde,
  0x6b93dddb,0x6f52c06c,0x6211e6b5,0x66d0fb02,
  0x5e9f46bf,0x5a5e5b08,0x571d7dd1,0x53dc6066,
  0x4d9b3063,0x495a2dd4,0x44190b0d,0x40d816ba,
  0xaca5c697,0xa864db20,0xa527fdf9,0xa1e6e04e,
  0xbfa1b04b,0xbb60adfc,0xb6238b25,0xb2e29692,
  0x8aad2b2f,0x8e6c3698,0x832f1041,0x87ee0df6,
  0x99a95df3,0x9d684044,0x902b669d,0x94ea7b2a,
  0xe0b41de7,0xe4750050,0xe9362689,0xedf73b3e,
  0xf3b06b3b,0xf771768c,0xfa325055,0xfef34de2,
  0xc6bcf05f,0xc27dede8,0xcf3ecb31,0xcbffd686,
  0xd5b88683,0xd1799b34,0xdc3abded,0xd8fba05a,
  0x690ce0ee,0x6dcdfd59,0x608edb80,0x644fc637,
  0x7a089632,0x7ec98b85,0x738aad5c,0x774bb0eb,
  0x4f040d56,0x4bc510e1,0x46863638,0x42472b8f,
  0x5c007b8a,0x58c1663d,0x558240e4,0x51435d53,
  0x251d3b9e,0x21dc2629,0x2c9f00f0,0x285e1d47,
  0x36194d42,0x32d850f5,0x3f9b762c,0x3b5a6b9b,
  0x0315d626,0x07d4cb91,0x0a97ed48,0x0e56f0ff,
  0x1011a0fa,0x14d0bd4d,0x19939b94,0x1d528623,
  0xf12f560e,0xf5ee4bb9,0xf8ad6d60,0xfc6c70d7,
  0xe22b20d2,0xe6ea3d65,0xeba91bbc,0xef68060b,
  0xd727bbb6,0xd3e6a601,0xdea580d8,0xda649d6f,
  0xc423cd6a,0xc0e2d0dd,0xcda1f604,0xc960ebb3,
  0xbd3e8d7e,0xb9ff90c9,0xb4bcb610,0xb07daba7,
  0xae3afba2,0xaafbe615,0xa7b8c0cc,0xa379dd7b,
  0x9b3660c6,0x9ff77d71,0x92b45ba8,0x9675461f,
  0x8832161a,0x8cf30bad,0x81b02d74,0x857130c3,
  0x5d8a9099,0x594b8d2e,0x5408abf7,0x50c9b640,
  0x4e8ee645,0x4a4ffbf2,0x470cdd2b,0x43cdc09c,
  0x7b827d21,0x7f436096,0x7200464f,0x76c15bf8,
  0x68860bfd,0x6c47164a,0x61043093,0x65c52d24,
  0x119b4be9,0x155a565e,0x18197087,0x1cd86d30,
  0x029f3d35,0x065e2082,0x0b1d065b,0x0fdc1bec,
  0x3793a651,0x3352bbe6,0x3e119d3f,0x3ad08088,
  0x2497d08d,0x2056cd3a,0x2d15ebe3,0x29d4f654,
  0xc5a92679,0xc1683bce,0xcc2b1d17,0xc8ea00a0,
  0xd6ad50a5,0xd26c4d12,0xdf2f6bcb,0xdbee767c,
  0xe3a1cbc1,0xe760d676,0xea23f0af,0xeee2ed18,
  0xf0a5bd1d,0xf464a0aa,0xf9278673,0xfde69bc4,
  0x89b8fd09,0x8d79e0be,0x803ac667,0x84fbdbd0,
  0x9abc8bd5,0x9e7d9662,0x933eb0bb,0x97ffad0c,
  0xafb010b1,0xab710d06,0xa6322bdf,0xa2f33668,
  0xbcb4666d,0xb8757bda,0xb5365d03,0xb1f740b4};

ogg_sync_state *ogg_sync_create(void){
  ogg_sync_state *oy=_ogg_calloc(1,sizeof(*oy));
  memset(oy,0,sizeof(*oy));
  oy->bufferpool=ogg_buffer_create();
  return oy;
}

int ogg_sync_destroy(ogg_sync_state *oy){
  if(oy){
    ogg_sync_reset(oy);
    ogg_buffer_destroy(oy->bufferpool);
    memset(oy,0,sizeof(*oy));
    _ogg_free(oy);
  }
  return OGG_SUCCESS;
}

unsigned char *ogg_sync_bufferin(ogg_sync_state *oy, long bytes){
  
  /* [allocate and] expose a buffer for data submission.

     If there is no head fragment
       allocate one and expose it
     else
       if the current head fragment has sufficient unused space
         expose it
       else
         if the current head fragment is unused
           resize and expose it
         else
           allocate new fragment and expose it
  */

  /* base case; fifo uninitialized */
  if(!oy->fifo_head){
    oy->fifo_head=oy->fifo_tail=ogg_buffer_alloc(oy->bufferpool,bytes);
    return oy->fifo_head->buffer->data;
  }
  
  /* space left in current fragment case */
  if(oy->fifo_head->buffer->size-
     oy->fifo_head->length-
     oy->fifo_head->begin >= bytes)
    return oy->fifo_head->buffer->data+
      oy->fifo_head->length+oy->fifo_head->begin;

  /* current fragment is unused, but too small */
  if(!oy->fifo_head->length){
    ogg_buffer_realloc(oy->fifo_head,bytes);
    return oy->fifo_head->buffer->data+oy->fifo_head->begin;
  }
  
  /* current fragment used/full; get new fragment */
  {
    ogg_reference *new=ogg_buffer_alloc(oy->bufferpool,bytes);
    oy->fifo_head->next=new;
    oy->fifo_head=new;
  }
  return oy->fifo_head->buffer->data;
}

int ogg_sync_wrote(ogg_sync_state *oy, long bytes){ 
  if(!oy->fifo_head)return OGG_EINVAL;
  if(oy->fifo_head->buffer->size-oy->fifo_head->length-oy->fifo_head->begin < 
     bytes)return OGG_EINVAL;
  oy->fifo_head->length+=bytes;
  oy->fifo_fill+=bytes;
  return OGG_SUCCESS;
}

static ogg_uint32_t _checksum(ogg_reference *or, int bytes){
  ogg_uint32_t crc_reg=0;
  int j,post;

  while(or){
    unsigned char *data=or->buffer->data+or->begin;
    post=(bytes<or->length?bytes:or->length);
    for(j=0;j<post;++j)
      crc_reg=(crc_reg<<8)^crc_lookup[((crc_reg >> 24)&0xff)^data[j]];
    bytes-=j;
    or=or->next;
  }

  return crc_reg;
}


/* sync the stream.  This is meant to be useful for finding page
   boundaries.

   return values for this:
  -n) skipped n bytes
   0) page not ready; more data (no bytes skipped)
   n) page synced at current location; page length n bytes
   
*/

long ogg_sync_pageseek(ogg_sync_state *oy,ogg_page *og){
  oggbyte_buffer page;
  long           bytes,ret=0;

  ogg_page_release(og);

  bytes=oy->fifo_fill;
  oggbyte_init(&page,oy->fifo_tail);

  if(oy->headerbytes==0){
    if(bytes<27)goto sync_out; /* not enough for even a minimal header */
    
    /* verify capture pattern */
    if(oggbyte_read1(&page,0)!=(int)'O' ||
       oggbyte_read1(&page,1)!=(int)'g' ||
       oggbyte_read1(&page,2)!=(int)'g' ||
       oggbyte_read1(&page,3)!=(int)'S'    ) goto sync_fail;

    oy->headerbytes=oggbyte_read1(&page,26)+27;
  }
  if(bytes<oy->headerbytes)goto sync_out; /* not enough for header +
                                             seg table */
  if(oy->bodybytes==0){
    int i;
    /* count up body length in the segment table */
    for(i=0;i<oy->headerbytes-27;i++)
      oy->bodybytes+=oggbyte_read1(&page,27+i);
  }
  
  if(oy->bodybytes+oy->headerbytes>bytes)goto sync_out;

  /* we have what appears to be a complete page; last test: verify
     checksum */
  {
    ogg_uint32_t chksum=oggbyte_read4(&page,22);
    oggbyte_set4(&page,0,22);

    /* Compare checksums; memory continues to be common access */
    if(chksum!=_checksum(oy->fifo_tail,oy->bodybytes+oy->headerbytes)){
      
      /* D'oh.  Mismatch! Corrupt page (or miscapture and not a page
         at all). replace the computed checksum with the one actually
         read in; remember all the memory is common access */
      
      oggbyte_set4(&page,chksum,22);
      goto sync_fail;
    }
    oggbyte_set4(&page,chksum,22);
  }

  /* We have a page.  Set up page return. */
  if(og){
    /* set up page output */
    og->header=ogg_buffer_split(&oy->fifo_tail,&oy->fifo_head,oy->headerbytes);
    og->header_len=oy->headerbytes;
    og->body=ogg_buffer_split(&oy->fifo_tail,&oy->fifo_head,oy->bodybytes);
    og->body_len=oy->bodybytes;
  }else{
    /* simply advance */
    oy->fifo_tail=
      ogg_buffer_pretruncate(oy->fifo_tail,oy->headerbytes+oy->bodybytes);
    if(!oy->fifo_tail)oy->fifo_head=0;
  }
  
  ret=oy->headerbytes+oy->bodybytes;
  oy->unsynced=0;
  oy->headerbytes=0;
  oy->bodybytes=0;
  oy->fifo_fill-=ret;

  return ret;
  
 sync_fail:

  oy->headerbytes=0;
  oy->bodybytes=0;
  oy->fifo_tail=ogg_buffer_pretruncate(oy->fifo_tail,1);
  ret--;
  
  /* search forward through fragments for possible capture */
  while(oy->fifo_tail){
    /* invariant: fifo_cursor points to a position in fifo_tail */
    unsigned char *now=oy->fifo_tail->buffer->data+oy->fifo_tail->begin;
    unsigned char *next=memchr(now, 'O', oy->fifo_tail->length);