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

 *                                                                  *

 * THIS FILE IS PART OF THE OggTheora SOFTWARE 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 OggTheora SOURCE CODE IS (C) COPYRIGHT 1994-2009             *

 * by the Xiph.Org Foundation and contributors http://www.xiph.org/ *

 *                                                                  *

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

  function: packing variable sized words into an octet stream

  last mod: $Id$

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

#include <string.h>

#include <stdlib.h>

#include "bitpack.h"

/*We're 'MSb' endian; if we write a word but read individual bits,

   then we'll read the MSb first.*/

void oc_pack_readinit(oc_pack_buf *_b,unsigned char *_buf,long _bytes){

  memset(_b,0,sizeof(*_b));

  _b->ptr=_buf;

  _b->stop=_buf+_bytes;

}

static oc_pb_window oc_pack_refill(oc_pack_buf *_b,int _bits){

  const unsigned char *ptr;

  const unsigned char *stop;

  oc_pb_window         window;

  int                  available;

  unsigned             shift;

  stop=_b->stop;

  ptr=_b->ptr;

  window=_b->window;

  available=_b->bits;

  shift=OC_PB_WINDOW_SIZE-available;

  while(7<shift&&ptr<stop){

    shift-=8;

    window|=(oc_pb_window)*ptr++<<shift;

  }

  _b->ptr=ptr;

  available=OC_PB_WINDOW_SIZE-shift;

  if(_bits>available){

    if(ptr>=stop){

      _b->eof=1;

      available=OC_LOTS_OF_BITS;

    }

    else window|=*ptr>>(available&7);

  }

  _b->bits=available;

  return window;

}

int oc_pack_look1(oc_pack_buf *_b){

  oc_pb_window window;

  int          available;

  window=_b->window;

  available=_b->bits;

  if(available<1)_b->window=window=oc_pack_refill(_b,1);

  return window>>OC_PB_WINDOW_SIZE-1;

}

void oc_pack_adv1(oc_pack_buf *_b){

  _b->window<<=1;

  _b->bits--;

}

/*Here we assume that 0<=_bits&&_bits<=32.*/

long oc_pack_read_c(oc_pack_buf *_b,int _bits){

  oc_pb_window window;

  int          available;

  long         result;

  window=_b->window;

  available=_b->bits;

  if(_bits==0)return 0;

  if(available<_bits){

    window=oc_pack_refill(_b,_bits);

    available=_b->bits;

  }

  result=window>>OC_PB_WINDOW_SIZE-_bits;

  available-=_bits;

  window<<=1;

  window<<=_bits-1;

  _b->window=window;

  _b->bits=available;

  return result;

}

int oc_pack_read1_c(oc_pack_buf *_b){

  oc_pb_window window;

  int          available;

  int          result;

  window=_b->window;

  available=_b->bits;

  if(available<1){

    window=oc_pack_refill(_b,1);

    available=_b->bits;

  }

  result=window>>OC_PB_WINDOW_SIZE-1;

  available--;

  window<<=1;

  _b->window=window;

  _b->bits=available;

  return result;

}

long oc_pack_bytes_left(oc_pack_buf *_b){

  if(_b->eof)return -1;

  return _b->stop-_b->ptr+(_b->bits>>3);

}