bitpack.h

/********************************************************************
 *                                                                  *
 * 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                      *
 * https://www.xiph.org/                                            *
 *                                                                  *
 ********************************************************************

  function: packing variable sized words into an octet stream

 ********************************************************************/
#if !defined(_bitpack_H)
# define _bitpack_H (1)
# include <stddef.h>
# include <limits.h>
# include "internal.h"



typedef size_t             oc_pb_window;
typedef struct oc_pack_buf oc_pack_buf;



/*Custom bitpacker implementations.*/
# if defined(OC_ARM_ASM)
#  include "arm/armbits.h"
# endif

# if !defined(oc_pack_read)
#  define oc_pack_read oc_pack_read_c
# endif
# if !defined(oc_pack_read1)
#  define oc_pack_read1 oc_pack_read1_c
# endif
# if !defined(oc_huff_token_decode)
#  define oc_huff_token_decode oc_huff_token_decode_c
# endif

# define OC_PB_WINDOW_SIZE ((int)sizeof(oc_pb_window)*CHAR_BIT)
/*This is meant to be a large, positive constant that can still be efficiently
   loaded as an immediate (on platforms like ARM, for example).
  Even relatively modest values like 100 would work fine.*/
# define OC_LOTS_OF_BITS (0x40000000)



struct oc_pack_buf{
  const unsigned char *stop;
  const unsigned char *ptr;
  oc_pb_window         window;
  int                  bits;
  int                  eof;
};

void oc_pack_readinit(oc_pack_buf *_b,unsigned char *_buf,long _bytes);
int oc_pack_look1(oc_pack_buf *_b);
void oc_pack_adv1(oc_pack_buf *_b);
/*Here we assume 0<=_bits&&_bits<=32.*/
long oc_pack_read_c(oc_pack_buf *_b,int _bits);
int oc_pack_read1_c(oc_pack_buf *_b);
/* returns -1 for read beyond EOF, or the number of whole bytes available */
long oc_pack_bytes_left(oc_pack_buf *_b);

/*These two functions are implemented locally in huffdec.c*/
/*Read in bits without advancing the bitptr.
  Here we assume 0<=_bits&&_bits<=32.*/
/*static int oc_pack_look(oc_pack_buf *_b,int _bits);*/
/*static void oc_pack_adv(oc_pack_buf *_b,int _bits);*/

#endif