
/*!
 *************************************************************************************
 * \file biaridecod.c
 *
 * \brief
 *    binary arithmetic decoder routines
 * \date
 *    21. Oct 2000
 * \author
 *    Main contributors (see contributors.h for copyright, address and affiliation details)
 *    - Detlev Marpe                    <marpe@hhi.de>
 *    - Gabi Blaettermann               <blaetter@hhi.de>
 *************************************************************************************
 */

#include <stdlib.h>

#include "global.h"
#include "memalloc.h"

extern int symbolCount;

int binCount = 0;

#define Dbuffer         (dep->Dbuffer)
#define Dbits_to_go     (dep->Dbits_to_go)
#define Dcodestrm       (dep->Dcodestrm)
#define Dcodestrm_len   (dep->Dcodestrm_len)

#define B_BITS    10  // Number of bits to represent the whole coding interval
#define HALF      (1 << (B_BITS-1))
#define QUARTER   (1 << (B_BITS-2))

/* Range table for  LPS */
const byte rLPS_table_64x4[64][4]=
{
  { 128, 176, 208, 240},
  { 128, 167, 197, 227},
  { 128, 158, 187, 216},
  { 123, 150, 178, 205},
  { 116, 142, 169, 195},
  { 111, 135, 160, 185},
  { 105, 128, 152, 175},
  { 100, 122, 144, 166},
  {  95, 116, 137, 158},
  {  90, 110, 130, 150},
  {  85, 104, 123, 142},
  {  81,  99, 117, 135},
  {  77,  94, 111, 128},
  {  73,  89, 105, 122},
  {  69,  85, 100, 116},
  {  66,  80,  95, 110},
  {  62,  76,  90, 104},
  {  59,  72,  86,  99},
  {  56,  69,  81,  94},
  {  53,  65,  77,  89},
  {  51,  62,  73,  85},
  {  48,  59,  69,  80},
  {  46,  56,  66,  76},
  {  43,  53,  63,  72},
  {  41,  50,  59,  69},
  {  39,  48,  56,  65},
  {  37,  45,  54,  62},
  {  35,  43,  51,  59},
  {  33,  41,  48,  56},
  {  32,  39,  46,  53},
  {  30,  37,  43,  50},
  {  29,  35,  41,  48},
  {  27,  33,  39,  45},
  {  26,  31,  37,  43},
  {  24,  30,  35,  41},
  {  23,  28,  33,  39},
  {  22,  27,  32,  37},
  {  21,  26,  30,  35},
  {  20,  24,  29,  33},
  {  19,  23,  27,  31},
  {  18,  22,  26,  30},
  {  17,  21,  25,  28},
  {  16,  20,  23,  27},
  {  15,  19,  22,  25},
  {  14,  18,  21,  24},
  {  14,  17,  20,  23},
  {  13,  16,  19,  22},
  {  12,  15,  18,  21},
  {  12,  14,  17,  20},
  {  11,  14,  16,  19},
  {  11,  13,  15,  18},
  {  10,  12,  15,  17},
  {  10,  12,  14,  16},
  {   9,  11,  13,  15},
  {   9,  11,  12,  14},
  {   8,  10,  12,  14},
  {   8,   9,  11,  13},
  {   7,   9,  11,  12},
  {   7,   9,  10,  12},
  {   7,   8,  10,  11},
  {   6,   8,   9,  11},
  {   6,   7,   9,  10},
  {   6,   7,   8,   9},
  {   2,   2,   2,   2}
};


const unsigned short AC_next_state_MPS_64[64] =
{
  1,2,3,4,5,6,7,8,9,10,
  11,12,13,14,15,16,17,18,19,20,
  21,22,23,24,25,26,27,28,29,30,
  31,32,33,34,35,36,37,38,39,40,
  41,42,43,44,45,46,47,48,49,50,
  51,52,53,54,55,56,57,58,59,60,
  61,62,62,63
};


const unsigned short AC_next_state_LPS_64[64] =
{
  0, 0, 1, 2, 2, 4, 4, 5, 6, 7,
  8, 9, 9,11,11,12,13,13,15,15,
  16,16,18,18,19,19,21,21,22,22,
  23,24,24,25,26,26,27,27,28,29,
  29,30,30,30,31,32,32,33,33,33,
  34,34,35,35,35,36,36,36,37,37,
  37,38,38,63
};

/************************************************************************
 * M a c r o s
 ************************************************************************
 */

#define get_byte(){                                         \
                    Dbuffer = Dcodestrm[(*Dcodestrm_len)++];\
                    Dbits_to_go = 7;                        \
                  }


/************************************************************************
 ************************************************************************
                      init / exit decoder
 ************************************************************************
 ************************************************************************/


/*!
 ************************************************************************
 * \brief
 *    Allocates memory for the DecodingEnvironment struct
 * \return DecodingContextPtr
 *    allocates memory
 ************************************************************************
 */
DecodingEnvironmentPtr arideco_create_decoding_environment()
{
  DecodingEnvironmentPtr dep;

  if ((dep = calloc(1,sizeof(DecodingEnvironment))) == NULL)
    no_mem_exit("arideco_create_decoding_environment: dep");
  return dep;
}


/*!
 ***********************************************************************
 * \brief
 *    Frees memory of the DecodingEnvironment struct
 ***********************************************************************
 */
void arideco_delete_decoding_environment(DecodingEnvironmentPtr dep)
{
  if (dep == NULL)
  {
    snprintf(errortext, ET_SIZE, "Error freeing dep (NULL pointer)");
    error (errortext, 200);
  }
  else
    free(dep);
}


/*!
 ************************************************************************
 * \brief
 *    Initializes the DecodingEnvironment for the arithmetic coder
 ************************************************************************
 */
void arideco_start_decoding(DecodingEnvironmentPtr dep, unsigned char *cpixcode,
                            int firstbyte, int *cpixcode_len, int slice_type )
{

  int value = 0;

  Dcodestrm = cpixcode;
  Dcodestrm_len = cpixcode_len;
  *Dcodestrm_len = firstbyte;

  {
    int i;
    Dbits_to_go = 0;
    for (i = 0; i < B_BITS -1 ; i++) // insertion of redundant bit
    {
      if (--Dbits_to_go < 0)
        get_byte();
      value = (value<<1)  | ((Dbuffer >> Dbits_to_go) & 0x01);
    }
  }
  dep->Drange = HALF-2;
  dep->Dvalue = value;
}


/*!
 ************************************************************************
 * \brief
 *    arideco_bits_read
 ************************************************************************
 */
int arideco_bits_read(DecodingEnvironmentPtr dep)
{
  return 8 * ((*Dcodestrm_len)-1) + (8 - Dbits_to_go) - 16;
}


/*!
 ************************************************************************
 * \brief
 *    arideco_done_decoding():
 ************************************************************************
 */
void arideco_done_decoding(DecodingEnvironmentPtr dep)
{
  (*Dcodestrm_len)++;
}


/*!
 ************************************************************************
 * \brief
 *    biari_decode_symbol():
 * \return
 *    the decoded symbol
 ************************************************************************
 */
unsigned int biari_decode_symbol(DecodingEnvironmentPtr dep, BiContextTypePtr bi_ct )
{
  register unsigned int bit = bi_ct->MPS;
  register unsigned int value = dep->Dvalue;
  register unsigned int range = dep->Drange;
  register unsigned int rLPS = (unsigned int) rLPS_table_64x4[bi_ct->state][(range>>6) & 0x03];

#if (2==TRACE)
  fprintf(p_trace, "%d  0x%04x  %d  %d\n", binCount++, dep->Drange, bi_ct->state, bi_ct->MPS );
#endif

  range -= rLPS;

  if (value < range) /* MPS */
    bi_ct->state = AC_next_state_MPS_64[bi_ct->state]; // next state
  else              /* LPS */
  {
    value -= range;
    range = rLPS;
    bit = !bit;
    if (!bi_ct->state)       // switch meaning of MPS if necessary
      bi_ct->MPS ^= 0x01;
    bi_ct->state = AC_next_state_LPS_64[bi_ct->state]; // next state
  }

  while (range < QUARTER)
  {
    /* Double range */
    range <<= 1;
    if (--Dbits_to_go < 0)
      get_byte();
    /* Shift in next bit and add to value */
    value = (value << 1) | ((Dbuffer >> Dbits_to_go) & 0x01);

  }

  dep->Drange = range;
  dep->Dvalue = value;

  return(bit);
}


/*!
 ************************************************************************
 * \brief
 *    biari_decode_symbol_eq_prob():
 * \return
 *    the decoded symbol
 ************************************************************************
 */
unsigned int biari_decode_symbol_eq_prob(DecodingEnvironmentPtr dep)
{
  register unsigned int bit = 0;
  register unsigned int value  = (dep->Dvalue<<1);

#if TRACE
//  fprintf(p_trace, "%d  0x%04x\n", binCount++, dep->Drange );
#endif

  if (--Dbits_to_go < 0)
    get_byte();
  /* Shift in next bit and add to value */
  value |= (Dbuffer >> Dbits_to_go) &  0x01;
  if (value >= dep->Drange)
  {
    bit = 1;
    value -= dep->Drange;
  }

  dep->Dvalue = value;

  return(bit);
}

/*!
 ************************************************************************
 * \brief
 *    biari_decode_symbol_final():
 * \return
 *    the decoded symbol
 ************************************************************************
 */
unsigned int biari_decode_final(DecodingEnvironmentPtr dep)
{
  register unsigned int value  = dep->Dvalue;
  register unsigned int range  = dep->Drange - 2;

#if (2==TRACE)
  fprintf(p_trace, "%d  0x%04x\n", binCount++, dep->Drange );
#endif

  if (value >= range)
  {
    return 1;
  }
  else
  {
    while (range < QUARTER)
    {
    /* Double range */
      range <<= 1;
      if (--Dbits_to_go < 0)
        get_byte();
      /* Shift in next bit and add to value */
      value = (value << 1) | ((Dbuffer >> Dbits_to_go) & 0x01);
    }
    dep->Dvalue = value;
    dep->Drange = range;
    return 0;
  }
}


/*!
 ************************************************************************
 * \brief
 *    Initializes a given context with some pre-defined probability state
 ************************************************************************
 */
void biari_init_context (struct img_par* img, BiContextTypePtr ctx, const int* ini)
{
  int pstate;

  pstate = ((ini[0]* imax(0,img->qp) )>>4) + ini[1];
  pstate = iClip3(1, 126, pstate);

  if ( pstate >= 64 )
  {
    ctx->state  = (unsigned short) (pstate - 64);
    ctx->MPS    = 1;
  }
  else
  {
    ctx->state  = (unsigned short) (63 - pstate);
    ctx->MPS    = 0;
  }
}