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/** \file     BinDecoder.h

 *  \brief    Low level binary symbol writer

 */

#pragma once

#include "CommonLib/Contexts.h"

#include "CommonLib/BitStream.h"      // complete type needed to inline readByte/readByteFlag below

#include "CommonLib/dtrace_next.h"    // DTRACE macros (no-ops in release) used by the inlined bodies

namespace vvdec

{

class InputBitstream;

class BinDecoder

{

public:

  BinDecoder()  = default;

  ~BinDecoder() = default;

  void      init    ( InputBitstream* bitstream );

  void      uninit  ();

  void      start   ();

  void      finish  ();

  void      reset   ( int qp, int initId );

  const Ctx& getCtx() const           { return m_Ctx; }

  void       setCtx( const Ctx& ctx ) { m_Ctx = ctx; }

  unsigned          decodeBin           ( unsigned ctxId );

  unsigned          decodeBinEP         ();

  unsigned          decodeBinsEP        ( unsigned numBins  );

  unsigned          decodeRemAbsEP      ( unsigned goRicePar, unsigned cutoff, int maxLog2TrDynamicRange );

  unsigned          decodeBinTrm        ();

  void              align               ();

#if ENABLE_TRACING

  unsigned          getNumBitsRead() const;

#endif

private:

  unsigned          decodeAlignedBinsEP ( unsigned numBins  );

  Ctx m_Ctx;

protected:

  InputBitstream* m_Bitstream  = nullptr;

  uint32_t        m_Range      = 0;

  uint32_t        m_Value      = 0;

  int32_t         m_bitsNeeded = 0;

};

// ---------------------------------------------------------------------------

// Hot-path bin decoders are defined here (not in BinDecoder.cpp) and forced

// ALWAYS_INLINE so they inline into the CABAC parser hot loops (residual_coding,

// coding_tree, ...) which live in a different translation unit. This keeps

// m_Range/m_Value/m_bitsNeeded in registers across consecutive bins instead of

// reloading/storing them through `this` on every bin. Pure relocation: bodies

// are identical to the previous out-of-line definitions -> bit-exact output.

// ---------------------------------------------------------------------------

ALWAYS_INLINE unsigned BinDecoder::decodeBinEP()

{

  unsigned value = m_Value << 1;

  if (++m_bitsNeeded >= 0) {

    value += m_Bitstream->readByte();

    m_bitsNeeded = -8;

  }

  unsigned bin = 0;

  unsigned SR = m_Range << 7;

  if (value >= SR) {

    value -= SR;

    bin = 1;

  }

  m_Value = value;

  DTRACE(g_trace_ctx, D_CABAC,

         "%d"

         "  "

         "%d"

         "  EP=%d \n",

         DTRACE_GET_COUNTER(g_trace_ctx, D_CABAC), m_Range, bin);

  return bin;

}

ALWAYS_INLINE unsigned BinDecoder::decodeBinTrm()

{

  m_Range    -= 2;

  unsigned SR = m_Range << 7;

  DTRACE( g_trace_ctx, D_CABAC, "%d" " binTrm  range=" "%d" "  bin=%d\n" , DTRACE_GET_COUNTER( g_trace_ctx, D_CABAC ), m_Range, m_Value >= SR );

  if( m_Value >= SR )

  {

    return 1;

  }

  else

  {

    if( m_Range < 256 )

    {

      m_Range += m_Range;

      m_Value += m_Value;

      if( ++m_bitsNeeded == 0 )

      {

        m_Value      += m_Bitstream->readByte();

        m_bitsNeeded  = -8;

      }

    }

    return 0;

  }

}

ALWAYS_INLINE unsigned BinDecoder::decodeBin( unsigned ctxId )

{

  BinProbModel& rcProbModel = m_Ctx[ctxId];

  unsigned bin, LPS, s0, s1;

  uint32_t range      = m_Range;

  uint32_t value      = m_Value;

  int32_t  bitsNeeded = m_bitsNeeded;

  rcProbModel.lpsmps( range, LPS, bin, s0, s1 );

  DTRACE( g_trace_ctx, D_CABAC, "%d" " %d " "%d" "  " "[%d:%d]" "  " "%2d(MPS=%d)"  "  " , DTRACE_GET_COUNTER( g_trace_ctx, D_CABAC ), 666, range, range-LPS, LPS, ( unsigned int )( rcProbModel.state() ), value < ( ( range - LPS ) << 7 ) );

  range      -= LPS;

  uint32_t SR = range << 7;

  int b = ~( ( int( value ) - int( SR ) ) >> 31 );

  int a = ~b & ( ( int( range ) - 256 ) >> 31 );

  int numBits  = ( a & rcProbModel.getRenormBitsRange( range ) ) | ( b & rcProbModel.getRenormBitsLPS( LPS ) );

  value       -= b & SR;

  value      <<= numBits;

  range       &=  ~b;

  range       |= ( b & LPS );

  range      <<= numBits;

  bin         ^= b;

  bin         &= 1;

  bitsNeeded  += numBits & ( a | b );

  const int c = ~(bitsNeeded >> 31);

  value      += uint32_t( m_Bitstream->readByteFlag( c ) ) << ( bitsNeeded & 31 );

  bitsNeeded -= c & 8;

  m_Range      = range;

  m_Value      = value;

  m_bitsNeeded = bitsNeeded;

  rcProbModel.update( bin, s0, s1 );

  DTRACE_WITHOUT_COUNT( g_trace_ctx, D_CABAC, "  -  " "%d" "\n", bin );

  return  bin;

}

}