/* -----------------------------------------------------------------------------

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other Intellectual Property Rights other than the copyrights concerning 

the Software are granted under this license.

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Copyright (c) 2019-2026, Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. & The VVenC Authors.

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     this list of conditions and the following disclaimer.

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------------------------------------------------------------------------------------------- */

/** \file     BitStream.cpp

    \brief    class for handling bitstream

*/

#include "BitStream.h"

#include "dtrace_next.h"

#include <stdint.h>

#include <vector>

#include <string.h>

#include <memory.h>

//! \ingroup CommonLib

//! \{

namespace vvenc {

// ====================================================================================================================

// Constructor / destructor / create / destroy

// ====================================================================================================================

OutputBitstream::OutputBitstream()

{

  clear();

}

OutputBitstream::~OutputBitstream()

{

}

InputBitstream::InputBitstream()

: m_fifo()

, m_emulationPreventionByteLocation()

, m_fifo_idx(0)

, m_num_held_bits(0)

, m_held_bits(0)

, m_numBitsRead(0)

{ }

InputBitstream::InputBitstream(const InputBitstream &src)

: m_fifo(src.m_fifo)

, m_emulationPreventionByteLocation(src.m_emulationPreventionByteLocation)

, m_fifo_idx(src.m_fifo_idx)

, m_num_held_bits(src.m_num_held_bits)

, m_held_bits(src.m_held_bits)

, m_numBitsRead(src.m_numBitsRead)

{ }

// ====================================================================================================================

// Public member functions

// ====================================================================================================================

void InputBitstream::resetToStart()

{

  m_fifo_idx=0;

  m_num_held_bits=0;

  m_held_bits=0;

  m_numBitsRead=0;

}

uint8_t* OutputBitstream::getByteStream() const

{

  return (uint8_t*) &m_fifo.front();

}

uint32_t OutputBitstream::getByteStreamLength()

{

  return uint32_t(m_fifo.size());

}

void OutputBitstream::clear()

{

  m_fifo.clear();

  m_held_bits = 0;

  m_num_held_bits = 0;

}

void OutputBitstream::write   ( uint32_t uiBits, uint32_t uiNumberOfBits )

{

  CHECK( uiNumberOfBits > 32, "Number of bits is exceeds '32'" );

  CHECK( uiNumberOfBits != 32 && (uiBits & (~0u << uiNumberOfBits)) != 0, "Unsupported parameters" );

  /* any modulo 8 remainder of num_total_bits cannot be written this time,

   * and will be held until next time. */

  uint32_t num_total_bits = uiNumberOfBits + m_num_held_bits;

  uint32_t next_num_held_bits = num_total_bits % 8;

  /* form a byte aligned word (write_bits), by concatenating any held bits

   * with the new bits, discarding the bits that will form the next_held_bits.

   * eg: H = held bits, V = n new bits        /---- next_held_bits

   * len(H)=7, len(V)=1: ... ---- HHHH HHHV . 0000 0000, next_num_held_bits=0

   * len(H)=7, len(V)=2: ... ---- HHHH HHHV . V000 0000, next_num_held_bits=1

   * if total_bits < 8, the value of v_ is not used */

  uint8_t next_held_bits = uiBits << (8 - next_num_held_bits);

  if (!(num_total_bits >> 3))

  {

    /* insufficient bits accumulated to write out, append new_held_bits to

     * current held_bits */

    /* NB, this requires that v only contains 0 in bit positions {31..n} */

    m_held_bits |= next_held_bits;

    m_num_held_bits = next_num_held_bits;

    return;

  }

  /* topword serves to justify held_bits to align with the msb of uiBits */

  uint32_t topword = (uiNumberOfBits - next_num_held_bits) & ~((1 << 3) -1);

  uint32_t write_bits = (uint32_t)(((uint64_t)m_held_bits << topword) | (uiBits >> next_num_held_bits));

  switch (num_total_bits >> 3)

  {

  case 4: m_fifo.push_back(write_bits >> 24);

  case 3: m_fifo.push_back(write_bits >> 16);

  case 2: m_fifo.push_back(write_bits >> 8);

  case 1: m_fifo.push_back(write_bits);

  }

  DTRACE( g_trace_ctx, D_BITSTREAM, " %5d: %0X\n", (int)(m_fifo.size() - 1), m_fifo.back() );

  m_held_bits = next_held_bits;

  m_num_held_bits = next_num_held_bits;

}

void OutputBitstream::writeAlignOne()

{

  uint32_t num_bits = getNumBitsUntilByteAligned();

  write((1 << num_bits) - 1, num_bits);

  return;

}

void OutputBitstream::writeAlignZero()

{

  if (0 == m_num_held_bits)

  {

    return;

  }

  m_fifo.push_back(m_held_bits);

  m_held_bits = 0;

  m_num_held_bits = 0;

}

/**

 - add substream to the end of the current bitstream

 .

 \param  pcSubstream  substream to be added

 */

void OutputBitstream::addSubstream( const OutputBitstream* pcSubstream )

{

  uint32_t uiNumBits = pcSubstream->getNumberOfWrittenBits();

  const std::vector<uint8_t>& rbsp = pcSubstream->getFIFO();

  for (std::vector<uint8_t>::const_iterator it = rbsp.begin(); it != rbsp.end();)

  {

    write(*it++, 8);

  }

  if (uiNumBits&0x7)

  {

    write(pcSubstream->getHeldBits()>>(8-(uiNumBits&0x7)), uiNumBits&0x7);

  }

}

void OutputBitstream::writeByteAlignment()

{

  write( 1, 1);

  writeAlignZero();

}

int OutputBitstream::countStartCodeEmulations()

{

  uint32_t cnt = 0;

  std::vector<uint8_t>& rbsp   = getFIFO();

  for (std::vector<uint8_t>::iterator it = rbsp.begin(); it != rbsp.end();)

  {

    std::vector<uint8_t>::iterator found = it;

    do

    {

      // find the next emulated 00 00 {00,01,02,03}

      // NB, end()-1, prevents finding a trailing two byte sequence

      found = search_n(found, rbsp.end()-1, 2, 0);

      found++;

      // if not found, found == end, otherwise found = second zero byte

      if (found == rbsp.end())

      {

        break;

      }

      if (*(++found) <= 3)

      {

        break;

      }

    } while (true);

    it = found;

    if (found != rbsp.end())

    {

      cnt++;

    }

  }

  return cnt;

}

/**

 * read uiNumberOfBits from bitstream without updating the bitstream

 * state, storing the result in ruiBits.

 *

 * If reading uiNumberOfBits would overrun the bitstream buffer,

 * the bitstream is effectively padded with sufficient zero-bits to

 * avoid the overrun.

 */

void InputBitstream::pseudoRead ( uint32_t uiNumberOfBits, uint32_t& ruiBits )

{

  uint32_t saved_num_held_bits = m_num_held_bits;

  uint8_t saved_held_bits = m_held_bits;

  uint32_t saved_fifo_idx = m_fifo_idx;

  uint32_t num_bits_to_read = std::min(uiNumberOfBits, getNumBitsLeft());

  read(num_bits_to_read, ruiBits);

  ruiBits <<= (uiNumberOfBits - num_bits_to_read);

  m_fifo_idx = saved_fifo_idx;

  m_held_bits = saved_held_bits;

  m_num_held_bits = saved_num_held_bits;

}

void InputBitstream::read (uint32_t uiNumberOfBits, uint32_t& ruiBits)

{

  CHECK( uiNumberOfBits > 32, "Too many bits read" );

  m_numBitsRead += uiNumberOfBits;

  /* NB, bits are extracted from the MSB of each byte. */

  uint32_t retval = 0;

  if (uiNumberOfBits <= m_num_held_bits)

  {

    /* n=1, len(H)=7:   -VHH HHHH, shift_down=6, mask=0xfe

     * n=3, len(H)=7:   -VVV HHHH, shift_down=4, mask=0xf8

     */

    retval = m_held_bits >> (m_num_held_bits - uiNumberOfBits);

    retval &= ~(0xff << uiNumberOfBits);

    m_num_held_bits -= uiNumberOfBits;

    ruiBits = retval;

    return;

  }

  /* all num_held_bits will go into retval

   *   => need to mask leftover bits from previous extractions

   *   => align retval with top of extracted word */

  /* n=5, len(H)=3: ---- -VVV, mask=0x07, shift_up=5-3=2,

   * n=9, len(H)=3: ---- -VVV, mask=0x07, shift_up=9-3=6 */

  uiNumberOfBits -= m_num_held_bits;

  retval = m_held_bits & ~(0xff << m_num_held_bits);

  retval <<= uiNumberOfBits;

  /* number of whole bytes that need to be loaded to form retval */

  /* n=32, len(H)=0, load 4bytes, shift_down=0

   * n=32, len(H)=1, load 4bytes, shift_down=1

   * n=31, len(H)=1, load 4bytes, shift_down=1+1

   * n=8,  len(H)=0, load 1byte,  shift_down=0

   * n=8,  len(H)=3, load 1byte,  shift_down=3

   * n=5,  len(H)=1, load 1byte,  shift_down=1+3

   */

  uint32_t aligned_word = 0;

  uint32_t num_bytes_to_load = (uiNumberOfBits - 1) >> 3;

  CHECK(m_fifo_idx + num_bytes_to_load >= m_fifo.size(), "Exceeded FIFO size");

  switch (num_bytes_to_load)

  {

  case 3: aligned_word  = m_fifo[m_fifo_idx++] << 24;

  case 2: aligned_word |= m_fifo[m_fifo_idx++] << 16;

  case 1: aligned_word |= m_fifo[m_fifo_idx++] <<  8;

  case 0: aligned_word |= m_fifo[m_fifo_idx++];

  }

  /* resolve remainder bits */

  uint32_t next_num_held_bits = (32 - uiNumberOfBits) % 8;

  /* copy required part of aligned_word into retval */

  retval |= aligned_word >> next_num_held_bits;

  /* store held bits */

  m_num_held_bits = next_num_held_bits;

  m_held_bits = aligned_word;

  ruiBits = retval;

}

/**

 * insert the contents of the bytealigned (and flushed) bitstream src

 * into this at byte position pos.

 */

void OutputBitstream::insertAt(const OutputBitstream& src, uint32_t pos)

{

  CHECK(0 != src.getNumberOfWrittenBits() % 8, "Number of written bits is not a multiple of 8");

  std::vector<uint8_t>::iterator at = m_fifo.begin() + pos;

  m_fifo.insert(at, src.m_fifo.begin(), src.m_fifo.end());

}

uint32_t InputBitstream::readOutTrailingBits ()

{

  uint32_t count=0;

  uint32_t uiBits = 0;

  while ( ( getNumBitsLeft() > 0 ) && (getNumBitsUntilByteAligned()!=0) )

  {

    count++;

    read ( 1, uiBits );

  }

  return count;

}

/**

 Extract substream from the current bitstream.

 \param  uiNumBits    number of bits to transfer

 */

InputBitstream *InputBitstream::extractSubstream( uint32_t uiNumBits )

{

  uint32_t uiNumBytes = uiNumBits/8;

  InputBitstream *pResult = new InputBitstream;

  std::vector<uint8_t> &buf = pResult->getFifo();

  buf.reserve((uiNumBits+7)>>3);

  if (m_num_held_bits == 0)

  {

    std::size_t currentOutputBufferSize=buf.size();

    const uint32_t uiNumBytesToReadFromFifo = std::min<uint32_t>(uiNumBytes, (uint32_t)m_fifo.size() - m_fifo_idx);

    buf.resize(currentOutputBufferSize+uiNumBytes);

    memcpy(&(buf[currentOutputBufferSize]), &(m_fifo[m_fifo_idx]), uiNumBytesToReadFromFifo); m_fifo_idx+=uiNumBytesToReadFromFifo;

    if (uiNumBytesToReadFromFifo != uiNumBytes)

    {

      memset(&(buf[currentOutputBufferSize+uiNumBytesToReadFromFifo]), 0, uiNumBytes - uiNumBytesToReadFromFifo);

    }

  }

  else

  {

    for (uint32_t ui = 0; ui < uiNumBytes; ui++)

    {

      uint32_t uiByte;

      read(8, uiByte);

      buf.push_back(uiByte);

    }

  }

  if (uiNumBits&0x7)

  {

    uint32_t uiByte = 0;

    read(uiNumBits&0x7, uiByte);

    uiByte <<= 8-(uiNumBits&0x7);

    buf.push_back(uiByte);

  }

  return pResult;

}

uint32_t InputBitstream::readByteAlignment()

{

  uint32_t code = 0;

  read( 1, code );

  CHECK(code != 1, "Code is not '1'");

  uint32_t numBits = getNumBitsUntilByteAligned();

  if(numBits)

  {

    CHECK(numBits > getNumBitsLeft(), "More bits available than left");

    read( numBits, code );

    CHECK(code != 0, "Code not '0'");

  }

  return numBits+1;

}

} // namespace vvenc

//! \}