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

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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.h

    \brief    class for handling bitstream (header)

*/

#pragma once

#include "CommonDef.h"

#include <stdint.h>

#include <vector>

//! \ingroup CommonLib

//! \{

namespace vvenc {

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

// Class definition

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

/**

 * Model of a writable bitstream that accumulates bits to produce a

 * bytestream.

 */

class OutputBitstream

{

  /**

   * FIFO for storage of bytes.  Use:

   *  - fifo.push_back(x) to append words

   *  - fifo.clear() to empty the FIFO

   *  - &fifo.front() to get a pointer to the data array.

   *    NB, this pointer is only valid until the next push_back()/clear()

   */

  std::vector<uint8_t> m_fifo;

  uint32_t m_num_held_bits; /// number of bits not flushed to bytestream.

  uint8_t  m_held_bits; /// the bits held and not flushed to bytestream.

                             /// this value is always msb-aligned, bigendian.

public:

  // create / destroy

  OutputBitstream();

  ~OutputBitstream();

  // interface for encoding

  /**

   * append uiNumberOfBits least significant bits of uiBits to

   * the current bitstream

   */

  void        write           ( uint32_t uiBits, uint32_t uiNumberOfBits );

  /** insert one bits until the bitstream is byte-aligned */

  void        writeAlignOne   ();

  /** insert zero bits until the bitstream is byte-aligned */

  void        writeAlignZero  ();

  // utility functions

  /**

   * Return a pointer to the start of the byte-stream buffer.

   * Pointer is valid until the next write/flush/reset call.

   * NB, data is arranged such that subsequent bytes in the

   * bytestream are stored in ascending addresses.

   */

  uint8_t* getByteStream() const;

  /**

   * Return the number of valid bytes available from  getByteStream()

   */

  uint32_t getByteStreamLength();

  /**

   * Reset all internal state.

   */

  void clear();

  /**

   * returns the number of bits that need to be written to

   * achieve byte alignment.

   */

  int getNumBitsUntilByteAligned() const { return (8 - m_num_held_bits) & 0x7; }

  /**

   * Return the number of bits that have been written since the last clear()

   */

  uint32_t getNumberOfWrittenBits() const { return uint32_t(m_fifo.size()) * 8 + m_num_held_bits; }

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

  /**

   * Return a reference to the internal fifo

   */

  std::vector<uint8_t>& getFIFO() { return m_fifo; }

  uint8_t getHeldBits() const { return m_held_bits; }

  //OutputBitstream& operator= (const OutputBitstream& src);

  /** Return a reference to the internal fifo */

  const std::vector<uint8_t>& getFIFO() const { return m_fifo; }

  void addSubstream( const OutputBitstream* pcSubstream );

  void writeByteAlignment();

  //! returns the number of start code emulations contained in the current buffer

  int countStartCodeEmulations();

};

/**

 * Model of an input bitstream that extracts bits from a predefined

 * bytestream.

 */

class InputBitstream

{

protected:

  std::vector<uint8_t> m_fifo; /// FIFO for storage of complete bytes

  std::vector<uint32_t>    m_emulationPreventionByteLocation;

  uint32_t m_fifo_idx; /// Read index into m_fifo

  uint32_t m_num_held_bits;

  uint8_t m_held_bits;

  uint32_t  m_numBitsRead;

public:

  /**

   * Create a new bitstream reader object that reads from buf.

   */

  InputBitstream();

  virtual ~InputBitstream() { }

  InputBitstream(const InputBitstream &src);

  void resetToStart();

  // interface for decoding

  void        pseudoRead      ( uint32_t uiNumberOfBits, uint32_t& ruiBits );

  void        read            ( uint32_t uiNumberOfBits, uint32_t& ruiBits );

  void        readByte        ( uint32_t &ruiBits )

  {

    CHECK( m_fifo_idx >= m_fifo.size(), "FIFO exceeded" );

    ruiBits = m_fifo[m_fifo_idx++];

#if ENABLE_TRACING

    m_numBitsRead += 8;

#endif

  }

  void        peekPreviousByte( uint32_t &byte )

  {

    CHECK( m_fifo_idx == 0, "FIFO empty" );

    byte = m_fifo[m_fifo_idx - 1];

  }

  uint32_t readOutTrailingBits ();

  uint8_t  getHeldBits() const { return m_held_bits; }

  OutputBitstream& operator= (const OutputBitstream& src);

  uint32_t getByteLocation              ( )                     { return m_fifo_idx                    ; }

  // Peek at bits in word-storage. Used in determining if we have completed reading of current bitstream and therefore slice in LCEC.

  uint32_t peekBits (uint32_t uiBits) { uint32_t tmp; pseudoRead(uiBits, tmp); return tmp; }

  // utility functions

  uint32_t read(uint32_t numberOfBits)      { uint32_t tmp; read(numberOfBits, tmp); return tmp; }

  uint32_t readByte()                   { uint32_t tmp; readByte( tmp ); return tmp; }

  uint32_t getNumBitsUntilByteAligned() { return m_num_held_bits & (0x7); }

  uint32_t getNumBitsLeft()             { return 8*((uint32_t)m_fifo.size() - m_fifo_idx) + m_num_held_bits; }

  InputBitstream *extractSubstream( uint32_t uiNumBits ); // Read the nominated number of bits, and return as a bitstream.

  uint32_t getNumBitsRead()            { return m_numBitsRead; }

  uint32_t readByteAlignment();

  void     pushEmulationPreventionByteLocation ( uint32_t pos )                         { m_emulationPreventionByteLocation.push_back( pos ); }

  uint32_t numEmulationPreventionBytesRead     ()                                   { return (uint32_t) m_emulationPreventionByteLocation.size();    }

  const std::vector<uint32_t> &getEmulationPreventionByteLocation  () const              { return m_emulationPreventionByteLocation;           }

  uint32_t getEmulationPreventionByteLocation  ( uint32_t idx )                         { return m_emulationPreventionByteLocation[ idx ];    }

  void     clearEmulationPreventionByteLocation()                                   { m_emulationPreventionByteLocation.clear();          }

  void     setEmulationPreventionByteLocation  ( const std::vector<uint32_t> &vec )     { m_emulationPreventionByteLocation = vec;            }

  const std::vector<uint8_t> &getFifo() const { return m_fifo; }

        std::vector<uint8_t> &getFifo()       { return m_fifo; }

};

} // namespace vvenc

//! \}