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the Software are granted under this license.

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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 <stdint.h>
#include <vector>
#include <stdio.h>
#include "CommonDef.h"

namespace vvdec
{

// ====================================================================================================================
// 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  ()          { 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    ( 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 = 0;   /// Read index into m_fifo

  uint32_t m_num_held_bits = 0;
  uint8_t  m_held_bits     = 0;
  uint32_t m_numBitsRead   = 0;

public:
  /**
   * Create a new bitstream reader object that reads from buf.
   */
  InputBitstream()                            = default;
  ~InputBitstream()                           = default;
  InputBitstream( const InputBitstream& src ) = default;
  InputBitstream( InputBitstream&& src )      = default;

  void resetToStart();
  
  void inputZeroByte() { m_fifo.push_back(0); };

  // interface for decoding
  void pseudoRead( uint32_t uiNumberOfBits, uint32_t& ruiBits );
  void read      ( uint32_t uiNumberOfBits, uint32_t& ruiBits );
  void readByte  ( uint32_t& ruiBits )
  {
    ruiBits = m_fifo[m_fifo_idx++];
#if ENABLE_TRACING
    m_numBitsRead += 8;
#endif
  }
  
  // In the function initBitstream, add a Byte at the end of m_fifo
  // In the past, readByteFlag judged whether to read data according to the flag, so it would not cross the boundary
  // Now, in order to speed up, readByteFlag will definitely read data, so it may cross the boundary
  void readByteFlag(uint32_t& ruiBits, int flag) {
    ruiBits = flag & m_fifo[m_fifo_idx];
    m_fifo_idx += flag & 1;
#if ENABLE_TRACING
    m_numBitsRead += flag & 8;
#endif
  }

  void peekPreviousByte( uint32_t& byte ) { byte = m_fifo[m_fifo_idx - 1]; }

  uint32_t         readOutTrailingBits();
  uint8_t          getHeldBits() { 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 readByteFlag(int flag)
  {
    uint32_t tmp;
    readByteFlag(tmp, flag);
    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; }
  uint32_t        getNumBitsRead()                        { return m_numBitsRead; }
  uint32_t        readByteAlignment();
  InputBitstream* extractSubstream( uint32_t uiNumBits );   // Read the nominated number of bits, and return as a bitstream.

  void                         pushEmulationPreventionByteLocation( uint32_t pos )                    { m_emulationPreventionByteLocation.push_back( pos ); }
  uint32_t                     numEmulationPreventionBytesRead()                                      { return (uint32_t) m_emulationPreventionByteLocation.size(); }
  uint32_t                     getEmulationPreventionByteLocation( uint32_t idx )                     { return m_emulationPreventionByteLocation[idx]; }
  const std::vector<uint32_t>& getEmulationPreventionByteLocation() const                             { return m_emulationPreventionByteLocation; }
  void                         setEmulationPreventionByteLocation( const std::vector<uint32_t>& vec ) { m_emulationPreventionByteLocation = vec; }
  void                         clearEmulationPreventionByteLocation()                                 { m_emulationPreventionByteLocation.clear(); }

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

}
