AnnexBread.h

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/* The copyright in this software is being made available under the BSD
 * License, included below. This software may be subject to other third party
 * and contributor rights, including patent rights, and no such rights are
 * granted under this license.
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 * Copyright (c) 2010-2017, ITU/ISO/IEC
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
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 *    this list of conditions and the following disclaimer.
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 *    and/or other materials provided with the distribution.
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 */

#pragma once

#ifndef __ANNEXBREAD__
#define __ANNEXBREAD__

#include <stdint.h>
#include <istream>
#include <vector>

#include "TLibCommon/CommonDef.h"


class InputByteStream
{
public:
  InputByteStream(std::istream& istream)
  : m_NumFutureBytes(0)
  , m_FutureBytes(0)
  , m_Input(istream)
  {
    istream.exceptions(std::istream::eofbit | std::istream::badbit);
  }

  Void reset()
  {
    m_NumFutureBytes = 0;
    m_FutureBytes = 0;
  }

  Bool eofBeforeNBytes(UInt n)
  {
    assert(n <= 4);
    if (m_NumFutureBytes >= n)
    {
      return false;
    }

    n -= m_NumFutureBytes;
    try
    {
      for (UInt i = 0; i < n; i++)
      {
        m_FutureBytes = (m_FutureBytes << 8) | m_Input.get();
        m_NumFutureBytes++;
      }
    }
    catch (...)
    {
      return true;
    }
    return false;
  }

  uint32_t peekBytes(UInt n)
  {
    eofBeforeNBytes(n);
    return m_FutureBytes >> 8*(m_NumFutureBytes - n);
  }

  uint8_t readByte()
  {
    if (!m_NumFutureBytes)
    {
      uint8_t byte = m_Input.get();
      return byte;
    }
    m_NumFutureBytes--;
    uint8_t wanted_byte = m_FutureBytes >> 8*m_NumFutureBytes;
    m_FutureBytes &= ~(0xff << 8*m_NumFutureBytes);
    return wanted_byte;
  }

  uint32_t readBytes(UInt n)
  {
    uint32_t val = 0;
    for (UInt i = 0; i < n; i++)
    {
      val = (val << 8) | readByte();
    }
    return val;
  }

#if RExt__DECODER_DEBUG_BIT_STATISTICS
  UInt GetNumBufferedBytes() const { return m_NumFutureBytes; }
#endif

private:
  UInt m_NumFutureBytes; /* number of valid bytes in m_FutureBytes */
  uint32_t m_FutureBytes; /* bytes that have been peeked */
  std::istream& m_Input; /* Input stream to read from */
};

struct AnnexBStats
{
  UInt m_numLeadingZero8BitsBytes;
  UInt m_numZeroByteBytes;
  UInt m_numStartCodePrefixBytes;
  UInt m_numBytesInNALUnit;
  UInt m_numTrailingZero8BitsBytes;

  AnnexBStats& operator+=(const AnnexBStats& rhs)
  {
    this->m_numLeadingZero8BitsBytes += rhs.m_numLeadingZero8BitsBytes;
    this->m_numZeroByteBytes += rhs.m_numZeroByteBytes;
    this->m_numStartCodePrefixBytes += rhs.m_numStartCodePrefixBytes;
    this->m_numBytesInNALUnit += rhs.m_numBytesInNALUnit;
    this->m_numTrailingZero8BitsBytes += rhs.m_numTrailingZero8BitsBytes;
    return *this;
  }
};

Bool byteStreamNALUnit(InputByteStream& bs, std::vector<uint8_t>& nalUnit, AnnexBStats& stats);


#endif