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Karsten Suehring authoredKarsten Suehring authored
BitStream.h 8.08 KiB
/* The copyright in this software is being made available under the BSD
* License, included below. This software may be subject to other third party
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* granted under this license.
*
* Copyright (c) 2010-2019, ITU/ISO/IEC
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
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* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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*/
/** \file BitStream.h
\brief class for handling bitstream (header)
*/
#ifndef __BITSTREAM__
#define __BITSTREAM__
#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000
#include <stdint.h>
#include <vector>
#include <stdio.h>
#include "CommonDef.h"
//! \ingroup CommonLib
//! \{
// ====================================================================================================================
// 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; /// 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 () { 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; }
};
//! \}
#endif