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/*************************************************************************
This project implements a complete(!) JPEG (Recommendation ITU-T
T.81 | ISO/IEC 10918-1) codec, plus a library that can be used to
encode and decode JPEG streams.
It also implements ISO/IEC 18477 aka JPEG XT which is an extension
towards intermediate, high-dynamic-range lossy and lossless coding
of JPEG. In specific, it supports ISO/IEC 18477-3/-6/-7/-8 encoding.
Note that only Profiles C and D of ISO/IEC 18477-7 are supported
here. Check the JPEG XT reference software for a full implementation
of ISO/IEC 18477-7.
Copyright (C) 2012-2018 Thomas Richter, University of Stuttgart and
Accusoft. (C) 2019-2020 Thomas Richter, Fraunhofer IIS.
This program is available under two licenses, GPLv3 and the ITU
Software licence Annex A Option 2, RAND conditions.
For the full text of the GPU license option, see README.license.gpl.
For the full text of the ITU license option, see README.license.itu.
You may freely select between these two options.
For the GPL option, please note the following:
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*************************************************************************/
/*
** This class implements a decoder for a single group of bits in a huffman
** decoder.
**
** $Id: huffmandecoder.hpp,v 1.13 2014/11/12 21:24:45 thor Exp $
**
*/
#ifndef CODING_HUFFMANDECODER_HPP
#define CODING_HUFFMANDECODER_HPP
/// Includes
#include "tools/environment.hpp"
#include "io/bytestream.hpp"
#include "std/string.hpp"
///
/// class HuffmanDecoder
// This class decodes a group of bits from the IO stream, generating a symbol. This
// is the base class.
class HuffmanDecoder : public JKeeper {
//
// Decoder table: Delivers for each 8-bit value the symbol.
UBYTE m_ucSymbol[256];
//
// Decoder length: Delivers for each 8-bit value the length of the symbol in bits.
UBYTE m_ucLength[256];
//
// If 8 bits are not sufficient, here are pointers that each point to a 256 byte
// array indexed by the LSBs.
UBYTE *m_pucSymbol[256];
//
// And ditto for the length.
UBYTE *m_pucLength[256];
//
public:
HuffmanDecoder(class Environ *env,
UBYTE *&symbols,UBYTE *&sizes,UBYTE **&lsbsymb,UBYTE **&lsbsize)
: JKeeper(env)
{
symbols = m_ucSymbol;
sizes = m_ucLength;
lsbsymb = m_pucSymbol;
lsbsize = m_pucLength;
// Fill the unused area with invalid sizes.
memset(m_ucLength ,0xff,sizeof(m_ucLength));
memset(m_pucSymbol,0 ,sizeof(m_pucSymbol));
memset(m_pucLength,0 ,sizeof(m_pucLength));
}
//
~HuffmanDecoder(void)
{
int i;
for(i = 0;i < 256;i++) {
if (m_pucSymbol[i]) m_pEnviron->FreeMem(m_pucSymbol[i],256 * sizeof(UBYTE));
if (m_pucLength[i]) m_pEnviron->FreeMem(m_pucLength[i],256 * sizeof(UBYTE));
}
}
//
// Decode the next symbol.
UBYTE Get(BitStream<false> *io)
{
UWORD data;
UBYTE symbol;
UBYTE size;
UBYTE lsb,msb;
data = io->PeekWord();
msb = data >> 8;
if (likely(m_ucLength[msb])) {
symbol = m_ucSymbol[msb];
size = m_ucLength[msb];
} else {
lsb = data;
symbol = m_pucSymbol[msb][lsb];
size = m_pucLength[msb][lsb];
}
io->SkipBits(size);
return symbol;
}
};
///
///
#endif
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