144 lines
3.3 KiB
C++
144 lines
3.3 KiB
C++
/*
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Copyright (C) 2002 Andrea Mazzoleni ( http://advancemame.sf.net )
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Copyright (C) 2001-4 Igor Pavlov ( http://www.7-zip.org )
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License version 2.1 as published by the Free Software Foundation.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef __COMPRESSION_RANGECODER_H
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#define __COMPRESSION_RANGECODER_H
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#include "inbyte.h"
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namespace NCompression {
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namespace NArithmetic {
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const UINT32 kNumTopBits = 24;
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const UINT32 kTopValue = (1 << kNumTopBits);
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class CRangeDecoder
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{
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public:
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NStream::CInByte m_Stream;
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UINT32 m_Range;
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UINT32 m_Code;
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UINT32 m_Word;
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void Normalize()
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{
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while (m_Range < kTopValue)
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{
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m_Code = (m_Code << 8) | m_Stream.ReadByte();
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m_Range <<= 8;
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}
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}
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void Init(ISequentialInStream *aStream)
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{
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m_Stream.Init(aStream);
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m_Code = 0;
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m_Range = UINT32(-1);
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for(int i = 0; i < 5; i++)
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m_Code = (m_Code << 8) | m_Stream.ReadByte();
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}
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UINT32 GetThreshold(UINT32 aTotal)
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{
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return (m_Code) / ( m_Range /= aTotal);
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}
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void Decode(UINT32 aStart, UINT32 aSize, UINT32 aTotal)
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{
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m_Code -= aStart * m_Range;
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m_Range *= aSize;
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Normalize();
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}
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/*
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UINT32 DecodeDirectBitsDiv(UINT32 aNumTotalBits)
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{
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m_Range >>= aNumTotalBits;
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UINT32 aThreshold = m_Code / m_Range;
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m_Code -= aThreshold * m_Range;
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Normalize();
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return aThreshold;
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}
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UINT32 DecodeDirectBitsDiv2(UINT32 aNumTotalBits)
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{
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if (aNumTotalBits <= kNumBottomBits)
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return DecodeDirectBitsDiv(aNumTotalBits);
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UINT32 aResult = DecodeDirectBitsDiv(aNumTotalBits - kNumBottomBits) << kNumBottomBits;
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return (aResult | DecodeDirectBitsDiv(kNumBottomBits));
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}
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*/
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UINT32 DecodeDirectBits(UINT32 aNumTotalBits)
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{
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UINT32 aRange = m_Range;
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UINT32 aCode = m_Code;
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UINT32 aResult = 0;
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for (UINT32 i = aNumTotalBits; i > 0; i--)
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{
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aRange >>= 1;
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/*
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aResult <<= 1;
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if (aCode >= aRange)
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{
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aCode -= aRange;
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aResult |= 1;
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}
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*/
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UINT32 t = (aCode - aRange) >> 31;
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aCode -= aRange & (t - 1);
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// aRange = aRangeTmp + ((aRange & 1) & (1 - t));
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aResult = (aResult << 1) | (1 - t);
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if (aRange < kTopValue)
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{
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aCode = (aCode << 8) | m_Stream.ReadByte();
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aRange <<= 8;
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}
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}
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m_Range = aRange;
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m_Code = aCode;
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return aResult;
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}
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UINT32 DecodeBit(UINT32 aSize0, UINT32 aNumTotalBits)
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{
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UINT32 aNewBound = (m_Range >> aNumTotalBits) * aSize0;
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UINT32 aSymbol;
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if (m_Code < aNewBound)
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{
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aSymbol = 0;
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m_Range = aNewBound;
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}
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else
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{
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aSymbol = 1;
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m_Code -= aNewBound;
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m_Range -= aNewBound;
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}
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Normalize();
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return aSymbol;
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}
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UINT64 GetProcessedSize() {return m_Stream.GetProcessedSize(); }
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};
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}}
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#endif
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