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https://github.com/SatDump/SatDump
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73 lines
1.9 KiB
C++
73 lines
1.9 KiB
C++
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/*
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* Copyright 2011-2019, European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT)
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "CACModel.h"
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void COMP::CACModel::Rescale()
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{
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COMP_TRYTHIS_SPEED
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unsigned __int32 cum = 0UL;
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unsigned __int32 *pC = m_CumFreq + m_NbSymbols;
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unsigned __int32 *pF = m_Freq + m_NbSymbols;
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for (int i = m_NbSymbols + 1; i; i--, pF--)
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{
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*pC-- = cum;
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cum += (*pF = (*pF + 1UL) >> 1);
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}
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COMP_CATCHTHIS_SPEED
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}
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void COMP::CACModel::Start()
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{
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COMP_TRYTHIS
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for (unsigned int i = 0; i <= m_NbSymbols; i++)
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{
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m_Freq[i] = 1;
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m_CumFreq[i] = m_NbSymbols - i;
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m_SymbolToIndex[i] = i + 1;
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m_IndexToSymbol[i] = i - 1;
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}
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m_SymbolToIndex[m_NbSymbols] = m_NbSymbols;
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m_IndexToSymbol[0] = 0;
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m_Freq[0] = 0;
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COMP_CATCHTHIS
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}
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void COMP::CACModel::UpdateLps(const unsigned int i_Index)
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{
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COMP_TRYTHIS_SPEED
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#ifdef _DEBUG
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Assert(i_Index > 1 && i_Index <= m_NbSymbols, Util::CParamException());
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#endif
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if (m_CumFreq[0] >= m_MaxFreq)
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Rescale();
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unsigned int i = i_Index;
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if (m_Freq[i] == m_Freq[i - 1])
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{
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for (i--; m_Freq[i] == m_Freq[i - 1]; i--)
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;
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unsigned int symbol = m_IndexToSymbol[i];
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m_IndexToSymbol[i] = m_IndexToSymbol[i_Index];
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m_IndexToSymbol[i_Index] = symbol;
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m_SymbolToIndex[symbol] = i_Index;
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m_SymbolToIndex[m_IndexToSymbol[i]] = i;
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}
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m_Freq[i]++;
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while (i)
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m_CumFreq[--i]++;
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COMP_CATCHTHIS_SPEED
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}
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