87 lines
3.1 KiB
C++
87 lines
3.1 KiB
C++
/***************************************************************************
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* Copyright (C) 2021 - 2022 by Federico Amedeo Izzo IU2NUO, *
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* Niccolò Izzo IU2KIN *
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* Frederik Saraci IU2NRO *
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* Silvano Seva IU2KWO *
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* *
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* Adapted from original code written by Rob Riggs, Mobilinkd LLC *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 3 of the License, or *
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* (at your option) any later version. *
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* *
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* This program 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 *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, see <http://www.gnu.org/licenses/> *
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***************************************************************************/
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#ifndef M17_INTERLEAVER_H
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#define M17_INTERLEAVER_H
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#ifndef __cplusplus
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#error This header is C++ only!
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#endif
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#include "M17Utils.hpp"
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namespace M17
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{
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/**
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* Interleave a block of data using the quadratic permutation polynomial from
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* M17 protocol specification. Polynomial used is P(x) = 45*x + 92*x^2.
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*
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* \param data: input byte array.
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*/
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template < size_t N >
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void interleave(std::array< uint8_t, N >& data)
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{
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std::array< uint8_t, N > interleaved;
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static constexpr size_t F1 = 45;
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static constexpr size_t F2 = 92;
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static constexpr size_t NB = N*8;
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for(size_t i = 0; i < NB; i++)
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{
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size_t index = ((F1 * i) + (F2 * i * i)) % NB;
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setBit(interleaved, index, getBit(data, i));
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}
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std::copy(interleaved.begin(), interleaved.end(), data.begin());
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}
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/**
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* Perform the deinterleaving operation on a block of data previously interleaved
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* using the quadratic permutation polynomial from M17 protocol specification.
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* Polynomial used is P(x) = 45*x + 92*x^2.
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*
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* \param data: input byte array.
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*/
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template < size_t N >
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void deinterleave(std::array< uint8_t, N >& data)
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{
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std::array< uint8_t, N > deinterleaved;
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static constexpr size_t F1 = 45;
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static constexpr size_t F2 = 92;
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static constexpr size_t NB = N*8;
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for(size_t i = 0; i < NB; i++)
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{
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size_t index = ((F1 * i) + (F2 * i * i)) % NB;
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setBit(deinterleaved, i, getBit(data, index));
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}
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std::copy(deinterleaved.begin(), deinterleaved.end(), data.begin());
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}
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} // namespace M17
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#endif // M17_INTERLEAVER_H
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