mirror of
https://github.com/hb9fxq/gr-digitalhf
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51 lines
1.4 KiB
C
51 lines
1.4 KiB
C
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/* -*- c++ -*- */
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/*
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* Copyright 2018 hcab14@mail.com.
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*
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* This 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, or (at your option)
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* any later version.
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*
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* This software 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 software; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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namespace gr {
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namespace digitalhf {
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#include <array>
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#include <cmath>
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#include <cstdint>
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template<size_t N>
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class llr_to_prob {
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public:
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llr_to_prob()
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: _table() {
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for (int i=0; i<N; ++i) { // llr -> probability(1)
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float const x = -7.0f + 14.0f*float(i)/float(N-1);
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_table[i] = std::uint8_t(0.5f + 255.0f/(1.0f + std::exp(x)));
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}
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}
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virtual ~llr_to_prob() {}
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std::uint8_t table_lookup(float llr) const {
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float const x = (7.0f + std::max(-7.0f, std::min(+7.0f, llr)))/14.0f; // \in [0,1]
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return _table[int(0.5 + (N-1)*x)];
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}
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protected:
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private:
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std::array<std::uint8_t, N> _table;
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} ;
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} // namespace digitalhf
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} // namespace gr
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