kopia lustrzana https://github.com/f4exb/sdrangel
111 wiersze
2.2 KiB
C++
111 wiersze
2.2 KiB
C++
// Copyright 2020 Rob Riggs <rob@mobilinkd.com>
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// All rights reserved.
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#pragma once
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#include <array>
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#include <cstdint>
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#include <algorithm>
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#include <utility>
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#include "export.h"
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namespace modemm17 {
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// Parts are adapted from:
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// http://aqdi.com/articles/using-the-golay-error-detection-and-correction-code-3/
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namespace Golay24_detail
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{
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// Need a constexpr sort.
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// https://stackoverflow.com/a/40030044/854133
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template<class T>
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static void swap(T& l, T& r)
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{
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T tmp = std::move(l);
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l = std::move(r);
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r = std::move(tmp);
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}
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template <typename T, size_t N>
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struct array
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{
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constexpr T& operator[](size_t i) {
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return arr[i];
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}
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constexpr const T& operator[](size_t i) const {
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return arr[i];
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}
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constexpr const T* begin() const {
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return arr;
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}
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constexpr const T* end() const {
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return arr + N;
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}
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T arr[N];
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};
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template <typename T, size_t N>
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static void sort_impl(array<T, N> &array, size_t left, size_t right)
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{
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if (left < right)
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{
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size_t m = left;
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for (size_t i = left + 1; i<right; i++)
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if (array[i]<array[left])
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swap(array[++m], array[i]);
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swap(array[left], array[m]);
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sort_impl(array, left, m);
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sort_impl(array, m + 1, right);
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}
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}
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template <typename T, size_t N>
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static array<T, N> sort(array<T, N> array)
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{
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auto sorted = array;
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sort_impl(sorted, 0, N);
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return sorted;
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}
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} // Golay24_detail
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struct MODEMM17_API Golay24
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{
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#pragma pack(push, 1)
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struct SyndromeMapEntry
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{
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uint32_t a{0};
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uint16_t b{0};
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};
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#pragma pack(pop)
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static const uint16_t POLY = 0xC75;
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static const size_t LUT_SIZE = 2048;
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static std::array<SyndromeMapEntry, LUT_SIZE> LUT;
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Golay24();
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static uint32_t encode23(uint16_t data);
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static uint32_t encode24(uint16_t data);
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static bool decode(uint32_t input, uint32_t& output);
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private:
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static bool parity(uint32_t codeword);
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static SyndromeMapEntry makeSyndromeMapEntry(uint64_t val);
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static uint32_t syndrome(uint32_t codeword);
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static uint64_t makeSME(uint64_t syndrome, uint32_t bits);
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static std::array<SyndromeMapEntry, LUT_SIZE> make_lut();
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};
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} // modemm17
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