kopia lustrzana https://github.com/f4exb/sdrangel
80 wiersze
1.7 KiB
C++
80 wiersze
1.7 KiB
C++
// Copyright 2020 modemm17 LLC.
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#pragma once
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#include <array>
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#include <cstdint>
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#include <cstddef>
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namespace modemm17
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{
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namespace detail
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{
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// M17 randomization matrix.
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static const std::array<uint8_t, 46> DC = std::array<uint8_t, 46>{
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0xd6, 0xb5, 0xe2, 0x30, 0x82, 0xFF, 0x84, 0x62,
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0xba, 0x4e, 0x96, 0x90, 0xd8, 0x98, 0xdd, 0x5d,
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0x0c, 0xc8, 0x52, 0x43, 0x91, 0x1d, 0xf8, 0x6e,
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0x68, 0x2F, 0x35, 0xda, 0x14, 0xea, 0xcd, 0x76,
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0x19, 0x8d, 0xd5, 0x80, 0xd1, 0x33, 0x87, 0x13,
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0x57, 0x18, 0x2d, 0x29, 0x78, 0xc3};
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}
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template <size_t N = 368>
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struct M17Randomizer
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{
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std::array<int8_t, N> dc_;
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M17Randomizer()
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{
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size_t i = 0;
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for (auto b : detail::DC)
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{
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for (size_t j = 0; j != 8; ++j)
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{
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dc_[i++] = (b >> (7 - j)) & 1 ? -1 : 1;
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}
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}
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}
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// Randomize and derandomize are the same operation.
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void operator()(std::array<int8_t, N>& frame)
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{
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for (size_t i = 0; i != N; ++i)
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{
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frame[i] *= dc_[i];
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}
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}
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void randomize(std::array<int8_t, N>& frame)
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{
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for (size_t i = 0; i != N; ++i)
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{
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frame[i] ^= (dc_[i] == -1);
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}
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}
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};
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template <size_t N = 46>
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struct M17ByteRandomizer
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{
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// Randomize and derandomize are the same operation.
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void operator()(std::array<uint8_t, N>& frame)
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{
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for (size_t i = 0; i != N; ++i)
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{
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for (size_t j = 8; j != 0; --j)
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{
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uint8_t mask = 1 << (j - 1);
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frame[i] = (frame[i] & ~mask) | ((frame[i] & mask) ^ (detail::DC[i] & mask));
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}
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}
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}
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};
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} // modemm17
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