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81 lines
2.8 KiB
C++
81 lines
2.8 KiB
C++
///////////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2019, 2021 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
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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 as 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 V3 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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#include "math.h"
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#include <bitset>
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namespace leansdr
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{
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int hamming_weight(uint8_t x)
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{
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static const int lut[16] = {0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4};
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return lut[x & 15] + lut[x >> 4];
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}
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int hamming_weight(uint16_t x)
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{
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return hamming_weight((uint8_t)x) + hamming_weight((uint8_t)(x >> 8));
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}
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int hamming_weight(uint32_t x)
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{
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return std::bitset<32>(x).count();
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// x = x - ((x >> 1) & 0x55555555);
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// x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
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// return (((x + (x >> 4)) & 0x0F0F0F0F) * 0x01010101) >> 24;
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// return hamming_weight((uint16_t)x) + hamming_weight((uint16_t)(x >> 16));
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}
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int hamming_weight(uint64_t x)
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{
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return std::bitset<64>(x).count();
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// x = x - ((x >> 1) & 0x5555555555555555);
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// x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333);
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// return (((x + (x >> 4)) & 0x0F0F0F0F0F0F0F0F) * 0x0101010101010101) >> 56;
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// return hamming_weight((uint32_t)x) + hamming_weight((uint32_t)(x >> 32));
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}
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unsigned char parity(uint8_t x)
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{
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x ^= x >> 4;
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return (0x6996 >> (x & 15)) & 1; // 16-entry look-up table
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}
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unsigned char parity(uint16_t x)
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{
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return parity((uint8_t)(x ^ (x >> 8)));
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}
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unsigned char parity(uint32_t x)
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{
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return parity((uint16_t)(x ^ (x >> 16)));
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}
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unsigned char parity(uint64_t x)
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{
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return parity((uint32_t)(x ^ (x >> 32)));
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}
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int log2i(uint64_t x)
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{
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int n = -1;
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for (; x; ++n, x >>= 1);
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return n;
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}
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} // leansdr
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