mirror of https://github.com/f4exb/sdrangel.git
65 lines
1.4 KiB
C++
65 lines
1.4 KiB
C++
#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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