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62 lines
1.5 KiB
C++
62 lines
1.5 KiB
C++
/*
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Encoder for Polarization-Adjusted Convolutional codes
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Copyright 2025 Ahmet Inan <inan@aicodix.de>
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*/
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#pragma once
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#include "polar_helper.hh"
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namespace CODE {
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template <typename TYPE>
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class PACEncoder
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{
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typedef PolarHelper<TYPE> PH;
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static bool get(const uint32_t *bits, int idx)
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{
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return (bits[idx/32] >> (idx%32)) & 1;
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}
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static bool conv(int *state, bool input)
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{
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#if 0
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// 1011011
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bool b1 = (*state >> 1) & 1;
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bool b3 = (*state >> 3) & 1;
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bool b4 = (*state >> 4) & 1;
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bool b6 = (*state >> 6) & 1;
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bool output = input ^ b1 ^ b3 ^ b4 ^ b6;
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#else
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// 1101101
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bool b2 = (*state >> 2) & 1;
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bool b3 = (*state >> 3) & 1;
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bool b5 = (*state >> 5) & 1;
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bool b6 = (*state >> 6) & 1;
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bool output = input ^ b2 ^ b3 ^ b5 ^ b6;
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#endif
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*state = ((*state & 126) << 1) | (input ? 2 : 0) | (output ? 1 : 0);
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return output;
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}
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public:
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void operator()(TYPE *codeword, const TYPE *message, const uint32_t *frozen, int level)
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{
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int length = 1 << level;
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int state = 0;
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for (int i = 0; i < length; i += 2) {
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TYPE msg0 = get(frozen, i) ? PH::one() : *message++;
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TYPE msg1 = get(frozen, i+1) ? PH::one() : *message++;
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msg0 = 1 - 2 * conv(&state, msg0 < 0);
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msg1 = 1 - 2 * conv(&state, msg1 < 0);
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codeword[i] = PH::qmul(msg0, msg1);
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codeword[i+1] = msg1;
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}
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for (int h = 2; h < length; h *= 2)
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for (int i = 0; i < length; i += 2 * h)
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for (int j = i; j < i + h; ++j)
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codeword[j] = PH::qmul(codeword[j], codeword[j+h]);
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}
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};
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}
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