Node / RFnexus / code.git / files / short_bch_code_encoder.hh

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/*

Encoder for short BCH codes

Copyright 2020 Ahmet Inan <inan@aicodix.de>

*/

#pragma once

namespace CODE {

template <int N, int K, int G>

class ShortBCHCodeEncoder

{

static const int P = N - K;

static const int W = 1 << K;

short par[W];

static_assert(N < 8 * sizeof(int), "codeword type not wide enough");

static_assert(P < 8 * sizeof(par[0]), "parity type not wide enough");

static int modgen(int inp)

{

for (int i = K-1; i >= 0; --i) {

int tmp = inp >> (i+P);

inp ^= (tmp & 1) * (G << i);

}

return inp;

}

public:

ShortBCHCodeEncoder()

{

for (int i = 0; i < W; ++i)

par[i] = modgen(i << P);

}

int operator()(int msg)

{

return (msg << P) | par[msg];

}

int operator()(int8_t *code, int msg)

{

int cw = (*this)(msg);

for (int i = 0; i < N; ++i)

code[i] = 1 - 2 * ((cw >> i) & 1);

return cw;

}

};

}