Mirror/aicodix___code
1
0
Fork 0
mirror of https://github.com/aicodix/code.git synced 2026-04-27 14:30:36 +00:00
Code Issues Projects Releases Packages Wiki Activity

encoder and soft decoder for augmented Hadamard codes

Browse source
This commit is contained in:
Ahmet Inan 2020-06-11 23:11:31 +02:00
commit 43c5d6a91a
4 changed files with 242 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

56
hadamard_decoder.hh Normal file
View file

@ -0,0 +1,56 @@
/*
Soft decoder for augmented Hadamard codes
Copyright 2020 Ahmet Inan <inan@aicodix.de>
*/
#pragma once
namespace CODE {
template <int K>
class HadamardDecoder
{
static const int W = 1 << K;
static const int N = 1 << (K - 1);
int8_t mod[W*N];
static bool parity(unsigned x)
{
x ^= x >> 16;
x ^= x >> 8;
x ^= x >> 4;
x ^= x >> 2;
x ^= x >> 1;
return x & 1;
}
public:
HadamardDecoder()
{
for (int msg = 0; msg < W; ++msg)
for (int i = 0; i < N; ++i)
mod[msg*N+i] = 1 - 2 * parity(msg&(i|N));
}
int operator()(const int8_t *code)
{
int word = 0, best = 0, next = 0;
for (int msg = 0; msg < W; ++msg) {
int sum = 0;
for (int i = 0; i < N; ++i)
sum += mod[msg*N+i] * code[i];
if (sum > best) {
next = best;
best = sum;
word = msg;
} else if (sum > next) {
next = sum;
}
}
if (best == next)
return -1;
return word;
}
};
}