1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
/* -*- c++ -*- */
/*
* Copyright (C) Miklos Maroti 2015
* Obtained from https://gitlab.com/phorvath/smogcli2
* Copyright 2020 Daniel Estevez <daniel@destevez.net> (adaptation to gr-satellites)
*
* This file is part of gr-satellites
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#include "ra_encoder.h"
#include "ra_lfsr.h"
/* --- REPEAT ACCUMULATE ENCODER: rate 1/4, punctured, twisted parallel --- */
void ra_encoder_init(struct ra_context* ctx, const ra_word_t* packet)
{
ctx->ra_packet = packet;
ctx->ra_nextword = 0;
ctx->ra_passno = 0;
ra_lfsr_init(ctx, 0);
}
ra_word_t ra_encoder_next(struct ra_context* ctx)
{
ra_index_t pos;
ra_word_t word;
uint8_t count;
word = ctx->ra_nextword;
count = ctx->ra_passno == 0 ? 1 : RA_PUNCTURE_RATE;
do {
word = (word >> 1) | (word << RA_BITSHIFT);
pos = ra_lfsr_next(ctx);
word ^= ctx->ra_packet[pos];
} while (pos != ctx->ra_passno && --count != 0);
if (count != 0) {
ctx->ra_nextword = 0;
ctx->ra_passno = (ctx->ra_passno + 1) % 4;
ra_lfsr_init(ctx, ctx->ra_passno);
} else
ctx->ra_nextword = word;
return word;
}
void ra_encoder(struct ra_context* ctx, const ra_word_t* packet, ra_word_t* output)
{
ra_encoder_init(ctx, packet);
for (ra_index_t i = 0; i < ctx->ra_code_length; i++)
*(output++) = ra_encoder_next(ctx);
}
|
