123 lines
3.3 KiB
C++
123 lines
3.3 KiB
C++
/* -*- c++ -*- */
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/*
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* gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
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*
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* Copyright (C) 2016, Libre Space Foundation <http://librespacefoundation.org/>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <gnuradio/io_signature.h>
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#include <satnogs/whitening.h>
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#include <satnogs/utils.h>
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namespace gr {
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namespace satnogs {
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/**
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* Data whitening and de-whitening class
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* @param mask the polynomial mask
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* @param seed the initial seed
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* @param order the order of the shift register. This is equal to the
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* number of memory stages.
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*/
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whitening::whitening (uint32_t mask, uint32_t seed, uint32_t order) :
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d_lfsr(mask, seed, order)
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{
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}
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/**
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* Resets the scrambler (or the descrambler) to the initial stage and
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* the initial seed.
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*/
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void
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whitening::reset ()
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{
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d_lfsr.reset();
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}
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/**
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* Performs data scrambling
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* @param out the output buffer
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* @param in the input buffer
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* @param len the number of the bytes to be scrambled
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*/
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void
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whitening::scramble (uint8_t* out, const uint8_t* in, size_t len)
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{
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size_t i;
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uint8_t b;
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for(i = 0; i < len; i++){
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b = d_lfsr.next_bit();
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b |= d_lfsr.next_bit() << 1;
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b |= d_lfsr.next_bit() << 2;
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b |= d_lfsr.next_bit() << 3;
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b |= d_lfsr.next_bit() << 4;
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b |= d_lfsr.next_bit() << 5;
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b |= d_lfsr.next_bit() << 6;
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b |= d_lfsr.next_bit() << 7;
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out[i] = in[i] ^ b;
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}
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}
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/**
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* Performs data de-scrambling
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* @param out the output buffer
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* @param in the input buffer
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* @param len the number of the bytes to be de-scrambled
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*/
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void
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whitening::descramble (uint8_t* out, const uint8_t* in, size_t len)
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{
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scramble(out, in, len);
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}
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/**
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* Performs data scrambling. The input and output buffer
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* contain one bit per byte
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* @param out the output buffer
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* @param in the input buffer
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* @param bits_num the number of bits to be scrambled
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*/
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void
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whitening::scramble_one_bit_per_byte (uint8_t* out, const uint8_t* in,
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size_t bits_num)
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{
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size_t i;
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for(i = 0; i < bits_num; i++){
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out[i] = in[i] ^ d_lfsr.next_bit();
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}
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}
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/**
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* Performs data descrambling. The input and output buffer
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* contain one bit per byte
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* @param out the output buffer
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* @param in the input buffer
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* @param bits_num the number of bits to be descrambled
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*/
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void
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whitening::descramble_one_bit_per_byte (uint8_t* out, const uint8_t* in,
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size_t bits_num)
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{
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scramble_one_bit_per_byte(out, in, bits_num);
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}
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} /* namespace satnogs */
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} /* namespace gr */
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