mirror of
https://github.com/f4exb/sdrangel.git
synced 2024-11-25 09:18:54 -05:00
131 lines
4.1 KiB
C++
131 lines
4.1 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
|
|
// Copyright (C) 2020-2021 Jon Beniston, M7RCE <jon@beniston.com> //
|
|
// //
|
|
// This program is free software; you can redistribute it and/or modify //
|
|
// it under the terms of the GNU General Public License as published by //
|
|
// the Free Software Foundation as version 3 of the License, or //
|
|
// (at your option) any later version. //
|
|
// //
|
|
// This program is distributed in the hope that it will be useful, //
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of //
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
|
|
// GNU General Public License V3 for more details. //
|
|
// //
|
|
// You should have received a copy of the GNU General Public License //
|
|
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
|
|
///////////////////////////////////////////////////////////////////////////////////
|
|
|
|
#include "lfsr.h"
|
|
#include "popcount.h"
|
|
|
|
// Shift LFSR one bit
|
|
int LFSR::shift()
|
|
{
|
|
int bit;
|
|
|
|
bit = (popcount(m_sr & m_polynomial) & 1) ^ 1;
|
|
m_sr = (m_sr << 1) | bit;
|
|
return bit;
|
|
}
|
|
|
|
// Scramble a single bit
|
|
int LFSR::scramble(int bit_in)
|
|
{
|
|
int bit_out;
|
|
|
|
bit_out = (popcount(m_sr & m_polynomial) & 1) ^ bit_in;
|
|
m_sr = (m_sr << 1) | bit_out;
|
|
return bit_out;
|
|
}
|
|
|
|
// Scramble data using LFSR - LSB first
|
|
void LFSR::scramble(uint8_t *data, int length)
|
|
{
|
|
uint8_t byte_in, byte_out;
|
|
int bit_in, bit_out;
|
|
|
|
for(int i = 0; i < length; i++)
|
|
{
|
|
byte_in = data[i];
|
|
byte_out = 0;
|
|
for (int j = 0; j < 8; j++)
|
|
{
|
|
bit_in = (byte_in >> j) & 1;
|
|
bit_out = (popcount(m_sr & m_polynomial) & 1) ^ bit_in;
|
|
m_sr = (m_sr << 1) | bit_out;
|
|
byte_out = byte_out | (bit_out << j);
|
|
}
|
|
data[i] = byte_out;
|
|
}
|
|
}
|
|
|
|
// Descramble data using LFSR - LSB first
|
|
void LFSR::descramble(uint8_t *data, int length)
|
|
{
|
|
uint8_t byte_in, byte_out;
|
|
int bit_in, bit_out;
|
|
|
|
for(int i = 0; i < length; i++)
|
|
{
|
|
byte_in = data[i];
|
|
byte_out = 0;
|
|
for (int j = 0; j < 8; j++)
|
|
{
|
|
bit_in = (byte_in >> j) & 1;
|
|
bit_out = (popcount(m_sr & m_polynomial) & 1) ^ bit_in;
|
|
m_sr = (m_sr << 1) | bit_in;
|
|
byte_out = byte_out | (bit_out << j);
|
|
}
|
|
data[i] = byte_out;
|
|
}
|
|
}
|
|
|
|
// XOR data with rand_bits of LFSR - LSB first
|
|
void LFSR::randomize(uint8_t *data, int length)
|
|
{
|
|
uint8_t byte_in, byte_out;
|
|
int bit_in, bit_out, bit;
|
|
|
|
for(int i = 0; i < length; i++)
|
|
{
|
|
byte_in = data[i];
|
|
byte_out = 0;
|
|
for (int j = 0; j < 8; j++)
|
|
{
|
|
// XOR input bit with specified bit from SR
|
|
bit_in = (byte_in >> j) & 1;
|
|
//bit_out = ((m_sr >> m_rand_bit) & 1) ^ bit_in;
|
|
bit_out = (popcount(m_sr & m_rand_bits) & 1) ^ bit_in;
|
|
byte_out = byte_out | (bit_out << j);
|
|
// Update LFSR
|
|
bit = popcount(m_sr & m_polynomial) & 1;
|
|
m_sr = (m_sr << 1) | bit;
|
|
}
|
|
data[i] = byte_out;
|
|
}
|
|
}
|
|
|
|
// XOR data with rand_bits of LFSR - MSB first
|
|
void LFSR::randomizeMSB(const uint8_t *dataIn, uint8_t *dataOut, int length)
|
|
{
|
|
uint8_t byte_in, byte_out;
|
|
int bit_in, bit_out, bit;
|
|
|
|
for(int i = 0; i < length; i++)
|
|
{
|
|
byte_in = dataIn[i];
|
|
byte_out = 0;
|
|
for (int j = 7; j >= 0; j--)
|
|
{
|
|
// XOR input bit with selected bits from SR
|
|
bit_in = (byte_in >> j) & 1;
|
|
bit_out = (popcount(m_sr & m_rand_bits) & 1) ^ bit_in;
|
|
byte_out = byte_out | (bit_out << j);
|
|
// Update LFSR
|
|
bit = popcount(m_sr & m_polynomial) & 1;
|
|
m_sr = (m_sr << 1) | bit;
|
|
}
|
|
dataOut[i] = byte_out;
|
|
}
|
|
}
|