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/*
Copyright (C) 2005, 2006, 2007, 2008, 2009 Her Majesty the Queen in Right
of Canada (Communications Research Center Canada)
*/
/*
This file is part of ODR-DabMux.
ODR-DabMux 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, either version 3 of the
License, or (at your option) any later version.
ODR-DabMux 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 for more details.
You should have received a copy of the GNU General Public License
along with ODR-DabMux. If not, see <http://www.gnu.org/licenses/>.
*/
#include "prbs.h"
#include <string.h>
#include <limits.h>
/*
* Generate a parity check for a 32-bit word.
*/
static uint32_t parity_check(uint32_t prbs_accum)
{
uint32_t mask = 1;
uint32_t parity = 0;
for (int i = 0; i < 32; ++i) {
parity ^= ((prbs_accum & mask) != 0);
mask <<= 1;
}
return parity;
}
void PrbsGenerator::setup(uint32_t polynomial)
{
this->polynomial = polynomial;
this->accum = 0;
gen_prbs_table();
gen_weight_table();
}
uint8_t PrbsGenerator::step()
{
accum = update_prbs();
return accum & 0xff;
}
void PrbsGenerator::rewind()
{
while (accum < polynomial) {
accum <<= 1;
accum |= 1;
}
}
void PrbsGenerator::gen_prbs_table()
{
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 256; ++j) {
uint32_t prbs_accum = ((uint32_t)j << (i * 8));
for (int k = 0; k < 8; ++k) {
prbs_accum = (prbs_accum << 1)
^ parity_check(prbs_accum & polynomial);
}
prbs_table[i][j] = (prbs_accum & 0xff);
}
}
}
uint32_t PrbsGenerator::update_prbs()
{
uint8_t acc_lsb = 0;
for (int i = 0; i < 4; ++i ) {
acc_lsb ^= prbs_table [i] [ (accum >> (i * 8) ) & 0xff ];
}
return (accum << 8) ^ ((uint32_t)acc_lsb);
}
void PrbsGenerator::gen_weight_table()
{
for (int i = 0; i < 256; ++i) {
uint8_t mask = 1;
uint8_t ones_count = 0;
for (int j = 0; j < 8; ++j) {
ones_count += ((i & mask) != 0);
mask = mask << 1;
}
weight[i] = ones_count;
}
}
size_t PrbsGenerator::error_count(
uint8_t *rx_data,
size_t rx_data_length)
{
uint32_t error_count = 0;
uint32_t prbs_accum = 0;
/* seed the PRBS accumulator */
for (int i = 0; i < 4; ++i) {
prbs_accum = (prbs_accum << 8) ^ (rx_data[i] ^ polarity_mask);
}
/* check the received data */
for (size_t i = 0; i < rx_data_length; ++i) {
uint8_t error_pattern =
(prbs_accum >> 24) ^ (rx_data[i] ^ polarity_mask);
if (error_pattern != 0) {
error_count += weight[error_pattern];
}
prbs_accum = update_prbs();
}
return error_count;
}
void PrbsGenerator::gen_sequence(
uint8_t *tx_data,
size_t tx_data_length,
uint32_t polynomial)
{
uint32_t prbs_accum = 0;
while (prbs_accum < polynomial) {
prbs_accum <<= 1;
prbs_accum |= 1;
}
for (size_t i = 0; i < tx_data_length; i++) {
prbs_accum = update_prbs();
tx_data[i] = (uint8_t)(prbs_accum & 0xff);
}
}
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