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/*
Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Her Majesty
the Queen in Right of Canada (Communications Research Center Canada)
*/
/*
This file is part of ODR-DabMod.
ODR-DabMod 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-DabMod 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-DabMod. If not, see <http://www.gnu.org/licenses/>.
*/
#include "PrbsGenerator.h"
#include "PcDebug.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdexcept>
PrbsGenerator::PrbsGenerator(size_t framesize, uint32_t polynomial,
uint32_t accum, size_t init) :
ModCodec(ModFormat(0), ModFormat(framesize)),
d_framesize(framesize),
d_polynomial(polynomial),
d_accum(accum),
d_accum_init(accum),
d_init(init)
{
PDEBUG("PrbsGenerator::PrbsGenerator(%zu, %u, %u, %zu) @ %p\n",
framesize, polynomial, accum, init, this);
gen_prbs_table();
gen_weight_table();
}
PrbsGenerator::~PrbsGenerator()
{
PDEBUG("PrbsGenerator::~PrbsGenerator() @ %p\n", this);
}
/*
* Generate a table of matrix products to update a 32-bit PRBS generator.
*/
void PrbsGenerator::gen_prbs_table()
{
int i;
for (i = 0; i < 4; ++i) {
int j;
for (j = 0; j < 256; ++j) {
uint32_t prbs_accum = ((uint32_t)j << (i * 8));
int k;
for (k = 0; k < 8; ++k) {
prbs_accum = (prbs_accum << 1)
^ parity_check(prbs_accum & d_polynomial);
}
d_prbs_table[i][j] = (prbs_accum & 0xff);
}
}
}
/*
* Generate the weight table.
*/
void PrbsGenerator::gen_weight_table()
{
int i;
for (i = 0; i < 256; ++i) {
unsigned char mask=1U, ones_count = 0U;
int j;
for (j = 0; j < 8; ++j) {
ones_count += ((i & mask) != 0U);
mask = mask << 1;
}
d_weight[i] = ones_count;
}
}
/*
* Generate a parity check for a 32-bit word.
*/
uint32_t PrbsGenerator::parity_check(uint32_t prbs_accum)
{
uint32_t mask=1UL, parity=0UL;
int i;
for (i = 0; i < 32; ++i) {
parity ^= ((prbs_accum & mask) != 0UL);
mask <<= 1;
}
return parity;
}
/*
* Update a 32-bit PRBS generator eight bits at a time.
*/
uint32_t PrbsGenerator::update_prbs()
{
unsigned char acc_lsb = 0;
int i;
for (i = 0; i < 4; ++i) {
// PDEBUG("0x%x = 0x%x ^ 0x%x\n",
// acc_lsb ^ d_prbs_table [i][(d_accum >> (i * 8)) & 0xff],
// acc_lsb, d_prbs_table [i][(d_accum >> (i * 8)) & 0xff]);
acc_lsb ^= d_prbs_table[i][(d_accum >> (i * 8)) & 0xff];
}
return (d_accum << 8) ^ ((uint32_t)acc_lsb);
}
int PrbsGenerator::process(Buffer* const dataIn, Buffer* dataOut)
{
PDEBUG("PrbsGenerator::process(dataIn: %p, dataOut: %p)\n",
dataIn, dataOut);
dataOut->setLength(d_framesize);
unsigned char* out = reinterpret_cast<unsigned char*>(dataOut->getData());
// Initialization
if (d_accum_init) {
d_accum = d_accum_init;
} else {
d_accum = 0;
while (d_accum < d_polynomial) {
d_accum <<= 1;
d_accum |= 1;
}
}
//PDEBUG("Polynomial: 0x%x\n", d_polynomial);
//PDEBUG("Init accum: 0x%x\n", d_accum);
size_t i = 0;
while (i < d_init) {
out[i++] = 0xff;
}
for (; i < d_framesize; ++i) {
// Writting data
d_accum = update_prbs();
if ((d_accum_init == 0xa9) && (i % 188 == 0)) { // DVB energy dispersal
out[i] = 0;
} else {
out[i] = (unsigned char)(d_accum & 0xff);
}
//PDEBUG("accum: 0x%x\n", d_accum);
}
if ((dataIn != NULL) && dataIn->getLength()) {
PDEBUG(" mixing input\n");
const unsigned char* in = reinterpret_cast<const unsigned char*>(dataIn->getData());
if (dataIn->getLength() != dataOut->getLength()) {
PDEBUG("%zu != %zu\n", dataIn->getLength(), dataOut->getLength());
throw std::runtime_error("PrbsGenerator::process "
"input size is not equal to output size!\n");
}
for (size_t i = 0; i < dataOut->getLength(); ++i) {
out[i] ^= in[i];
}
}
return dataOut->getLength();
}
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