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authorMatthias (think) <matthias@mpb.li>2012-07-11 11:49:12 +0200
committerMatthias (think) <matthias@mpb.li>2012-07-11 11:49:12 +0200
commite92f9c408634810828e75d4ad6da408e1c142195 (patch)
treed4e622617f58a70ed3dd2e57418f73f412e7193b /src/PrbsGenerator.cpp
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Diffstat (limited to 'src/PrbsGenerator.cpp')
-rw-r--r--src/PrbsGenerator.cpp174
1 files changed, 174 insertions, 0 deletions
diff --git a/src/PrbsGenerator.cpp b/src/PrbsGenerator.cpp
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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 CRC-DADMOD.
+
+ CRC-DADMOD 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.
+
+ CRC-DADMOD 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 CRC-DADMOD. 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();
+}