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PRBS: a Pseudo-random binary sequence (PRBS) generator class.

Implemeted with a Galois LFSR for speed and flexibility compared to Fibonacci version.

Aliases for three popular PRBS' are added for convenience - PRBS9, PRBS15 and PRBS64.

Note that we can't test PRBS64 completely, because the sequence is too long to
be generated.

Change-Id: Ib5331ba5d0b5819929541686fdd87905e2177b74
changes/64/2764/2
Alexander Chemeris 5 years ago committed by Tom Tsou
parent
commit
082bbbf8fe
  1. 1
      .gitignore
  2. 4
      CommonLibs/Makefile.am
  3. 110
      CommonLibs/PRBS.h
  4. 42
      CommonLibs/PRBSTest.cpp

1
.gitignore vendored

@ -15,6 +15,7 @@ CommonLibs/SocketsTest
CommonLibs/TimevalTest
CommonLibs/URLEncodeTest
CommonLibs/VectorTest
CommonLibs/PRBSTest
# automake/autoconf
*.in

4
CommonLibs/Makefile.am

@ -42,6 +42,7 @@ libcommon_la_SOURCES = \
noinst_PROGRAMS = \
BitVectorTest \
PRBSTest \
InterthreadTest \
SocketsTest \
TimevalTest \
@ -53,6 +54,7 @@ noinst_PROGRAMS = \
noinst_HEADERS = \
BitVector.h \
PRBS.h \
Interthread.h \
LinkedLists.h \
Sockets.h \
@ -66,6 +68,8 @@ noinst_HEADERS = \
BitVectorTest_SOURCES = BitVectorTest.cpp
BitVectorTest_LDADD = libcommon.la $(SQLITE3_LIBS)
PRBSTest_SOURCES = PRBSTest.cpp
InterthreadTest_SOURCES = InterthreadTest.cpp
InterthreadTest_LDADD = libcommon.la
InterthreadTest_LDFLAGS = -lpthread

110
CommonLibs/PRBS.h

@ -0,0 +1,110 @@
/*
* Copyright (C) 2017 Alexander Chemeris <Alexander.Chemeris@fairwaves.co>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef PRBS_H
#define PRBS_H
#include <stdint.h>
#include <assert.h>
/** Pseudo-random binary sequence (PRBS) generator (a Galois LFSR implementation). */
class PRBS {
public:
PRBS(unsigned wLen, uint64_t wCoeff, uint64_t wState = 0x01)
: mCoeff(wCoeff), mStartState(wState), mState(wState), mLen(wLen)
{ assert(wLen<=64); }
/**@name Accessors */
//@{
uint64_t coeff() const { return mCoeff; }
uint64_t state() const { return mState; }
void state(uint64_t state) { mState = state & mask(); }
unsigned size() const { return mLen; }
//@}
/**
Calculate one bit of a PRBS
*/
unsigned generateBit()
{
const unsigned result = mState & 0x01;
processBit(result);
return result;
}
/**
Update the generator state by one bit.
If you want to synchronize your PRBS to a known state, call this function
size() times passing your PRBS to it bit by bit.
*/
void processBit(unsigned inBit)
{
mState >>= 1;
if (inBit) mState ^= mCoeff;
}
/** Return true when PRBS is wrapping through initial state */
bool isFinished() const { return mStartState == mState; }
protected:
uint64_t mCoeff; ///< polynomial coefficients. LSB is zero exponent.
uint64_t mStartState; ///< initial shift register state.
uint64_t mState; ///< shift register state.
unsigned mLen; ///< number of bits used in shift register
/** Return mask for the state register */
uint64_t mask() const { return (mLen==64)?0xFFFFFFFFFFFFFFFFUL:((1<<mLen)-1); }
};
/**
A standard 9-bit based pseudorandom binary sequence (PRBS) generator.
Polynomial: x^9 + x^5 + 1
*/
class PRBS9 : public PRBS {
public:
PRBS9(uint64_t wState = 0x01)
: PRBS(9, 0x0110, wState)
{}
};
/**
A standard 15-bit based pseudorandom binary sequence (PRBS) generator.
Polynomial: x^15 + x^14 + 1
*/
class PRBS15 : public PRBS {
public:
PRBS15(uint64_t wState = 0x01)
: PRBS(15, 0x6000, wState)
{}
};
/**
A standard 64-bit based pseudorandom binary sequence (PRBS) generator.
Polynomial: x^64 + x^63 + x^61 + x^60 + 1
*/
class PRBS64 : public PRBS {
public:
PRBS64(uint64_t wState = 0x01)
: PRBS(64, 0xD800000000000000ULL, wState)
{}
};
#endif // PRBS_H

42
CommonLibs/PRBSTest.cpp

@ -0,0 +1,42 @@
/*
* Copyright (C) 2017 Alexander Chemeris <Alexander.Chemeris@fairwaves.co>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "PRBS.h"
#include <iostream>
#include <cstdlib>
#include <assert.h>
void testPrbs(PRBS &prbs, uint64_t expectedPeriod)
{
uint64_t period = 0;
do {
std::cout << prbs.generateBit();
period++;
} while (!prbs.isFinished());
std::cout << std::endl;
std::cout << "Period: " << period << std::endl;
assert(period == expectedPeriod);
}
int main(int argc, char *argv[])
{
PRBS9 prbs9(0x01);
testPrbs(prbs9, (1<<9)-1);
PRBS15 prbs15(0x01);
testPrbs(prbs15, (1<<15)-1);
}
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