| /* |
| * 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 |