| /* |
| * Copyright 2008, 2009 Free Software Foundation, Inc. |
| * |
| * This software is distributed under the terms of the GNU Affero Public License. |
| * See the COPYING file in the main directory for details. |
| * |
| * This use of this software may be subject to additional restrictions. |
| * See the LEGAL file in the main directory for details. |
| |
| This program is free software: you can redistribute it and/or modify |
| it under the terms of the GNU Affero General Public License as published by |
| the Free Software Foundation, either version 3 of the License, or |
| (at your option) any later version. |
| |
| This program 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 Affero General Public License for more details. |
| |
| You should have received a copy of the GNU Affero General Public License |
| along with this program. If not, see <http://www.gnu.org/licenses/>. |
| |
| */ |
| |
| |
| #ifndef FECVECTORS_H |
| #define FECVECTORS_H |
| |
| #include "Vector.h" |
| #include <stdint.h> |
| |
| |
| class BitVector; |
| class SoftVector; |
| |
| |
| |
| /** Shift-register (LFSR) generator. */ |
| class Generator { |
| |
| private: |
| |
| uint64_t mCoeff; ///< polynomial coefficients. LSB is zero exponent. |
| uint64_t mState; ///< shift register state. LSB is most recent. |
| uint64_t mMask; ///< mask for reading state |
| unsigned mLen; ///< number of bits used in shift register |
| unsigned mLen_1; ///< mLen - 1 |
| |
| public: |
| |
| Generator(uint64_t wCoeff, unsigned wLen) |
| :mCoeff(wCoeff),mState(0), |
| mMask((1ULL<<wLen)-1), |
| mLen(wLen),mLen_1(wLen-1) |
| { assert(wLen<64); } |
| |
| void clear() { mState=0; } |
| |
| /**@name Accessors */ |
| //@{ |
| uint64_t state() const { return mState & mMask; } |
| unsigned size() const { return mLen; } |
| //@} |
| |
| /** |
| Calculate one bit of a syndrome. |
| This is in the .h for inlining. |
| */ |
| void syndromeShift(unsigned inBit) |
| { |
| const unsigned fb = (mState>>(mLen_1)) & 0x01; |
| mState = (mState<<1) ^ (inBit & 0x01); |
| if (fb) mState ^= mCoeff; |
| } |
| |
| /** |
| Update the generator state by one cycle. |
| This is in the .h for inlining. |
| */ |
| void encoderShift(unsigned inBit) |
| { |
| const unsigned fb = ((mState>>(mLen_1)) ^ inBit) & 0x01; |
| mState <<= 1; |
| if (fb) mState ^= mCoeff; |
| } |
| |
| |
| }; |
| |
| |
| |
| |
| /** Parity (CRC-type) generator and checker based on a Generator. */ |
| class Parity : public Generator { |
| |
| protected: |
| |
| unsigned mCodewordSize; |
| |
| public: |
| |
| Parity(uint64_t wCoefficients, unsigned wParitySize, unsigned wCodewordSize) |
| :Generator(wCoefficients, wParitySize), |
| mCodewordSize(wCodewordSize) |
| { } |
| |
| /** Compute the parity word and write it into the target segment. */ |
| void writeParityWord(const BitVector& data, BitVector& parityWordTarget, bool invert=true); |
| |
| /** Compute the syndrome of a received sequence. */ |
| uint64_t syndrome(const BitVector& receivedCodeword); |
| }; |
| |
| |
| |
| |
| /** |
| Class to represent convolutional coders/decoders of rate 1/2, memory length 4. |
| This is the "workhorse" coder for most GSM channels. |
| */ |
| class ViterbiR2O4 { |
| |
| private: |
| /**name Lots of precomputed elements so the compiler can optimize like hell. */ |
| //@{ |
| /**@name Core values. */ |
| //@{ |
| static const unsigned mIRate = 2; ///< reciprocal of rate |
| static const unsigned mOrder = 4; ///< memory length of generators |
| //@} |
| /**@name Derived values. */ |
| //@{ |
| static const unsigned mIStates = 0x01 << mOrder; ///< number of states, number of survivors |
| static const uint32_t mSMask = mIStates-1; ///< survivor mask |
| static const uint32_t mCMask = (mSMask<<1) | 0x01; ///< candidate mask |
| static const uint32_t mOMask = (0x01<<mIRate)-1; ///< ouput mask, all iRate low bits set |
| static const unsigned mNumCands = mIStates*2; ///< number of candidates to generate during branching |
| static const unsigned mDeferral = 6*mOrder; ///< deferral to be used |
| //@} |
| //@} |
| |
| /** Precomputed tables. */ |
| //@{ |
| uint32_t mCoeffs[mIRate]; ///< polynomial for each generator |
| uint32_t mStateTable[mIRate][2*mIStates]; ///< precomputed generator output tables |
| uint32_t mGeneratorTable[2*mIStates]; ///< precomputed coder output table |
| //@} |
| |
| public: |
| |
| /** |
| A candidate sequence in a Viterbi decoder. |
| The 32-bit state register can support a deferral of 6 with a 4th-order coder. |
| */ |
| typedef struct candStruct { |
| uint32_t iState; ///< encoder input associated with this candidate |
| uint32_t oState; ///< encoder output associated with this candidate |
| float cost; ///< cost (metric value), float to support soft inputs |
| } vCand; |
| |
| /** Clear a structure. */ |
| void clear(vCand& v) |
| { |
| v.iState=0; |
| v.oState=0; |
| v.cost=0; |
| } |
| |
| |
| private: |
| |
| /**@name Survivors and candidates. */ |
| //@{ |
| vCand mSurvivors[mIStates]; ///< current survivor pool |
| vCand mCandidates[2*mIStates]; ///< current candidate pool |
| //@} |
| |
| public: |
| |
| unsigned iRate() const { return mIRate; } |
| uint32_t cMask() const { return mCMask; } |
| uint32_t stateTable(unsigned g, unsigned i) const { return mStateTable[g][i]; } |
| unsigned deferral() const { return mDeferral; } |
| |
| |
| ViterbiR2O4(); |
| |
| /** Set all cost metrics to zero. */ |
| void initializeStates(); |
| |
| /** |
| Full cycle of the Viterbi algorithm: branch, metrics, prune, select. |
| @return reference to minimum-cost candidate. |
| */ |
| const vCand& step(uint32_t inSample, const float *probs, const float *iprobs); |
| |
| private: |
| |
| /** Branch survivors into new candidates. */ |
| void branchCandidates(); |
| |
| /** Compute cost metrics for soft-inputs. */ |
| void getSoftCostMetrics(uint32_t inSample, const float *probs, const float *iprobs); |
| |
| /** Select survivors from the candidate set. */ |
| void pruneCandidates(); |
| |
| /** Find the minimum cost survivor. */ |
| const vCand& minCost() const; |
| |
| /** |
| Precompute the state tables. |
| @param g Generator index 0..((1/rate)-1) |
| */ |
| void computeStateTables(unsigned g); |
| |
| /** |
| Precompute the generator outputs. |
| mCoeffs must be defined first. |
| */ |
| void computeGeneratorTable(); |
| |
| }; |
| |
| |
| |
| |
| class BitVector : public Vector<char> { |
| |
| |
| public: |
| |
| /**@name Constructors. */ |
| //@{ |
| |
| /**@name Casts of Vector constructors. */ |
| //@{ |
| BitVector(char* wData, char* wStart, char* wEnd) |
| :Vector<char>(wData,wStart,wEnd) |
| { } |
| BitVector(size_t len=0):Vector<char>(len) {} |
| BitVector(const Vector<char>& source):Vector<char>(source) {} |
| BitVector(Vector<char>& source):Vector<char>(source) {} |
| BitVector(const Vector<char>& source1, const Vector<char> source2):Vector<char>(source1,source2) {} |
| //@} |
| |
| /** Construct from a string of "0" and "1". */ |
| BitVector(const char* valString); |
| //@} |
| |
| /** Index a single bit. */ |
| bool bit(size_t index) const |
| { |
| // We put this code in .h for fast inlining. |
| const char *dp = mStart+index; |
| assert(dp<mEnd); |
| return (*dp) & 0x01; |
| } |
| |
| /**@name Casts and overrides of Vector operators. */ |
| //@{ |
| BitVector segment(size_t start, size_t span) |
| { |
| char* wStart = mStart + start; |
| char* wEnd = wStart + span; |
| assert(wEnd<=mEnd); |
| return BitVector(NULL,wStart,wEnd); |
| } |
| |
| BitVector alias() |
| { return segment(0,size()); } |
| |
| const BitVector segment(size_t start, size_t span) const |
| { return (BitVector)(Vector<char>::segment(start,span)); } |
| |
| BitVector head(size_t span) { return segment(0,span); } |
| const BitVector head(size_t span) const { return segment(0,span); } |
| BitVector tail(size_t start) { return segment(start,size()-start); } |
| const BitVector tail(size_t start) const { return segment(start,size()-start); } |
| //@} |
| |
| |
| void zero() { fill(0); } |
| |
| /**@name FEC operations. */ |
| //@{ |
| /** Calculate the syndrome of the vector with the given Generator. */ |
| uint64_t syndrome(Generator& gen) const; |
| /** Calculate the parity word for the vector with the given Generator. */ |
| uint64_t parity(Generator& gen) const; |
| /** Encode the signal with the GSM rate 1/2 convolutional encoder. */ |
| void encode(const ViterbiR2O4& encoder, BitVector& target); |
| //@} |
| |
| |
| /** Invert 0<->1. */ |
| void invert(); |
| |
| /**@name Byte-wise operations. */ |
| //@{ |
| /** Reverse an 8-bit vector. */ |
| void reverse8(); |
| /** Reverse groups of 8 within the vector (byte reversal). */ |
| void LSB8MSB(); |
| //@} |
| |
| /**@name Serialization and deserialization. */ |
| //@{ |
| uint64_t peekField(size_t readIndex, unsigned length) const; |
| uint64_t peekFieldReversed(size_t readIndex, unsigned length) const; |
| uint64_t readField(size_t& readIndex, unsigned length) const; |
| uint64_t readFieldReversed(size_t& readIndex, unsigned length) const; |
| void fillField(size_t writeIndex, uint64_t value, unsigned length); |
| void fillFieldReversed(size_t writeIndex, uint64_t value, unsigned length); |
| void writeField(size_t& writeIndex, uint64_t value, unsigned length); |
| void writeFieldReversed(size_t& writeIndex, uint64_t value, unsigned length); |
| void write0(size_t& writeIndex) { writeField(writeIndex,0,1); } |
| void write1(size_t& writeIndex) { writeField(writeIndex,1,1); } |
| |
| //@} |
| |
| /** Sum of bits. */ |
| unsigned sum() const; |
| |
| /** Reorder bits, dest[i] = this[map[i]]. */ |
| void map(const unsigned *map, size_t mapSize, BitVector& dest) const; |
| |
| /** Reorder bits, dest[map[i]] = this[i]. */ |
| void unmap(const unsigned *map, size_t mapSize, BitVector& dest) const; |
| |
| /** Pack into a char array. */ |
| void pack(unsigned char*) const; |
| |
| /** Unpack from a char array. */ |
| void unpack(const unsigned char*); |
| |
| /** Make a hexdump string. */ |
| void hex(std::ostream&) const; |
| std::string hexstr() const; |
| |
| /** Unpack from a hexdump string. |
| * @returns true on success, false on error. */ |
| bool unhex(const char*); |
| |
| void set(BitVector other) // That's right. No ampersand. |
| { |
| clear(); |
| mData=other.mData; |
| mStart=other.mStart; |
| mEnd=other.mEnd; |
| other.mData=NULL; |
| } |
| |
| void settfb(int i, int j) const |
| { |
| mStart[i] = j; |
| } |
| |
| }; |
| |
| |
| |
| std::ostream& operator<<(std::ostream&, const BitVector&); |
| |
| |
| |
| |
| |
| |
| /** |
| The SoftVector class is used to represent a soft-decision signal. |
| Values 0..1 represent probabilities that a bit is "true". |
| */ |
| class SoftVector: public Vector<float> { |
| |
| public: |
| |
| /** Build a SoftVector of a given length. */ |
| SoftVector(size_t wSize=0):Vector<float>(wSize) {} |
| |
| /** Construct a SoftVector from a C string of "0", "1", and "X". */ |
| SoftVector(const char* valString); |
| |
| /** Construct a SoftVector from a BitVector. */ |
| SoftVector(const BitVector& source); |
| |
| /** |
| Wrap a SoftVector around a block of floats. |
| The block will be delete[]ed upon desctuction. |
| */ |
| SoftVector(float *wData, unsigned length) |
| :Vector<float>(wData,length) |
| {} |
| |
| SoftVector(float* wData, float* wStart, float* wEnd) |
| :Vector<float>(wData,wStart,wEnd) |
| { } |
| |
| /** |
| Casting from a Vector<float>. |
| Note that this is NOT pass-by-reference. |
| */ |
| SoftVector(Vector<float> source) |
| :Vector<float>(source) |
| {} |
| |
| |
| /**@name Casts and overrides of Vector operators. */ |
| //@{ |
| SoftVector segment(size_t start, size_t span) |
| { |
| float* wStart = mStart + start; |
| float* wEnd = wStart + span; |
| assert(wEnd<=mEnd); |
| return SoftVector(NULL,wStart,wEnd); |
| } |
| |
| SoftVector alias() |
| { return segment(0,size()); } |
| |
| const SoftVector segment(size_t start, size_t span) const |
| { return (SoftVector)(Vector<float>::segment(start,span)); } |
| |
| SoftVector head(size_t span) { return segment(0,span); } |
| const SoftVector head(size_t span) const { return segment(0,span); } |
| SoftVector tail(size_t start) { return segment(start,size()-start); } |
| const SoftVector tail(size_t start) const { return segment(start,size()-start); } |
| //@} |
| |
| /** Decode soft symbols with the GSM rate-1/2 Viterbi decoder. */ |
| void decode(ViterbiR2O4 &decoder, BitVector& target) const; |
| |
| // (pat) How good is the SoftVector in the sense of the bits being solid? |
| // Result of 1 is perfect and 0 means all the bits were 0.5 |
| // If plow is non-NULL, also return the lowest energy bit. |
| float getEnergy(float *low=0) const; |
| |
| /** Fill with "unknown" values. */ |
| void unknown() { fill(0.5F); } |
| |
| /** Return a hard bit value from a given index by slicing. */ |
| bool bit(size_t index) const |
| { |
| const float *dp = mStart+index; |
| assert(dp<mEnd); |
| return (*dp)>0.5F; |
| } |
| |
| /** Slice the whole signal into bits. */ |
| BitVector sliced() const; |
| |
| }; |
| |
| |
| |
| std::ostream& operator<<(std::ostream&, const SoftVector&); |
| |
| |
| |
| |
| |
| |
| #endif |
| // vim: ts=4 sw=4 |