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Diffstat (limited to 'CommonLibs/BitVector.h')
-rw-r--r-- | CommonLibs/BitVector.h | 441 |
1 files changed, 441 insertions, 0 deletions
diff --git a/CommonLibs/BitVector.h b/CommonLibs/BitVector.h new file mode 100644 index 0000000..572e6b4 --- /dev/null +++ b/CommonLibs/BitVector.h @@ -0,0 +1,441 @@ +/* +* 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); + //@} + + /** 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; + + /** Unpack from a hexdump string. + * @returns true on success, false on error. */ + bool unhex(const char*); + +}; + + + +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; + + /** 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 |