581 lines
12 KiB
C++
581 lines
12 KiB
C++
/*
|
|
* 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/>.
|
|
|
|
*/
|
|
|
|
|
|
|
|
|
|
#include "BitVector.h"
|
|
#include <iostream>
|
|
|
|
using namespace std;
|
|
|
|
|
|
/**
|
|
Apply a Galois polymonial to a binary seqeunce.
|
|
@param val The input sequence.
|
|
@param poly The polynomial.
|
|
@param order The order of the polynomial.
|
|
@return Single-bit result.
|
|
*/
|
|
unsigned applyPoly(uint64_t val, uint64_t poly, unsigned order)
|
|
{
|
|
uint64_t prod = val & poly;
|
|
unsigned sum = prod;
|
|
for (unsigned i=1; i<order; i++) sum ^= prod>>i;
|
|
return sum & 0x01;
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
BitVector::BitVector(const char *valString)
|
|
:Vector<char>(strlen(valString))
|
|
{
|
|
uint32_t accum = 0;
|
|
for (size_t i=0; i<size(); i++) {
|
|
accum <<= 1;
|
|
if (valString[i]=='1') accum |= 0x01;
|
|
mStart[i] = accum;
|
|
}
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
uint64_t BitVector::peekField(size_t readIndex, unsigned length) const
|
|
{
|
|
uint64_t accum = 0;
|
|
char *dp = mStart + readIndex;
|
|
assert(dp+length <= mEnd);
|
|
for (unsigned i=0; i<length; i++) {
|
|
accum = (accum<<1) | ((*dp++) & 0x01);
|
|
}
|
|
return accum;
|
|
}
|
|
|
|
|
|
|
|
|
|
uint64_t BitVector::peekFieldReversed(size_t readIndex, unsigned length) const
|
|
{
|
|
uint64_t accum = 0;
|
|
char *dp = mStart + readIndex + length - 1;
|
|
assert(dp<mEnd);
|
|
for (int i=(length-1); i>=0; i--) {
|
|
accum = (accum<<1) | ((*dp--) & 0x01);
|
|
}
|
|
return accum;
|
|
}
|
|
|
|
|
|
|
|
|
|
uint64_t BitVector::readField(size_t& readIndex, unsigned length) const
|
|
{
|
|
const uint64_t retVal = peekField(readIndex,length);
|
|
readIndex += length;
|
|
return retVal;
|
|
}
|
|
|
|
|
|
uint64_t BitVector::readFieldReversed(size_t& readIndex, unsigned length) const
|
|
{
|
|
const uint64_t retVal = peekFieldReversed(readIndex,length);
|
|
readIndex += length;
|
|
return retVal;
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
void BitVector::fillField(size_t writeIndex, uint64_t value, unsigned length)
|
|
{
|
|
char *dpBase = mStart + writeIndex;
|
|
char *dp = dpBase + length - 1;
|
|
assert(dp < mEnd);
|
|
while (dp>=dpBase) {
|
|
*dp-- = value & 0x01;
|
|
value >>= 1;
|
|
}
|
|
}
|
|
|
|
|
|
void BitVector::fillFieldReversed(size_t writeIndex, uint64_t value, unsigned length)
|
|
{
|
|
char *dp = mStart + writeIndex;
|
|
char *dpEnd = dp + length - 1;
|
|
assert(dpEnd < mEnd);
|
|
while (dp<=dpEnd) {
|
|
*dp++ = value & 0x01;
|
|
value >>= 1;
|
|
}
|
|
}
|
|
|
|
|
|
|
|
|
|
void BitVector::writeField(size_t& writeIndex, uint64_t value, unsigned length)
|
|
{
|
|
fillField(writeIndex,value,length);
|
|
writeIndex += length;
|
|
}
|
|
|
|
|
|
void BitVector::writeFieldReversed(size_t& writeIndex, uint64_t value, unsigned length)
|
|
{
|
|
fillFieldReversed(writeIndex,value,length);
|
|
writeIndex += length;
|
|
}
|
|
|
|
|
|
void BitVector::invert()
|
|
{
|
|
for (size_t i=0; i<size(); i++) {
|
|
mStart[i] = ~mStart[i];
|
|
}
|
|
}
|
|
|
|
|
|
|
|
|
|
void BitVector::reverse8()
|
|
{
|
|
assert(size()>=8);
|
|
|
|
char tmp0 = mStart[0];
|
|
mStart[0] = mStart[7];
|
|
mStart[7] = tmp0;
|
|
|
|
char tmp1 = mStart[1];
|
|
mStart[1] = mStart[6];
|
|
mStart[6] = tmp1;
|
|
|
|
char tmp2 = mStart[2];
|
|
mStart[2] = mStart[5];
|
|
mStart[5] = tmp2;
|
|
|
|
char tmp3 = mStart[3];
|
|
mStart[3] = mStart[4];
|
|
mStart[4] = tmp3;
|
|
}
|
|
|
|
|
|
|
|
void BitVector::LSB8MSB()
|
|
{
|
|
if (size()<8) return;
|
|
size_t size8 = 8*(size()/8);
|
|
size_t iTop = size8 - 8;
|
|
for (size_t i=0; i<=iTop; i+=8) segment(i,8).reverse8();
|
|
}
|
|
|
|
|
|
|
|
uint64_t BitVector::syndrome(Generator& gen) const
|
|
{
|
|
gen.clear();
|
|
const char *dp = mStart;
|
|
while (dp<mEnd) gen.syndromeShift(*dp++);
|
|
return gen.state();
|
|
}
|
|
|
|
|
|
uint64_t BitVector::parity(Generator& gen) const
|
|
{
|
|
gen.clear();
|
|
const char *dp = mStart;
|
|
while (dp<mEnd) gen.encoderShift(*dp++);
|
|
return gen.state();
|
|
}
|
|
|
|
|
|
void BitVector::encode(const ViterbiR2O4& coder, BitVector& target)
|
|
{
|
|
size_t sz = size();
|
|
assert(sz*coder.iRate() == target.size());
|
|
|
|
// Build a "history" array where each element contains the full history.
|
|
uint32_t history[sz];
|
|
uint32_t accum = 0;
|
|
for (size_t i=0; i<sz; i++) {
|
|
accum = (accum<<1) | bit(i);
|
|
history[i] = accum;
|
|
}
|
|
|
|
// Look up histories in the pre-generated state table.
|
|
char *op = target.begin();
|
|
for (size_t i=0; i<sz; i++) {
|
|
unsigned index = coder.cMask() & history[i];
|
|
for (unsigned g=0; g<coder.iRate(); g++) {
|
|
*op++ = coder.stateTable(g,index);
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
unsigned BitVector::sum() const
|
|
{
|
|
unsigned sum = 0;
|
|
for (size_t i=0; i<size(); i++) sum += mStart[i] & 0x01;
|
|
return sum;
|
|
}
|
|
|
|
|
|
|
|
|
|
void BitVector::map(const unsigned *map, size_t mapSize, BitVector& dest) const
|
|
{
|
|
for (unsigned i=0; i<mapSize; i++) {
|
|
dest.mStart[i] = mStart[map[i]];
|
|
}
|
|
}
|
|
|
|
|
|
|
|
|
|
void BitVector::unmap(const unsigned *map, size_t mapSize, BitVector& dest) const
|
|
{
|
|
for (unsigned i=0; i<mapSize; i++) {
|
|
dest.mStart[map[i]] = mStart[i];
|
|
}
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
ostream& operator<<(ostream& os, const BitVector& hv)
|
|
{
|
|
for (size_t i=0; i<hv.size(); i++) {
|
|
if (hv.bit(i)) os << '1';
|
|
else os << '0';
|
|
}
|
|
return os;
|
|
}
|
|
|
|
|
|
|
|
|
|
ViterbiR2O4::ViterbiR2O4()
|
|
{
|
|
assert(mDeferral < 32);
|
|
mCoeffs[0] = 0x019;
|
|
mCoeffs[1] = 0x01b;
|
|
computeStateTables(0);
|
|
computeStateTables(1);
|
|
computeGeneratorTable();
|
|
}
|
|
|
|
|
|
|
|
|
|
void ViterbiR2O4::initializeStates()
|
|
{
|
|
for (unsigned i=0; i<mIStates; i++) clear(mSurvivors[i]);
|
|
for (unsigned i=0; i<mNumCands; i++) clear(mCandidates[i]);
|
|
}
|
|
|
|
|
|
|
|
void ViterbiR2O4::computeStateTables(unsigned g)
|
|
{
|
|
assert(g<mIRate);
|
|
for (unsigned state=0; state<mIStates; state++) {
|
|
// 0 input
|
|
uint32_t inputVal = state<<1;
|
|
mStateTable[g][inputVal] = applyPoly(inputVal, mCoeffs[g], mOrder+1);
|
|
// 1 input
|
|
inputVal |= 1;
|
|
mStateTable[g][inputVal] = applyPoly(inputVal, mCoeffs[g], mOrder+1);
|
|
}
|
|
}
|
|
|
|
void ViterbiR2O4::computeGeneratorTable()
|
|
{
|
|
for (unsigned index=0; index<mIStates*2; index++) {
|
|
mGeneratorTable[index] = (mStateTable[0][index]<<1) | mStateTable[1][index];
|
|
}
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
void ViterbiR2O4::branchCandidates()
|
|
{
|
|
// Branch to generate new input states.
|
|
const vCand *sp = mSurvivors;
|
|
for (unsigned i=0; i<mNumCands; i+=2) {
|
|
// extend and suffix
|
|
const uint32_t iState0 = (sp->iState) << 1; // input state for 0
|
|
const uint32_t iState1 = iState0 | 0x01; // input state for 1
|
|
const uint32_t oStateShifted = (sp->oState) << mIRate; // shifted output
|
|
const float cost = sp->cost;
|
|
sp++;
|
|
// 0 input extension
|
|
mCandidates[i].cost = cost;
|
|
mCandidates[i].oState = oStateShifted | mGeneratorTable[iState0 & mCMask];
|
|
mCandidates[i].iState = iState0;
|
|
// 1 input extension
|
|
mCandidates[i+1].cost = cost;
|
|
mCandidates[i+1].oState = oStateShifted | mGeneratorTable[iState1 & mCMask];
|
|
mCandidates[i+1].iState = iState1;
|
|
}
|
|
}
|
|
|
|
|
|
void ViterbiR2O4::getSoftCostMetrics(const uint32_t inSample, const float *matchCost, const float *mismatchCost)
|
|
{
|
|
const float *cTab[2] = {matchCost,mismatchCost};
|
|
for (unsigned i=0; i<mNumCands; i++) {
|
|
vCand& thisCand = mCandidates[i];
|
|
// We examine input bits 2 at a time for a rate 1/2 coder.
|
|
const unsigned mismatched = inSample ^ (thisCand.oState);
|
|
thisCand.cost += cTab[mismatched&0x01][1] + cTab[(mismatched>>1)&0x01][0];
|
|
}
|
|
}
|
|
|
|
|
|
void ViterbiR2O4::pruneCandidates()
|
|
{
|
|
const vCand* c1 = mCandidates; // 0-prefix
|
|
const vCand* c2 = mCandidates + mIStates; // 1-prefix
|
|
for (unsigned i=0; i<mIStates; i++) {
|
|
if (c1[i].cost < c2[i].cost) mSurvivors[i] = c1[i];
|
|
else mSurvivors[i] = c2[i];
|
|
}
|
|
}
|
|
|
|
|
|
const ViterbiR2O4::vCand& ViterbiR2O4::minCost() const
|
|
{
|
|
int minIndex = 0;
|
|
float minCost = mSurvivors[0].cost;
|
|
for (unsigned i=1; i<mIStates; i++) {
|
|
const float thisCost = mSurvivors[i].cost;
|
|
if (thisCost>=minCost) continue;
|
|
minCost = thisCost;
|
|
minIndex=i;
|
|
}
|
|
return mSurvivors[minIndex];
|
|
}
|
|
|
|
|
|
const ViterbiR2O4::vCand& ViterbiR2O4::step(uint32_t inSample, const float *probs, const float *iprobs)
|
|
{
|
|
branchCandidates();
|
|
getSoftCostMetrics(inSample,probs,iprobs);
|
|
pruneCandidates();
|
|
return minCost();
|
|
}
|
|
|
|
|
|
uint64_t Parity::syndrome(const BitVector& receivedCodeword)
|
|
{
|
|
return receivedCodeword.syndrome(*this);
|
|
}
|
|
|
|
|
|
void Parity::writeParityWord(const BitVector& data, BitVector& parityTarget, bool invert)
|
|
{
|
|
uint64_t pWord = data.parity(*this);
|
|
if (invert) pWord = ~pWord;
|
|
parityTarget.fillField(0,pWord,size());
|
|
}
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
SoftVector::SoftVector(const BitVector& source)
|
|
{
|
|
resize(source.size());
|
|
for (size_t i=0; i<size(); i++) {
|
|
if (source.bit(i)) mStart[i]=1.0F;
|
|
else mStart[i]=0.0F;
|
|
}
|
|
}
|
|
|
|
|
|
BitVector SoftVector::sliced() const
|
|
{
|
|
size_t sz = size();
|
|
BitVector newSig(sz);
|
|
for (size_t i=0; i<sz; i++) {
|
|
if (mStart[i]>0.5F) newSig[i]=1;
|
|
else newSig[i] = 0;
|
|
}
|
|
return newSig;
|
|
}
|
|
|
|
|
|
|
|
void SoftVector::decode(ViterbiR2O4 &decoder, BitVector& target) const
|
|
{
|
|
const size_t sz = size();
|
|
const unsigned deferral = decoder.deferral();
|
|
const size_t ctsz = sz + deferral*decoder.iRate();
|
|
assert(sz <= decoder.iRate()*target.size());
|
|
|
|
// Build a "history" array where each element contains the full history.
|
|
uint32_t history[ctsz];
|
|
{
|
|
BitVector bits = sliced();
|
|
uint32_t accum = 0;
|
|
for (size_t i=0; i<sz; i++) {
|
|
accum = (accum<<1) | bits.bit(i);
|
|
history[i] = accum;
|
|
}
|
|
// Repeat last bit at the end.
|
|
for (size_t i=sz; i<ctsz; i++) {
|
|
accum = (accum<<1) | (accum & 0x01);
|
|
history[i] = accum;
|
|
}
|
|
}
|
|
|
|
// Precompute metric tables.
|
|
float matchCostTable[ctsz];
|
|
float mismatchCostTable[ctsz];
|
|
{
|
|
const float *dp = mStart;
|
|
for (size_t i=0; i<sz; i++) {
|
|
// pVal is the probability that a bit is correct.
|
|
// ipVal is the probability that a bit is incorrect.
|
|
float pVal = dp[i];
|
|
if (pVal>0.5F) pVal = 1.0F-pVal;
|
|
float ipVal = 1.0F-pVal;
|
|
// This is a cheap approximation to an ideal cost function.
|
|
if (pVal<0.01F) pVal = 0.01;
|
|
if (ipVal<0.01F) ipVal = 0.01;
|
|
matchCostTable[i] = 0.25F/ipVal;
|
|
mismatchCostTable[i] = 0.25F/pVal;
|
|
}
|
|
|
|
// pad end of table with unknowns
|
|
for (size_t i=sz; i<ctsz; i++) {
|
|
matchCostTable[i] = 0.5F;
|
|
mismatchCostTable[i] = 0.5F;
|
|
}
|
|
}
|
|
|
|
{
|
|
decoder.initializeStates();
|
|
// Each sample of history[] carries its history.
|
|
// So we only have to process every iRate-th sample.
|
|
const unsigned step = decoder.iRate();
|
|
// input pointer
|
|
const uint32_t *ip = history + step - 1;
|
|
// output pointers
|
|
char *op = target.begin();
|
|
const char *const opt = target.end();
|
|
// table pointers
|
|
const float* match = matchCostTable;
|
|
const float* mismatch = mismatchCostTable;
|
|
size_t oCount = 0;
|
|
while (op<opt) {
|
|
// Viterbi algorithm
|
|
assert(match-matchCostTable<sizeof(matchCostTable)/sizeof(matchCostTable[0])-1);
|
|
assert(mismatch-mismatchCostTable<sizeof(mismatchCostTable)/sizeof(mismatchCostTable[0])-1);
|
|
const ViterbiR2O4::vCand &minCost = decoder.step(*ip, match, mismatch);
|
|
ip += step;
|
|
match += step;
|
|
mismatch += step;
|
|
// output
|
|
if (oCount>=deferral) *op++ = (minCost.iState >> deferral)&0x01;
|
|
oCount++;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
|
|
|
|
ostream& operator<<(ostream& os, const SoftVector& sv)
|
|
{
|
|
for (size_t i=0; i<sv.size(); i++) {
|
|
if (sv[i]<0.25) os << "0";
|
|
else if (sv[i]>0.75) os << "1";
|
|
else os << "-";
|
|
}
|
|
return os;
|
|
}
|
|
|
|
|
|
|
|
void BitVector::pack(unsigned char* targ) const
|
|
{
|
|
// Assumes MSB-first packing.
|
|
unsigned bytes = size()/8;
|
|
for (unsigned i=0; i<bytes; i++) {
|
|
targ[i] = peekField(i*8,8);
|
|
}
|
|
unsigned whole = bytes*8;
|
|
unsigned rem = size() - whole;
|
|
if (rem==0) return;
|
|
targ[bytes] = peekField(whole,rem) << (8-rem);
|
|
}
|
|
|
|
|
|
void BitVector::unpack(const unsigned char* src)
|
|
{
|
|
// Assumes MSB-first packing.
|
|
unsigned bytes = size()/8;
|
|
for (unsigned i=0; i<bytes; i++) {
|
|
fillField(i*8,src[i],8);
|
|
}
|
|
unsigned whole = bytes*8;
|
|
unsigned rem = size() - whole;
|
|
if (rem==0) return;
|
|
fillField(whole,src[bytes],rem);
|
|
}
|
|
|
|
void BitVector::hex(ostream& os) const
|
|
{
|
|
os << std::hex;
|
|
int v=0;
|
|
unsigned digits = size()/4;
|
|
size_t wp=0;
|
|
for (unsigned i=0; i<digits; i++) {
|
|
os << readField(wp,4);
|
|
}
|
|
os << std::dec;
|
|
}
|
|
|
|
// vim: ts=4 sw=4
|