dburgess | 82c46ff | 2011-10-07 02:40:51 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2008, 2009 Free Software Foundation, Inc. |
| 3 | * |
| 4 | * |
| 5 | * This software is distributed under the terms of the GNU Affero Public License. |
| 6 | * See the COPYING file in the main directory for details. |
| 7 | * |
| 8 | * This use of this software may be subject to additional restrictions. |
| 9 | * See the LEGAL file in the main directory for details. |
| 10 | |
| 11 | This program is free software: you can redistribute it and/or modify |
| 12 | it under the terms of the GNU Affero General Public License as published by |
| 13 | the Free Software Foundation, either version 3 of the License, or |
| 14 | (at your option) any later version. |
| 15 | |
| 16 | This program is distributed in the hope that it will be useful, |
| 17 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 18 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 19 | GNU Affero General Public License for more details. |
| 20 | |
| 21 | You should have received a copy of the GNU Affero General Public License |
| 22 | along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 23 | |
| 24 | */ |
| 25 | |
| 26 | |
| 27 | |
| 28 | |
| 29 | #include "BitVector.h" |
| 30 | #include <iostream> |
| 31 | #include <stdio.h> |
| 32 | |
| 33 | using namespace std; |
| 34 | |
| 35 | |
| 36 | /** |
| 37 | Apply a Galois polymonial to a binary seqeunce. |
| 38 | @param val The input sequence. |
| 39 | @param poly The polynomial. |
| 40 | @param order The order of the polynomial. |
| 41 | @return Single-bit result. |
| 42 | */ |
| 43 | unsigned applyPoly(uint64_t val, uint64_t poly, unsigned order) |
| 44 | { |
| 45 | uint64_t prod = val & poly; |
| 46 | unsigned sum = prod; |
| 47 | for (unsigned i=1; i<order; i++) sum ^= prod>>i; |
| 48 | return sum & 0x01; |
| 49 | } |
| 50 | |
| 51 | |
| 52 | |
| 53 | |
| 54 | |
| 55 | |
| 56 | BitVector::BitVector(const char *valString) |
| 57 | :Vector<char>(strlen(valString)) |
| 58 | { |
| 59 | uint32_t accum = 0; |
| 60 | for (size_t i=0; i<size(); i++) { |
| 61 | accum <<= 1; |
| 62 | if (valString[i]=='1') accum |= 0x01; |
| 63 | mStart[i] = accum; |
| 64 | } |
| 65 | } |
| 66 | |
| 67 | |
| 68 | |
| 69 | |
| 70 | |
| 71 | uint64_t BitVector::peekField(size_t readIndex, unsigned length) const |
| 72 | { |
| 73 | uint64_t accum = 0; |
| 74 | char *dp = mStart + readIndex; |
| 75 | assert(dp+length <= mEnd); |
| 76 | for (unsigned i=0; i<length; i++) { |
| 77 | accum = (accum<<1) | ((*dp++) & 0x01); |
| 78 | } |
| 79 | return accum; |
| 80 | } |
| 81 | |
| 82 | |
| 83 | |
| 84 | |
| 85 | uint64_t BitVector::peekFieldReversed(size_t readIndex, unsigned length) const |
| 86 | { |
| 87 | uint64_t accum = 0; |
| 88 | char *dp = mStart + readIndex + length - 1; |
| 89 | assert(dp<mEnd); |
| 90 | for (int i=(length-1); i>=0; i--) { |
| 91 | accum = (accum<<1) | ((*dp--) & 0x01); |
| 92 | } |
| 93 | return accum; |
| 94 | } |
| 95 | |
| 96 | |
| 97 | |
| 98 | |
| 99 | uint64_t BitVector::readField(size_t& readIndex, unsigned length) const |
| 100 | { |
| 101 | const uint64_t retVal = peekField(readIndex,length); |
| 102 | readIndex += length; |
| 103 | return retVal; |
| 104 | } |
| 105 | |
| 106 | |
| 107 | uint64_t BitVector::readFieldReversed(size_t& readIndex, unsigned length) const |
| 108 | { |
| 109 | const uint64_t retVal = peekFieldReversed(readIndex,length); |
| 110 | readIndex += length; |
| 111 | return retVal; |
| 112 | } |
| 113 | |
| 114 | |
| 115 | |
| 116 | |
| 117 | |
| 118 | void BitVector::fillField(size_t writeIndex, uint64_t value, unsigned length) |
| 119 | { |
| 120 | char *dpBase = mStart + writeIndex; |
| 121 | char *dp = dpBase + length - 1; |
| 122 | assert(dp < mEnd); |
| 123 | while (dp>=dpBase) { |
| 124 | *dp-- = value & 0x01; |
| 125 | value >>= 1; |
| 126 | } |
| 127 | } |
| 128 | |
| 129 | |
| 130 | void BitVector::fillFieldReversed(size_t writeIndex, uint64_t value, unsigned length) |
| 131 | { |
| 132 | char *dp = mStart + writeIndex; |
| 133 | char *dpEnd = dp + length - 1; |
| 134 | assert(dpEnd < mEnd); |
| 135 | while (dp<=dpEnd) { |
| 136 | *dp++ = value & 0x01; |
| 137 | value >>= 1; |
| 138 | } |
| 139 | } |
| 140 | |
| 141 | |
| 142 | |
| 143 | |
| 144 | void BitVector::writeField(size_t& writeIndex, uint64_t value, unsigned length) |
| 145 | { |
| 146 | fillField(writeIndex,value,length); |
| 147 | writeIndex += length; |
| 148 | } |
| 149 | |
| 150 | |
| 151 | void BitVector::writeFieldReversed(size_t& writeIndex, uint64_t value, unsigned length) |
| 152 | { |
| 153 | fillFieldReversed(writeIndex,value,length); |
| 154 | writeIndex += length; |
| 155 | } |
| 156 | |
| 157 | |
| 158 | void BitVector::invert() |
| 159 | { |
| 160 | for (size_t i=0; i<size(); i++) { |
| 161 | mStart[i] = ~mStart[i]; |
| 162 | } |
| 163 | } |
| 164 | |
| 165 | |
| 166 | |
| 167 | |
| 168 | void BitVector::reverse8() |
| 169 | { |
| 170 | assert(size()>=8); |
| 171 | |
| 172 | char tmp0 = mStart[0]; |
| 173 | mStart[0] = mStart[7]; |
| 174 | mStart[7] = tmp0; |
| 175 | |
| 176 | char tmp1 = mStart[1]; |
| 177 | mStart[1] = mStart[6]; |
| 178 | mStart[6] = tmp1; |
| 179 | |
| 180 | char tmp2 = mStart[2]; |
| 181 | mStart[2] = mStart[5]; |
| 182 | mStart[5] = tmp2; |
| 183 | |
| 184 | char tmp3 = mStart[3]; |
| 185 | mStart[3] = mStart[4]; |
| 186 | mStart[4] = tmp3; |
| 187 | } |
| 188 | |
| 189 | |
| 190 | |
| 191 | void BitVector::LSB8MSB() |
| 192 | { |
| 193 | if (size()<8) return; |
| 194 | size_t size8 = 8*(size()/8); |
| 195 | size_t iTop = size8 - 8; |
| 196 | for (size_t i=0; i<=iTop; i+=8) segment(i,8).reverse8(); |
| 197 | } |
| 198 | |
| 199 | |
| 200 | |
| 201 | uint64_t BitVector::syndrome(Generator& gen) const |
| 202 | { |
| 203 | gen.clear(); |
| 204 | const char *dp = mStart; |
| 205 | while (dp<mEnd) gen.syndromeShift(*dp++); |
| 206 | return gen.state(); |
| 207 | } |
| 208 | |
| 209 | |
| 210 | uint64_t BitVector::parity(Generator& gen) const |
| 211 | { |
| 212 | gen.clear(); |
| 213 | const char *dp = mStart; |
| 214 | while (dp<mEnd) gen.encoderShift(*dp++); |
| 215 | return gen.state(); |
| 216 | } |
| 217 | |
| 218 | |
| 219 | void BitVector::encode(const ViterbiR2O4& coder, BitVector& target) |
| 220 | { |
| 221 | size_t sz = size(); |
| 222 | assert(sz*coder.iRate() == target.size()); |
| 223 | |
| 224 | // Build a "history" array where each element contains the full history. |
| 225 | uint32_t history[sz]; |
| 226 | uint32_t accum = 0; |
| 227 | for (size_t i=0; i<sz; i++) { |
| 228 | accum = (accum<<1) | bit(i); |
| 229 | history[i] = accum; |
| 230 | } |
| 231 | |
| 232 | // Look up histories in the pre-generated state table. |
| 233 | char *op = target.begin(); |
| 234 | for (size_t i=0; i<sz; i++) { |
| 235 | unsigned index = coder.cMask() & history[i]; |
| 236 | for (unsigned g=0; g<coder.iRate(); g++) { |
| 237 | *op++ = coder.stateTable(g,index); |
| 238 | } |
| 239 | } |
| 240 | } |
| 241 | |
| 242 | |
| 243 | |
| 244 | unsigned BitVector::sum() const |
| 245 | { |
| 246 | unsigned sum = 0; |
| 247 | for (size_t i=0; i<size(); i++) sum += mStart[i] & 0x01; |
| 248 | return sum; |
| 249 | } |
| 250 | |
| 251 | |
| 252 | |
| 253 | |
| 254 | void BitVector::map(const unsigned *map, size_t mapSize, BitVector& dest) const |
| 255 | { |
| 256 | for (unsigned i=0; i<mapSize; i++) { |
| 257 | dest.mStart[i] = mStart[map[i]]; |
| 258 | } |
| 259 | } |
| 260 | |
| 261 | |
| 262 | |
| 263 | |
| 264 | void BitVector::unmap(const unsigned *map, size_t mapSize, BitVector& dest) const |
| 265 | { |
| 266 | for (unsigned i=0; i<mapSize; i++) { |
| 267 | dest.mStart[map[i]] = mStart[i]; |
| 268 | } |
| 269 | } |
| 270 | |
| 271 | |
| 272 | |
| 273 | |
| 274 | |
| 275 | |
| 276 | |
| 277 | |
| 278 | |
| 279 | |
| 280 | ostream& operator<<(ostream& os, const BitVector& hv) |
| 281 | { |
| 282 | for (size_t i=0; i<hv.size(); i++) { |
| 283 | if (hv.bit(i)) os << '1'; |
| 284 | else os << '0'; |
| 285 | } |
| 286 | return os; |
| 287 | } |
| 288 | |
| 289 | |
| 290 | |
| 291 | |
| 292 | ViterbiR2O4::ViterbiR2O4() |
| 293 | { |
| 294 | assert(mDeferral < 32); |
| 295 | mCoeffs[0] = 0x019; |
| 296 | mCoeffs[1] = 0x01b; |
| 297 | computeStateTables(0); |
| 298 | computeStateTables(1); |
| 299 | computeGeneratorTable(); |
| 300 | } |
| 301 | |
| 302 | |
| 303 | |
| 304 | |
| 305 | void ViterbiR2O4::initializeStates() |
| 306 | { |
| 307 | for (unsigned i=0; i<mIStates; i++) clear(mSurvivors[i]); |
| 308 | for (unsigned i=0; i<mNumCands; i++) clear(mCandidates[i]); |
| 309 | } |
| 310 | |
| 311 | |
| 312 | |
| 313 | void ViterbiR2O4::computeStateTables(unsigned g) |
| 314 | { |
| 315 | assert(g<mIRate); |
| 316 | for (unsigned state=0; state<mIStates; state++) { |
| 317 | // 0 input |
| 318 | uint32_t inputVal = state<<1; |
| 319 | mStateTable[g][inputVal] = applyPoly(inputVal, mCoeffs[g], mOrder+1); |
| 320 | // 1 input |
| 321 | inputVal |= 1; |
| 322 | mStateTable[g][inputVal] = applyPoly(inputVal, mCoeffs[g], mOrder+1); |
| 323 | } |
| 324 | } |
| 325 | |
| 326 | void ViterbiR2O4::computeGeneratorTable() |
| 327 | { |
| 328 | for (unsigned index=0; index<mIStates*2; index++) { |
| 329 | mGeneratorTable[index] = (mStateTable[0][index]<<1) | mStateTable[1][index]; |
| 330 | } |
| 331 | } |
| 332 | |
| 333 | |
| 334 | |
| 335 | |
| 336 | |
| 337 | |
| 338 | void ViterbiR2O4::branchCandidates() |
| 339 | { |
| 340 | // Branch to generate new input states. |
| 341 | const vCand *sp = mSurvivors; |
| 342 | for (unsigned i=0; i<mNumCands; i+=2) { |
| 343 | // extend and suffix |
| 344 | const uint32_t iState0 = (sp->iState) << 1; // input state for 0 |
| 345 | const uint32_t iState1 = iState0 | 0x01; // input state for 1 |
| 346 | const uint32_t oStateShifted = (sp->oState) << mIRate; // shifted output |
| 347 | const float cost = sp->cost; |
| 348 | sp++; |
| 349 | // 0 input extension |
| 350 | mCandidates[i].cost = cost; |
| 351 | mCandidates[i].oState = oStateShifted | mGeneratorTable[iState0 & mCMask]; |
| 352 | mCandidates[i].iState = iState0; |
| 353 | // 1 input extension |
| 354 | mCandidates[i+1].cost = cost; |
| 355 | mCandidates[i+1].oState = oStateShifted | mGeneratorTable[iState1 & mCMask]; |
| 356 | mCandidates[i+1].iState = iState1; |
| 357 | } |
| 358 | } |
| 359 | |
| 360 | |
| 361 | void ViterbiR2O4::getSoftCostMetrics(const uint32_t inSample, const float *matchCost, const float *mismatchCost) |
| 362 | { |
| 363 | const float *cTab[2] = {matchCost,mismatchCost}; |
| 364 | for (unsigned i=0; i<mNumCands; i++) { |
| 365 | vCand& thisCand = mCandidates[i]; |
| 366 | // We examine input bits 2 at a time for a rate 1/2 coder. |
| 367 | const unsigned mismatched = inSample ^ (thisCand.oState); |
| 368 | thisCand.cost += cTab[mismatched&0x01][1] + cTab[(mismatched>>1)&0x01][0]; |
| 369 | } |
| 370 | } |
| 371 | |
| 372 | |
| 373 | void ViterbiR2O4::pruneCandidates() |
| 374 | { |
| 375 | const vCand* c1 = mCandidates; // 0-prefix |
| 376 | const vCand* c2 = mCandidates + mIStates; // 1-prefix |
| 377 | for (unsigned i=0; i<mIStates; i++) { |
| 378 | if (c1[i].cost < c2[i].cost) mSurvivors[i] = c1[i]; |
| 379 | else mSurvivors[i] = c2[i]; |
| 380 | } |
| 381 | } |
| 382 | |
| 383 | |
| 384 | const ViterbiR2O4::vCand& ViterbiR2O4::minCost() const |
| 385 | { |
| 386 | int minIndex = 0; |
| 387 | float minCost = mSurvivors[0].cost; |
| 388 | for (unsigned i=1; i<mIStates; i++) { |
| 389 | const float thisCost = mSurvivors[i].cost; |
| 390 | if (thisCost>=minCost) continue; |
| 391 | minCost = thisCost; |
| 392 | minIndex=i; |
| 393 | } |
| 394 | return mSurvivors[minIndex]; |
| 395 | } |
| 396 | |
| 397 | |
| 398 | const ViterbiR2O4::vCand& ViterbiR2O4::step(uint32_t inSample, const float *probs, const float *iprobs) |
| 399 | { |
| 400 | branchCandidates(); |
| 401 | getSoftCostMetrics(inSample,probs,iprobs); |
| 402 | pruneCandidates(); |
| 403 | return minCost(); |
| 404 | } |
| 405 | |
| 406 | |
| 407 | uint64_t Parity::syndrome(const BitVector& receivedCodeword) |
| 408 | { |
| 409 | return receivedCodeword.syndrome(*this); |
| 410 | } |
| 411 | |
| 412 | |
| 413 | void Parity::writeParityWord(const BitVector& data, BitVector& parityTarget, bool invert) |
| 414 | { |
| 415 | uint64_t pWord = data.parity(*this); |
| 416 | if (invert) pWord = ~pWord; |
| 417 | parityTarget.fillField(0,pWord,size()); |
| 418 | } |
| 419 | |
| 420 | |
| 421 | |
| 422 | |
| 423 | |
| 424 | |
| 425 | |
| 426 | |
| 427 | |
| 428 | SoftVector::SoftVector(const BitVector& source) |
| 429 | { |
| 430 | resize(source.size()); |
| 431 | for (size_t i=0; i<size(); i++) { |
| 432 | if (source.bit(i)) mStart[i]=1.0F; |
| 433 | else mStart[i]=0.0F; |
| 434 | } |
| 435 | } |
| 436 | |
| 437 | |
| 438 | BitVector SoftVector::sliced() const |
| 439 | { |
| 440 | size_t sz = size(); |
| 441 | BitVector newSig(sz); |
| 442 | for (size_t i=0; i<sz; i++) { |
| 443 | if (mStart[i]>0.5F) newSig[i]=1; |
| 444 | else newSig[i] = 0; |
| 445 | } |
| 446 | return newSig; |
| 447 | } |
| 448 | |
| 449 | |
| 450 | |
| 451 | void SoftVector::decode(ViterbiR2O4 &decoder, BitVector& target) const |
| 452 | { |
| 453 | const size_t sz = size(); |
| 454 | const unsigned deferral = decoder.deferral(); |
| 455 | const size_t ctsz = sz + deferral*decoder.iRate(); |
| 456 | assert(sz <= decoder.iRate()*target.size()); |
| 457 | |
| 458 | // Build a "history" array where each element contains the full history. |
| 459 | uint32_t history[ctsz]; |
| 460 | { |
| 461 | BitVector bits = sliced(); |
| 462 | uint32_t accum = 0; |
| 463 | for (size_t i=0; i<sz; i++) { |
| 464 | accum = (accum<<1) | bits.bit(i); |
| 465 | history[i] = accum; |
| 466 | } |
| 467 | // Repeat last bit at the end. |
| 468 | for (size_t i=sz; i<ctsz; i++) { |
| 469 | accum = (accum<<1) | (accum & 0x01); |
| 470 | history[i] = accum; |
| 471 | } |
| 472 | } |
| 473 | |
| 474 | // Precompute metric tables. |
| 475 | float matchCostTable[ctsz]; |
| 476 | float mismatchCostTable[ctsz]; |
| 477 | { |
| 478 | const float *dp = mStart; |
| 479 | for (size_t i=0; i<sz; i++) { |
| 480 | // pVal is the probability that a bit is correct. |
| 481 | // ipVal is the probability that a bit is incorrect. |
| 482 | float pVal = dp[i]; |
| 483 | if (pVal>0.5F) pVal = 1.0F-pVal; |
| 484 | float ipVal = 1.0F-pVal; |
| 485 | // This is a cheap approximation to an ideal cost function. |
| 486 | if (pVal<0.01F) pVal = 0.01; |
| 487 | if (ipVal<0.01F) ipVal = 0.01; |
| 488 | matchCostTable[i] = 0.25F/ipVal; |
| 489 | mismatchCostTable[i] = 0.25F/pVal; |
| 490 | } |
| 491 | |
| 492 | // pad end of table with unknowns |
| 493 | for (size_t i=sz; i<ctsz; i++) { |
| 494 | matchCostTable[i] = 0.5F; |
| 495 | mismatchCostTable[i] = 0.5F; |
| 496 | } |
| 497 | } |
| 498 | |
| 499 | { |
| 500 | decoder.initializeStates(); |
| 501 | // Each sample of history[] carries its history. |
| 502 | // So we only have to process every iRate-th sample. |
| 503 | const unsigned step = decoder.iRate(); |
| 504 | // input pointer |
| 505 | const uint32_t *ip = history + step - 1; |
| 506 | // output pointers |
| 507 | char *op = target.begin(); |
| 508 | const char *const opt = target.end(); |
| 509 | // table pointers |
| 510 | const float* match = matchCostTable; |
| 511 | const float* mismatch = mismatchCostTable; |
| 512 | size_t oCount = 0; |
| 513 | while (op<opt) { |
| 514 | // Viterbi algorithm |
| 515 | assert(match-matchCostTable<sizeof(matchCostTable)/sizeof(matchCostTable[0])-1); |
| 516 | assert(mismatch-mismatchCostTable<sizeof(mismatchCostTable)/sizeof(mismatchCostTable[0])-1); |
| 517 | const ViterbiR2O4::vCand &minCost = decoder.step(*ip, match, mismatch); |
| 518 | ip += step; |
| 519 | match += step; |
| 520 | mismatch += step; |
| 521 | // output |
| 522 | if (oCount>=deferral) *op++ = (minCost.iState >> deferral)&0x01; |
| 523 | oCount++; |
| 524 | } |
| 525 | } |
| 526 | } |
| 527 | |
| 528 | |
| 529 | |
| 530 | |
| 531 | ostream& operator<<(ostream& os, const SoftVector& sv) |
| 532 | { |
| 533 | for (size_t i=0; i<sv.size(); i++) { |
| 534 | if (sv[i]<0.25) os << "0"; |
| 535 | else if (sv[i]>0.75) os << "1"; |
| 536 | else os << "-"; |
| 537 | } |
| 538 | return os; |
| 539 | } |
| 540 | |
| 541 | |
| 542 | |
| 543 | void BitVector::pack(unsigned char* targ) const |
| 544 | { |
| 545 | // Assumes MSB-first packing. |
| 546 | unsigned bytes = size()/8; |
| 547 | for (unsigned i=0; i<bytes; i++) { |
| 548 | targ[i] = peekField(i*8,8); |
| 549 | } |
| 550 | unsigned whole = bytes*8; |
| 551 | unsigned rem = size() - whole; |
| 552 | if (rem==0) return; |
| 553 | targ[bytes] = peekField(whole,rem) << (8-rem); |
| 554 | } |
| 555 | |
| 556 | |
| 557 | void BitVector::unpack(const unsigned char* src) |
| 558 | { |
| 559 | // Assumes MSB-first packing. |
| 560 | unsigned bytes = size()/8; |
| 561 | for (unsigned i=0; i<bytes; i++) { |
| 562 | fillField(i*8,src[i],8); |
| 563 | } |
| 564 | unsigned whole = bytes*8; |
| 565 | unsigned rem = size() - whole; |
| 566 | if (rem==0) return; |
kurtis.heimerl | 7645fca | 2012-03-08 07:13:15 +0000 | [diff] [blame] | 567 | fillField(whole,src[bytes] >> (8-rem),rem); |
dburgess | 82c46ff | 2011-10-07 02:40:51 +0000 | [diff] [blame] | 568 | } |
| 569 | |
| 570 | void BitVector::hex(ostream& os) const |
| 571 | { |
| 572 | os << std::hex; |
| 573 | unsigned digits = size()/4; |
| 574 | size_t wp=0; |
| 575 | for (unsigned i=0; i<digits; i++) { |
| 576 | os << readField(wp,4); |
| 577 | } |
| 578 | os << std::dec; |
| 579 | } |
| 580 | |
| 581 | bool BitVector::unhex(const char* src) |
| 582 | { |
| 583 | // Assumes MSB-first packing. |
| 584 | unsigned int val; |
| 585 | unsigned digits = size()/4; |
| 586 | for (unsigned i=0; i<digits; i++) { |
| 587 | if (sscanf(src+i, "%1x", &val) < 1) { |
| 588 | return false; |
| 589 | } |
| 590 | fillField(i*4,val,4); |
| 591 | } |
| 592 | unsigned whole = digits*4; |
| 593 | unsigned rem = size() - whole; |
| 594 | if (rem>0) { |
| 595 | if (sscanf(src+digits, "%1x", &val) < 1) { |
| 596 | return false; |
| 597 | } |
| 598 | fillField(whole,val,rem); |
| 599 | } |
| 600 | return true; |
| 601 | } |
| 602 | |
| 603 | // vim: ts=4 sw=4 |