kesavand | c71914f | 2022-03-25 11:19:03 +0530 | [diff] [blame^] | 1 | // Copyright 2019+ Klaus Post. All rights reserved. |
| 2 | // License information can be found in the LICENSE file. |
| 3 | // Based on work by Yann Collet, released under BSD License. |
| 4 | |
| 5 | package zstd |
| 6 | |
| 7 | import "fmt" |
| 8 | |
| 9 | const ( |
| 10 | betterLongTableBits = 19 // Bits used in the long match table |
| 11 | betterLongTableSize = 1 << betterLongTableBits // Size of the table |
| 12 | betterLongLen = 8 // Bytes used for table hash |
| 13 | |
| 14 | // Note: Increasing the short table bits or making the hash shorter |
| 15 | // can actually lead to compression degradation since it will 'steal' more from the |
| 16 | // long match table and match offsets are quite big. |
| 17 | // This greatly depends on the type of input. |
| 18 | betterShortTableBits = 13 // Bits used in the short match table |
| 19 | betterShortTableSize = 1 << betterShortTableBits // Size of the table |
| 20 | betterShortLen = 5 // Bytes used for table hash |
| 21 | |
| 22 | betterLongTableShardCnt = 1 << (betterLongTableBits - dictShardBits) // Number of shards in the table |
| 23 | betterLongTableShardSize = betterLongTableSize / betterLongTableShardCnt // Size of an individual shard |
| 24 | |
| 25 | betterShortTableShardCnt = 1 << (betterShortTableBits - dictShardBits) // Number of shards in the table |
| 26 | betterShortTableShardSize = betterShortTableSize / betterShortTableShardCnt // Size of an individual shard |
| 27 | ) |
| 28 | |
| 29 | type prevEntry struct { |
| 30 | offset int32 |
| 31 | prev int32 |
| 32 | } |
| 33 | |
| 34 | // betterFastEncoder uses 2 tables, one for short matches (5 bytes) and one for long matches. |
| 35 | // The long match table contains the previous entry with the same hash, |
| 36 | // effectively making it a "chain" of length 2. |
| 37 | // When we find a long match we choose between the two values and select the longest. |
| 38 | // When we find a short match, after checking the long, we check if we can find a long at n+1 |
| 39 | // and that it is longer (lazy matching). |
| 40 | type betterFastEncoder struct { |
| 41 | fastBase |
| 42 | table [betterShortTableSize]tableEntry |
| 43 | longTable [betterLongTableSize]prevEntry |
| 44 | } |
| 45 | |
| 46 | type betterFastEncoderDict struct { |
| 47 | betterFastEncoder |
| 48 | dictTable []tableEntry |
| 49 | dictLongTable []prevEntry |
| 50 | shortTableShardDirty [betterShortTableShardCnt]bool |
| 51 | longTableShardDirty [betterLongTableShardCnt]bool |
| 52 | allDirty bool |
| 53 | } |
| 54 | |
| 55 | // Encode improves compression... |
| 56 | func (e *betterFastEncoder) Encode(blk *blockEnc, src []byte) { |
| 57 | const ( |
| 58 | // Input margin is the number of bytes we read (8) |
| 59 | // and the maximum we will read ahead (2) |
| 60 | inputMargin = 8 + 2 |
| 61 | minNonLiteralBlockSize = 16 |
| 62 | ) |
| 63 | |
| 64 | // Protect against e.cur wraparound. |
| 65 | for e.cur >= bufferReset { |
| 66 | if len(e.hist) == 0 { |
| 67 | for i := range e.table[:] { |
| 68 | e.table[i] = tableEntry{} |
| 69 | } |
| 70 | for i := range e.longTable[:] { |
| 71 | e.longTable[i] = prevEntry{} |
| 72 | } |
| 73 | e.cur = e.maxMatchOff |
| 74 | break |
| 75 | } |
| 76 | // Shift down everything in the table that isn't already too far away. |
| 77 | minOff := e.cur + int32(len(e.hist)) - e.maxMatchOff |
| 78 | for i := range e.table[:] { |
| 79 | v := e.table[i].offset |
| 80 | if v < minOff { |
| 81 | v = 0 |
| 82 | } else { |
| 83 | v = v - e.cur + e.maxMatchOff |
| 84 | } |
| 85 | e.table[i].offset = v |
| 86 | } |
| 87 | for i := range e.longTable[:] { |
| 88 | v := e.longTable[i].offset |
| 89 | v2 := e.longTable[i].prev |
| 90 | if v < minOff { |
| 91 | v = 0 |
| 92 | v2 = 0 |
| 93 | } else { |
| 94 | v = v - e.cur + e.maxMatchOff |
| 95 | if v2 < minOff { |
| 96 | v2 = 0 |
| 97 | } else { |
| 98 | v2 = v2 - e.cur + e.maxMatchOff |
| 99 | } |
| 100 | } |
| 101 | e.longTable[i] = prevEntry{ |
| 102 | offset: v, |
| 103 | prev: v2, |
| 104 | } |
| 105 | } |
| 106 | e.cur = e.maxMatchOff |
| 107 | break |
| 108 | } |
| 109 | |
| 110 | s := e.addBlock(src) |
| 111 | blk.size = len(src) |
| 112 | if len(src) < minNonLiteralBlockSize { |
| 113 | blk.extraLits = len(src) |
| 114 | blk.literals = blk.literals[:len(src)] |
| 115 | copy(blk.literals, src) |
| 116 | return |
| 117 | } |
| 118 | |
| 119 | // Override src |
| 120 | src = e.hist |
| 121 | sLimit := int32(len(src)) - inputMargin |
| 122 | // stepSize is the number of bytes to skip on every main loop iteration. |
| 123 | // It should be >= 1. |
| 124 | const stepSize = 1 |
| 125 | |
| 126 | const kSearchStrength = 9 |
| 127 | |
| 128 | // nextEmit is where in src the next emitLiteral should start from. |
| 129 | nextEmit := s |
| 130 | cv := load6432(src, s) |
| 131 | |
| 132 | // Relative offsets |
| 133 | offset1 := int32(blk.recentOffsets[0]) |
| 134 | offset2 := int32(blk.recentOffsets[1]) |
| 135 | |
| 136 | addLiterals := func(s *seq, until int32) { |
| 137 | if until == nextEmit { |
| 138 | return |
| 139 | } |
| 140 | blk.literals = append(blk.literals, src[nextEmit:until]...) |
| 141 | s.litLen = uint32(until - nextEmit) |
| 142 | } |
| 143 | if debugEncoder { |
| 144 | println("recent offsets:", blk.recentOffsets) |
| 145 | } |
| 146 | |
| 147 | encodeLoop: |
| 148 | for { |
| 149 | var t int32 |
| 150 | // We allow the encoder to optionally turn off repeat offsets across blocks |
| 151 | canRepeat := len(blk.sequences) > 2 |
| 152 | var matched int32 |
| 153 | |
| 154 | for { |
| 155 | if debugAsserts && canRepeat && offset1 == 0 { |
| 156 | panic("offset0 was 0") |
| 157 | } |
| 158 | |
| 159 | nextHashS := hashLen(cv, betterShortTableBits, betterShortLen) |
| 160 | nextHashL := hashLen(cv, betterLongTableBits, betterLongLen) |
| 161 | candidateL := e.longTable[nextHashL] |
| 162 | candidateS := e.table[nextHashS] |
| 163 | |
| 164 | const repOff = 1 |
| 165 | repIndex := s - offset1 + repOff |
| 166 | off := s + e.cur |
| 167 | e.longTable[nextHashL] = prevEntry{offset: off, prev: candidateL.offset} |
| 168 | e.table[nextHashS] = tableEntry{offset: off, val: uint32(cv)} |
| 169 | |
| 170 | if canRepeat { |
| 171 | if repIndex >= 0 && load3232(src, repIndex) == uint32(cv>>(repOff*8)) { |
| 172 | // Consider history as well. |
| 173 | var seq seq |
| 174 | lenght := 4 + e.matchlen(s+4+repOff, repIndex+4, src) |
| 175 | |
| 176 | seq.matchLen = uint32(lenght - zstdMinMatch) |
| 177 | |
| 178 | // We might be able to match backwards. |
| 179 | // Extend as long as we can. |
| 180 | start := s + repOff |
| 181 | // We end the search early, so we don't risk 0 literals |
| 182 | // and have to do special offset treatment. |
| 183 | startLimit := nextEmit + 1 |
| 184 | |
| 185 | tMin := s - e.maxMatchOff |
| 186 | if tMin < 0 { |
| 187 | tMin = 0 |
| 188 | } |
| 189 | for repIndex > tMin && start > startLimit && src[repIndex-1] == src[start-1] && seq.matchLen < maxMatchLength-zstdMinMatch-1 { |
| 190 | repIndex-- |
| 191 | start-- |
| 192 | seq.matchLen++ |
| 193 | } |
| 194 | addLiterals(&seq, start) |
| 195 | |
| 196 | // rep 0 |
| 197 | seq.offset = 1 |
| 198 | if debugSequences { |
| 199 | println("repeat sequence", seq, "next s:", s) |
| 200 | } |
| 201 | blk.sequences = append(blk.sequences, seq) |
| 202 | |
| 203 | // Index match start+1 (long) -> s - 1 |
| 204 | index0 := s + repOff |
| 205 | s += lenght + repOff |
| 206 | |
| 207 | nextEmit = s |
| 208 | if s >= sLimit { |
| 209 | if debugEncoder { |
| 210 | println("repeat ended", s, lenght) |
| 211 | |
| 212 | } |
| 213 | break encodeLoop |
| 214 | } |
| 215 | // Index skipped... |
| 216 | for index0 < s-1 { |
| 217 | cv0 := load6432(src, index0) |
| 218 | cv1 := cv0 >> 8 |
| 219 | h0 := hashLen(cv0, betterLongTableBits, betterLongLen) |
| 220 | off := index0 + e.cur |
| 221 | e.longTable[h0] = prevEntry{offset: off, prev: e.longTable[h0].offset} |
| 222 | e.table[hashLen(cv1, betterShortTableBits, betterShortLen)] = tableEntry{offset: off + 1, val: uint32(cv1)} |
| 223 | index0 += 2 |
| 224 | } |
| 225 | cv = load6432(src, s) |
| 226 | continue |
| 227 | } |
| 228 | const repOff2 = 1 |
| 229 | |
| 230 | // We deviate from the reference encoder and also check offset 2. |
| 231 | // Still slower and not much better, so disabled. |
| 232 | // repIndex = s - offset2 + repOff2 |
| 233 | if false && repIndex >= 0 && load6432(src, repIndex) == load6432(src, s+repOff) { |
| 234 | // Consider history as well. |
| 235 | var seq seq |
| 236 | lenght := 8 + e.matchlen(s+8+repOff2, repIndex+8, src) |
| 237 | |
| 238 | seq.matchLen = uint32(lenght - zstdMinMatch) |
| 239 | |
| 240 | // We might be able to match backwards. |
| 241 | // Extend as long as we can. |
| 242 | start := s + repOff2 |
| 243 | // We end the search early, so we don't risk 0 literals |
| 244 | // and have to do special offset treatment. |
| 245 | startLimit := nextEmit + 1 |
| 246 | |
| 247 | tMin := s - e.maxMatchOff |
| 248 | if tMin < 0 { |
| 249 | tMin = 0 |
| 250 | } |
| 251 | for repIndex > tMin && start > startLimit && src[repIndex-1] == src[start-1] && seq.matchLen < maxMatchLength-zstdMinMatch-1 { |
| 252 | repIndex-- |
| 253 | start-- |
| 254 | seq.matchLen++ |
| 255 | } |
| 256 | addLiterals(&seq, start) |
| 257 | |
| 258 | // rep 2 |
| 259 | seq.offset = 2 |
| 260 | if debugSequences { |
| 261 | println("repeat sequence 2", seq, "next s:", s) |
| 262 | } |
| 263 | blk.sequences = append(blk.sequences, seq) |
| 264 | |
| 265 | index0 := s + repOff2 |
| 266 | s += lenght + repOff2 |
| 267 | nextEmit = s |
| 268 | if s >= sLimit { |
| 269 | if debugEncoder { |
| 270 | println("repeat ended", s, lenght) |
| 271 | |
| 272 | } |
| 273 | break encodeLoop |
| 274 | } |
| 275 | |
| 276 | // Index skipped... |
| 277 | for index0 < s-1 { |
| 278 | cv0 := load6432(src, index0) |
| 279 | cv1 := cv0 >> 8 |
| 280 | h0 := hashLen(cv0, betterLongTableBits, betterLongLen) |
| 281 | off := index0 + e.cur |
| 282 | e.longTable[h0] = prevEntry{offset: off, prev: e.longTable[h0].offset} |
| 283 | e.table[hashLen(cv1, betterShortTableBits, betterShortLen)] = tableEntry{offset: off + 1, val: uint32(cv1)} |
| 284 | index0 += 2 |
| 285 | } |
| 286 | cv = load6432(src, s) |
| 287 | // Swap offsets |
| 288 | offset1, offset2 = offset2, offset1 |
| 289 | continue |
| 290 | } |
| 291 | } |
| 292 | // Find the offsets of our two matches. |
| 293 | coffsetL := candidateL.offset - e.cur |
| 294 | coffsetLP := candidateL.prev - e.cur |
| 295 | |
| 296 | // Check if we have a long match. |
| 297 | if s-coffsetL < e.maxMatchOff && cv == load6432(src, coffsetL) { |
| 298 | // Found a long match, at least 8 bytes. |
| 299 | matched = e.matchlen(s+8, coffsetL+8, src) + 8 |
| 300 | t = coffsetL |
| 301 | if debugAsserts && s <= t { |
| 302 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 303 | } |
| 304 | if debugAsserts && s-t > e.maxMatchOff { |
| 305 | panic("s - t >e.maxMatchOff") |
| 306 | } |
| 307 | if debugMatches { |
| 308 | println("long match") |
| 309 | } |
| 310 | |
| 311 | if s-coffsetLP < e.maxMatchOff && cv == load6432(src, coffsetLP) { |
| 312 | // Found a long match, at least 8 bytes. |
| 313 | prevMatch := e.matchlen(s+8, coffsetLP+8, src) + 8 |
| 314 | if prevMatch > matched { |
| 315 | matched = prevMatch |
| 316 | t = coffsetLP |
| 317 | } |
| 318 | if debugAsserts && s <= t { |
| 319 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 320 | } |
| 321 | if debugAsserts && s-t > e.maxMatchOff { |
| 322 | panic("s - t >e.maxMatchOff") |
| 323 | } |
| 324 | if debugMatches { |
| 325 | println("long match") |
| 326 | } |
| 327 | } |
| 328 | break |
| 329 | } |
| 330 | |
| 331 | // Check if we have a long match on prev. |
| 332 | if s-coffsetLP < e.maxMatchOff && cv == load6432(src, coffsetLP) { |
| 333 | // Found a long match, at least 8 bytes. |
| 334 | matched = e.matchlen(s+8, coffsetLP+8, src) + 8 |
| 335 | t = coffsetLP |
| 336 | if debugAsserts && s <= t { |
| 337 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 338 | } |
| 339 | if debugAsserts && s-t > e.maxMatchOff { |
| 340 | panic("s - t >e.maxMatchOff") |
| 341 | } |
| 342 | if debugMatches { |
| 343 | println("long match") |
| 344 | } |
| 345 | break |
| 346 | } |
| 347 | |
| 348 | coffsetS := candidateS.offset - e.cur |
| 349 | |
| 350 | // Check if we have a short match. |
| 351 | if s-coffsetS < e.maxMatchOff && uint32(cv) == candidateS.val { |
| 352 | // found a regular match |
| 353 | matched = e.matchlen(s+4, coffsetS+4, src) + 4 |
| 354 | |
| 355 | // See if we can find a long match at s+1 |
| 356 | const checkAt = 1 |
| 357 | cv := load6432(src, s+checkAt) |
| 358 | nextHashL = hashLen(cv, betterLongTableBits, betterLongLen) |
| 359 | candidateL = e.longTable[nextHashL] |
| 360 | coffsetL = candidateL.offset - e.cur |
| 361 | |
| 362 | // We can store it, since we have at least a 4 byte match. |
| 363 | e.longTable[nextHashL] = prevEntry{offset: s + checkAt + e.cur, prev: candidateL.offset} |
| 364 | if s-coffsetL < e.maxMatchOff && cv == load6432(src, coffsetL) { |
| 365 | // Found a long match, at least 8 bytes. |
| 366 | matchedNext := e.matchlen(s+8+checkAt, coffsetL+8, src) + 8 |
| 367 | if matchedNext > matched { |
| 368 | t = coffsetL |
| 369 | s += checkAt |
| 370 | matched = matchedNext |
| 371 | if debugMatches { |
| 372 | println("long match (after short)") |
| 373 | } |
| 374 | break |
| 375 | } |
| 376 | } |
| 377 | |
| 378 | // Check prev long... |
| 379 | coffsetL = candidateL.prev - e.cur |
| 380 | if s-coffsetL < e.maxMatchOff && cv == load6432(src, coffsetL) { |
| 381 | // Found a long match, at least 8 bytes. |
| 382 | matchedNext := e.matchlen(s+8+checkAt, coffsetL+8, src) + 8 |
| 383 | if matchedNext > matched { |
| 384 | t = coffsetL |
| 385 | s += checkAt |
| 386 | matched = matchedNext |
| 387 | if debugMatches { |
| 388 | println("prev long match (after short)") |
| 389 | } |
| 390 | break |
| 391 | } |
| 392 | } |
| 393 | t = coffsetS |
| 394 | if debugAsserts && s <= t { |
| 395 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 396 | } |
| 397 | if debugAsserts && s-t > e.maxMatchOff { |
| 398 | panic("s - t >e.maxMatchOff") |
| 399 | } |
| 400 | if debugAsserts && t < 0 { |
| 401 | panic("t<0") |
| 402 | } |
| 403 | if debugMatches { |
| 404 | println("short match") |
| 405 | } |
| 406 | break |
| 407 | } |
| 408 | |
| 409 | // No match found, move forward in input. |
| 410 | s += stepSize + ((s - nextEmit) >> (kSearchStrength - 1)) |
| 411 | if s >= sLimit { |
| 412 | break encodeLoop |
| 413 | } |
| 414 | cv = load6432(src, s) |
| 415 | } |
| 416 | |
| 417 | // Try to find a better match by searching for a long match at the end of the current best match |
| 418 | if s+matched < sLimit { |
| 419 | nextHashL := hashLen(load6432(src, s+matched), betterLongTableBits, betterLongLen) |
| 420 | cv := load3232(src, s) |
| 421 | candidateL := e.longTable[nextHashL] |
| 422 | coffsetL := candidateL.offset - e.cur - matched |
| 423 | if coffsetL >= 0 && coffsetL < s && s-coffsetL < e.maxMatchOff && cv == load3232(src, coffsetL) { |
| 424 | // Found a long match, at least 4 bytes. |
| 425 | matchedNext := e.matchlen(s+4, coffsetL+4, src) + 4 |
| 426 | if matchedNext > matched { |
| 427 | t = coffsetL |
| 428 | matched = matchedNext |
| 429 | if debugMatches { |
| 430 | println("long match at end-of-match") |
| 431 | } |
| 432 | } |
| 433 | } |
| 434 | |
| 435 | // Check prev long... |
| 436 | if true { |
| 437 | coffsetL = candidateL.prev - e.cur - matched |
| 438 | if coffsetL >= 0 && coffsetL < s && s-coffsetL < e.maxMatchOff && cv == load3232(src, coffsetL) { |
| 439 | // Found a long match, at least 4 bytes. |
| 440 | matchedNext := e.matchlen(s+4, coffsetL+4, src) + 4 |
| 441 | if matchedNext > matched { |
| 442 | t = coffsetL |
| 443 | matched = matchedNext |
| 444 | if debugMatches { |
| 445 | println("prev long match at end-of-match") |
| 446 | } |
| 447 | } |
| 448 | } |
| 449 | } |
| 450 | } |
| 451 | // A match has been found. Update recent offsets. |
| 452 | offset2 = offset1 |
| 453 | offset1 = s - t |
| 454 | |
| 455 | if debugAsserts && s <= t { |
| 456 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 457 | } |
| 458 | |
| 459 | if debugAsserts && canRepeat && int(offset1) > len(src) { |
| 460 | panic("invalid offset") |
| 461 | } |
| 462 | |
| 463 | // Extend the n-byte match as long as possible. |
| 464 | l := matched |
| 465 | |
| 466 | // Extend backwards |
| 467 | tMin := s - e.maxMatchOff |
| 468 | if tMin < 0 { |
| 469 | tMin = 0 |
| 470 | } |
| 471 | for t > tMin && s > nextEmit && src[t-1] == src[s-1] && l < maxMatchLength { |
| 472 | s-- |
| 473 | t-- |
| 474 | l++ |
| 475 | } |
| 476 | |
| 477 | // Write our sequence |
| 478 | var seq seq |
| 479 | seq.litLen = uint32(s - nextEmit) |
| 480 | seq.matchLen = uint32(l - zstdMinMatch) |
| 481 | if seq.litLen > 0 { |
| 482 | blk.literals = append(blk.literals, src[nextEmit:s]...) |
| 483 | } |
| 484 | seq.offset = uint32(s-t) + 3 |
| 485 | s += l |
| 486 | if debugSequences { |
| 487 | println("sequence", seq, "next s:", s) |
| 488 | } |
| 489 | blk.sequences = append(blk.sequences, seq) |
| 490 | nextEmit = s |
| 491 | if s >= sLimit { |
| 492 | break encodeLoop |
| 493 | } |
| 494 | |
| 495 | // Index match start+1 (long) -> s - 1 |
| 496 | index0 := s - l + 1 |
| 497 | for index0 < s-1 { |
| 498 | cv0 := load6432(src, index0) |
| 499 | cv1 := cv0 >> 8 |
| 500 | h0 := hashLen(cv0, betterLongTableBits, betterLongLen) |
| 501 | off := index0 + e.cur |
| 502 | e.longTable[h0] = prevEntry{offset: off, prev: e.longTable[h0].offset} |
| 503 | e.table[hashLen(cv1, betterShortTableBits, betterShortLen)] = tableEntry{offset: off + 1, val: uint32(cv1)} |
| 504 | index0 += 2 |
| 505 | } |
| 506 | |
| 507 | cv = load6432(src, s) |
| 508 | if !canRepeat { |
| 509 | continue |
| 510 | } |
| 511 | |
| 512 | // Check offset 2 |
| 513 | for { |
| 514 | o2 := s - offset2 |
| 515 | if load3232(src, o2) != uint32(cv) { |
| 516 | // Do regular search |
| 517 | break |
| 518 | } |
| 519 | |
| 520 | // Store this, since we have it. |
| 521 | nextHashS := hashLen(cv, betterShortTableBits, betterShortLen) |
| 522 | nextHashL := hashLen(cv, betterLongTableBits, betterLongLen) |
| 523 | |
| 524 | // We have at least 4 byte match. |
| 525 | // No need to check backwards. We come straight from a match |
| 526 | l := 4 + e.matchlen(s+4, o2+4, src) |
| 527 | |
| 528 | e.longTable[nextHashL] = prevEntry{offset: s + e.cur, prev: e.longTable[nextHashL].offset} |
| 529 | e.table[nextHashS] = tableEntry{offset: s + e.cur, val: uint32(cv)} |
| 530 | seq.matchLen = uint32(l) - zstdMinMatch |
| 531 | seq.litLen = 0 |
| 532 | |
| 533 | // Since litlen is always 0, this is offset 1. |
| 534 | seq.offset = 1 |
| 535 | s += l |
| 536 | nextEmit = s |
| 537 | if debugSequences { |
| 538 | println("sequence", seq, "next s:", s) |
| 539 | } |
| 540 | blk.sequences = append(blk.sequences, seq) |
| 541 | |
| 542 | // Swap offset 1 and 2. |
| 543 | offset1, offset2 = offset2, offset1 |
| 544 | if s >= sLimit { |
| 545 | // Finished |
| 546 | break encodeLoop |
| 547 | } |
| 548 | cv = load6432(src, s) |
| 549 | } |
| 550 | } |
| 551 | |
| 552 | if int(nextEmit) < len(src) { |
| 553 | blk.literals = append(blk.literals, src[nextEmit:]...) |
| 554 | blk.extraLits = len(src) - int(nextEmit) |
| 555 | } |
| 556 | blk.recentOffsets[0] = uint32(offset1) |
| 557 | blk.recentOffsets[1] = uint32(offset2) |
| 558 | if debugEncoder { |
| 559 | println("returning, recent offsets:", blk.recentOffsets, "extra literals:", blk.extraLits) |
| 560 | } |
| 561 | } |
| 562 | |
| 563 | // EncodeNoHist will encode a block with no history and no following blocks. |
| 564 | // Most notable difference is that src will not be copied for history and |
| 565 | // we do not need to check for max match length. |
| 566 | func (e *betterFastEncoder) EncodeNoHist(blk *blockEnc, src []byte) { |
| 567 | e.ensureHist(len(src)) |
| 568 | e.Encode(blk, src) |
| 569 | } |
| 570 | |
| 571 | // Encode improves compression... |
| 572 | func (e *betterFastEncoderDict) Encode(blk *blockEnc, src []byte) { |
| 573 | const ( |
| 574 | // Input margin is the number of bytes we read (8) |
| 575 | // and the maximum we will read ahead (2) |
| 576 | inputMargin = 8 + 2 |
| 577 | minNonLiteralBlockSize = 16 |
| 578 | ) |
| 579 | |
| 580 | // Protect against e.cur wraparound. |
| 581 | for e.cur >= bufferReset { |
| 582 | if len(e.hist) == 0 { |
| 583 | for i := range e.table[:] { |
| 584 | e.table[i] = tableEntry{} |
| 585 | } |
| 586 | for i := range e.longTable[:] { |
| 587 | e.longTable[i] = prevEntry{} |
| 588 | } |
| 589 | e.cur = e.maxMatchOff |
| 590 | e.allDirty = true |
| 591 | break |
| 592 | } |
| 593 | // Shift down everything in the table that isn't already too far away. |
| 594 | minOff := e.cur + int32(len(e.hist)) - e.maxMatchOff |
| 595 | for i := range e.table[:] { |
| 596 | v := e.table[i].offset |
| 597 | if v < minOff { |
| 598 | v = 0 |
| 599 | } else { |
| 600 | v = v - e.cur + e.maxMatchOff |
| 601 | } |
| 602 | e.table[i].offset = v |
| 603 | } |
| 604 | for i := range e.longTable[:] { |
| 605 | v := e.longTable[i].offset |
| 606 | v2 := e.longTable[i].prev |
| 607 | if v < minOff { |
| 608 | v = 0 |
| 609 | v2 = 0 |
| 610 | } else { |
| 611 | v = v - e.cur + e.maxMatchOff |
| 612 | if v2 < minOff { |
| 613 | v2 = 0 |
| 614 | } else { |
| 615 | v2 = v2 - e.cur + e.maxMatchOff |
| 616 | } |
| 617 | } |
| 618 | e.longTable[i] = prevEntry{ |
| 619 | offset: v, |
| 620 | prev: v2, |
| 621 | } |
| 622 | } |
| 623 | e.allDirty = true |
| 624 | e.cur = e.maxMatchOff |
| 625 | break |
| 626 | } |
| 627 | |
| 628 | s := e.addBlock(src) |
| 629 | blk.size = len(src) |
| 630 | if len(src) < minNonLiteralBlockSize { |
| 631 | blk.extraLits = len(src) |
| 632 | blk.literals = blk.literals[:len(src)] |
| 633 | copy(blk.literals, src) |
| 634 | return |
| 635 | } |
| 636 | |
| 637 | // Override src |
| 638 | src = e.hist |
| 639 | sLimit := int32(len(src)) - inputMargin |
| 640 | // stepSize is the number of bytes to skip on every main loop iteration. |
| 641 | // It should be >= 1. |
| 642 | const stepSize = 1 |
| 643 | |
| 644 | const kSearchStrength = 9 |
| 645 | |
| 646 | // nextEmit is where in src the next emitLiteral should start from. |
| 647 | nextEmit := s |
| 648 | cv := load6432(src, s) |
| 649 | |
| 650 | // Relative offsets |
| 651 | offset1 := int32(blk.recentOffsets[0]) |
| 652 | offset2 := int32(blk.recentOffsets[1]) |
| 653 | |
| 654 | addLiterals := func(s *seq, until int32) { |
| 655 | if until == nextEmit { |
| 656 | return |
| 657 | } |
| 658 | blk.literals = append(blk.literals, src[nextEmit:until]...) |
| 659 | s.litLen = uint32(until - nextEmit) |
| 660 | } |
| 661 | if debugEncoder { |
| 662 | println("recent offsets:", blk.recentOffsets) |
| 663 | } |
| 664 | |
| 665 | encodeLoop: |
| 666 | for { |
| 667 | var t int32 |
| 668 | // We allow the encoder to optionally turn off repeat offsets across blocks |
| 669 | canRepeat := len(blk.sequences) > 2 |
| 670 | var matched int32 |
| 671 | |
| 672 | for { |
| 673 | if debugAsserts && canRepeat && offset1 == 0 { |
| 674 | panic("offset0 was 0") |
| 675 | } |
| 676 | |
| 677 | nextHashS := hashLen(cv, betterShortTableBits, betterShortLen) |
| 678 | nextHashL := hashLen(cv, betterLongTableBits, betterLongLen) |
| 679 | candidateL := e.longTable[nextHashL] |
| 680 | candidateS := e.table[nextHashS] |
| 681 | |
| 682 | const repOff = 1 |
| 683 | repIndex := s - offset1 + repOff |
| 684 | off := s + e.cur |
| 685 | e.longTable[nextHashL] = prevEntry{offset: off, prev: candidateL.offset} |
| 686 | e.markLongShardDirty(nextHashL) |
| 687 | e.table[nextHashS] = tableEntry{offset: off, val: uint32(cv)} |
| 688 | e.markShortShardDirty(nextHashS) |
| 689 | |
| 690 | if canRepeat { |
| 691 | if repIndex >= 0 && load3232(src, repIndex) == uint32(cv>>(repOff*8)) { |
| 692 | // Consider history as well. |
| 693 | var seq seq |
| 694 | lenght := 4 + e.matchlen(s+4+repOff, repIndex+4, src) |
| 695 | |
| 696 | seq.matchLen = uint32(lenght - zstdMinMatch) |
| 697 | |
| 698 | // We might be able to match backwards. |
| 699 | // Extend as long as we can. |
| 700 | start := s + repOff |
| 701 | // We end the search early, so we don't risk 0 literals |
| 702 | // and have to do special offset treatment. |
| 703 | startLimit := nextEmit + 1 |
| 704 | |
| 705 | tMin := s - e.maxMatchOff |
| 706 | if tMin < 0 { |
| 707 | tMin = 0 |
| 708 | } |
| 709 | for repIndex > tMin && start > startLimit && src[repIndex-1] == src[start-1] && seq.matchLen < maxMatchLength-zstdMinMatch-1 { |
| 710 | repIndex-- |
| 711 | start-- |
| 712 | seq.matchLen++ |
| 713 | } |
| 714 | addLiterals(&seq, start) |
| 715 | |
| 716 | // rep 0 |
| 717 | seq.offset = 1 |
| 718 | if debugSequences { |
| 719 | println("repeat sequence", seq, "next s:", s) |
| 720 | } |
| 721 | blk.sequences = append(blk.sequences, seq) |
| 722 | |
| 723 | // Index match start+1 (long) -> s - 1 |
| 724 | index0 := s + repOff |
| 725 | s += lenght + repOff |
| 726 | |
| 727 | nextEmit = s |
| 728 | if s >= sLimit { |
| 729 | if debugEncoder { |
| 730 | println("repeat ended", s, lenght) |
| 731 | |
| 732 | } |
| 733 | break encodeLoop |
| 734 | } |
| 735 | // Index skipped... |
| 736 | for index0 < s-1 { |
| 737 | cv0 := load6432(src, index0) |
| 738 | cv1 := cv0 >> 8 |
| 739 | h0 := hashLen(cv0, betterLongTableBits, betterLongLen) |
| 740 | off := index0 + e.cur |
| 741 | e.longTable[h0] = prevEntry{offset: off, prev: e.longTable[h0].offset} |
| 742 | e.markLongShardDirty(h0) |
| 743 | h1 := hashLen(cv1, betterShortTableBits, betterShortLen) |
| 744 | e.table[h1] = tableEntry{offset: off + 1, val: uint32(cv1)} |
| 745 | e.markShortShardDirty(h1) |
| 746 | index0 += 2 |
| 747 | } |
| 748 | cv = load6432(src, s) |
| 749 | continue |
| 750 | } |
| 751 | const repOff2 = 1 |
| 752 | |
| 753 | // We deviate from the reference encoder and also check offset 2. |
| 754 | // Still slower and not much better, so disabled. |
| 755 | // repIndex = s - offset2 + repOff2 |
| 756 | if false && repIndex >= 0 && load6432(src, repIndex) == load6432(src, s+repOff) { |
| 757 | // Consider history as well. |
| 758 | var seq seq |
| 759 | lenght := 8 + e.matchlen(s+8+repOff2, repIndex+8, src) |
| 760 | |
| 761 | seq.matchLen = uint32(lenght - zstdMinMatch) |
| 762 | |
| 763 | // We might be able to match backwards. |
| 764 | // Extend as long as we can. |
| 765 | start := s + repOff2 |
| 766 | // We end the search early, so we don't risk 0 literals |
| 767 | // and have to do special offset treatment. |
| 768 | startLimit := nextEmit + 1 |
| 769 | |
| 770 | tMin := s - e.maxMatchOff |
| 771 | if tMin < 0 { |
| 772 | tMin = 0 |
| 773 | } |
| 774 | for repIndex > tMin && start > startLimit && src[repIndex-1] == src[start-1] && seq.matchLen < maxMatchLength-zstdMinMatch-1 { |
| 775 | repIndex-- |
| 776 | start-- |
| 777 | seq.matchLen++ |
| 778 | } |
| 779 | addLiterals(&seq, start) |
| 780 | |
| 781 | // rep 2 |
| 782 | seq.offset = 2 |
| 783 | if debugSequences { |
| 784 | println("repeat sequence 2", seq, "next s:", s) |
| 785 | } |
| 786 | blk.sequences = append(blk.sequences, seq) |
| 787 | |
| 788 | index0 := s + repOff2 |
| 789 | s += lenght + repOff2 |
| 790 | nextEmit = s |
| 791 | if s >= sLimit { |
| 792 | if debugEncoder { |
| 793 | println("repeat ended", s, lenght) |
| 794 | |
| 795 | } |
| 796 | break encodeLoop |
| 797 | } |
| 798 | |
| 799 | // Index skipped... |
| 800 | for index0 < s-1 { |
| 801 | cv0 := load6432(src, index0) |
| 802 | cv1 := cv0 >> 8 |
| 803 | h0 := hashLen(cv0, betterLongTableBits, betterLongLen) |
| 804 | off := index0 + e.cur |
| 805 | e.longTable[h0] = prevEntry{offset: off, prev: e.longTable[h0].offset} |
| 806 | e.markLongShardDirty(h0) |
| 807 | h1 := hashLen(cv1, betterShortTableBits, betterShortLen) |
| 808 | e.table[h1] = tableEntry{offset: off + 1, val: uint32(cv1)} |
| 809 | e.markShortShardDirty(h1) |
| 810 | index0 += 2 |
| 811 | } |
| 812 | cv = load6432(src, s) |
| 813 | // Swap offsets |
| 814 | offset1, offset2 = offset2, offset1 |
| 815 | continue |
| 816 | } |
| 817 | } |
| 818 | // Find the offsets of our two matches. |
| 819 | coffsetL := candidateL.offset - e.cur |
| 820 | coffsetLP := candidateL.prev - e.cur |
| 821 | |
| 822 | // Check if we have a long match. |
| 823 | if s-coffsetL < e.maxMatchOff && cv == load6432(src, coffsetL) { |
| 824 | // Found a long match, at least 8 bytes. |
| 825 | matched = e.matchlen(s+8, coffsetL+8, src) + 8 |
| 826 | t = coffsetL |
| 827 | if debugAsserts && s <= t { |
| 828 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 829 | } |
| 830 | if debugAsserts && s-t > e.maxMatchOff { |
| 831 | panic("s - t >e.maxMatchOff") |
| 832 | } |
| 833 | if debugMatches { |
| 834 | println("long match") |
| 835 | } |
| 836 | |
| 837 | if s-coffsetLP < e.maxMatchOff && cv == load6432(src, coffsetLP) { |
| 838 | // Found a long match, at least 8 bytes. |
| 839 | prevMatch := e.matchlen(s+8, coffsetLP+8, src) + 8 |
| 840 | if prevMatch > matched { |
| 841 | matched = prevMatch |
| 842 | t = coffsetLP |
| 843 | } |
| 844 | if debugAsserts && s <= t { |
| 845 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 846 | } |
| 847 | if debugAsserts && s-t > e.maxMatchOff { |
| 848 | panic("s - t >e.maxMatchOff") |
| 849 | } |
| 850 | if debugMatches { |
| 851 | println("long match") |
| 852 | } |
| 853 | } |
| 854 | break |
| 855 | } |
| 856 | |
| 857 | // Check if we have a long match on prev. |
| 858 | if s-coffsetLP < e.maxMatchOff && cv == load6432(src, coffsetLP) { |
| 859 | // Found a long match, at least 8 bytes. |
| 860 | matched = e.matchlen(s+8, coffsetLP+8, src) + 8 |
| 861 | t = coffsetLP |
| 862 | if debugAsserts && s <= t { |
| 863 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 864 | } |
| 865 | if debugAsserts && s-t > e.maxMatchOff { |
| 866 | panic("s - t >e.maxMatchOff") |
| 867 | } |
| 868 | if debugMatches { |
| 869 | println("long match") |
| 870 | } |
| 871 | break |
| 872 | } |
| 873 | |
| 874 | coffsetS := candidateS.offset - e.cur |
| 875 | |
| 876 | // Check if we have a short match. |
| 877 | if s-coffsetS < e.maxMatchOff && uint32(cv) == candidateS.val { |
| 878 | // found a regular match |
| 879 | matched = e.matchlen(s+4, coffsetS+4, src) + 4 |
| 880 | |
| 881 | // See if we can find a long match at s+1 |
| 882 | const checkAt = 1 |
| 883 | cv := load6432(src, s+checkAt) |
| 884 | nextHashL = hashLen(cv, betterLongTableBits, betterLongLen) |
| 885 | candidateL = e.longTable[nextHashL] |
| 886 | coffsetL = candidateL.offset - e.cur |
| 887 | |
| 888 | // We can store it, since we have at least a 4 byte match. |
| 889 | e.longTable[nextHashL] = prevEntry{offset: s + checkAt + e.cur, prev: candidateL.offset} |
| 890 | e.markLongShardDirty(nextHashL) |
| 891 | if s-coffsetL < e.maxMatchOff && cv == load6432(src, coffsetL) { |
| 892 | // Found a long match, at least 8 bytes. |
| 893 | matchedNext := e.matchlen(s+8+checkAt, coffsetL+8, src) + 8 |
| 894 | if matchedNext > matched { |
| 895 | t = coffsetL |
| 896 | s += checkAt |
| 897 | matched = matchedNext |
| 898 | if debugMatches { |
| 899 | println("long match (after short)") |
| 900 | } |
| 901 | break |
| 902 | } |
| 903 | } |
| 904 | |
| 905 | // Check prev long... |
| 906 | coffsetL = candidateL.prev - e.cur |
| 907 | if s-coffsetL < e.maxMatchOff && cv == load6432(src, coffsetL) { |
| 908 | // Found a long match, at least 8 bytes. |
| 909 | matchedNext := e.matchlen(s+8+checkAt, coffsetL+8, src) + 8 |
| 910 | if matchedNext > matched { |
| 911 | t = coffsetL |
| 912 | s += checkAt |
| 913 | matched = matchedNext |
| 914 | if debugMatches { |
| 915 | println("prev long match (after short)") |
| 916 | } |
| 917 | break |
| 918 | } |
| 919 | } |
| 920 | t = coffsetS |
| 921 | if debugAsserts && s <= t { |
| 922 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 923 | } |
| 924 | if debugAsserts && s-t > e.maxMatchOff { |
| 925 | panic("s - t >e.maxMatchOff") |
| 926 | } |
| 927 | if debugAsserts && t < 0 { |
| 928 | panic("t<0") |
| 929 | } |
| 930 | if debugMatches { |
| 931 | println("short match") |
| 932 | } |
| 933 | break |
| 934 | } |
| 935 | |
| 936 | // No match found, move forward in input. |
| 937 | s += stepSize + ((s - nextEmit) >> (kSearchStrength - 1)) |
| 938 | if s >= sLimit { |
| 939 | break encodeLoop |
| 940 | } |
| 941 | cv = load6432(src, s) |
| 942 | } |
| 943 | // Try to find a better match by searching for a long match at the end of the current best match |
| 944 | if s+matched < sLimit { |
| 945 | nextHashL := hashLen(load6432(src, s+matched), betterLongTableBits, betterLongLen) |
| 946 | cv := load3232(src, s) |
| 947 | candidateL := e.longTable[nextHashL] |
| 948 | coffsetL := candidateL.offset - e.cur - matched |
| 949 | if coffsetL >= 0 && coffsetL < s && s-coffsetL < e.maxMatchOff && cv == load3232(src, coffsetL) { |
| 950 | // Found a long match, at least 4 bytes. |
| 951 | matchedNext := e.matchlen(s+4, coffsetL+4, src) + 4 |
| 952 | if matchedNext > matched { |
| 953 | t = coffsetL |
| 954 | matched = matchedNext |
| 955 | if debugMatches { |
| 956 | println("long match at end-of-match") |
| 957 | } |
| 958 | } |
| 959 | } |
| 960 | |
| 961 | // Check prev long... |
| 962 | if true { |
| 963 | coffsetL = candidateL.prev - e.cur - matched |
| 964 | if coffsetL >= 0 && coffsetL < s && s-coffsetL < e.maxMatchOff && cv == load3232(src, coffsetL) { |
| 965 | // Found a long match, at least 4 bytes. |
| 966 | matchedNext := e.matchlen(s+4, coffsetL+4, src) + 4 |
| 967 | if matchedNext > matched { |
| 968 | t = coffsetL |
| 969 | matched = matchedNext |
| 970 | if debugMatches { |
| 971 | println("prev long match at end-of-match") |
| 972 | } |
| 973 | } |
| 974 | } |
| 975 | } |
| 976 | } |
| 977 | // A match has been found. Update recent offsets. |
| 978 | offset2 = offset1 |
| 979 | offset1 = s - t |
| 980 | |
| 981 | if debugAsserts && s <= t { |
| 982 | panic(fmt.Sprintf("s (%d) <= t (%d)", s, t)) |
| 983 | } |
| 984 | |
| 985 | if debugAsserts && canRepeat && int(offset1) > len(src) { |
| 986 | panic("invalid offset") |
| 987 | } |
| 988 | |
| 989 | // Extend the n-byte match as long as possible. |
| 990 | l := matched |
| 991 | |
| 992 | // Extend backwards |
| 993 | tMin := s - e.maxMatchOff |
| 994 | if tMin < 0 { |
| 995 | tMin = 0 |
| 996 | } |
| 997 | for t > tMin && s > nextEmit && src[t-1] == src[s-1] && l < maxMatchLength { |
| 998 | s-- |
| 999 | t-- |
| 1000 | l++ |
| 1001 | } |
| 1002 | |
| 1003 | // Write our sequence |
| 1004 | var seq seq |
| 1005 | seq.litLen = uint32(s - nextEmit) |
| 1006 | seq.matchLen = uint32(l - zstdMinMatch) |
| 1007 | if seq.litLen > 0 { |
| 1008 | blk.literals = append(blk.literals, src[nextEmit:s]...) |
| 1009 | } |
| 1010 | seq.offset = uint32(s-t) + 3 |
| 1011 | s += l |
| 1012 | if debugSequences { |
| 1013 | println("sequence", seq, "next s:", s) |
| 1014 | } |
| 1015 | blk.sequences = append(blk.sequences, seq) |
| 1016 | nextEmit = s |
| 1017 | if s >= sLimit { |
| 1018 | break encodeLoop |
| 1019 | } |
| 1020 | |
| 1021 | // Index match start+1 (long) -> s - 1 |
| 1022 | index0 := s - l + 1 |
| 1023 | for index0 < s-1 { |
| 1024 | cv0 := load6432(src, index0) |
| 1025 | cv1 := cv0 >> 8 |
| 1026 | h0 := hashLen(cv0, betterLongTableBits, betterLongLen) |
| 1027 | off := index0 + e.cur |
| 1028 | e.longTable[h0] = prevEntry{offset: off, prev: e.longTable[h0].offset} |
| 1029 | e.markLongShardDirty(h0) |
| 1030 | h1 := hashLen(cv1, betterShortTableBits, betterShortLen) |
| 1031 | e.table[h1] = tableEntry{offset: off + 1, val: uint32(cv1)} |
| 1032 | e.markShortShardDirty(h1) |
| 1033 | index0 += 2 |
| 1034 | } |
| 1035 | |
| 1036 | cv = load6432(src, s) |
| 1037 | if !canRepeat { |
| 1038 | continue |
| 1039 | } |
| 1040 | |
| 1041 | // Check offset 2 |
| 1042 | for { |
| 1043 | o2 := s - offset2 |
| 1044 | if load3232(src, o2) != uint32(cv) { |
| 1045 | // Do regular search |
| 1046 | break |
| 1047 | } |
| 1048 | |
| 1049 | // Store this, since we have it. |
| 1050 | nextHashS := hashLen(cv, betterShortTableBits, betterShortLen) |
| 1051 | nextHashL := hashLen(cv, betterLongTableBits, betterLongLen) |
| 1052 | |
| 1053 | // We have at least 4 byte match. |
| 1054 | // No need to check backwards. We come straight from a match |
| 1055 | l := 4 + e.matchlen(s+4, o2+4, src) |
| 1056 | |
| 1057 | e.longTable[nextHashL] = prevEntry{offset: s + e.cur, prev: e.longTable[nextHashL].offset} |
| 1058 | e.markLongShardDirty(nextHashL) |
| 1059 | e.table[nextHashS] = tableEntry{offset: s + e.cur, val: uint32(cv)} |
| 1060 | e.markShortShardDirty(nextHashS) |
| 1061 | seq.matchLen = uint32(l) - zstdMinMatch |
| 1062 | seq.litLen = 0 |
| 1063 | |
| 1064 | // Since litlen is always 0, this is offset 1. |
| 1065 | seq.offset = 1 |
| 1066 | s += l |
| 1067 | nextEmit = s |
| 1068 | if debugSequences { |
| 1069 | println("sequence", seq, "next s:", s) |
| 1070 | } |
| 1071 | blk.sequences = append(blk.sequences, seq) |
| 1072 | |
| 1073 | // Swap offset 1 and 2. |
| 1074 | offset1, offset2 = offset2, offset1 |
| 1075 | if s >= sLimit { |
| 1076 | // Finished |
| 1077 | break encodeLoop |
| 1078 | } |
| 1079 | cv = load6432(src, s) |
| 1080 | } |
| 1081 | } |
| 1082 | |
| 1083 | if int(nextEmit) < len(src) { |
| 1084 | blk.literals = append(blk.literals, src[nextEmit:]...) |
| 1085 | blk.extraLits = len(src) - int(nextEmit) |
| 1086 | } |
| 1087 | blk.recentOffsets[0] = uint32(offset1) |
| 1088 | blk.recentOffsets[1] = uint32(offset2) |
| 1089 | if debugEncoder { |
| 1090 | println("returning, recent offsets:", blk.recentOffsets, "extra literals:", blk.extraLits) |
| 1091 | } |
| 1092 | } |
| 1093 | |
| 1094 | // ResetDict will reset and set a dictionary if not nil |
| 1095 | func (e *betterFastEncoder) Reset(d *dict, singleBlock bool) { |
| 1096 | e.resetBase(d, singleBlock) |
| 1097 | if d != nil { |
| 1098 | panic("betterFastEncoder: Reset with dict") |
| 1099 | } |
| 1100 | } |
| 1101 | |
| 1102 | // ResetDict will reset and set a dictionary if not nil |
| 1103 | func (e *betterFastEncoderDict) Reset(d *dict, singleBlock bool) { |
| 1104 | e.resetBase(d, singleBlock) |
| 1105 | if d == nil { |
| 1106 | return |
| 1107 | } |
| 1108 | // Init or copy dict table |
| 1109 | if len(e.dictTable) != len(e.table) || d.id != e.lastDictID { |
| 1110 | if len(e.dictTable) != len(e.table) { |
| 1111 | e.dictTable = make([]tableEntry, len(e.table)) |
| 1112 | } |
| 1113 | end := int32(len(d.content)) - 8 + e.maxMatchOff |
| 1114 | for i := e.maxMatchOff; i < end; i += 4 { |
| 1115 | const hashLog = betterShortTableBits |
| 1116 | |
| 1117 | cv := load6432(d.content, i-e.maxMatchOff) |
| 1118 | nextHash := hashLen(cv, hashLog, betterShortLen) // 0 -> 4 |
| 1119 | nextHash1 := hashLen(cv>>8, hashLog, betterShortLen) // 1 -> 5 |
| 1120 | nextHash2 := hashLen(cv>>16, hashLog, betterShortLen) // 2 -> 6 |
| 1121 | nextHash3 := hashLen(cv>>24, hashLog, betterShortLen) // 3 -> 7 |
| 1122 | e.dictTable[nextHash] = tableEntry{ |
| 1123 | val: uint32(cv), |
| 1124 | offset: i, |
| 1125 | } |
| 1126 | e.dictTable[nextHash1] = tableEntry{ |
| 1127 | val: uint32(cv >> 8), |
| 1128 | offset: i + 1, |
| 1129 | } |
| 1130 | e.dictTable[nextHash2] = tableEntry{ |
| 1131 | val: uint32(cv >> 16), |
| 1132 | offset: i + 2, |
| 1133 | } |
| 1134 | e.dictTable[nextHash3] = tableEntry{ |
| 1135 | val: uint32(cv >> 24), |
| 1136 | offset: i + 3, |
| 1137 | } |
| 1138 | } |
| 1139 | e.lastDictID = d.id |
| 1140 | e.allDirty = true |
| 1141 | } |
| 1142 | |
| 1143 | // Init or copy dict table |
| 1144 | if len(e.dictLongTable) != len(e.longTable) || d.id != e.lastDictID { |
| 1145 | if len(e.dictLongTable) != len(e.longTable) { |
| 1146 | e.dictLongTable = make([]prevEntry, len(e.longTable)) |
| 1147 | } |
| 1148 | if len(d.content) >= 8 { |
| 1149 | cv := load6432(d.content, 0) |
| 1150 | h := hashLen(cv, betterLongTableBits, betterLongLen) |
| 1151 | e.dictLongTable[h] = prevEntry{ |
| 1152 | offset: e.maxMatchOff, |
| 1153 | prev: e.dictLongTable[h].offset, |
| 1154 | } |
| 1155 | |
| 1156 | end := int32(len(d.content)) - 8 + e.maxMatchOff |
| 1157 | off := 8 // First to read |
| 1158 | for i := e.maxMatchOff + 1; i < end; i++ { |
| 1159 | cv = cv>>8 | (uint64(d.content[off]) << 56) |
| 1160 | h := hashLen(cv, betterLongTableBits, betterLongLen) |
| 1161 | e.dictLongTable[h] = prevEntry{ |
| 1162 | offset: i, |
| 1163 | prev: e.dictLongTable[h].offset, |
| 1164 | } |
| 1165 | off++ |
| 1166 | } |
| 1167 | } |
| 1168 | e.lastDictID = d.id |
| 1169 | e.allDirty = true |
| 1170 | } |
| 1171 | |
| 1172 | // Reset table to initial state |
| 1173 | { |
| 1174 | dirtyShardCnt := 0 |
| 1175 | if !e.allDirty { |
| 1176 | for i := range e.shortTableShardDirty { |
| 1177 | if e.shortTableShardDirty[i] { |
| 1178 | dirtyShardCnt++ |
| 1179 | } |
| 1180 | } |
| 1181 | } |
| 1182 | const shardCnt = betterShortTableShardCnt |
| 1183 | const shardSize = betterShortTableShardSize |
| 1184 | if e.allDirty || dirtyShardCnt > shardCnt*4/6 { |
| 1185 | copy(e.table[:], e.dictTable) |
| 1186 | for i := range e.shortTableShardDirty { |
| 1187 | e.shortTableShardDirty[i] = false |
| 1188 | } |
| 1189 | } else { |
| 1190 | for i := range e.shortTableShardDirty { |
| 1191 | if !e.shortTableShardDirty[i] { |
| 1192 | continue |
| 1193 | } |
| 1194 | |
| 1195 | copy(e.table[i*shardSize:(i+1)*shardSize], e.dictTable[i*shardSize:(i+1)*shardSize]) |
| 1196 | e.shortTableShardDirty[i] = false |
| 1197 | } |
| 1198 | } |
| 1199 | } |
| 1200 | { |
| 1201 | dirtyShardCnt := 0 |
| 1202 | if !e.allDirty { |
| 1203 | for i := range e.shortTableShardDirty { |
| 1204 | if e.shortTableShardDirty[i] { |
| 1205 | dirtyShardCnt++ |
| 1206 | } |
| 1207 | } |
| 1208 | } |
| 1209 | const shardCnt = betterLongTableShardCnt |
| 1210 | const shardSize = betterLongTableShardSize |
| 1211 | if e.allDirty || dirtyShardCnt > shardCnt*4/6 { |
| 1212 | copy(e.longTable[:], e.dictLongTable) |
| 1213 | for i := range e.longTableShardDirty { |
| 1214 | e.longTableShardDirty[i] = false |
| 1215 | } |
| 1216 | } else { |
| 1217 | for i := range e.longTableShardDirty { |
| 1218 | if !e.longTableShardDirty[i] { |
| 1219 | continue |
| 1220 | } |
| 1221 | |
| 1222 | copy(e.longTable[i*shardSize:(i+1)*shardSize], e.dictLongTable[i*shardSize:(i+1)*shardSize]) |
| 1223 | e.longTableShardDirty[i] = false |
| 1224 | } |
| 1225 | } |
| 1226 | } |
| 1227 | e.cur = e.maxMatchOff |
| 1228 | e.allDirty = false |
| 1229 | } |
| 1230 | |
| 1231 | func (e *betterFastEncoderDict) markLongShardDirty(entryNum uint32) { |
| 1232 | e.longTableShardDirty[entryNum/betterLongTableShardSize] = true |
| 1233 | } |
| 1234 | |
| 1235 | func (e *betterFastEncoderDict) markShortShardDirty(entryNum uint32) { |
| 1236 | e.shortTableShardDirty[entryNum/betterShortTableShardSize] = true |
| 1237 | } |