blob: e1be092f3267cb3af5f79f5f9ef5f933cb552c59 [file] [log] [blame]
khenaidoo26721882021-08-11 17:42:52 -04001// 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
5package zstd
6
7import (
8 "errors"
9 "fmt"
10 "math"
11 "math/bits"
12
13 "github.com/klauspost/compress/huff0"
14)
15
16type blockEnc struct {
17 size int
18 literals []byte
19 sequences []seq
20 coders seqCoders
21 litEnc *huff0.Scratch
22 dictLitEnc *huff0.Scratch
23 wr bitWriter
24
25 extraLits int
26 output []byte
27 recentOffsets [3]uint32
28 prevRecentOffsets [3]uint32
29
30 last bool
31 lowMem bool
32}
33
34// init should be used once the block has been created.
35// If called more than once, the effect is the same as calling reset.
36func (b *blockEnc) init() {
37 if b.lowMem {
38 // 1K literals
39 if cap(b.literals) < 1<<10 {
40 b.literals = make([]byte, 0, 1<<10)
41 }
42 const defSeqs = 20
43 if cap(b.sequences) < defSeqs {
44 b.sequences = make([]seq, 0, defSeqs)
45 }
46 // 1K
47 if cap(b.output) < 1<<10 {
48 b.output = make([]byte, 0, 1<<10)
49 }
50 } else {
51 if cap(b.literals) < maxCompressedBlockSize {
52 b.literals = make([]byte, 0, maxCompressedBlockSize)
53 }
54 const defSeqs = 200
55 if cap(b.sequences) < defSeqs {
56 b.sequences = make([]seq, 0, defSeqs)
57 }
58 if cap(b.output) < maxCompressedBlockSize {
59 b.output = make([]byte, 0, maxCompressedBlockSize)
60 }
61 }
62
63 if b.coders.mlEnc == nil {
64 b.coders.mlEnc = &fseEncoder{}
65 b.coders.mlPrev = &fseEncoder{}
66 b.coders.ofEnc = &fseEncoder{}
67 b.coders.ofPrev = &fseEncoder{}
68 b.coders.llEnc = &fseEncoder{}
69 b.coders.llPrev = &fseEncoder{}
70 }
71 b.litEnc = &huff0.Scratch{WantLogLess: 4}
72 b.reset(nil)
73}
74
75// initNewEncode can be used to reset offsets and encoders to the initial state.
76func (b *blockEnc) initNewEncode() {
77 b.recentOffsets = [3]uint32{1, 4, 8}
78 b.litEnc.Reuse = huff0.ReusePolicyNone
79 b.coders.setPrev(nil, nil, nil)
80}
81
82// reset will reset the block for a new encode, but in the same stream,
83// meaning that state will be carried over, but the block content is reset.
84// If a previous block is provided, the recent offsets are carried over.
85func (b *blockEnc) reset(prev *blockEnc) {
86 b.extraLits = 0
87 b.literals = b.literals[:0]
88 b.size = 0
89 b.sequences = b.sequences[:0]
90 b.output = b.output[:0]
91 b.last = false
92 if prev != nil {
93 b.recentOffsets = prev.prevRecentOffsets
94 }
95 b.dictLitEnc = nil
96}
97
98// reset will reset the block for a new encode, but in the same stream,
99// meaning that state will be carried over, but the block content is reset.
100// If a previous block is provided, the recent offsets are carried over.
101func (b *blockEnc) swapEncoders(prev *blockEnc) {
102 b.coders.swap(&prev.coders)
103 b.litEnc, prev.litEnc = prev.litEnc, b.litEnc
104}
105
106// blockHeader contains the information for a block header.
107type blockHeader uint32
108
109// setLast sets the 'last' indicator on a block.
110func (h *blockHeader) setLast(b bool) {
111 if b {
112 *h = *h | 1
113 } else {
114 const mask = (1 << 24) - 2
115 *h = *h & mask
116 }
117}
118
119// setSize will store the compressed size of a block.
120func (h *blockHeader) setSize(v uint32) {
121 const mask = 7
122 *h = (*h)&mask | blockHeader(v<<3)
123}
124
125// setType sets the block type.
126func (h *blockHeader) setType(t blockType) {
127 const mask = 1 | (((1 << 24) - 1) ^ 7)
128 *h = (*h & mask) | blockHeader(t<<1)
129}
130
131// appendTo will append the block header to a slice.
132func (h blockHeader) appendTo(b []byte) []byte {
133 return append(b, uint8(h), uint8(h>>8), uint8(h>>16))
134}
135
136// String returns a string representation of the block.
137func (h blockHeader) String() string {
138 return fmt.Sprintf("Type: %d, Size: %d, Last:%t", (h>>1)&3, h>>3, h&1 == 1)
139}
140
141// literalsHeader contains literals header information.
142type literalsHeader uint64
143
144// setType can be used to set the type of literal block.
145func (h *literalsHeader) setType(t literalsBlockType) {
146 const mask = math.MaxUint64 - 3
147 *h = (*h & mask) | literalsHeader(t)
148}
149
150// setSize can be used to set a single size, for uncompressed and RLE content.
151func (h *literalsHeader) setSize(regenLen int) {
152 inBits := bits.Len32(uint32(regenLen))
153 // Only retain 2 bits
154 const mask = 3
155 lh := uint64(*h & mask)
156 switch {
157 case inBits < 5:
158 lh |= (uint64(regenLen) << 3) | (1 << 60)
159 if debug {
160 got := int(lh>>3) & 0xff
161 if got != regenLen {
162 panic(fmt.Sprint("litRegenSize = ", regenLen, "(want) != ", got, "(got)"))
163 }
164 }
165 case inBits < 12:
166 lh |= (1 << 2) | (uint64(regenLen) << 4) | (2 << 60)
167 case inBits < 20:
168 lh |= (3 << 2) | (uint64(regenLen) << 4) | (3 << 60)
169 default:
170 panic(fmt.Errorf("internal error: block too big (%d)", regenLen))
171 }
172 *h = literalsHeader(lh)
173}
174
175// setSizes will set the size of a compressed literals section and the input length.
176func (h *literalsHeader) setSizes(compLen, inLen int, single bool) {
177 compBits, inBits := bits.Len32(uint32(compLen)), bits.Len32(uint32(inLen))
178 // Only retain 2 bits
179 const mask = 3
180 lh := uint64(*h & mask)
181 switch {
182 case compBits <= 10 && inBits <= 10:
183 if !single {
184 lh |= 1 << 2
185 }
186 lh |= (uint64(inLen) << 4) | (uint64(compLen) << (10 + 4)) | (3 << 60)
187 if debug {
188 const mmask = (1 << 24) - 1
189 n := (lh >> 4) & mmask
190 if int(n&1023) != inLen {
191 panic(fmt.Sprint("regensize:", int(n&1023), "!=", inLen, inBits))
192 }
193 if int(n>>10) != compLen {
194 panic(fmt.Sprint("compsize:", int(n>>10), "!=", compLen, compBits))
195 }
196 }
197 case compBits <= 14 && inBits <= 14:
198 lh |= (2 << 2) | (uint64(inLen) << 4) | (uint64(compLen) << (14 + 4)) | (4 << 60)
199 if single {
200 panic("single stream used with more than 10 bits length.")
201 }
202 case compBits <= 18 && inBits <= 18:
203 lh |= (3 << 2) | (uint64(inLen) << 4) | (uint64(compLen) << (18 + 4)) | (5 << 60)
204 if single {
205 panic("single stream used with more than 10 bits length.")
206 }
207 default:
208 panic("internal error: block too big")
209 }
210 *h = literalsHeader(lh)
211}
212
213// appendTo will append the literals header to a byte slice.
214func (h literalsHeader) appendTo(b []byte) []byte {
215 size := uint8(h >> 60)
216 switch size {
217 case 1:
218 b = append(b, uint8(h))
219 case 2:
220 b = append(b, uint8(h), uint8(h>>8))
221 case 3:
222 b = append(b, uint8(h), uint8(h>>8), uint8(h>>16))
223 case 4:
224 b = append(b, uint8(h), uint8(h>>8), uint8(h>>16), uint8(h>>24))
225 case 5:
226 b = append(b, uint8(h), uint8(h>>8), uint8(h>>16), uint8(h>>24), uint8(h>>32))
227 default:
228 panic(fmt.Errorf("internal error: literalsHeader has invalid size (%d)", size))
229 }
230 return b
231}
232
233// size returns the output size with currently set values.
234func (h literalsHeader) size() int {
235 return int(h >> 60)
236}
237
238func (h literalsHeader) String() string {
239 return fmt.Sprintf("Type: %d, SizeFormat: %d, Size: 0x%d, Bytes:%d", literalsBlockType(h&3), (h>>2)&3, h&((1<<60)-1)>>4, h>>60)
240}
241
242// pushOffsets will push the recent offsets to the backup store.
243func (b *blockEnc) pushOffsets() {
244 b.prevRecentOffsets = b.recentOffsets
245}
246
247// pushOffsets will push the recent offsets to the backup store.
248func (b *blockEnc) popOffsets() {
249 b.recentOffsets = b.prevRecentOffsets
250}
251
252// matchOffset will adjust recent offsets and return the adjusted one,
253// if it matches a previous offset.
254func (b *blockEnc) matchOffset(offset, lits uint32) uint32 {
255 // Check if offset is one of the recent offsets.
256 // Adjusts the output offset accordingly.
257 // Gives a tiny bit of compression, typically around 1%.
258 if true {
259 if lits > 0 {
260 switch offset {
261 case b.recentOffsets[0]:
262 offset = 1
263 case b.recentOffsets[1]:
264 b.recentOffsets[1] = b.recentOffsets[0]
265 b.recentOffsets[0] = offset
266 offset = 2
267 case b.recentOffsets[2]:
268 b.recentOffsets[2] = b.recentOffsets[1]
269 b.recentOffsets[1] = b.recentOffsets[0]
270 b.recentOffsets[0] = offset
271 offset = 3
272 default:
273 b.recentOffsets[2] = b.recentOffsets[1]
274 b.recentOffsets[1] = b.recentOffsets[0]
275 b.recentOffsets[0] = offset
276 offset += 3
277 }
278 } else {
279 switch offset {
280 case b.recentOffsets[1]:
281 b.recentOffsets[1] = b.recentOffsets[0]
282 b.recentOffsets[0] = offset
283 offset = 1
284 case b.recentOffsets[2]:
285 b.recentOffsets[2] = b.recentOffsets[1]
286 b.recentOffsets[1] = b.recentOffsets[0]
287 b.recentOffsets[0] = offset
288 offset = 2
289 case b.recentOffsets[0] - 1:
290 b.recentOffsets[2] = b.recentOffsets[1]
291 b.recentOffsets[1] = b.recentOffsets[0]
292 b.recentOffsets[0] = offset
293 offset = 3
294 default:
295 b.recentOffsets[2] = b.recentOffsets[1]
296 b.recentOffsets[1] = b.recentOffsets[0]
297 b.recentOffsets[0] = offset
298 offset += 3
299 }
300 }
301 } else {
302 offset += 3
303 }
304 return offset
305}
306
307// encodeRaw can be used to set the output to a raw representation of supplied bytes.
308func (b *blockEnc) encodeRaw(a []byte) {
309 var bh blockHeader
310 bh.setLast(b.last)
311 bh.setSize(uint32(len(a)))
312 bh.setType(blockTypeRaw)
313 b.output = bh.appendTo(b.output[:0])
314 b.output = append(b.output, a...)
315 if debug {
316 println("Adding RAW block, length", len(a), "last:", b.last)
317 }
318}
319
320// encodeRaw can be used to set the output to a raw representation of supplied bytes.
321func (b *blockEnc) encodeRawTo(dst, src []byte) []byte {
322 var bh blockHeader
323 bh.setLast(b.last)
324 bh.setSize(uint32(len(src)))
325 bh.setType(blockTypeRaw)
326 dst = bh.appendTo(dst)
327 dst = append(dst, src...)
328 if debug {
329 println("Adding RAW block, length", len(src), "last:", b.last)
330 }
331 return dst
332}
333
334// encodeLits can be used if the block is only litLen.
335func (b *blockEnc) encodeLits(lits []byte, raw bool) error {
336 var bh blockHeader
337 bh.setLast(b.last)
338 bh.setSize(uint32(len(lits)))
339
340 // Don't compress extremely small blocks
341 if len(lits) < 8 || (len(lits) < 32 && b.dictLitEnc == nil) || raw {
342 if debug {
343 println("Adding RAW block, length", len(lits), "last:", b.last)
344 }
345 bh.setType(blockTypeRaw)
346 b.output = bh.appendTo(b.output)
347 b.output = append(b.output, lits...)
348 return nil
349 }
350
351 var (
352 out []byte
353 reUsed, single bool
354 err error
355 )
356 if b.dictLitEnc != nil {
357 b.litEnc.TransferCTable(b.dictLitEnc)
358 b.litEnc.Reuse = huff0.ReusePolicyAllow
359 b.dictLitEnc = nil
360 }
361 if len(lits) >= 1024 {
362 // Use 4 Streams.
363 out, reUsed, err = huff0.Compress4X(lits, b.litEnc)
364 } else if len(lits) > 32 {
365 // Use 1 stream
366 single = true
367 out, reUsed, err = huff0.Compress1X(lits, b.litEnc)
368 } else {
369 err = huff0.ErrIncompressible
370 }
371
372 switch err {
373 case huff0.ErrIncompressible:
374 if debug {
375 println("Adding RAW block, length", len(lits), "last:", b.last)
376 }
377 bh.setType(blockTypeRaw)
378 b.output = bh.appendTo(b.output)
379 b.output = append(b.output, lits...)
380 return nil
381 case huff0.ErrUseRLE:
382 if debug {
383 println("Adding RLE block, length", len(lits))
384 }
385 bh.setType(blockTypeRLE)
386 b.output = bh.appendTo(b.output)
387 b.output = append(b.output, lits[0])
388 return nil
389 case nil:
390 default:
391 return err
392 }
393 // Compressed...
394 // Now, allow reuse
395 b.litEnc.Reuse = huff0.ReusePolicyAllow
396 bh.setType(blockTypeCompressed)
397 var lh literalsHeader
398 if reUsed {
399 if debug {
400 println("Reused tree, compressed to", len(out))
401 }
402 lh.setType(literalsBlockTreeless)
403 } else {
404 if debug {
405 println("New tree, compressed to", len(out), "tree size:", len(b.litEnc.OutTable))
406 }
407 lh.setType(literalsBlockCompressed)
408 }
409 // Set sizes
410 lh.setSizes(len(out), len(lits), single)
411 bh.setSize(uint32(len(out) + lh.size() + 1))
412
413 // Write block headers.
414 b.output = bh.appendTo(b.output)
415 b.output = lh.appendTo(b.output)
416 // Add compressed data.
417 b.output = append(b.output, out...)
418 // No sequences.
419 b.output = append(b.output, 0)
420 return nil
421}
422
423// fuzzFseEncoder can be used to fuzz the FSE encoder.
424func fuzzFseEncoder(data []byte) int {
425 if len(data) > maxSequences || len(data) < 2 {
426 return 0
427 }
428 enc := fseEncoder{}
429 hist := enc.Histogram()[:256]
430 maxSym := uint8(0)
431 for i, v := range data {
432 v = v & 63
433 data[i] = v
434 hist[v]++
435 if v > maxSym {
436 maxSym = v
437 }
438 }
439 if maxSym == 0 {
440 // All 0
441 return 0
442 }
443 maxCount := func(a []uint32) int {
444 var max uint32
445 for _, v := range a {
446 if v > max {
447 max = v
448 }
449 }
450 return int(max)
451 }
452 cnt := maxCount(hist[:maxSym])
453 if cnt == len(data) {
454 // RLE
455 return 0
456 }
457 enc.HistogramFinished(maxSym, cnt)
458 err := enc.normalizeCount(len(data))
459 if err != nil {
460 return 0
461 }
462 _, err = enc.writeCount(nil)
463 if err != nil {
464 panic(err)
465 }
466 return 1
467}
468
469// encode will encode the block and append the output in b.output.
470// Previous offset codes must be pushed if more blocks are expected.
471func (b *blockEnc) encode(org []byte, raw, rawAllLits bool) error {
472 if len(b.sequences) == 0 {
473 return b.encodeLits(b.literals, rawAllLits)
474 }
475 // We want some difference to at least account for the headers.
476 saved := b.size - len(b.literals) - (b.size >> 5)
477 if saved < 16 {
478 if org == nil {
479 return errIncompressible
480 }
481 b.popOffsets()
482 return b.encodeLits(org, rawAllLits)
483 }
484
485 var bh blockHeader
486 var lh literalsHeader
487 bh.setLast(b.last)
488 bh.setType(blockTypeCompressed)
489 // Store offset of the block header. Needed when we know the size.
490 bhOffset := len(b.output)
491 b.output = bh.appendTo(b.output)
492
493 var (
494 out []byte
495 reUsed, single bool
496 err error
497 )
498 if b.dictLitEnc != nil {
499 b.litEnc.TransferCTable(b.dictLitEnc)
500 b.litEnc.Reuse = huff0.ReusePolicyAllow
501 b.dictLitEnc = nil
502 }
503 if len(b.literals) >= 1024 && !raw {
504 // Use 4 Streams.
505 out, reUsed, err = huff0.Compress4X(b.literals, b.litEnc)
506 } else if len(b.literals) > 32 && !raw {
507 // Use 1 stream
508 single = true
509 out, reUsed, err = huff0.Compress1X(b.literals, b.litEnc)
510 } else {
511 err = huff0.ErrIncompressible
512 }
513
514 switch err {
515 case huff0.ErrIncompressible:
516 lh.setType(literalsBlockRaw)
517 lh.setSize(len(b.literals))
518 b.output = lh.appendTo(b.output)
519 b.output = append(b.output, b.literals...)
520 if debug {
521 println("Adding literals RAW, length", len(b.literals))
522 }
523 case huff0.ErrUseRLE:
524 lh.setType(literalsBlockRLE)
525 lh.setSize(len(b.literals))
526 b.output = lh.appendTo(b.output)
527 b.output = append(b.output, b.literals[0])
528 if debug {
529 println("Adding literals RLE")
530 }
531 case nil:
532 // Compressed litLen...
533 if reUsed {
534 if debug {
535 println("reused tree")
536 }
537 lh.setType(literalsBlockTreeless)
538 } else {
539 if debug {
540 println("new tree, size:", len(b.litEnc.OutTable))
541 }
542 lh.setType(literalsBlockCompressed)
543 if debug {
544 _, _, err := huff0.ReadTable(out, nil)
545 if err != nil {
546 panic(err)
547 }
548 }
549 }
550 lh.setSizes(len(out), len(b.literals), single)
551 if debug {
552 printf("Compressed %d literals to %d bytes", len(b.literals), len(out))
553 println("Adding literal header:", lh)
554 }
555 b.output = lh.appendTo(b.output)
556 b.output = append(b.output, out...)
557 b.litEnc.Reuse = huff0.ReusePolicyAllow
558 if debug {
559 println("Adding literals compressed")
560 }
561 default:
562 if debug {
563 println("Adding literals ERROR:", err)
564 }
565 return err
566 }
567 // Sequence compression
568
569 // Write the number of sequences
570 switch {
571 case len(b.sequences) < 128:
572 b.output = append(b.output, uint8(len(b.sequences)))
573 case len(b.sequences) < 0x7f00: // TODO: this could be wrong
574 n := len(b.sequences)
575 b.output = append(b.output, 128+uint8(n>>8), uint8(n))
576 default:
577 n := len(b.sequences) - 0x7f00
578 b.output = append(b.output, 255, uint8(n), uint8(n>>8))
579 }
580 if debug {
581 println("Encoding", len(b.sequences), "sequences")
582 }
583 b.genCodes()
584 llEnc := b.coders.llEnc
585 ofEnc := b.coders.ofEnc
586 mlEnc := b.coders.mlEnc
587 err = llEnc.normalizeCount(len(b.sequences))
588 if err != nil {
589 return err
590 }
591 err = ofEnc.normalizeCount(len(b.sequences))
592 if err != nil {
593 return err
594 }
595 err = mlEnc.normalizeCount(len(b.sequences))
596 if err != nil {
597 return err
598 }
599
600 // Choose the best compression mode for each type.
601 // Will evaluate the new vs predefined and previous.
602 chooseComp := func(cur, prev, preDef *fseEncoder) (*fseEncoder, seqCompMode) {
603 // See if predefined/previous is better
604 hist := cur.count[:cur.symbolLen]
605 nSize := cur.approxSize(hist) + cur.maxHeaderSize()
606 predefSize := preDef.approxSize(hist)
607 prevSize := prev.approxSize(hist)
608
609 // Add a small penalty for new encoders.
610 // Don't bother with extremely small (<2 byte gains).
611 nSize = nSize + (nSize+2*8*16)>>4
612 switch {
613 case predefSize <= prevSize && predefSize <= nSize || forcePreDef:
614 if debug {
615 println("Using predefined", predefSize>>3, "<=", nSize>>3)
616 }
617 return preDef, compModePredefined
618 case prevSize <= nSize:
619 if debug {
620 println("Using previous", prevSize>>3, "<=", nSize>>3)
621 }
622 return prev, compModeRepeat
623 default:
624 if debug {
625 println("Using new, predef", predefSize>>3, ". previous:", prevSize>>3, ">", nSize>>3, "header max:", cur.maxHeaderSize()>>3, "bytes")
626 println("tl:", cur.actualTableLog, "symbolLen:", cur.symbolLen, "norm:", cur.norm[:cur.symbolLen], "hist", cur.count[:cur.symbolLen])
627 }
628 return cur, compModeFSE
629 }
630 }
631
632 // Write compression mode
633 var mode uint8
634 if llEnc.useRLE {
635 mode |= uint8(compModeRLE) << 6
636 llEnc.setRLE(b.sequences[0].llCode)
637 if debug {
638 println("llEnc.useRLE")
639 }
640 } else {
641 var m seqCompMode
642 llEnc, m = chooseComp(llEnc, b.coders.llPrev, &fsePredefEnc[tableLiteralLengths])
643 mode |= uint8(m) << 6
644 }
645 if ofEnc.useRLE {
646 mode |= uint8(compModeRLE) << 4
647 ofEnc.setRLE(b.sequences[0].ofCode)
648 if debug {
649 println("ofEnc.useRLE")
650 }
651 } else {
652 var m seqCompMode
653 ofEnc, m = chooseComp(ofEnc, b.coders.ofPrev, &fsePredefEnc[tableOffsets])
654 mode |= uint8(m) << 4
655 }
656
657 if mlEnc.useRLE {
658 mode |= uint8(compModeRLE) << 2
659 mlEnc.setRLE(b.sequences[0].mlCode)
660 if debug {
661 println("mlEnc.useRLE, code: ", b.sequences[0].mlCode, "value", b.sequences[0].matchLen)
662 }
663 } else {
664 var m seqCompMode
665 mlEnc, m = chooseComp(mlEnc, b.coders.mlPrev, &fsePredefEnc[tableMatchLengths])
666 mode |= uint8(m) << 2
667 }
668 b.output = append(b.output, mode)
669 if debug {
670 printf("Compression modes: 0b%b", mode)
671 }
672 b.output, err = llEnc.writeCount(b.output)
673 if err != nil {
674 return err
675 }
676 start := len(b.output)
677 b.output, err = ofEnc.writeCount(b.output)
678 if err != nil {
679 return err
680 }
681 if false {
682 println("block:", b.output[start:], "tablelog", ofEnc.actualTableLog, "maxcount:", ofEnc.maxCount)
683 fmt.Printf("selected TableLog: %d, Symbol length: %d\n", ofEnc.actualTableLog, ofEnc.symbolLen)
684 for i, v := range ofEnc.norm[:ofEnc.symbolLen] {
685 fmt.Printf("%3d: %5d -> %4d \n", i, ofEnc.count[i], v)
686 }
687 }
688 b.output, err = mlEnc.writeCount(b.output)
689 if err != nil {
690 return err
691 }
692
693 // Maybe in block?
694 wr := &b.wr
695 wr.reset(b.output)
696
697 var ll, of, ml cState
698
699 // Current sequence
700 seq := len(b.sequences) - 1
701 s := b.sequences[seq]
702 llEnc.setBits(llBitsTable[:])
703 mlEnc.setBits(mlBitsTable[:])
704 ofEnc.setBits(nil)
705
706 llTT, ofTT, mlTT := llEnc.ct.symbolTT[:256], ofEnc.ct.symbolTT[:256], mlEnc.ct.symbolTT[:256]
707
708 // We have 3 bounds checks here (and in the loop).
709 // Since we are iterating backwards it is kinda hard to avoid.
710 llB, ofB, mlB := llTT[s.llCode], ofTT[s.ofCode], mlTT[s.mlCode]
711 ll.init(wr, &llEnc.ct, llB)
712 of.init(wr, &ofEnc.ct, ofB)
713 wr.flush32()
714 ml.init(wr, &mlEnc.ct, mlB)
715
716 // Each of these lookups also generates a bounds check.
717 wr.addBits32NC(s.litLen, llB.outBits)
718 wr.addBits32NC(s.matchLen, mlB.outBits)
719 wr.flush32()
720 wr.addBits32NC(s.offset, ofB.outBits)
721 if debugSequences {
722 println("Encoded seq", seq, s, "codes:", s.llCode, s.mlCode, s.ofCode, "states:", ll.state, ml.state, of.state, "bits:", llB, mlB, ofB)
723 }
724 seq--
725 if llEnc.maxBits+mlEnc.maxBits+ofEnc.maxBits <= 32 {
726 // No need to flush (common)
727 for seq >= 0 {
728 s = b.sequences[seq]
729 wr.flush32()
730 llB, ofB, mlB := llTT[s.llCode], ofTT[s.ofCode], mlTT[s.mlCode]
731 // tabelog max is 8 for all.
732 of.encode(ofB)
733 ml.encode(mlB)
734 ll.encode(llB)
735 wr.flush32()
736
737 // We checked that all can stay within 32 bits
738 wr.addBits32NC(s.litLen, llB.outBits)
739 wr.addBits32NC(s.matchLen, mlB.outBits)
740 wr.addBits32NC(s.offset, ofB.outBits)
741
742 if debugSequences {
743 println("Encoded seq", seq, s)
744 }
745
746 seq--
747 }
748 } else {
749 for seq >= 0 {
750 s = b.sequences[seq]
751 wr.flush32()
752 llB, ofB, mlB := llTT[s.llCode], ofTT[s.ofCode], mlTT[s.mlCode]
753 // tabelog max is below 8 for each.
754 of.encode(ofB)
755 ml.encode(mlB)
756 ll.encode(llB)
757 wr.flush32()
758
759 // ml+ll = max 32 bits total
760 wr.addBits32NC(s.litLen, llB.outBits)
761 wr.addBits32NC(s.matchLen, mlB.outBits)
762 wr.flush32()
763 wr.addBits32NC(s.offset, ofB.outBits)
764
765 if debugSequences {
766 println("Encoded seq", seq, s)
767 }
768
769 seq--
770 }
771 }
772 ml.flush(mlEnc.actualTableLog)
773 of.flush(ofEnc.actualTableLog)
774 ll.flush(llEnc.actualTableLog)
775 err = wr.close()
776 if err != nil {
777 return err
778 }
779 b.output = wr.out
780
781 if len(b.output)-3-bhOffset >= b.size {
782 // Maybe even add a bigger margin.
783 b.litEnc.Reuse = huff0.ReusePolicyNone
784 return errIncompressible
785 }
786
787 // Size is output minus block header.
788 bh.setSize(uint32(len(b.output)-bhOffset) - 3)
789 if debug {
790 println("Rewriting block header", bh)
791 }
792 _ = bh.appendTo(b.output[bhOffset:bhOffset])
793 b.coders.setPrev(llEnc, mlEnc, ofEnc)
794 return nil
795}
796
797var errIncompressible = errors.New("incompressible")
798
799func (b *blockEnc) genCodes() {
800 if len(b.sequences) == 0 {
801 // nothing to do
802 return
803 }
804
805 if len(b.sequences) > math.MaxUint16 {
806 panic("can only encode up to 64K sequences")
807 }
808 // No bounds checks after here:
809 llH := b.coders.llEnc.Histogram()[:256]
810 ofH := b.coders.ofEnc.Histogram()[:256]
811 mlH := b.coders.mlEnc.Histogram()[:256]
812 for i := range llH {
813 llH[i] = 0
814 }
815 for i := range ofH {
816 ofH[i] = 0
817 }
818 for i := range mlH {
819 mlH[i] = 0
820 }
821
822 var llMax, ofMax, mlMax uint8
823 for i, seq := range b.sequences {
824 v := llCode(seq.litLen)
825 seq.llCode = v
826 llH[v]++
827 if v > llMax {
828 llMax = v
829 }
830
831 v = ofCode(seq.offset)
832 seq.ofCode = v
833 ofH[v]++
834 if v > ofMax {
835 ofMax = v
836 }
837
838 v = mlCode(seq.matchLen)
839 seq.mlCode = v
840 mlH[v]++
841 if v > mlMax {
842 mlMax = v
843 if debugAsserts && mlMax > maxMatchLengthSymbol {
844 panic(fmt.Errorf("mlMax > maxMatchLengthSymbol (%d), matchlen: %d", mlMax, seq.matchLen))
845 }
846 }
847 b.sequences[i] = seq
848 }
849 maxCount := func(a []uint32) int {
850 var max uint32
851 for _, v := range a {
852 if v > max {
853 max = v
854 }
855 }
856 return int(max)
857 }
858 if debugAsserts && mlMax > maxMatchLengthSymbol {
859 panic(fmt.Errorf("mlMax > maxMatchLengthSymbol (%d)", mlMax))
860 }
861 if debugAsserts && ofMax > maxOffsetBits {
862 panic(fmt.Errorf("ofMax > maxOffsetBits (%d)", ofMax))
863 }
864 if debugAsserts && llMax > maxLiteralLengthSymbol {
865 panic(fmt.Errorf("llMax > maxLiteralLengthSymbol (%d)", llMax))
866 }
867
868 b.coders.mlEnc.HistogramFinished(mlMax, maxCount(mlH[:mlMax+1]))
869 b.coders.ofEnc.HistogramFinished(ofMax, maxCount(ofH[:ofMax+1]))
870 b.coders.llEnc.HistogramFinished(llMax, maxCount(llH[:llMax+1]))
871}