Update dependencies (#5518)

vendor/github.com/klauspost/compress/zstd/enc_dfast.go

@@ -4,14 +4,22 @@
 
 package zstd
 
+import "fmt"
+
 const (
 	dFastLongTableBits = 17                      // Bits used in the long match table
 	dFastLongTableSize = 1 << dFastLongTableBits // Size of the table
 	dFastLongTableMask = dFastLongTableSize - 1  // Mask for table indices. Redundant, but can eliminate bounds checks.
+	dFastLongLen       = 8                       // Bytes used for table hash
+
+	dLongTableShardCnt  = 1 << (dFastLongTableBits - dictShardBits) // Number of shards in the table
+	dLongTableShardSize = dFastLongTableSize / tableShardCnt        // Size of an individual shard
 
 	dFastShortTableBits = tableBits                // Bits used in the short match table
 	dFastShortTableSize = 1 << dFastShortTableBits // Size of the table
 	dFastShortTableMask = dFastShortTableSize - 1  // Mask for table indices. Redundant, but can eliminate bounds checks.
+	dFastShortLen       = 5                        // Bytes used for table hash
+
 )
 
 type doubleFastEncoder struct {
@@ -19,6 +27,13 @@ type doubleFastEncoder struct {
 	longTable [dFastLongTableSize]tableEntry
 }
 
+type doubleFastEncoderDict struct {
+	fastEncoderDict
+	longTable           [dFastLongTableSize]tableEntry
+	dictLongTable       []tableEntry
+	longTableShardDirty [dLongTableShardCnt]bool
+}
+
 // Encode mimmics functionality in zstd_dfast.c
 func (e *doubleFastEncoder) Encode(blk *blockEnc, src []byte) {
 	const (
@@ -29,7 +44,7 @@ func (e *doubleFastEncoder) Encode(blk *blockEnc, src []byte) {
 	)
 
 	// Protect against e.cur wraparound.
-	for e.cur > (1<<30)+e.maxMatchOff {
+	for e.cur >= bufferReset {
 		if len(e.hist) == 0 {
 			for i := range e.table[:] {
 				e.table[i] = tableEntry{}
@@ -61,6 +76,7 @@ func (e *doubleFastEncoder) Encode(blk *blockEnc, src []byte) {
 			e.longTable[i].offset = v
 		}
 		e.cur = e.maxMatchOff
+		break
 	}
 
 	s := e.addBlock(src)
@@ -77,10 +93,7 @@ func (e *doubleFastEncoder) Encode(blk *blockEnc, src []byte) {
 	sLimit := int32(len(src)) - inputMargin
 	// stepSize is the number of bytes to skip on every main loop iteration.
 	// It should be >= 1.
-	stepSize := int32(e.o.targetLength)
-	if stepSize == 0 {
-		stepSize++
-	}
+	const stepSize = 1
 
 	const kSearchStrength = 8
 
@@ -99,7 +112,7 @@ func (e *doubleFastEncoder) Encode(blk *blockEnc, src []byte) {
 		blk.literals = append(blk.literals, src[nextEmit:until]...)
 		s.litLen = uint32(until - nextEmit)
 	}
-	if debug {
+	if debugEncoder {
 		println("recent offsets:", blk.recentOffsets)
 	}
 
@@ -110,12 +123,12 @@ encodeLoop:
 		canRepeat := len(blk.sequences) > 2
 
 		for {
-			if debug && canRepeat && offset1 == 0 {
+			if debugAsserts && canRepeat && offset1 == 0 {
 				panic("offset0 was 0")
 			}
 
-			nextHashS := hash5(cv, dFastShortTableBits)
-			nextHashL := hash8(cv, dFastLongTableBits)
+			nextHashS := hashLen(cv, dFastShortTableBits, dFastShortLen)
+			nextHashL := hashLen(cv, dFastLongTableBits, dFastLongLen)
 			candidateL := e.longTable[nextHashL]
 			candidateS := e.table[nextHashS]
 
@@ -160,7 +173,7 @@ encodeLoop:
 					s += lenght + repOff
 					nextEmit = s
 					if s >= sLimit {
-						if debug {
+						if debugEncoder {
 							println("repeat ended", s, lenght)
 
 						}
@@ -169,55 +182,6 @@ encodeLoop:
 					cv = load6432(src, s)
 					continue
 				}
-				const repOff2 = 1
-				// We deviate from the reference encoder and also check offset 2.
-				// Slower and not consistently better, so disabled.
-				// repIndex = s - offset2 + repOff2
-				if false && repIndex >= 0 && load3232(src, repIndex) == uint32(cv>>(repOff2*8)) {
-					// Consider history as well.
-					var seq seq
-					lenght := 4 + e.matchlen(s+4+repOff2, repIndex+4, src)
-
-					seq.matchLen = uint32(lenght - zstdMinMatch)
-
-					// We might be able to match backwards.
-					// Extend as long as we can.
-					start := s + repOff2
-					// We end the search early, so we don't risk 0 literals
-					// and have to do special offset treatment.
-					startLimit := nextEmit + 1
-
-					tMin := s - e.maxMatchOff
-					if tMin < 0 {
-						tMin = 0
-					}
-					for repIndex > tMin && start > startLimit && src[repIndex-1] == src[start-1] && seq.matchLen < maxMatchLength-zstdMinMatch-1 {
-						repIndex--
-						start--
-						seq.matchLen++
-					}
-					addLiterals(&seq, start)
-
-					// rep 2
-					seq.offset = 2
-					if debugSequences {
-						println("repeat sequence 2", seq, "next s:", s)
-					}
-					blk.sequences = append(blk.sequences, seq)
-					s += lenght + repOff2
-					nextEmit = s
-					if s >= sLimit {
-						if debug {
-							println("repeat ended", s, lenght)
-
-						}
-						break encodeLoop
-					}
-					cv = load6432(src, s)
-					// Swap offsets
-					offset1, offset2 = offset2, offset1
-					continue
-				}
 			}
 			// Find the offsets of our two matches.
 			coffsetL := s - (candidateL.offset - e.cur)
@@ -229,10 +193,10 @@ encodeLoop:
 				// Reference encoder checks all 8 bytes, we only check 4,
 				// but the likelihood of both the first 4 bytes and the hash matching should be enough.
 				t = candidateL.offset - e.cur
-				if debug && s <= t {
-					panic("s <= t")
+				if debugAsserts && s <= t {
+					panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
 				}
-				if debug && s-t > e.maxMatchOff {
+				if debugAsserts && s-t > e.maxMatchOff {
 					panic("s - t >e.maxMatchOff")
 				}
 				if debugMatches {
@@ -247,7 +211,7 @@ encodeLoop:
 				// See if we can find a long match at s+1
 				const checkAt = 1
 				cv := load6432(src, s+checkAt)
-				nextHashL = hash8(cv, dFastLongTableBits)
+				nextHashL = hashLen(cv, dFastLongTableBits, dFastLongLen)
 				candidateL = e.longTable[nextHashL]
 				coffsetL = s - (candidateL.offset - e.cur) + checkAt
 
@@ -266,13 +230,13 @@ encodeLoop:
 				}
 
 				t = candidateS.offset - e.cur
-				if debug && s <= t {
-					panic("s <= t")
+				if debugAsserts && s <= t {
+					panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
 				}
-				if debug && s-t > e.maxMatchOff {
+				if debugAsserts && s-t > e.maxMatchOff {
 					panic("s - t >e.maxMatchOff")
 				}
-				if debug && t < 0 {
+				if debugAsserts && t < 0 {
 					panic("t<0")
 				}
 				if debugMatches {
@@ -294,11 +258,11 @@ encodeLoop:
 		offset2 = offset1
 		offset1 = s - t
 
-		if debug && s <= t {
-			panic("s <= t")
+		if debugAsserts && s <= t {
+			panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
 		}
 
-		if debug && canRepeat && int(offset1) > len(src) {
+		if debugAsserts && canRepeat && int(offset1) > len(src) {
 			panic("invalid offset")
 		}
 
@@ -343,16 +307,16 @@ encodeLoop:
 		cv1 := load6432(src, index1)
 		te0 := tableEntry{offset: index0 + e.cur, val: uint32(cv0)}
 		te1 := tableEntry{offset: index1 + e.cur, val: uint32(cv1)}
-		e.longTable[hash8(cv0, dFastLongTableBits)] = te0
-		e.longTable[hash8(cv1, dFastLongTableBits)] = te1
+		e.longTable[hashLen(cv0, dFastLongTableBits, dFastLongLen)] = te0
+		e.longTable[hashLen(cv1, dFastLongTableBits, dFastLongLen)] = te1
 		cv0 >>= 8
 		cv1 >>= 8
 		te0.offset++
 		te1.offset++
 		te0.val = uint32(cv0)
 		te1.val = uint32(cv1)
-		e.table[hash5(cv0, dFastShortTableBits)] = te0
-		e.table[hash5(cv1, dFastShortTableBits)] = te1
+		e.table[hashLen(cv0, dFastShortTableBits, dFastShortLen)] = te0
+		e.table[hashLen(cv1, dFastShortTableBits, dFastShortLen)] = te1
 
 		cv = load6432(src, s)
 
@@ -369,8 +333,8 @@ encodeLoop:
 			}
 
 			// Store this, since we have it.
-			nextHashS := hash5(cv1>>8, dFastShortTableBits)
-			nextHashL := hash8(cv, dFastLongTableBits)
+			nextHashS := hashLen(cv, dFastShortTableBits, dFastShortLen)
+			nextHashL := hashLen(cv, dFastLongTableBits, dFastLongLen)
 
 			// We have at least 4 byte match.
 			// No need to check backwards. We come straight from a match
@@ -407,7 +371,7 @@ encodeLoop:
 	}
 	blk.recentOffsets[0] = uint32(offset1)
 	blk.recentOffsets[1] = uint32(offset2)
-	if debug {
+	if debugEncoder {
 		println("returning, recent offsets:", blk.recentOffsets, "extra literals:", blk.extraLits)
 	}
 }
@@ -424,7 +388,7 @@ func (e *doubleFastEncoder) EncodeNoHist(blk *blockEnc, src []byte) {
 	)
 
 	// Protect against e.cur wraparound.
-	if e.cur > (1<<30)+e.maxMatchOff {
+	if e.cur >= bufferReset {
 		for i := range e.table[:] {
 			e.table[i] = tableEntry{}
 		}
@@ -447,10 +411,7 @@ func (e *doubleFastEncoder) EncodeNoHist(blk *blockEnc, src []byte) {
 	sLimit := int32(len(src)) - inputMargin
 	// stepSize is the number of bytes to skip on every main loop iteration.
 	// It should be >= 1.
-	stepSize := int32(e.o.targetLength)
-	if stepSize == 0 {
-		stepSize++
-	}
+	const stepSize = 1
 
 	const kSearchStrength = 8
 
@@ -469,7 +430,7 @@ func (e *doubleFastEncoder) EncodeNoHist(blk *blockEnc, src []byte) {
 		blk.literals = append(blk.literals, src[nextEmit:until]...)
 		s.litLen = uint32(until - nextEmit)
 	}
-	if debug {
+	if debugEncoder {
 		println("recent offsets:", blk.recentOffsets)
 	}
 
@@ -478,8 +439,8 @@ encodeLoop:
 		var t int32
 		for {
 
-			nextHashS := hash5(cv, dFastShortTableBits)
-			nextHashL := hash8(cv, dFastLongTableBits)
+			nextHashS := hashLen(cv, dFastShortTableBits, dFastShortLen)
+			nextHashL := hashLen(cv, dFastLongTableBits, dFastLongLen)
 			candidateL := e.longTable[nextHashL]
 			candidateS := e.table[nextHashS]
 
@@ -525,7 +486,7 @@ encodeLoop:
 					s += length + repOff
 					nextEmit = s
 					if s >= sLimit {
-						if debug {
+						if debugEncoder {
 							println("repeat ended", s, length)
 
 						}
@@ -545,10 +506,10 @@ encodeLoop:
 				// Reference encoder checks all 8 bytes, we only check 4,
 				// but the likelihood of both the first 4 bytes and the hash matching should be enough.
 				t = candidateL.offset - e.cur
-				if debug && s <= t {
-					panic("s <= t")
+				if debugAsserts && s <= t {
+					panic(fmt.Sprintf("s (%d) <= t (%d). cur: %d", s, t, e.cur))
 				}
-				if debug && s-t > e.maxMatchOff {
+				if debugAsserts && s-t > e.maxMatchOff {
 					panic("s - t >e.maxMatchOff")
 				}
 				if debugMatches {
@@ -563,7 +524,7 @@ encodeLoop:
 				// See if we can find a long match at s+1
 				const checkAt = 1
 				cv := load6432(src, s+checkAt)
-				nextHashL = hash8(cv, dFastLongTableBits)
+				nextHashL = hashLen(cv, dFastLongTableBits, dFastLongLen)
 				candidateL = e.longTable[nextHashL]
 				coffsetL = s - (candidateL.offset - e.cur) + checkAt
 
@@ -582,13 +543,13 @@ encodeLoop:
 				}
 
 				t = candidateS.offset - e.cur
-				if debug && s <= t {
-					panic("s <= t")
+				if debugAsserts && s <= t {
+					panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
 				}
-				if debug && s-t > e.maxMatchOff {
+				if debugAsserts && s-t > e.maxMatchOff {
 					panic("s - t >e.maxMatchOff")
 				}
-				if debug && t < 0 {
+				if debugAsserts && t < 0 {
 					panic("t<0")
 				}
 				if debugMatches {
@@ -610,8 +571,8 @@ encodeLoop:
 		offset2 = offset1
 		offset1 = s - t
 
-		if debug && s <= t {
-			panic("s <= t")
+		if debugAsserts && s <= t {
+			panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
 		}
 
 		// Extend the 4-byte match as long as possible.
@@ -656,16 +617,16 @@ encodeLoop:
 		cv1 := load6432(src, index1)
 		te0 := tableEntry{offset: index0 + e.cur, val: uint32(cv0)}
 		te1 := tableEntry{offset: index1 + e.cur, val: uint32(cv1)}
-		e.longTable[hash8(cv0, dFastLongTableBits)] = te0
-		e.longTable[hash8(cv1, dFastLongTableBits)] = te1
+		e.longTable[hashLen(cv0, dFastLongTableBits, dFastLongLen)] = te0
+		e.longTable[hashLen(cv1, dFastLongTableBits, dFastLongLen)] = te1
 		cv0 >>= 8
 		cv1 >>= 8
 		te0.offset++
 		te1.offset++
 		te0.val = uint32(cv0)
 		te1.val = uint32(cv1)
-		e.table[hash5(cv0, dFastShortTableBits)] = te0
-		e.table[hash5(cv1, dFastShortTableBits)] = te1
+		e.table[hashLen(cv0, dFastShortTableBits, dFastShortLen)] = te0
+		e.table[hashLen(cv1, dFastShortTableBits, dFastShortLen)] = te1
 
 		cv = load6432(src, s)
 
@@ -682,8 +643,8 @@ encodeLoop:
 			}
 
 			// Store this, since we have it.
-			nextHashS := hash5(cv1>>8, dFastShortTableBits)
-			nextHashL := hash8(cv, dFastLongTableBits)
+			nextHashS := hashLen(cv1>>8, dFastShortTableBits, dFastShortLen)
+			nextHashL := hashLen(cv, dFastLongTableBits, dFastLongLen)
 
 			// We have at least 4 byte match.
 			// No need to check backwards. We come straight from a match
@@ -719,8 +680,445 @@ encodeLoop:
 		blk.literals = append(blk.literals, src[nextEmit:]...)
 		blk.extraLits = len(src) - int(nextEmit)
 	}
-	if debug {
+	if debugEncoder {
 		println("returning, recent offsets:", blk.recentOffsets, "extra literals:", blk.extraLits)
 	}
 
+	// We do not store history, so we must offset e.cur to avoid false matches for next user.
+	if e.cur < bufferReset {
+		e.cur += int32(len(src))
+	}
+}
+
+// Encode will encode the content, with a dictionary if initialized for it.
+func (e *doubleFastEncoderDict) Encode(blk *blockEnc, src []byte) {
+	const (
+		// Input margin is the number of bytes we read (8)
+		// and the maximum we will read ahead (2)
+		inputMargin            = 8 + 2
+		minNonLiteralBlockSize = 16
+	)
+
+	// Protect against e.cur wraparound.
+	for e.cur >= bufferReset {
+		if len(e.hist) == 0 {
+			for i := range e.table[:] {
+				e.table[i] = tableEntry{}
+			}
+			for i := range e.longTable[:] {
+				e.longTable[i] = tableEntry{}
+			}
+			e.markAllShardsDirty()
+			e.cur = e.maxMatchOff
+			break
+		}
+		// Shift down everything in the table that isn't already too far away.
+		minOff := e.cur + int32(len(e.hist)) - e.maxMatchOff
+		for i := range e.table[:] {
+			v := e.table[i].offset
+			if v < minOff {
+				v = 0
+			} else {
+				v = v - e.cur + e.maxMatchOff
+			}
+			e.table[i].offset = v
+		}
+		for i := range e.longTable[:] {
+			v := e.longTable[i].offset
+			if v < minOff {
+				v = 0
+			} else {
+				v = v - e.cur + e.maxMatchOff
+			}
+			e.longTable[i].offset = v
+		}
+		e.markAllShardsDirty()
+		e.cur = e.maxMatchOff
+		break
+	}
+
+	s := e.addBlock(src)
+	blk.size = len(src)
+	if len(src) < minNonLiteralBlockSize {
+		blk.extraLits = len(src)
+		blk.literals = blk.literals[:len(src)]
+		copy(blk.literals, src)
+		return
+	}
+
+	// Override src
+	src = e.hist
+	sLimit := int32(len(src)) - inputMargin
+	// stepSize is the number of bytes to skip on every main loop iteration.
+	// It should be >= 1.
+	const stepSize = 1
+
+	const kSearchStrength = 8
+
+	// nextEmit is where in src the next emitLiteral should start from.
+	nextEmit := s
+	cv := load6432(src, s)
+
+	// Relative offsets
+	offset1 := int32(blk.recentOffsets[0])
+	offset2 := int32(blk.recentOffsets[1])
+
+	addLiterals := func(s *seq, until int32) {
+		if until == nextEmit {
+			return
+		}
+		blk.literals = append(blk.literals, src[nextEmit:until]...)
+		s.litLen = uint32(until - nextEmit)
+	}
+	if debugEncoder {
+		println("recent offsets:", blk.recentOffsets)
+	}
+
+encodeLoop:
+	for {
+		var t int32
+		// We allow the encoder to optionally turn off repeat offsets across blocks
+		canRepeat := len(blk.sequences) > 2
+
+		for {
+			if debugAsserts && canRepeat && offset1 == 0 {
+				panic("offset0 was 0")
+			}
+
+			nextHashS := hashLen(cv, dFastShortTableBits, dFastShortLen)
+			nextHashL := hashLen(cv, dFastLongTableBits, dFastLongLen)
+			candidateL := e.longTable[nextHashL]
+			candidateS := e.table[nextHashS]
+
+			const repOff = 1
+			repIndex := s - offset1 + repOff
+			entry := tableEntry{offset: s + e.cur, val: uint32(cv)}
+			e.longTable[nextHashL] = entry
+			e.markLongShardDirty(nextHashL)
+			e.table[nextHashS] = entry
+			e.markShardDirty(nextHashS)
+
+			if canRepeat {
+				if repIndex >= 0 && load3232(src, repIndex) == uint32(cv>>(repOff*8)) {
+					// Consider history as well.
+					var seq seq
+					lenght := 4 + e.matchlen(s+4+repOff, repIndex+4, src)
+
+					seq.matchLen = uint32(lenght - zstdMinMatch)
+
+					// We might be able to match backwards.
+					// Extend as long as we can.
+					start := s + repOff
+					// We end the search early, so we don't risk 0 literals
+					// and have to do special offset treatment.
+					startLimit := nextEmit + 1
+
+					tMin := s - e.maxMatchOff
+					if tMin < 0 {
+						tMin = 0
+					}
+					for repIndex > tMin && start > startLimit && src[repIndex-1] == src[start-1] && seq.matchLen < maxMatchLength-zstdMinMatch-1 {
+						repIndex--
+						start--
+						seq.matchLen++
+					}
+					addLiterals(&seq, start)
+
+					// rep 0
+					seq.offset = 1
+					if debugSequences {
+						println("repeat sequence", seq, "next s:", s)
+					}
+					blk.sequences = append(blk.sequences, seq)
+					s += lenght + repOff
+					nextEmit = s
+					if s >= sLimit {
+						if debugEncoder {
+							println("repeat ended", s, lenght)
+
+						}
+						break encodeLoop
+					}
+					cv = load6432(src, s)
+					continue
+				}
+			}
+			// Find the offsets of our two matches.
+			coffsetL := s - (candidateL.offset - e.cur)
+			coffsetS := s - (candidateS.offset - e.cur)
+
+			// Check if we have a long match.
+			if coffsetL < e.maxMatchOff && uint32(cv) == candidateL.val {
+				// Found a long match, likely at least 8 bytes.
+				// Reference encoder checks all 8 bytes, we only check 4,
+				// but the likelihood of both the first 4 bytes and the hash matching should be enough.
+				t = candidateL.offset - e.cur
+				if debugAsserts && s <= t {
+					panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
+				}
+				if debugAsserts && s-t > e.maxMatchOff {
+					panic("s - t >e.maxMatchOff")
+				}
+				if debugMatches {
+					println("long match")
+				}
+				break
+			}
+
+			// Check if we have a short match.
+			if coffsetS < e.maxMatchOff && uint32(cv) == candidateS.val {
+				// found a regular match
+				// See if we can find a long match at s+1
+				const checkAt = 1
+				cv := load6432(src, s+checkAt)
+				nextHashL = hashLen(cv, dFastLongTableBits, dFastLongLen)
+				candidateL = e.longTable[nextHashL]
+				coffsetL = s - (candidateL.offset - e.cur) + checkAt
+
+				// We can store it, since we have at least a 4 byte match.
+				e.longTable[nextHashL] = tableEntry{offset: s + checkAt + e.cur, val: uint32(cv)}
+				e.markLongShardDirty(nextHashL)
+				if coffsetL < e.maxMatchOff && uint32(cv) == candidateL.val {
+					// Found a long match, likely at least 8 bytes.
+					// Reference encoder checks all 8 bytes, we only check 4,
+					// but the likelihood of both the first 4 bytes and the hash matching should be enough.
+					t = candidateL.offset - e.cur
+					s += checkAt
+					if debugMatches {
+						println("long match (after short)")
+					}
+					break
+				}
+
+				t = candidateS.offset - e.cur
+				if debugAsserts && s <= t {
+					panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
+				}
+				if debugAsserts && s-t > e.maxMatchOff {
+					panic("s - t >e.maxMatchOff")
+				}
+				if debugAsserts && t < 0 {
+					panic("t<0")
+				}
+				if debugMatches {
+					println("short match")
+				}
+				break
+			}
+
+			// No match found, move forward in input.
+			s += stepSize + ((s - nextEmit) >> (kSearchStrength - 1))
+			if s >= sLimit {
+				break encodeLoop
+			}
+			cv = load6432(src, s)
+		}
+
+		// A 4-byte match has been found. Update recent offsets.
+		// We'll later see if more than 4 bytes.
+		offset2 = offset1
+		offset1 = s - t
+
+		if debugAsserts && s <= t {
+			panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
+		}
+
+		if debugAsserts && canRepeat && int(offset1) > len(src) {
+			panic("invalid offset")
+		}
+
+		// Extend the 4-byte match as long as possible.
+		l := e.matchlen(s+4, t+4, src) + 4
+
+		// Extend backwards
+		tMin := s - e.maxMatchOff
+		if tMin < 0 {
+			tMin = 0
+		}
+		for t > tMin && s > nextEmit && src[t-1] == src[s-1] && l < maxMatchLength {
+			s--
+			t--
+			l++
+		}
+
+		// Write our sequence
+		var seq seq
+		seq.litLen = uint32(s - nextEmit)
+		seq.matchLen = uint32(l - zstdMinMatch)
+		if seq.litLen > 0 {
+			blk.literals = append(blk.literals, src[nextEmit:s]...)
+		}
+		seq.offset = uint32(s-t) + 3
+		s += l
+		if debugSequences {
+			println("sequence", seq, "next s:", s)
+		}
+		blk.sequences = append(blk.sequences, seq)
+		nextEmit = s
+		if s >= sLimit {
+			break encodeLoop
+		}
+
+		// Index match start+1 (long) and start+2 (short)
+		index0 := s - l + 1
+		// Index match end-2 (long) and end-1 (short)
+		index1 := s - 2
+
+		cv0 := load6432(src, index0)
+		cv1 := load6432(src, index1)
+		te0 := tableEntry{offset: index0 + e.cur, val: uint32(cv0)}
+		te1 := tableEntry{offset: index1 + e.cur, val: uint32(cv1)}
+		longHash1 := hashLen(cv0, dFastLongTableBits, dFastLongLen)
+		longHash2 := hashLen(cv0, dFastLongTableBits, dFastLongLen)
+		e.longTable[longHash1] = te0
+		e.longTable[longHash2] = te1
+		e.markLongShardDirty(longHash1)
+		e.markLongShardDirty(longHash2)
+		cv0 >>= 8
+		cv1 >>= 8
+		te0.offset++
+		te1.offset++
+		te0.val = uint32(cv0)
+		te1.val = uint32(cv1)
+		hashVal1 := hashLen(cv0, dFastShortTableBits, dFastShortLen)
+		hashVal2 := hashLen(cv1, dFastShortTableBits, dFastShortLen)
+		e.table[hashVal1] = te0
+		e.markShardDirty(hashVal1)
+		e.table[hashVal2] = te1
+		e.markShardDirty(hashVal2)
+
+		cv = load6432(src, s)
+
+		if !canRepeat {
+			continue
+		}
+
+		// Check offset 2
+		for {
+			o2 := s - offset2
+			if load3232(src, o2) != uint32(cv) {
+				// Do regular search
+				break
+			}
+
+			// Store this, since we have it.
+			nextHashS := hashLen(cv, dFastShortTableBits, dFastShortLen)
+			nextHashL := hashLen(cv, dFastLongTableBits, dFastLongLen)
+
+			// We have at least 4 byte match.
+			// No need to check backwards. We come straight from a match
+			l := 4 + e.matchlen(s+4, o2+4, src)
+
+			entry := tableEntry{offset: s + e.cur, val: uint32(cv)}
+			e.longTable[nextHashL] = entry
+			e.markLongShardDirty(nextHashL)
+			e.table[nextHashS] = entry
+			e.markShardDirty(nextHashS)
+			seq.matchLen = uint32(l) - zstdMinMatch
+			seq.litLen = 0
+
+			// Since litlen is always 0, this is offset 1.
+			seq.offset = 1
+			s += l
+			nextEmit = s
+			if debugSequences {
+				println("sequence", seq, "next s:", s)
+			}
+			blk.sequences = append(blk.sequences, seq)
+
+			// Swap offset 1 and 2.
+			offset1, offset2 = offset2, offset1
+			if s >= sLimit {
+				// Finished
+				break encodeLoop
+			}
+			cv = load6432(src, s)
+		}
+	}
+
+	if int(nextEmit) < len(src) {
+		blk.literals = append(blk.literals, src[nextEmit:]...)
+		blk.extraLits = len(src) - int(nextEmit)
+	}
+	blk.recentOffsets[0] = uint32(offset1)
+	blk.recentOffsets[1] = uint32(offset2)
+	if debugEncoder {
+		println("returning, recent offsets:", blk.recentOffsets, "extra literals:", blk.extraLits)
+	}
+	// If we encoded more than 64K mark all dirty.
+	if len(src) > 64<<10 {
+		e.markAllShardsDirty()
+	}
+}
+
+// ResetDict will reset and set a dictionary if not nil
+func (e *doubleFastEncoder) Reset(d *dict, singleBlock bool) {
+	e.fastEncoder.Reset(d, singleBlock)
+	if d != nil {
+		panic("doubleFastEncoder: Reset with dict not supported")
+	}
+}
+
+// ResetDict will reset and set a dictionary if not nil
+func (e *doubleFastEncoderDict) Reset(d *dict, singleBlock bool) {
+	allDirty := e.allDirty
+	e.fastEncoderDict.Reset(d, singleBlock)
+	if d == nil {
+		return
+	}
+
+	// Init or copy dict table
+	if len(e.dictLongTable) != len(e.longTable) || d.id != e.lastDictID {
+		if len(e.dictLongTable) != len(e.longTable) {
+			e.dictLongTable = make([]tableEntry, len(e.longTable))
+		}
+		if len(d.content) >= 8 {
+			cv := load6432(d.content, 0)
+			e.dictLongTable[hashLen(cv, dFastLongTableBits, dFastLongLen)] = tableEntry{
+				val:    uint32(cv),
+				offset: e.maxMatchOff,
+			}
+			end := int32(len(d.content)) - 8 + e.maxMatchOff
+			for i := e.maxMatchOff + 1; i < end; i++ {
+				cv = cv>>8 | (uint64(d.content[i-e.maxMatchOff+7]) << 56)
+				e.dictLongTable[hashLen(cv, dFastLongTableBits, dFastLongLen)] = tableEntry{
+					val:    uint32(cv),
+					offset: i,
+				}
+			}
+		}
+		e.lastDictID = d.id
+		e.allDirty = true
+	}
+	// Reset table to initial state
+	e.cur = e.maxMatchOff
+
+	dirtyShardCnt := 0
+	if !allDirty {
+		for i := range e.longTableShardDirty {
+			if e.longTableShardDirty[i] {
+				dirtyShardCnt++
+			}
+		}
+	}
+
+	if allDirty || dirtyShardCnt > dLongTableShardCnt/2 {
+		copy(e.longTable[:], e.dictLongTable)
+		for i := range e.longTableShardDirty {
+			e.longTableShardDirty[i] = false
+		}
+		return
+	}
+	for i := range e.longTableShardDirty {
+		if !e.longTableShardDirty[i] {
+			continue
+		}
+
+		copy(e.longTable[i*dLongTableShardSize:(i+1)*dLongTableShardSize], e.dictLongTable[i*dLongTableShardSize:(i+1)*dLongTableShardSize])
+		e.longTableShardDirty[i] = false
+	}
+}
+
+func (e *doubleFastEncoderDict) markLongShardDirty(entryNum uint32) {
+	e.longTableShardDirty[entryNum/dLongTableShardSize] = true
 }