diff options
Diffstat (limited to 'vendor/github.com/klauspost/compress/s2/encode_better.go')
| -rw-r--r-- | vendor/github.com/klauspost/compress/s2/encode_better.go | 431 |
1 files changed, 0 insertions, 431 deletions
diff --git a/vendor/github.com/klauspost/compress/s2/encode_better.go b/vendor/github.com/klauspost/compress/s2/encode_better.go deleted file mode 100644 index 943215b8a..000000000 --- a/vendor/github.com/klauspost/compress/s2/encode_better.go +++ /dev/null @@ -1,431 +0,0 @@ -// Copyright 2016 The Snappy-Go Authors. All rights reserved. -// Copyright (c) 2019 Klaus Post. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -package s2 - -import ( - "math/bits" -) - -// hash4 returns the hash of the lowest 4 bytes of u to fit in a hash table with h bits. -// Preferably h should be a constant and should always be <32. -func hash4(u uint64, h uint8) uint32 { - const prime4bytes = 2654435761 - return (uint32(u) * prime4bytes) >> ((32 - h) & 31) -} - -// hash5 returns the hash of the lowest 5 bytes of u to fit in a hash table with h bits. -// Preferably h should be a constant and should always be <64. -func hash5(u uint64, h uint8) uint32 { - const prime5bytes = 889523592379 - return uint32(((u << (64 - 40)) * prime5bytes) >> ((64 - h) & 63)) -} - -// hash7 returns the hash of the lowest 7 bytes of u to fit in a hash table with h bits. -// Preferably h should be a constant and should always be <64. -func hash7(u uint64, h uint8) uint32 { - const prime7bytes = 58295818150454627 - return uint32(((u << (64 - 56)) * prime7bytes) >> ((64 - h) & 63)) -} - -// hash8 returns the hash of u to fit in a hash table with h bits. -// Preferably h should be a constant and should always be <64. -func hash8(u uint64, h uint8) uint32 { - const prime8bytes = 0xcf1bbcdcb7a56463 - return uint32((u * prime8bytes) >> ((64 - h) & 63)) -} - -// encodeBlockBetter encodes a non-empty src to a guaranteed-large-enough dst. It -// assumes that the varint-encoded length of the decompressed bytes has already -// been written. -// -// It also assumes that: -// len(dst) >= MaxEncodedLen(len(src)) && -// minNonLiteralBlockSize <= len(src) && len(src) <= maxBlockSize -func encodeBlockBetterGo(dst, src []byte) (d int) { - // sLimit is when to stop looking for offset/length copies. The inputMargin - // lets us use a fast path for emitLiteral in the main loop, while we are - // looking for copies. - sLimit := len(src) - inputMargin - if len(src) < minNonLiteralBlockSize { - return 0 - } - - // Initialize the hash tables. - const ( - // Long hash matches. - lTableBits = 16 - maxLTableSize = 1 << lTableBits - - // Short hash matches. - sTableBits = 14 - maxSTableSize = 1 << sTableBits - ) - - var lTable [maxLTableSize]uint32 - var sTable [maxSTableSize]uint32 - - // Bail if we can't compress to at least this. - dstLimit := len(src) - len(src)>>5 - 6 - - // nextEmit is where in src the next emitLiteral should start from. - nextEmit := 0 - - // The encoded form must start with a literal, as there are no previous - // bytes to copy, so we start looking for hash matches at s == 1. - s := 1 - cv := load64(src, s) - - // We initialize repeat to 0, so we never match on first attempt - repeat := 0 - - for { - candidateL := 0 - nextS := 0 - for { - // Next src position to check - nextS = s + (s-nextEmit)>>7 + 1 - if nextS > sLimit { - goto emitRemainder - } - hashL := hash7(cv, lTableBits) - hashS := hash4(cv, sTableBits) - candidateL = int(lTable[hashL]) - candidateS := int(sTable[hashS]) - lTable[hashL] = uint32(s) - sTable[hashS] = uint32(s) - - // Check repeat at offset checkRep. - const checkRep = 1 - if false && uint32(cv>>(checkRep*8)) == load32(src, s-repeat+checkRep) { - base := s + checkRep - // Extend back - for i := base - repeat; base > nextEmit && i > 0 && src[i-1] == src[base-1]; { - i-- - base-- - } - d += emitLiteral(dst[d:], src[nextEmit:base]) - - // Extend forward - candidate := s - repeat + 4 + checkRep - s += 4 + checkRep - for s < len(src) { - if len(src)-s < 8 { - if src[s] == src[candidate] { - s++ - candidate++ - continue - } - break - } - if diff := load64(src, s) ^ load64(src, candidate); diff != 0 { - s += bits.TrailingZeros64(diff) >> 3 - break - } - s += 8 - candidate += 8 - } - if nextEmit > 0 { - // same as `add := emitCopy(dst[d:], repeat, s-base)` but skips storing offset. - d += emitRepeat(dst[d:], repeat, s-base) - } else { - // First match, cannot be repeat. - d += emitCopy(dst[d:], repeat, s-base) - } - nextEmit = s - if s >= sLimit { - goto emitRemainder - } - - cv = load64(src, s) - continue - } - - if uint32(cv) == load32(src, candidateL) { - break - } - - // Check our short candidate - if uint32(cv) == load32(src, candidateS) { - // Try a long candidate at s+1 - hashL = hash7(cv>>8, lTableBits) - candidateL = int(lTable[hashL]) - lTable[hashL] = uint32(s + 1) - if uint32(cv>>8) == load32(src, candidateL) { - s++ - break - } - // Use our short candidate. - candidateL = candidateS - break - } - - cv = load64(src, nextS) - s = nextS - } - - // Extend backwards - for candidateL > 0 && s > nextEmit && src[candidateL-1] == src[s-1] { - candidateL-- - s-- - } - - // Bail if we exceed the maximum size. - if d+(s-nextEmit) > dstLimit { - return 0 - } - - base := s - offset := base - candidateL - - // Extend the 4-byte match as long as possible. - s += 4 - candidateL += 4 - for s < len(src) { - if len(src)-s < 8 { - if src[s] == src[candidateL] { - s++ - candidateL++ - continue - } - break - } - if diff := load64(src, s) ^ load64(src, candidateL); diff != 0 { - s += bits.TrailingZeros64(diff) >> 3 - break - } - s += 8 - candidateL += 8 - } - - if offset > 65535 && s-base <= 5 && repeat != offset { - // Bail if the match is equal or worse to the encoding. - s = nextS + 1 - if s >= sLimit { - goto emitRemainder - } - cv = load64(src, s) - continue - } - - d += emitLiteral(dst[d:], src[nextEmit:base]) - if repeat == offset { - d += emitRepeat(dst[d:], offset, s-base) - } else { - d += emitCopy(dst[d:], offset, s-base) - repeat = offset - } - - nextEmit = s - if s >= sLimit { - goto emitRemainder - } - - if d > dstLimit { - // Do we have space for more, if not bail. - return 0 - } - // Index match start+1 (long) and start+2 (short) - index0 := base + 1 - // Index match end-2 (long) and end-1 (short) - index1 := s - 2 - - cv0 := load64(src, index0) - cv1 := load64(src, index1) - cv = load64(src, s) - lTable[hash7(cv0, lTableBits)] = uint32(index0) - lTable[hash7(cv0>>8, lTableBits)] = uint32(index0 + 1) - lTable[hash7(cv1, lTableBits)] = uint32(index1) - lTable[hash7(cv1>>8, lTableBits)] = uint32(index1 + 1) - sTable[hash4(cv0>>8, sTableBits)] = uint32(index0 + 1) - sTable[hash4(cv0>>16, sTableBits)] = uint32(index0 + 2) - sTable[hash4(cv1>>8, sTableBits)] = uint32(index1 + 1) - } - -emitRemainder: - if nextEmit < len(src) { - // Bail if we exceed the maximum size. - if d+len(src)-nextEmit > dstLimit { - return 0 - } - d += emitLiteral(dst[d:], src[nextEmit:]) - } - return d -} - -// encodeBlockBetterSnappyGo encodes a non-empty src to a guaranteed-large-enough dst. It -// assumes that the varint-encoded length of the decompressed bytes has already -// been written. -// -// It also assumes that: -// len(dst) >= MaxEncodedLen(len(src)) && -// minNonLiteralBlockSize <= len(src) && len(src) <= maxBlockSize -func encodeBlockBetterSnappyGo(dst, src []byte) (d int) { - // sLimit is when to stop looking for offset/length copies. The inputMargin - // lets us use a fast path for emitLiteral in the main loop, while we are - // looking for copies. - sLimit := len(src) - inputMargin - if len(src) < minNonLiteralBlockSize { - return 0 - } - - // Initialize the hash tables. - const ( - // Long hash matches. - lTableBits = 16 - maxLTableSize = 1 << lTableBits - - // Short hash matches. - sTableBits = 14 - maxSTableSize = 1 << sTableBits - ) - - var lTable [maxLTableSize]uint32 - var sTable [maxSTableSize]uint32 - - // Bail if we can't compress to at least this. - dstLimit := len(src) - len(src)>>5 - 6 - - // nextEmit is where in src the next emitLiteral should start from. - nextEmit := 0 - - // The encoded form must start with a literal, as there are no previous - // bytes to copy, so we start looking for hash matches at s == 1. - s := 1 - cv := load64(src, s) - - // We initialize repeat to 0, so we never match on first attempt - repeat := 0 - const maxSkip = 100 - - for { - candidateL := 0 - nextS := 0 - for { - // Next src position to check - nextS = (s-nextEmit)>>7 + 1 - if nextS > maxSkip { - nextS = s + maxSkip - } else { - nextS += s - } - - if nextS > sLimit { - goto emitRemainder - } - hashL := hash7(cv, lTableBits) - hashS := hash4(cv, sTableBits) - candidateL = int(lTable[hashL]) - candidateS := int(sTable[hashS]) - lTable[hashL] = uint32(s) - sTable[hashS] = uint32(s) - - if uint32(cv) == load32(src, candidateL) { - break - } - - // Check our short candidate - if uint32(cv) == load32(src, candidateS) { - // Try a long candidate at s+1 - hashL = hash7(cv>>8, lTableBits) - candidateL = int(lTable[hashL]) - lTable[hashL] = uint32(s + 1) - if uint32(cv>>8) == load32(src, candidateL) { - s++ - break - } - // Use our short candidate. - candidateL = candidateS - break - } - - cv = load64(src, nextS) - s = nextS - } - - // Extend backwards - for candidateL > 0 && s > nextEmit && src[candidateL-1] == src[s-1] { - candidateL-- - s-- - } - - // Bail if we exceed the maximum size. - if d+(s-nextEmit) > dstLimit { - return 0 - } - - base := s - offset := base - candidateL - - // Extend the 4-byte match as long as possible. - s += 4 - candidateL += 4 - for s < len(src) { - if len(src)-s < 8 { - if src[s] == src[candidateL] { - s++ - candidateL++ - continue - } - break - } - if diff := load64(src, s) ^ load64(src, candidateL); diff != 0 { - s += bits.TrailingZeros64(diff) >> 3 - break - } - s += 8 - candidateL += 8 - } - - if offset > 65535 && s-base <= 5 && repeat != offset { - // Bail if the match is equal or worse to the encoding. - s = nextS + 1 - if s >= sLimit { - goto emitRemainder - } - cv = load64(src, s) - continue - } - - d += emitLiteral(dst[d:], src[nextEmit:base]) - d += emitCopyNoRepeat(dst[d:], offset, s-base) - repeat = offset - - nextEmit = s - if s >= sLimit { - goto emitRemainder - } - - if d > dstLimit { - // Do we have space for more, if not bail. - return 0 - } - // Index match start+1 (long) and start+2 (short) - index0 := base + 1 - // Index match end-2 (long) and end-1 (short) - index1 := s - 2 - - cv0 := load64(src, index0) - cv1 := load64(src, index1) - cv = load64(src, s) - lTable[hash7(cv0, lTableBits)] = uint32(index0) - lTable[hash7(cv0>>8, lTableBits)] = uint32(index0 + 1) - lTable[hash7(cv1, lTableBits)] = uint32(index1) - lTable[hash7(cv1>>8, lTableBits)] = uint32(index1 + 1) - sTable[hash4(cv0>>8, sTableBits)] = uint32(index0 + 1) - sTable[hash4(cv0>>16, sTableBits)] = uint32(index0 + 2) - sTable[hash4(cv1>>8, sTableBits)] = uint32(index1 + 1) - } - -emitRemainder: - if nextEmit < len(src) { - // Bail if we exceed the maximum size. - if d+len(src)-nextEmit > dstLimit { - return 0 - } - d += emitLiteral(dst[d:], src[nextEmit:]) - } - return d -} |