From 98703eb204923f06555605c648fc165a55214520 Mon Sep 17 00:00:00 2001 From: Daniel J Walsh Date: Sun, 8 Jul 2018 07:55:30 -0400 Subject: Vendor in latest code for storage,image, buildah vendor in containers/storage vendor in containers/image vendor in projectatomic/buildah Signed-off-by: Daniel J Walsh Closes: #1114 Approved by: mheon --- vendor/github.com/ulikunitz/xz/lzma/hashtable.go | 309 +++++++++++++++++++++++ 1 file changed, 309 insertions(+) create mode 100644 vendor/github.com/ulikunitz/xz/lzma/hashtable.go (limited to 'vendor/github.com/ulikunitz/xz/lzma/hashtable.go') diff --git a/vendor/github.com/ulikunitz/xz/lzma/hashtable.go b/vendor/github.com/ulikunitz/xz/lzma/hashtable.go new file mode 100644 index 000000000..d786a9745 --- /dev/null +++ b/vendor/github.com/ulikunitz/xz/lzma/hashtable.go @@ -0,0 +1,309 @@ +// Copyright 2014-2017 Ulrich Kunitz. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package lzma + +import ( + "errors" + "fmt" + + "github.com/ulikunitz/xz/internal/hash" +) + +/* For compression we need to find byte sequences that match the byte + * sequence at the dictionary head. A hash table is a simple method to + * provide this capability. + */ + +// maxMatches limits the number of matches requested from the Matches +// function. This controls the speed of the overall encoding. +const maxMatches = 16 + +// shortDists defines the number of short distances supported by the +// implementation. +const shortDists = 8 + +// The minimum is somehow arbitrary but the maximum is limited by the +// memory requirements of the hash table. +const ( + minTableExponent = 9 + maxTableExponent = 20 +) + +// newRoller contains the function used to create an instance of the +// hash.Roller. +var newRoller = func(n int) hash.Roller { return hash.NewCyclicPoly(n) } + +// hashTable stores the hash table including the rolling hash method. +// +// We implement chained hashing into a circular buffer. Each entry in +// the circular buffer stores the delta distance to the next position with a +// word that has the same hash value. +type hashTable struct { + dict *encoderDict + // actual hash table + t []int64 + // circular list data with the offset to the next word + data []uint32 + front int + // mask for computing the index for the hash table + mask uint64 + // hash offset; initial value is -int64(wordLen) + hoff int64 + // length of the hashed word + wordLen int + // hash roller for computing the hash values for the Write + // method + wr hash.Roller + // hash roller for computing arbitrary hashes + hr hash.Roller + // preallocated slices + p [maxMatches]int64 + distances [maxMatches + shortDists]int +} + +// hashTableExponent derives the hash table exponent from the dictionary +// capacity. +func hashTableExponent(n uint32) int { + e := 30 - nlz32(n) + switch { + case e < minTableExponent: + e = minTableExponent + case e > maxTableExponent: + e = maxTableExponent + } + return e +} + +// newHashTable creates a new hash table for words of length wordLen +func newHashTable(capacity int, wordLen int) (t *hashTable, err error) { + if !(0 < capacity) { + return nil, errors.New( + "newHashTable: capacity must not be negative") + } + exp := hashTableExponent(uint32(capacity)) + if !(1 <= wordLen && wordLen <= 4) { + return nil, errors.New("newHashTable: " + + "argument wordLen out of range") + } + n := 1 << uint(exp) + if n <= 0 { + panic("newHashTable: exponent is too large") + } + t = &hashTable{ + t: make([]int64, n), + data: make([]uint32, capacity), + mask: (uint64(1) << uint(exp)) - 1, + hoff: -int64(wordLen), + wordLen: wordLen, + wr: newRoller(wordLen), + hr: newRoller(wordLen), + } + return t, nil +} + +func (t *hashTable) SetDict(d *encoderDict) { t.dict = d } + +// buffered returns the number of bytes that are currently hashed. +func (t *hashTable) buffered() int { + n := t.hoff + 1 + switch { + case n <= 0: + return 0 + case n >= int64(len(t.data)): + return len(t.data) + } + return int(n) +} + +// addIndex adds n to an index ensuring that is stays inside the +// circular buffer for the hash chain. +func (t *hashTable) addIndex(i, n int) int { + i += n - len(t.data) + if i < 0 { + i += len(t.data) + } + return i +} + +// putDelta puts the delta instance at the current front of the circular +// chain buffer. +func (t *hashTable) putDelta(delta uint32) { + t.data[t.front] = delta + t.front = t.addIndex(t.front, 1) +} + +// putEntry puts a new entry into the hash table. If there is already a +// value stored it is moved into the circular chain buffer. +func (t *hashTable) putEntry(h uint64, pos int64) { + if pos < 0 { + return + } + i := h & t.mask + old := t.t[i] - 1 + t.t[i] = pos + 1 + var delta int64 + if old >= 0 { + delta = pos - old + if delta > 1<<32-1 || delta > int64(t.buffered()) { + delta = 0 + } + } + t.putDelta(uint32(delta)) +} + +// WriteByte converts a single byte into a hash and puts them into the hash +// table. +func (t *hashTable) WriteByte(b byte) error { + h := t.wr.RollByte(b) + t.hoff++ + t.putEntry(h, t.hoff) + return nil +} + +// Write converts the bytes provided into hash tables and stores the +// abbreviated offsets into the hash table. The method will never return an +// error. +func (t *hashTable) Write(p []byte) (n int, err error) { + for _, b := range p { + // WriteByte doesn't generate an error. + t.WriteByte(b) + } + return len(p), nil +} + +// getMatches the matches for a specific hash. The functions returns the +// number of positions found. +// +// TODO: Make a getDistances because that we are actually interested in. +func (t *hashTable) getMatches(h uint64, positions []int64) (n int) { + if t.hoff < 0 || len(positions) == 0 { + return 0 + } + buffered := t.buffered() + tailPos := t.hoff + 1 - int64(buffered) + rear := t.front - buffered + if rear >= 0 { + rear -= len(t.data) + } + // get the slot for the hash + pos := t.t[h&t.mask] - 1 + delta := pos - tailPos + for { + if delta < 0 { + return n + } + positions[n] = tailPos + delta + n++ + if n >= len(positions) { + return n + } + i := rear + int(delta) + if i < 0 { + i += len(t.data) + } + u := t.data[i] + if u == 0 { + return n + } + delta -= int64(u) + } +} + +// hash computes the rolling hash for the word stored in p. For correct +// results its length must be equal to t.wordLen. +func (t *hashTable) hash(p []byte) uint64 { + var h uint64 + for _, b := range p { + h = t.hr.RollByte(b) + } + return h +} + +// Matches fills the positions slice with potential matches. The +// functions returns the number of positions filled into positions. The +// byte slice p must have word length of the hash table. +func (t *hashTable) Matches(p []byte, positions []int64) int { + if len(p) != t.wordLen { + panic(fmt.Errorf( + "byte slice must have length %d", t.wordLen)) + } + h := t.hash(p) + return t.getMatches(h, positions) +} + +// NextOp identifies the next operation using the hash table. +// +// TODO: Use all repetitions to find matches. +func (t *hashTable) NextOp(rep [4]uint32) operation { + // get positions + data := t.dict.data[:maxMatchLen] + n, _ := t.dict.buf.Peek(data) + data = data[:n] + var p []int64 + if n < t.wordLen { + p = t.p[:0] + } else { + p = t.p[:maxMatches] + n = t.Matches(data[:t.wordLen], p) + p = p[:n] + } + + // convert positions in potential distances + head := t.dict.head + dists := append(t.distances[:0], 1, 2, 3, 4, 5, 6, 7, 8) + for _, pos := range p { + dis := int(head - pos) + if dis > shortDists { + dists = append(dists, dis) + } + } + + // check distances + var m match + dictLen := t.dict.DictLen() + for _, dist := range dists { + if dist > dictLen { + continue + } + + // Here comes a trick. We are only interested in matches + // that are longer than the matches we have been found + // before. So before we test the whole byte sequence at + // the given distance, we test the first byte that would + // make the match longer. If it doesn't match the byte + // to match, we don't to care any longer. + i := t.dict.buf.rear - dist + m.n + if i < 0 { + i += len(t.dict.buf.data) + } + if t.dict.buf.data[i] != data[m.n] { + // We can't get a longer match. Jump to the next + // distance. + continue + } + + n := t.dict.buf.matchLen(dist, data) + switch n { + case 0: + continue + case 1: + if uint32(dist-minDistance) != rep[0] { + continue + } + } + if n > m.n { + m = match{int64(dist), n} + if n == len(data) { + // No better match will be found. + break + } + } + } + + if m.n == 0 { + return lit{data[0]} + } + return m +} -- cgit v1.2.3-54-g00ecf