forgejo/vendor/github.com/blevesearch/vellum/builder.go

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// Copyright (c) 2017 Couchbase, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package vellum
import (
"bytes"
"io"
)
var defaultBuilderOpts = &BuilderOpts{
Encoder: 1,
RegistryTableSize: 10000,
RegistryMRUSize: 2,
}
// A Builder is used to build a new FST. When possible data is
// streamed out to the underlying Writer as soon as possible.
type Builder struct {
unfinished *unfinishedNodes
registry *registry
last []byte
len int
lastAddr int
encoder encoder
opts *BuilderOpts
builderNodePool *builderNodePool
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}
const noneAddr = 1
const emptyAddr = 0
// NewBuilder returns a new Builder which will stream out the
// underlying representation to the provided Writer as the set is built.
func newBuilder(w io.Writer, opts *BuilderOpts) (*Builder, error) {
if opts == nil {
opts = defaultBuilderOpts
}
builderNodePool := &builderNodePool{}
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rv := &Builder{
unfinished: newUnfinishedNodes(builderNodePool),
registry: newRegistry(builderNodePool, opts.RegistryTableSize, opts.RegistryMRUSize),
builderNodePool: builderNodePool,
opts: opts,
lastAddr: noneAddr,
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}
var err error
rv.encoder, err = loadEncoder(opts.Encoder, w)
if err != nil {
return nil, err
}
err = rv.encoder.start()
if err != nil {
return nil, err
}
return rv, nil
}
func (b *Builder) Reset(w io.Writer) error {
b.unfinished.Reset()
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b.registry.Reset()
b.lastAddr = noneAddr
b.encoder.reset(w)
b.last = nil
b.len = 0
err := b.encoder.start()
if err != nil {
return err
}
return nil
}
// Insert the provided value to the set being built.
// NOTE: values must be inserted in lexicographical order.
func (b *Builder) Insert(key []byte, val uint64) error {
// ensure items are added in lexicographic order
if bytes.Compare(key, b.last) < 0 {
return ErrOutOfOrder
}
if len(key) == 0 {
b.len = 1
b.unfinished.setRootOutput(val)
return nil
}
prefixLen, out := b.unfinished.findCommonPrefixAndSetOutput(key, val)
b.len++
err := b.compileFrom(prefixLen)
if err != nil {
return err
}
b.copyLastKey(key)
b.unfinished.addSuffix(key[prefixLen:], out)
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return nil
}
func (b *Builder) copyLastKey(key []byte) {
if b.last == nil {
b.last = make([]byte, 0, 64)
} else {
b.last = b.last[:0]
}
b.last = append(b.last, key...)
}
// Close MUST be called after inserting all values.
func (b *Builder) Close() error {
err := b.compileFrom(0)
if err != nil {
return err
}
root := b.unfinished.popRoot()
rootAddr, err := b.compile(root)
if err != nil {
return err
}
return b.encoder.finish(b.len, rootAddr)
}
func (b *Builder) compileFrom(iState int) error {
addr := noneAddr
for iState+1 < len(b.unfinished.stack) {
var node *builderNode
if addr == noneAddr {
node = b.unfinished.popEmpty()
} else {
node = b.unfinished.popFreeze(addr)
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}
var err error
addr, err = b.compile(node)
if err != nil {
return nil
}
}
b.unfinished.topLastFreeze(addr)
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return nil
}
func (b *Builder) compile(node *builderNode) (int, error) {
if node.final && len(node.trans) == 0 &&
node.finalOutput == 0 {
return 0, nil
}
found, addr, entry := b.registry.entry(node)
if found {
return addr, nil
}
addr, err := b.encoder.encodeState(node, b.lastAddr)
if err != nil {
return 0, err
}
b.lastAddr = addr
entry.addr = addr
return addr, nil
}
type unfinishedNodes struct {
stack []*builderNodeUnfinished
// cache allocates a reasonable number of builderNodeUnfinished
// objects up front and tries to keep reusing them
// because the main data structure is a stack, we assume the
// same access pattern, and don't track items separately
// this means calls get() and pushXYZ() must be paired,
// as well as calls put() and popXYZ()
cache []builderNodeUnfinished
builderNodePool *builderNodePool
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}
func (u *unfinishedNodes) Reset() {
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u.stack = u.stack[:0]
for i := 0; i < len(u.cache); i++ {
u.cache[i] = builderNodeUnfinished{}
}
u.pushEmpty(false)
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}
func newUnfinishedNodes(p *builderNodePool) *unfinishedNodes {
rv := &unfinishedNodes{
stack: make([]*builderNodeUnfinished, 0, 64),
cache: make([]builderNodeUnfinished, 64),
builderNodePool: p,
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}
rv.pushEmpty(false)
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return rv
}
// get new builderNodeUnfinished, reusing cache if possible
func (u *unfinishedNodes) get() *builderNodeUnfinished {
if len(u.stack) < len(u.cache) {
return &u.cache[len(u.stack)]
}
// full now allocate a new one
return &builderNodeUnfinished{}
}
// return builderNodeUnfinished, clearing it for reuse
func (u *unfinishedNodes) put() {
if len(u.stack) >= len(u.cache) {
return
// do nothing, not part of cache
}
u.cache[len(u.stack)] = builderNodeUnfinished{}
}
func (u *unfinishedNodes) findCommonPrefixAndSetOutput(key []byte,
out uint64) (int, uint64) {
var i int
for i < len(key) {
if i >= len(u.stack) {
break
}
var addPrefix uint64
if !u.stack[i].hasLastT {
break
}
if u.stack[i].lastIn == key[i] {
commonPre := outputPrefix(u.stack[i].lastOut, out)
addPrefix = outputSub(u.stack[i].lastOut, commonPre)
out = outputSub(out, commonPre)
u.stack[i].lastOut = commonPre
i++
} else {
break
}
if addPrefix != 0 {
u.stack[i].addOutputPrefix(addPrefix)
}
}
return i, out
}
func (u *unfinishedNodes) pushEmpty(final bool) {
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next := u.get()
next.node = u.builderNodePool.Get()
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next.node.final = final
u.stack = append(u.stack, next)
}
func (u *unfinishedNodes) popRoot() *builderNode {
l := len(u.stack)
var unfinished *builderNodeUnfinished
u.stack, unfinished = u.stack[:l-1], u.stack[l-1]
rv := unfinished.node
u.put()
return rv
}
func (u *unfinishedNodes) popFreeze(addr int) *builderNode {
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l := len(u.stack)
var unfinished *builderNodeUnfinished
u.stack, unfinished = u.stack[:l-1], u.stack[l-1]
unfinished.lastCompiled(addr)
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rv := unfinished.node
u.put()
return rv
}
func (u *unfinishedNodes) popEmpty() *builderNode {
l := len(u.stack)
var unfinished *builderNodeUnfinished
u.stack, unfinished = u.stack[:l-1], u.stack[l-1]
rv := unfinished.node
u.put()
return rv
}
func (u *unfinishedNodes) setRootOutput(out uint64) {
u.stack[0].node.final = true
u.stack[0].node.finalOutput = out
}
func (u *unfinishedNodes) topLastFreeze(addr int) {
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last := len(u.stack) - 1
u.stack[last].lastCompiled(addr)
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}
func (u *unfinishedNodes) addSuffix(bs []byte, out uint64) {
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if len(bs) == 0 {
return
}
last := len(u.stack) - 1
u.stack[last].hasLastT = true
u.stack[last].lastIn = bs[0]
u.stack[last].lastOut = out
for _, b := range bs[1:] {
next := u.get()
next.node = u.builderNodePool.Get()
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next.hasLastT = true
next.lastIn = b
next.lastOut = 0
u.stack = append(u.stack, next)
}
u.pushEmpty(true)
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}
type builderNodeUnfinished struct {
node *builderNode
lastOut uint64
lastIn byte
hasLastT bool
}
func (b *builderNodeUnfinished) lastCompiled(addr int) {
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if b.hasLastT {
transIn := b.lastIn
transOut := b.lastOut
b.hasLastT = false
b.lastOut = 0
b.node.trans = append(b.node.trans, transition{
in: transIn,
out: transOut,
addr: addr,
})
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}
}
func (b *builderNodeUnfinished) addOutputPrefix(prefix uint64) {
if b.node.final {
b.node.finalOutput = outputCat(prefix, b.node.finalOutput)
}
for i := range b.node.trans {
b.node.trans[i].out = outputCat(prefix, b.node.trans[i].out)
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}
if b.hasLastT {
b.lastOut = outputCat(prefix, b.lastOut)
}
}
type builderNode struct {
finalOutput uint64
trans []transition
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final bool
// intrusive linked list
next *builderNode
}
// reset resets the receiver builderNode to a re-usable state.
func (n *builderNode) reset() {
n.final = false
n.finalOutput = 0
for i := range n.trans {
n.trans[i] = emptyTransition
}
n.trans = n.trans[:0]
n.next = nil
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}
func (n *builderNode) equiv(o *builderNode) bool {
if n.final != o.final {
return false
}
if n.finalOutput != o.finalOutput {
return false
}
if len(n.trans) != len(o.trans) {
return false
}
for i, ntrans := range n.trans {
otrans := o.trans[i]
if ntrans.in != otrans.in {
return false
}
if ntrans.addr != otrans.addr {
return false
}
if ntrans.out != otrans.out {
return false
}
}
return true
}
var emptyTransition = transition{}
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type transition struct {
out uint64
addr int
in byte
}
func outputPrefix(l, r uint64) uint64 {
if l < r {
return l
}
return r
}
func outputSub(l, r uint64) uint64 {
return l - r
}
func outputCat(l, r uint64) uint64 {
return l + r
}
// builderNodePool pools builderNodes using a singly linked list.
//
// NB: builderNode lifecylce is described by the following interactions -
// +------------------------+ +----------------------+
// | Unfinished Nodes | Transfer once | Registry |
// |(not frozen builderNode)|-----builderNode is ------->| (frozen builderNode) |
// +------------------------+ marked frozen +----------------------+
// ^ |
// | |
// | Put()
// | Get() on +-------------------+ when
// +-new char--------| builderNode Pool |<-----------evicted
// +-------------------+
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type builderNodePool struct {
head *builderNode
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}
func (p *builderNodePool) Get() *builderNode {
if p.head == nil {
return &builderNode{}
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}
head := p.head
p.head = p.head.next
return head
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}
func (p *builderNodePool) Put(v *builderNode) {
if v == nil {
return
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}
v.reset()
v.next = p.head
p.head = v
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}