mirror of
https://codeberg.org/forgejo/forgejo.git
synced 2024-11-26 09:09:36 -05:00
452 lines
10 KiB
Go
Vendored
452 lines
10 KiB
Go
Vendored
// 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
|
|
}
|
|
|
|
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{}
|
|
rv := &Builder{
|
|
unfinished: newUnfinishedNodes(builderNodePool),
|
|
registry: newRegistry(builderNodePool, opts.RegistryTableSize, opts.RegistryMRUSize),
|
|
builderNodePool: builderNodePool,
|
|
opts: opts,
|
|
lastAddr: noneAddr,
|
|
}
|
|
|
|
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()
|
|
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)
|
|
|
|
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)
|
|
}
|
|
var err error
|
|
addr, err = b.compile(node)
|
|
if err != nil {
|
|
return nil
|
|
}
|
|
}
|
|
b.unfinished.topLastFreeze(addr)
|
|
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
|
|
}
|
|
|
|
func (u *unfinishedNodes) Reset() {
|
|
u.stack = u.stack[:0]
|
|
for i := 0; i < len(u.cache); i++ {
|
|
u.cache[i] = builderNodeUnfinished{}
|
|
}
|
|
u.pushEmpty(false)
|
|
}
|
|
|
|
func newUnfinishedNodes(p *builderNodePool) *unfinishedNodes {
|
|
rv := &unfinishedNodes{
|
|
stack: make([]*builderNodeUnfinished, 0, 64),
|
|
cache: make([]builderNodeUnfinished, 64),
|
|
builderNodePool: p,
|
|
}
|
|
rv.pushEmpty(false)
|
|
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) {
|
|
next := u.get()
|
|
next.node = u.builderNodePool.Get()
|
|
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 {
|
|
l := len(u.stack)
|
|
var unfinished *builderNodeUnfinished
|
|
u.stack, unfinished = u.stack[:l-1], u.stack[l-1]
|
|
unfinished.lastCompiled(addr)
|
|
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) {
|
|
last := len(u.stack) - 1
|
|
u.stack[last].lastCompiled(addr)
|
|
}
|
|
|
|
func (u *unfinishedNodes) addSuffix(bs []byte, out uint64) {
|
|
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()
|
|
next.hasLastT = true
|
|
next.lastIn = b
|
|
next.lastOut = 0
|
|
u.stack = append(u.stack, next)
|
|
}
|
|
u.pushEmpty(true)
|
|
}
|
|
|
|
type builderNodeUnfinished struct {
|
|
node *builderNode
|
|
lastOut uint64
|
|
lastIn byte
|
|
hasLastT bool
|
|
}
|
|
|
|
func (b *builderNodeUnfinished) lastCompiled(addr int) {
|
|
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,
|
|
})
|
|
}
|
|
}
|
|
|
|
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)
|
|
}
|
|
if b.hasLastT {
|
|
b.lastOut = outputCat(prefix, b.lastOut)
|
|
}
|
|
}
|
|
|
|
type builderNode struct {
|
|
finalOutput uint64
|
|
trans []transition
|
|
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
|
|
}
|
|
|
|
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{}
|
|
|
|
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
|
|
// +-------------------+
|
|
type builderNodePool struct {
|
|
head *builderNode
|
|
}
|
|
|
|
func (p *builderNodePool) Get() *builderNode {
|
|
if p.head == nil {
|
|
return &builderNode{}
|
|
}
|
|
head := p.head
|
|
p.head = p.head.next
|
|
return head
|
|
}
|
|
|
|
func (p *builderNodePool) Put(v *builderNode) {
|
|
if v == nil {
|
|
return
|
|
}
|
|
v.reset()
|
|
v.next = p.head
|
|
p.head = v
|
|
}
|