1 files changed, 452 insertions, 0 deletions
diff --git a/vendor/github.com/blevesearch/vellum/builder.go b/vendor/github.com/blevesearch/vellum/builder.go
new file mode 100644
index 0000000000..f793329575
--- /dev/null
+++ b/vendor/github.com/blevesearch/vellum/builder.go
@@ -0,0 +1,452 @@
+//  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
+}