Update to last common bleve (#3986)

vendor/github.com/couchbase/vellum/fst_iterator.go

@@ -0,0 +1,276 @@
+//  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"
+)
+
+// Iterator represents a means of visity key/value pairs in order.
+type Iterator interface {
+
+	// Current() returns the key/value pair currently pointed to.
+	// The []byte of the key is ONLY guaranteed to be valid until
+	// another call to Next/Seek/Close.  If you need it beyond that
+	// point you MUST make a copy.
+	Current() ([]byte, uint64)
+
+	// Next() advances the iterator to the next key/value pair.
+	// If no more key/value pairs exist, ErrIteratorDone is returned.
+	Next() error
+
+	// Seek() advances the iterator the specified key, or the next key
+	// if it does not exist.
+	// If no keys exist after that point, ErrIteratorDone is returned.
+	Seek(key []byte) error
+
+	// Reset resets the Iterator' internal state to allow for iterator
+	// reuse (e.g. pooling).
+	Reset(f *FST, startKeyInclusive, endKeyExclusive []byte, aut Automaton) error
+
+	// Close() frees any resources held by this iterator.
+	Close() error
+}
+
+// FSTIterator is a structure for iterating key/value pairs in this FST in
+// lexicographic order.  Iterators should be constructed with the FSTIterator
+// method on the parent FST structure.
+type FSTIterator struct {
+	f   *FST
+	aut Automaton
+
+	startKeyInclusive []byte
+	endKeyExclusive   []byte
+
+	statesStack    []fstState
+	keysStack      []byte
+	keysPosStack   []int
+	valsStack      []uint64
+	autStatesStack []int
+
+	nextStart []byte
+}
+
+func newIterator(f *FST, startKeyInclusive, endKeyExclusive []byte,
+	aut Automaton) (*FSTIterator, error) {
+
+	rv := &FSTIterator{}
+	err := rv.Reset(f, startKeyInclusive, endKeyExclusive, aut)
+	if err != nil {
+		return nil, err
+	}
+	return rv, nil
+}
+
+// Reset resets the Iterator' internal state to allow for iterator
+// reuse (e.g. pooling).
+func (i *FSTIterator) Reset(f *FST, startKeyInclusive, endKeyExclusive []byte, aut Automaton) error {
+	if aut == nil {
+		aut = alwaysMatchAutomaton
+	}
+
+	i.f = f
+	i.startKeyInclusive = startKeyInclusive
+	i.endKeyExclusive = endKeyExclusive
+	i.aut = aut
+
+	return i.pointTo(startKeyInclusive)
+}
+
+// pointTo attempts to point us to the specified location
+func (i *FSTIterator) pointTo(key []byte) error {
+
+	// tried to seek before start
+	if bytes.Compare(key, i.startKeyInclusive) < 0 {
+		key = i.startKeyInclusive
+	}
+
+	// trid to see past end
+	if i.endKeyExclusive != nil && bytes.Compare(key, i.endKeyExclusive) > 0 {
+		key = i.endKeyExclusive
+	}
+
+	// reset any state, pointTo always starts over
+	i.statesStack = i.statesStack[:0]
+	i.keysStack = i.keysStack[:0]
+	i.keysPosStack = i.keysPosStack[:0]
+	i.valsStack = i.valsStack[:0]
+	i.autStatesStack = i.autStatesStack[:0]
+
+	root, err := i.f.decoder.stateAt(i.f.decoder.getRoot(), nil)
+	if err != nil {
+		return err
+	}
+
+	autStart := i.aut.Start()
+
+	maxQ := -1
+	// root is always part of the path
+	i.statesStack = append(i.statesStack, root)
+	i.autStatesStack = append(i.autStatesStack, autStart)
+	for j := 0; j < len(key); j++ {
+		curr := i.statesStack[len(i.statesStack)-1]
+		autCurr := i.autStatesStack[len(i.autStatesStack)-1]
+
+		pos, nextAddr, nextVal := curr.TransitionFor(key[j])
+		if nextAddr == noneAddr {
+			// needed transition doesn't exist
+			// find last trans before the one we needed
+			for q := 0; q < curr.NumTransitions(); q++ {
+				if curr.TransitionAt(q) < key[j] {
+					maxQ = q
+				}
+			}
+			break
+		}
+		autNext := i.aut.Accept(autCurr, key[j])
+
+		next, err := i.f.decoder.stateAt(nextAddr, nil)
+		if err != nil {
+			return err
+		}
+
+		i.statesStack = append(i.statesStack, next)
+		i.keysStack = append(i.keysStack, key[j])
+		i.keysPosStack = append(i.keysPosStack, pos)
+		i.valsStack = append(i.valsStack, nextVal)
+		i.autStatesStack = append(i.autStatesStack, autNext)
+		continue
+	}
+
+	if !i.statesStack[len(i.statesStack)-1].Final() || !i.aut.IsMatch(i.autStatesStack[len(i.autStatesStack)-1]) || bytes.Compare(i.keysStack, key) < 0 {
+		return i.next(maxQ)
+	}
+
+	return nil
+}
+
+// Current returns the key and value currently pointed to by the iterator.
+// If the iterator is not pointing at a valid value (because Iterator/Next/Seek)
+// returned an error previously, it may return nil,0.
+func (i *FSTIterator) Current() ([]byte, uint64) {
+	curr := i.statesStack[len(i.statesStack)-1]
+	if curr.Final() {
+		var total uint64
+		for _, v := range i.valsStack {
+			total += v
+		}
+		total += curr.FinalOutput()
+		return i.keysStack, total
+	}
+	return nil, 0
+}
+
+// Next advances this iterator to the next key/value pair.  If there is none
+// or the advancement goes beyond the configured endKeyExclusive, then
+// ErrIteratorDone is returned.
+func (i *FSTIterator) Next() error {
+	return i.next(-1)
+}
+
+func (i *FSTIterator) next(lastOffset int) error {
+
+	// remember where we started
+	if cap(i.nextStart) < len(i.keysStack) {
+		i.nextStart = make([]byte, len(i.keysStack))
+	} else {
+		i.nextStart = i.nextStart[0:len(i.keysStack)]
+	}
+	copy(i.nextStart, i.keysStack)
+
+	for true {
+		curr := i.statesStack[len(i.statesStack)-1]
+		autCurr := i.autStatesStack[len(i.autStatesStack)-1]
+
+		if curr.Final() && i.aut.IsMatch(autCurr) &&
+			bytes.Compare(i.keysStack, i.nextStart) > 0 {
+			// in final state greater than start key
+			return nil
+		}
+
+		nextOffset := lastOffset + 1
+		if nextOffset < curr.NumTransitions() {
+			t := curr.TransitionAt(nextOffset)
+			autNext := i.aut.Accept(autCurr, t)
+			if i.aut.CanMatch(autNext) {
+				pos, nextAddr, v := curr.TransitionFor(t)
+
+				// the next slot in the statesStack might have an
+				// fstState instance that we can reuse
+				var nextPrealloc fstState
+				if len(i.statesStack) < cap(i.statesStack) {
+					nextPrealloc = i.statesStack[0:cap(i.statesStack)][len(i.statesStack)]
+				}
+
+				// push onto stack
+				next, err := i.f.decoder.stateAt(nextAddr, nextPrealloc)
+				if err != nil {
+					return err
+				}
+				i.statesStack = append(i.statesStack, next)
+				i.keysStack = append(i.keysStack, t)
+				i.keysPosStack = append(i.keysPosStack, pos)
+				i.valsStack = append(i.valsStack, v)
+				i.autStatesStack = append(i.autStatesStack, autNext)
+				lastOffset = -1
+
+				// check to see if new keystack might have gone too far
+				if i.endKeyExclusive != nil && bytes.Compare(i.keysStack, i.endKeyExclusive) >= 0 {
+					return ErrIteratorDone
+				}
+			} else {
+				lastOffset = nextOffset
+			}
+
+			continue
+		}
+
+		if len(i.statesStack) > 1 {
+			// no transitions, and still room to pop
+			i.statesStack = i.statesStack[:len(i.statesStack)-1]
+			i.keysStack = i.keysStack[:len(i.keysStack)-1]
+			lastOffset = i.keysPosStack[len(i.keysPosStack)-1]
+
+			i.keysPosStack = i.keysPosStack[:len(i.keysPosStack)-1]
+			i.valsStack = i.valsStack[:len(i.valsStack)-1]
+			i.autStatesStack = i.autStatesStack[:len(i.autStatesStack)-1]
+			continue
+		} else {
+			// stack len is 1 (root), can't go back further, we're done
+			break
+		}
+
+	}
+
+	return ErrIteratorDone
+}
+
+// Seek advances this iterator to the specified key/value pair.  If this key
+// is not in the FST, Current() will return the next largest key.  If this
+// seek operation would go past the last key, or outside the configured
+// startKeyInclusive/endKeyExclusive then ErrIteratorDone is returned.
+func (i *FSTIterator) Seek(key []byte) error {
+	err := i.pointTo(key)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// Close will free any resources held by this iterator.
+func (i *FSTIterator) Close() error {
+	// at the moment we don't do anything, but wanted this for API completeness
+	return nil
+}