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iterator.go
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/
iterator.go
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// Copyright 2014 The Cayley Authors. All rights reserved.
//
// 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 memstore
import (
"fmt"
"math"
"strings"
"github.com/google/cayley/graph"
"github.com/google/cayley/graph/iterator"
"github.com/google/cayley/graph/memstore/b"
)
type Iterator struct {
uid uint64
ts *TripleStore
tags graph.Tagger
tree *b.Tree
iter *b.Enumerator
data string
result graph.Value
}
func cmp(a, b int64) int {
return int(a - b)
}
func NewIterator(tree *b.Tree, data string, ts *TripleStore) *Iterator {
iter, err := tree.SeekFirst()
if err != nil {
iter = nil
}
return &Iterator{
uid: iterator.NextUID(),
ts: ts,
tree: tree,
iter: iter,
data: data,
}
}
func (it *Iterator) UID() uint64 {
return it.uid
}
func (it *Iterator) Reset() {
var err error
it.iter, err = it.tree.SeekFirst()
if err != nil {
it.iter = nil
}
}
func (it *Iterator) Tagger() *graph.Tagger {
return &it.tags
}
func (it *Iterator) TagResults(dst map[string]graph.Value) {
for _, tag := range it.tags.Tags() {
dst[tag] = it.Result()
}
for tag, value := range it.tags.Fixed() {
dst[tag] = value
}
}
func (it *Iterator) Clone() graph.Iterator {
var iter *b.Enumerator
if it.result != nil {
var ok bool
iter, ok = it.tree.Seek(it.result.(int64))
if !ok {
panic("value unexpectedly missing")
}
} else {
var err error
iter, err = it.tree.SeekFirst()
if err != nil {
iter = nil
}
}
m := &Iterator{
uid: iterator.NextUID(),
ts: it.ts,
tree: it.tree,
iter: iter,
data: it.data,
}
m.tags.CopyFrom(it)
return m
}
func (it *Iterator) Close() {}
func (it *Iterator) checkValid(index int64) bool {
return it.ts.log[index].DeletedBy == 0
}
func (it *Iterator) Next() bool {
graph.NextLogIn(it)
if it.iter == nil {
return graph.NextLogOut(it, nil, false)
}
result, _, err := it.iter.Next()
if err != nil {
return graph.NextLogOut(it, nil, false)
}
if !it.checkValid(result) {
return it.Next()
}
it.result = result
return graph.NextLogOut(it, it.result, true)
}
func (it *Iterator) ResultTree() *graph.ResultTree {
return graph.NewResultTree(it.Result())
}
func (it *Iterator) Result() graph.Value {
return it.result
}
func (it *Iterator) NextPath() bool {
return false
}
// No subiterators.
func (it *Iterator) SubIterators() []graph.Iterator {
return nil
}
func (it *Iterator) Size() (int64, bool) {
return int64(it.tree.Len()), true
}
func (it *Iterator) Contains(v graph.Value) bool {
graph.ContainsLogIn(it, v)
if _, ok := it.tree.Get(v.(int64)); ok {
it.result = v
return graph.ContainsLogOut(it, v, true)
}
return graph.ContainsLogOut(it, v, false)
}
func (it *Iterator) DebugString(indent int) string {
size, _ := it.Size()
return fmt.Sprintf("%s(%s tags:%s size:%d %s)", strings.Repeat(" ", indent), it.Type(), it.tags.Tags(), size, it.data)
}
var memType graph.Type
func init() {
memType = graph.RegisterIterator("b+tree")
}
func Type() graph.Type { return memType }
func (it *Iterator) Type() graph.Type { return memType }
func (it *Iterator) Sorted() bool { return true }
func (it *Iterator) Optimize() (graph.Iterator, bool) {
return it, false
}
func (it *Iterator) Stats() graph.IteratorStats {
return graph.IteratorStats{
ContainsCost: int64(math.Log(float64(it.tree.Len()))) + 1,
NextCost: 1,
Size: int64(it.tree.Len()),
}
}