forked from cayleygraph/cayley
/
all_iterator.go
192 lines (163 loc) · 3.92 KB
/
all_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 leveldb
import (
"bytes"
ldbit "github.com/syndtr/goleveldb/leveldb/iterator"
"github.com/syndtr/goleveldb/leveldb/opt"
"github.com/google/cayley/graph"
"github.com/google/cayley/graph/iterator"
"github.com/google/cayley/quad"
)
type AllIterator struct {
uid uint64
tags graph.Tagger
prefix []byte
dir quad.Direction
open bool
iter ldbit.Iterator
qs *QuadStore
ro *opt.ReadOptions
result graph.Value
}
func NewAllIterator(prefix string, d quad.Direction, qs *QuadStore) *AllIterator {
opts := &opt.ReadOptions{
DontFillCache: true,
}
it := AllIterator{
uid: iterator.NextUID(),
ro: opts,
iter: qs.db.NewIterator(nil, opts),
prefix: []byte(prefix),
dir: d,
open: true,
qs: qs,
}
it.iter.Seek(it.prefix)
if !it.iter.Valid() {
// FIXME(kortschak) What are the semantics here? Is this iterator usable?
// If not, we should return nil *Iterator and an error.
it.open = false
it.iter.Release()
}
return &it
}
func (it *AllIterator) UID() uint64 {
return it.uid
}
func (it *AllIterator) Reset() {
if !it.open {
it.iter = it.qs.db.NewIterator(nil, it.ro)
it.open = true
}
it.iter.Seek(it.prefix)
if !it.iter.Valid() {
it.open = false
it.iter.Release()
}
}
func (it *AllIterator) Tagger() *graph.Tagger {
return &it.tags
}
func (it *AllIterator) 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 *AllIterator) Clone() graph.Iterator {
out := NewAllIterator(string(it.prefix), it.dir, it.qs)
out.tags.CopyFrom(it)
return out
}
func (it *AllIterator) Next() bool {
if !it.open {
it.result = nil
return false
}
var out []byte
out = make([]byte, len(it.iter.Key()))
copy(out, it.iter.Key())
it.iter.Next()
if !it.iter.Valid() {
it.Close()
}
if !bytes.HasPrefix(out, it.prefix) {
it.Close()
return false
}
it.result = Token(out)
return true
}
func (it *AllIterator) Err() error {
return it.iter.Error()
}
func (it *AllIterator) ResultTree() *graph.ResultTree {
return graph.NewResultTree(it.Result())
}
func (it *AllIterator) Result() graph.Value {
return it.result
}
func (it *AllIterator) NextPath() bool {
return false
}
// No subiterators.
func (it *AllIterator) SubIterators() []graph.Iterator {
return nil
}
func (it *AllIterator) Contains(v graph.Value) bool {
it.result = v
return true
}
func (it *AllIterator) Close() error {
if it.open {
it.iter.Release()
it.open = false
}
return nil
}
func (it *AllIterator) Size() (int64, bool) {
size, err := it.qs.SizeOfPrefix(it.prefix)
if err == nil {
return size, false
}
// INT64_MAX
return int64(^uint64(0) >> 1), false
}
func (it *AllIterator) Describe() graph.Description {
size, _ := it.Size()
return graph.Description{
UID: it.UID(),
Type: it.Type(),
Tags: it.tags.Tags(),
Size: size,
Direction: it.dir,
}
}
func (it *AllIterator) Type() graph.Type { return graph.All }
func (it *AllIterator) Sorted() bool { return false }
func (it *AllIterator) Optimize() (graph.Iterator, bool) {
return it, false
}
func (it *AllIterator) Stats() graph.IteratorStats {
s, _ := it.Size()
return graph.IteratorStats{
ContainsCost: 1,
NextCost: 2,
Size: s,
}
}
var _ graph.Nexter = &AllIterator{}