--- /dev/null
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package iterator
+
+import (
+ "github.com/syndtr/goleveldb/leveldb/errors"
+ "github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// IteratorIndexer is the interface that wraps CommonIterator and basic Get
+// method. IteratorIndexer provides index for indexed iterator.
+type IteratorIndexer interface {
+ CommonIterator
+
+ // Get returns a new data iterator for the current position, or nil if
+ // done.
+ Get() Iterator
+}
+
+type indexedIterator struct {
+ util.BasicReleaser
+ index IteratorIndexer
+ strict bool
+
+ data Iterator
+ err error
+ errf func(err error)
+ closed bool
+}
+
+func (i *indexedIterator) setData() {
+ if i.data != nil {
+ i.data.Release()
+ }
+ i.data = i.index.Get()
+}
+
+func (i *indexedIterator) clearData() {
+ if i.data != nil {
+ i.data.Release()
+ }
+ i.data = nil
+}
+
+func (i *indexedIterator) indexErr() {
+ if err := i.index.Error(); err != nil {
+ if i.errf != nil {
+ i.errf(err)
+ }
+ i.err = err
+ }
+}
+
+func (i *indexedIterator) dataErr() bool {
+ if err := i.data.Error(); err != nil {
+ if i.errf != nil {
+ i.errf(err)
+ }
+ if i.strict || !errors.IsCorrupted(err) {
+ i.err = err
+ return true
+ }
+ }
+ return false
+}
+
+func (i *indexedIterator) Valid() bool {
+ return i.data != nil && i.data.Valid()
+}
+
+func (i *indexedIterator) First() bool {
+ if i.err != nil {
+ return false
+ } else if i.Released() {
+ i.err = ErrIterReleased
+ return false
+ }
+
+ if !i.index.First() {
+ i.indexErr()
+ i.clearData()
+ return false
+ }
+ i.setData()
+ return i.Next()
+}
+
+func (i *indexedIterator) Last() bool {
+ if i.err != nil {
+ return false
+ } else if i.Released() {
+ i.err = ErrIterReleased
+ return false
+ }
+
+ if !i.index.Last() {
+ i.indexErr()
+ i.clearData()
+ return false
+ }
+ i.setData()
+ if !i.data.Last() {
+ if i.dataErr() {
+ return false
+ }
+ i.clearData()
+ return i.Prev()
+ }
+ return true
+}
+
+func (i *indexedIterator) Seek(key []byte) bool {
+ if i.err != nil {
+ return false
+ } else if i.Released() {
+ i.err = ErrIterReleased
+ return false
+ }
+
+ if !i.index.Seek(key) {
+ i.indexErr()
+ i.clearData()
+ return false
+ }
+ i.setData()
+ if !i.data.Seek(key) {
+ if i.dataErr() {
+ return false
+ }
+ i.clearData()
+ return i.Next()
+ }
+ return true
+}
+
+func (i *indexedIterator) Next() bool {
+ if i.err != nil {
+ return false
+ } else if i.Released() {
+ i.err = ErrIterReleased
+ return false
+ }
+
+ switch {
+ case i.data != nil && !i.data.Next():
+ if i.dataErr() {
+ return false
+ }
+ i.clearData()
+ fallthrough
+ case i.data == nil:
+ if !i.index.Next() {
+ i.indexErr()
+ return false
+ }
+ i.setData()
+ return i.Next()
+ }
+ return true
+}
+
+func (i *indexedIterator) Prev() bool {
+ if i.err != nil {
+ return false
+ } else if i.Released() {
+ i.err = ErrIterReleased
+ return false
+ }
+
+ switch {
+ case i.data != nil && !i.data.Prev():
+ if i.dataErr() {
+ return false
+ }
+ i.clearData()
+ fallthrough
+ case i.data == nil:
+ if !i.index.Prev() {
+ i.indexErr()
+ return false
+ }
+ i.setData()
+ if !i.data.Last() {
+ if i.dataErr() {
+ return false
+ }
+ i.clearData()
+ return i.Prev()
+ }
+ }
+ return true
+}
+
+func (i *indexedIterator) Key() []byte {
+ if i.data == nil {
+ return nil
+ }
+ return i.data.Key()
+}
+
+func (i *indexedIterator) Value() []byte {
+ if i.data == nil {
+ return nil
+ }
+ return i.data.Value()
+}
+
+func (i *indexedIterator) Release() {
+ i.clearData()
+ i.index.Release()
+ i.BasicReleaser.Release()
+}
+
+func (i *indexedIterator) Error() error {
+ if i.err != nil {
+ return i.err
+ }
+ if err := i.index.Error(); err != nil {
+ return err
+ }
+ return nil
+}
+
+func (i *indexedIterator) SetErrorCallback(f func(err error)) {
+ i.errf = f
+}
+
+// NewIndexedIterator returns an 'indexed iterator'. An index is iterator
+// that returns another iterator, a 'data iterator'. A 'data iterator' is the
+// iterator that contains actual key/value pairs.
+//
+// If strict is true the any 'corruption errors' (i.e errors.IsCorrupted(err) == true)
+// won't be ignored and will halt 'indexed iterator', otherwise the iterator will
+// continue to the next 'data iterator'. Corruption on 'index iterator' will not be
+// ignored and will halt the iterator.
+func NewIndexedIterator(index IteratorIndexer, strict bool) Iterator {
+ return &indexedIterator{index: index, strict: strict}
+}
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