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indexed_iter.go
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/
indexed_iter.go
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// 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/jbenet/go-ipfs/Godeps/_workspace/src/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
strictGet bool
data Iterator
err error
errf func(err error)
}
func (i *indexedIterator) setData() {
if i.data != nil {
i.data.Release()
}
i.data = i.index.Get()
if i.strictGet {
if err := i.data.Error(); err != nil {
i.err = err
}
}
}
func (i *indexedIterator) clearData() {
if i.data != nil {
i.data.Release()
}
i.data = nil
}
func (i *indexedIterator) dataErr() bool {
if i.errf != nil {
if err := i.data.Error(); err != nil {
i.errf(err)
}
}
if i.strict {
if err := i.data.Error(); err != nil {
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
}
if !i.index.First() {
i.clearData()
return false
}
i.setData()
return i.Next()
}
func (i *indexedIterator) Last() bool {
if i.err != nil {
return false
}
if !i.index.Last() {
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
}
if !i.index.Seek(key) {
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
}
switch {
case i.data != nil && !i.data.Next():
if i.dataErr() {
return false
}
i.clearData()
fallthrough
case i.data == nil:
if !i.index.Next() {
return false
}
i.setData()
return i.Next()
}
return true
}
func (i *indexedIterator) Prev() bool {
if i.err != nil {
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() {
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 then error yield by data iterator will halt the indexed
// iterator, on contrary if strict is false then the indexed iterator will
// ignore those error and move on to the next index. If strictGet is true and
// index.Get() yield an 'error iterator' then the indexed iterator will be halted.
// An 'error iterator' is iterator which its Error() method always return non-nil
// even before any 'seeks method' is called.
func NewIndexedIterator(index IteratorIndexer, strict, strictGet bool) Iterator {
return &indexedIterator{index: index, strict: strict, strictGet: strictGet}
}