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cleveldb_iterator.go
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cleveldb_iterator.go
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//go:build cleveldb
// +build cleveldb
package db
import (
"bytes"
"github.com/jmhodges/levigo"
)
// cLevelDBIterator is a cLevelDB iterator.
type cLevelDBIterator struct {
source *levigo.Iterator
start, end []byte
isReverse bool
isInvalid bool
key []byte
value []byte
}
var _ Iterator = (*cLevelDBIterator)(nil)
func newCLevelDBIterator(source *levigo.Iterator, start, end []byte, isReverse bool) *cLevelDBIterator {
if !isReverse {
if len(start) == 0 {
source.SeekToFirst()
} else {
source.Seek(start)
}
} else {
if len(end) == 0 {
source.SeekToLast()
} else {
source.Seek(end)
if source.Valid() {
eoakey := source.Key() // end or after key
if bytes.Compare(end, eoakey) <= 0 {
source.Prev()
}
} else {
source.SeekToLast()
}
}
}
return &cLevelDBIterator{
source: source,
start: start,
end: end,
isReverse: isReverse,
isInvalid: false,
}
}
// Valid implements Iterator.
func (itr *cLevelDBIterator) Valid() bool {
// Once invalid, forever invalid.
if itr.isInvalid {
return false
}
// If source is invalid, invalid.
if !itr.source.Valid() {
itr.invalidate()
return false
}
// If key is end or past it, invalid.
var start = itr.start
var end = itr.end
var key = itr.Key()
if !itr.isReverse {
if end != nil && bytes.Compare(end, key) <= 0 {
itr.invalidate()
return false
}
} else {
if start != nil && bytes.Compare(key, start) < 0 {
itr.invalidate()
return false
}
}
// It's valid.
return true
}
func (itr *cLevelDBIterator) invalidate() {
itr.isInvalid = true
itr.key = nil
itr.value = nil
}
// Key implements Iterator.
func (itr *cLevelDBIterator) Key() []byte {
itr.assertIsValid()
if itr.key == nil {
itr.key = itr.source.Key()
}
return itr.key
}
// Value implements Iterator.
func (itr *cLevelDBIterator) Value() []byte {
itr.assertIsValid()
if itr.value == nil {
itr.value = itr.source.Value()
}
return itr.value
}
// Next implements Iterator.
func (itr *cLevelDBIterator) Next() {
itr.assertIsValid()
itr.key = nil
itr.value = nil
if !itr.isReverse {
itr.source.Next()
} else {
itr.source.Prev()
}
}
// Error implements Iterator.
func (itr *cLevelDBIterator) Error() error {
return itr.source.GetError()
}
// Close implements Iterator.
func (itr *cLevelDBIterator) Close() error {
itr.source.Close()
return nil
}
func (itr *cLevelDBIterator) assertIsValid() {
if itr.isInvalid {
panic("iterator is invalid")
}
}