prometheus/storage/raw/leveldb/iterator.go

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// Copyright 2013 Prometheus Team
// 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
// TODO: Evaluate whether to use coding.Encoder for the key and values instead
// raw bytes for consistency reasons.
// Iterator wraps Levigo and LevelDB's iterator behaviors in a manner that is
// conducive to IO-free testing.
//
// It borrows some of the operational assumptions from goskiplist, which
// functions very similarly, in that it uses no separate Valid method to
// determine health. All methods that have a return signature of (ok bool)
// assume in the real LevelDB case that if ok == false that the iterator
// must be disposed of at this given instance and recreated if future
// work is desired. This is a quirk of LevelDB itself!
type Iterator interface {
// GetError reports low-level errors, if available. This should not indicate
// that the iterator is necessarily unhealthy but maybe that the underlying
// table is corrupted itself. See the notes above for (ok bool) return
// signatures to determine iterator health.
GetError() error
Key() []byte
Next() (ok bool)
Previous() (ok bool)
Seek(key []byte) (ok bool)
SeekToFirst() (ok bool)
SeekToLast() (ok bool)
Value() []byte
Close()
}