1 // Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
2 // All rights reserved.
4 // Use of this source code is governed by a BSD-style license that can be
5 // found in the LICENSE file.
7 // Package util provides utilities used throughout leveldb.
15 ErrReleased = errors.New("leveldb: resource already relesed")
16 ErrHasReleaser = errors.New("leveldb: releaser already defined")
19 // Releaser is the interface that wraps the basic Release method.
20 type Releaser interface {
21 // Release releases associated resources. Release should always success
22 // and can be called multipe times without causing error.
26 // ReleaseSetter is the interface that wraps the basic SetReleaser method.
27 type ReleaseSetter interface {
28 // SetReleaser associates the given releaser to the resources. The
29 // releaser will be called once coresponding resources released.
30 // Calling SetReleaser with nil will clear the releaser.
32 // This will panic if a releaser already present or coresponding
33 // resource is already released. Releaser should be cleared first
34 // before assigned a new one.
35 SetReleaser(releaser Releaser)
38 // BasicReleaser provides basic implementation of Releaser and ReleaseSetter.
39 type BasicReleaser struct {
44 // Released returns whether Release method already called.
45 func (r *BasicReleaser) Released() bool {
49 // Release implements Releaser.Release.
50 func (r *BasicReleaser) Release() {
52 if r.releaser != nil {
60 // SetReleaser implements ReleaseSetter.SetReleaser.
61 func (r *BasicReleaser) SetReleaser(releaser Releaser) {
65 if r.releaser != nil && releaser != nil {
71 type NoopReleaser struct{}
73 func (NoopReleaser) Release() {}