74 lines
1.9 KiB
Go
74 lines
1.9 KiB
Go
|
// Copyright (c) 2013, 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 util provides utilities used throughout leveldb.
|
||
|
|
package util
|
||
|
|
|
||
|
|
import (
|
||
|
|
"errors"
|
||
|
|
)
|
||
|
|
|
||
|
|
var (
|
||
|
|
ErrReleased = errors.New("leveldb: resource already relesed")
|
||
|
|
ErrHasReleaser = errors.New("leveldb: releaser already defined")
|
||
|
|
)
|
||
|
|
|
||
|
|
// Releaser is the interface that wraps the basic Release method.
|
||
|
|
type Releaser interface {
|
||
|
|
// Release releases associated resources. Release should always success
|
||
|
|
// and can be called multipe times without causing error.
|
||
|
|
Release()
|
||
|
|
}
|
||
|
|
|
||
|
|
// ReleaseSetter is the interface that wraps the basic SetReleaser method.
|
||
|
|
type ReleaseSetter interface {
|
||
|
|
// SetReleaser associates the given releaser to the resources. The
|
||
|
|
// releaser will be called once coresponding resources released.
|
||
|
|
// Calling SetReleaser with nil will clear the releaser.
|
||
|
|
//
|
||
|
|
// This will panic if a releaser already present or coresponding
|
||
|
|
// resource is already released. Releaser should be cleared first
|
||
|
|
// before assigned a new one.
|
||
|
|
SetReleaser(releaser Releaser)
|
||
|
|
}
|
||
|
|
|
||
|
|
// BasicReleaser provides basic implementation of Releaser and ReleaseSetter.
|
||
|
|
type BasicReleaser struct {
|
||
|
|
releaser Releaser
|
||
|
|
released bool
|
||
|
|
}
|
||
|
|
|
||
|
|
// Released returns whether Release method already called.
|
||
|
|
func (r *BasicReleaser) Released() bool {
|
||
|
|
return r.released
|
||
|
|
}
|
||
|
|
|
||
|
|
// Release implements Releaser.Release.
|
||
|
|
func (r *BasicReleaser) Release() {
|
||
|
|
if !r.released {
|
||
|
|
if r.releaser != nil {
|
||
|
|
r.releaser.Release()
|
||
|
|
r.releaser = nil
|
||
|
|
}
|
||
|
|
r.released = true
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// SetReleaser implements ReleaseSetter.SetReleaser.
|
||
|
|
func (r *BasicReleaser) SetReleaser(releaser Releaser) {
|
||
|
|
if r.released {
|
||
|
|
panic(ErrReleased)
|
||
|
|
}
|
||
|
|
if r.releaser != nil && releaser != nil {
|
||
|
|
panic(ErrHasReleaser)
|
||
|
|
}
|
||
|
|
r.releaser = releaser
|
||
|
|
}
|
||
|
|
|
||
|
|
type NoopReleaser struct{}
|
||
|
|
|
||
|
|
func (NoopReleaser) Release() {}
|