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// 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 multiple 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() {}
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