74 lines
1.9 KiB
Go
74 lines
1.9 KiB
Go
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// Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
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// All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// Package util provides utilities used throughout leveldb.
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package util
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import (
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"errors"
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)
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var (
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ErrReleased = errors.New("leveldb: resource already relesed")
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ErrHasReleaser = errors.New("leveldb: releaser already defined")
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)
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// Releaser is the interface that wraps the basic Release method.
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type Releaser interface {
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// Release releases associated resources. Release should always success
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// and can be called multiple times without causing error.
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Release()
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}
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// ReleaseSetter is the interface that wraps the basic SetReleaser method.
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type ReleaseSetter interface {
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// SetReleaser associates the given releaser to the resources. The
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// releaser will be called once coresponding resources released.
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// Calling SetReleaser with nil will clear the releaser.
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//
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// This will panic if a releaser already present or coresponding
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// resource is already released. Releaser should be cleared first
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// before assigned a new one.
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SetReleaser(releaser Releaser)
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}
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// BasicReleaser provides basic implementation of Releaser and ReleaseSetter.
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type BasicReleaser struct {
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releaser Releaser
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released bool
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}
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// Released returns whether Release method already called.
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func (r *BasicReleaser) Released() bool {
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return r.released
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}
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// Release implements Releaser.Release.
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func (r *BasicReleaser) Release() {
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if !r.released {
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if r.releaser != nil {
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r.releaser.Release()
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r.releaser = nil
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}
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r.released = true
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}
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}
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// SetReleaser implements ReleaseSetter.SetReleaser.
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func (r *BasicReleaser) SetReleaser(releaser Releaser) {
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if r.released {
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panic(ErrReleased)
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}
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if r.releaser != nil && releaser != nil {
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panic(ErrHasReleaser)
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}
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r.releaser = releaser
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}
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type NoopReleaser struct{}
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func (NoopReleaser) Release() {}
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