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// Copyright (c) 2012, 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 storage provides storage abstraction for LevelDB.
package storage
import (
"errors"
"fmt"
"io"
"github.com/syndtr/goleveldb/leveldb/util"
)
type FileType uint32
const (
TypeManifest FileType = 1 << iota
TypeJournal
TypeTable
TypeTemp
TypeAll = TypeManifest | TypeJournal | TypeTable | TypeTemp
)
func (t FileType) String() string {
switch t {
case TypeManifest:
return "manifest"
case TypeJournal:
return "journal"
case TypeTable:
return "table"
case TypeTemp:
return "temp"
}
return fmt.Sprintf("<unknown:%d>", t)
}
var (
ErrInvalidFile = errors.New("leveldb/storage: invalid file for argument")
ErrLocked = errors.New("leveldb/storage: already locked")
ErrClosed = errors.New("leveldb/storage: closed")
)
// Syncer is the interface that wraps basic Sync method.
type Syncer interface {
// Sync commits the current contents of the file to stable storage.
Sync() error
}
// Reader is the interface that groups the basic Read, Seek, ReadAt and Close
// methods.
type Reader interface {
io.ReadSeeker
io.ReaderAt
io.Closer
}
// Writer is the interface that groups the basic Write, Sync and Close
// methods.
type Writer interface {
io.WriteCloser
Syncer
}
// File is the file.
type File interface {
// Open opens the file for read. Returns os.ErrNotExist error
// if the file does not exist.
// Returns ErrClosed if the underlying storage is closed.
Open() (r Reader, err error)
// Create creates the file for writting. Truncate the file if
// already exist.
// Returns ErrClosed if the underlying storage is closed.
Create() (w Writer, err error)
// Replace replaces file with newfile.
// Returns ErrClosed if the underlying storage is closed.
Replace(newfile File) error
// Type returns the file type
Type() FileType
// Num returns the file number.
Num() uint64
// Remove removes the file.
// Returns ErrClosed if the underlying storage is closed.
Remove() error
}
// Storage is the storage.
type Storage interface {
// Lock locks the storage. Any subsequent attempt to call Lock will fail
// until the last lock released.
// After use the caller should call the Release method.
Lock() (l util.Releaser, err error)
// Log logs a string. This is used for logging. An implementation
// may write to a file, stdout or simply do nothing.
Log(str string)
// GetFile returns a file for the given number and type. GetFile will never
// returns nil, even if the underlying storage is closed.
GetFile(num uint64, t FileType) File
// GetFiles returns a slice of files that match the given file types.
// The file types may be OR'ed together.
GetFiles(t FileType) ([]File, error)
// GetManifest returns a manifest file. Returns os.ErrNotExist if manifest
// file does not exist.
GetManifest() (File, error)
// SetManifest sets the given file as manifest file. The given file should
// be a manifest file type or error will be returned.
SetManifest(f File) error
// Close closes the storage. It is valid to call Close multiple times.
// Other methods should not be called after the storage has been closed.
Close() error
}
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