blob: 9b30b6727fc3a487b9bf7dc0946a23054ea5410c [file] [log] [blame]
// Copyright (c) 2012, Suryandaru Triandana <>
// 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 (
type FileType int
const (
TypeManifest FileType = 1 << iota
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")
// ErrCorrupted is the type that wraps errors that indicate corruption of
// a file. Package storage has its own type instead of using
// errors.ErrCorrupted to prevent circular import.
type ErrCorrupted struct {
Fd FileDesc
Err error
func (e *ErrCorrupted) Error() string {
if !e.Fd.Nil() {
return fmt.Sprintf("%v [file=%v]", e.Err, e.Fd)
} else {
return e.Err.Error()
// 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 {
// Writer is the interface that groups the basic Write, Sync and Close
// methods.
type Writer interface {
type Lock interface {
// FileDesc is a file descriptor.
type FileDesc struct {
Type FileType
Num int64
func (fd FileDesc) String() string {
switch fd.Type {
case TypeManifest:
return fmt.Sprintf("MANIFEST-%06d", fd.Num)
case TypeJournal:
return fmt.Sprintf("%06d.log", fd.Num)
case TypeTable:
return fmt.Sprintf("%06d.ldb", fd.Num)
case TypeTemp:
return fmt.Sprintf("%06d.tmp", fd.Num)
return fmt.Sprintf("%#x-%d", fd.Type, fd.Num)
// Nil returns true if fd == (FileDesc{}).
func (fd FileDesc) Nil() bool {
return fd == (FileDesc{})
// FileDescOk returns true if fd is a valid file descriptor.
func FileDescOk(fd FileDesc) bool {
switch fd.Type {
case TypeManifest:
case TypeJournal:
case TypeTable:
case TypeTemp:
return false
return fd.Num >= 0
// Storage is the storage. A storage instance must be goroutine-safe.
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() (Lock, 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)
// SetMeta sets to point to the given fd, which then can be acquired using
// GetMeta method.
// SetMeta should be implemented in such way that changes should happened
// atomically.
SetMeta(fd FileDesc) error
// GetManifest returns a manifest file.
// Returns os.ErrNotExist if meta doesn't point to any fd, or point to fd
// that doesn't exist.
GetMeta() (FileDesc, error)
// List returns fds that match the given file types.
// The file types may be OR'ed together.
List(ft FileType) ([]FileDesc, error)
// Open opens file with the given fd read-only.
// Returns os.ErrNotExist error if the file does not exist.
// Returns ErrClosed if the underlying storage is closed.
Open(fd FileDesc) (Reader, error)
// Create creates file with the given fd, truncate if already exist and
// opens write-only.
// Returns ErrClosed if the underlying storage is closed.
Create(fd FileDesc) (Writer, error)
// Remove removes file with the given fd.
// Returns ErrClosed if the underlying storage is closed.
Remove(fd FileDesc) error
// Rename renames file from oldfd to newfd.
// Returns ErrClosed if the underlying storage is closed.
Rename(oldfd, newfd FileDesc) 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