// NewLevelDBStorage is a constructor of DataStorage.
func NewLevelDBStorage(cfg *conf.Config) (*LevelDBStorage, error) {
	ds := LevelDBStorage{
		cfg:            cfg,
		dbName:         cfg.DatabasePath,
		itemCache:      make(ItemCache),
		tmpItemCache:   make(ItemCache),
		closed:         false,
		forceFlushChan: make(chan bool, 1),
		flushSync:      &sync.WaitGroup{},
	}

	// LevelDB write options.
	opts := new(opt.Options)
	opts.Compression = opt.NoCompression
	opts.BlockCacheCapacity = 8 * 1024 * 1024
	opts.WriteBuffer = 8 * 1024 * 1024

	db, err := leveldb.OpenFile(cfg.DatabasePath, opts)
	if err != nil {
		return nil, err
	}
	ds.db = db
	go ds.periodicCacheFlush()
	return &ds, nil
}

func truno(t *testing.T, o *opt.Options, f func(h *dbHarness)) {
	for i := 0; i < 4; i++ {
		func() {
			switch i {
			case 0:
			case 1:
				if o == nil {
					o = &opt.Options{Filter: _bloom_filter}
				} else {
					old := o
					o = &opt.Options{}
					*o = *old
					o.Filter = _bloom_filter
				}
			case 2:
				if o == nil {
					o = &opt.Options{Compression: opt.NoCompression}
				} else {
					old := o
					o = &opt.Options{}
					*o = *old
					o.Compression = opt.NoCompression
				}
			}
			h := newDbHarnessWopt(t, o)
			defer h.close()
			switch i {
			case 3:
				h.reopenDB()
			}
			f(h)
		}()
	}
}

func (s *session) setOptions(o *opt.Options) {
	no := dupOptions(o)
	// Alternative filters.
	if filters := o.GetAltFilters(); len(filters) > 0 {
		no.AltFilters = make([]filter.Filter, len(filters))
		for i, filter := range filters {
			no.AltFilters[i] = &iFilter{filter}
		}
	}
	// Block cache.
	switch o.GetBlockCache() {
	case nil:
		no.BlockCache = cache.NewLRUCache(o.GetBlockCacheSize())
	case opt.NoCache:
		no.BlockCache = nil
	}
	// Comparer.
	s.icmp = &iComparer{o.GetComparer()}
	no.Comparer = s.icmp
	// Filter.
	if filter := o.GetFilter(); filter != nil {
		no.Filter = &iFilter{filter}
	}

	s.o = &cachedOptions{Options: no}
	s.o.cache()
}

func newSession(d storage.Storage, o *opt.Options) *session {
	s := new(session)
	s.stor = d
	s.cmp = &iComparer{o.GetComparer()}
	s.o = newIOptions(s, *o)
	s.tops = newTableOps(s, s.o.GetMaxOpenFiles())
	s.setVersion(&version{s: s})
	return s
}

func (self *leveldbProvider) createLevelDbOptions(typeName string) *opt.Options {
	comparer := self.typeName2Comparer[typeName]
	if comparer == nil {
		return nil
	} else {
		options := new(opt.Options)
		options.Comparer = comparer
		return options
	}
}

// OpenFile opens or creates a DB for the given path.
// The DB will be created if not exist, unless ErrorIfMissing is true.
// Also, if ErrorIfExist is true and the DB exist OpenFile will returns
// os.ErrExist error.
//
// OpenFile uses standard file-system backed storage implementation as
// desribed in the leveldb/storage package.
//
// OpenFile will return an error with type of ErrCorrupted if corruption
// detected in the DB. Corrupted DB can be recovered with Recover
// function.
//
// The returned DB instance is goroutine-safe.
// The DB must be closed after use, by calling Close method.
func OpenFile(path string, o *opt.Options) (db *DB, err error) {
	stor, err := storage.OpenFile(path, o.GetReadOnly())
	if err != nil {
		return
	}
	db, err = Open(stor, o)
	if err != nil {
		stor.Close()
	} else {
		db.closer = stor
	}
	return
}

func newSession(d desc.Desc, o *opt.Options) *session {
	s := new(session)
	s.desc = d
	s.o = &iOptions{s, o}
	s.cmp = &iComparer{o.GetComparer()}
	filter := o.GetFilter()
	if filter != nil {
		s.filter = &iFilter{filter}
	}
	s.tops = newTableOps(s, s.o.GetMaxOpenFiles())
	s.setVersion(&version{s: s})
	return s
}

func (s *session) setOptions(o *opt.Options) {
	s.o = &opt.Options{}
	if o != nil {
		*s.o = *o
	}
	// Alternative filters.
	if filters := o.GetAltFilters(); len(filters) > 0 {
		s.o.AltFilters = make([]filter.Filter, len(filters))
		for i, filter := range filters {
			s.o.AltFilters[i] = &iFilter{filter}
		}
	}
	// Block cache.
	switch o.GetBlockCache() {
	case nil:
		s.o.BlockCache = cache.NewLRUCache(opt.DefaultBlockCacheSize)
	case opt.NoCache:
		s.o.BlockCache = nil
	}
	// Comparer.
	s.cmp = &iComparer{o.GetComparer()}
	s.o.Comparer = s.cmp
	// Filter.
	if filter := o.GetFilter(); filter != nil {
		s.o.Filter = &iFilter{filter}
	}
}

// Open open or create database from given desc.
func Open(d desc.Desc, o *opt.Options) (db *DB, err error) {
	s := newSession(d, o)

	err = s.recover()
	if os.IsNotExist(err) && o.HasFlag(opt.OFCreateIfMissing) {
		err = s.create()
	} else if err == nil && o.HasFlag(opt.OFErrorIfExist) {
		err = os.ErrExist
	}
	if err != nil {
		return
	}

	return open(s)
}

func openSession(stor storage.Storage, o *opt.Options) (s *session, err error) {
	if stor == nil || o == nil {
		return nil, os.ErrInvalid
	}
	storLock, err := stor.Lock()
	if err != nil {
		return
	}
	s = new(session)
	s.stor = stor
	s.storLock = storLock
	s.cmp = &iComparer{o.GetComparer()}
	s.o = newIOptions(s, *o)
	s.tops = newTableOps(s, s.o.GetMaxOpenFiles())
	s.setVersion(&version{s: s})
	return
}

// Creates new initialized session instance.
func newSession(stor storage.Storage, o *opt.Options) (s *session, err error) {
	if stor == nil {
		return nil, os.ErrInvalid
	}
	storLock, err := stor.Lock()
	if err != nil {
		return
	}
	s = &session{
		stor:       stor,
		storLock:   storLock,
		stCompPtrs: make([]iKey, o.GetNumLevel()),
	}
	s.setOptions(o)
	s.tops = newTableOps(s, s.o.GetCachedOpenFiles())
	s.setVersion(newVersion(s))
	s.log("[email protected] F·NumFile S·FileSize N·Entry C·BadEntry B·BadBlock Ke·KeyError D·DroppedEntry L·Level Q·SeqNum T·TimeElapsed")
	return
}

func (self *Queue) open() error {
	self.Lock()
	defer self.Unlock()
	if regexp.MustCompile(`[^a-zA-Z0-9_]+`).MatchString(self.Name) {
		return errors.New("Queue name is not alphanumeric")
	}

	if len(self.Name) > 100 {
		return errors.New("Queue name is too long")
	}

	var options opt.Options
	options.BlockCacher = opt.NoCacher

	var err error
	self.db, err = leveldb.OpenFile(self.Path(), &options)
	if err != nil {
		return err
	}
	self.isOpened = true
	return self.initialize()
}

// NewWriter creates a new initialized table writer for the file.
//
// Table writer is not safe for concurrent use.
func NewWriter(f io.Writer, o *opt.Options) *Writer {
	w := &Writer{
		writer:          f,
		cmp:             o.GetComparer(),
		filter:          o.GetFilter(),
		compression:     o.GetCompression(),
		blockSize:       o.GetBlockSize(),
		comparerScratch: make([]byte, 0),
	}
	// data block
	w.dataBlock.restartInterval = o.GetBlockRestartInterval()
	// The first 20-bytes are used for encoding block handle.
	w.dataBlock.scratch = w.scratch[20:]
	// index block
	w.indexBlock.restartInterval = 1
	w.indexBlock.scratch = w.scratch[20:]
	// filter block
	if w.filter != nil {
		w.filterBlock.generator = w.filter.NewGenerator()
		w.filterBlock.flush(0)
	}
	return w
}

func applyConfig(o *opt.Options, config map[string]interface{}) (
	*opt.Options, error) {

	ro, ok := config["read_only"].(bool)
	if ok {
		o.ReadOnly = ro
	}

	cim, ok := config["create_if_missing"].(bool)
	if ok {
		o.ErrorIfMissing = !cim
	}

	eie, ok := config["error_if_exists"].(bool)
	if ok {
		o.ErrorIfExist = eie
	}

	wbs, ok := config["write_buffer_size"].(float64)
	if ok {
		o.WriteBuffer = int(wbs)
	}

	bs, ok := config["block_size"].(float64)
	if ok {
		o.BlockSize = int(bs)
	}

	bri, ok := config["block_restart_interval"].(float64)
	if ok {
		o.BlockRestartInterval = int(bri)
	}

	lcc, ok := config["lru_cache_capacity"].(float64)
	if ok {
		o.BlockCacheCapacity = int(lcc)
	}

	bfbpk, ok := config["bloom_filter_bits_per_key"].(float64)
	if ok {
		bf := filter.NewBloomFilter(int(bfbpk))
		o.Filter = bf
	}

	return o, nil
}

func (s *session) setOptions(o *opt.Options) {
	no := dupOptions(o)
	// Alternative filters.
	if filters := o.GetAltFilters(); len(filters) > 0 {
		no.AltFilters = make([]filter.Filter, len(filters))
		for i, filter := range filters {
			no.AltFilters[i] = &iFilter{filter}
		}
	}
	// Comparer.
	s.icmp = &iComparer{o.GetComparer()}
	no.Comparer = s.icmp
	// Filter.
	if filter := o.GetFilter(); filter != nil {
		no.Filter = &iFilter{filter}
	}

	s.o = &cachedOptions{Options: no}
	s.o.cache()
}

// NewReader creates a new initialized table reader for the file.
// The cache and bpool is optional and can be nil.
//
// The returned table reader instance is goroutine-safe.
func NewReader(f io.ReaderAt, size int64, cache cache.Namespace, bpool *util.BufferPool, o *opt.Options) *Reader {
	if bpool == nil {
		bpool = util.NewBufferPool(o.GetBlockSize() + blockTrailerLen)
	}
	r := &Reader{
		reader:     f,
		cache:      cache,
		bpool:      bpool,
		cmp:        o.GetComparer(),
		checksum:   o.GetStrict(opt.StrictBlockChecksum),
		strictIter: o.GetStrict(opt.StrictIterator),
	}
	if f == nil {
		r.err = errors.New("leveldb/table: Reader: nil file")
		return r
	}
	if size < footerLen {
		r.err = errors.New("leveldb/table: Reader: invalid table (file size is too small)")
		return r
	}
	var footer [footerLen]byte
	if _, err := r.reader.ReadAt(footer[:], size-footerLen); err != nil && err != io.EOF {
		r.err = fmt.Errorf("leveldb/table: Reader: invalid table (could not read footer): %v", err)
	}
	if string(footer[footerLen-len(magic):footerLen]) != magic {
		r.err = errors.New("leveldb/table: Reader: invalid table (bad magic number)")
		return r
	}
	// Decode the metaindex block handle.
	metaBH, n := decodeBlockHandle(footer[:])
	if n == 0 {
		r.err = errors.New("leveldb/table: Reader: invalid table (bad metaindex block handle)")
		return r
	}
	// Decode the index block handle.
	indexBH, n := decodeBlockHandle(footer[n:])
	if n == 0 {
		r.err = errors.New("leveldb/table: Reader: invalid table (bad index block handle)")
		return r
	}
	// Read index block.
	r.indexBlock, r.err = r.readBlock(indexBH, true)
	if r.err != nil {
		return r
	}
	// Read metaindex block.
	metaBlock, err := r.readBlock(metaBH, true)
	if err != nil {
		r.err = err
		return r
	}
	// Set data end.
	r.dataEnd = int64(metaBH.offset)
	metaIter := metaBlock.newIterator(nil, false, nil)
	for metaIter.Next() {
		key := string(metaIter.Key())
		if !strings.HasPrefix(key, "filter.") {
			continue
		}
		fn := key[7:]
		var filter filter.Filter
		if f0 := o.GetFilter(); f0 != nil && f0.Name() == fn {
			filter = f0
		} else {
			for _, f0 := range o.GetAltFilters() {
				if f0.Name() == fn {
					filter = f0
					break
				}
			}
		}
		if filter != nil {
			filterBH, n := decodeBlockHandle(metaIter.Value())
			if n == 0 {
				continue
			}
			// Update data end.
			r.dataEnd = int64(filterBH.offset)
			filterBlock, err := r.readFilterBlock(filterBH, filter)
			if err != nil {
				continue
			}
			r.filterBlock = filterBlock
			break
		}
	}
	metaIter.Release()
	return r
}

func newDbHarnessWopt(t *testing.T, o *opt.Options) *dbHarness {
	o.Flag |= opt.OFCreateIfMissing
	return newDbHarnessWoptRaw(t, o)
}

func recoverTable(s *session, o *opt.Options) error {
	// Get all tables and sort it by file number.
	tableFiles_, err := s.getFiles(storage.TypeTable)
	if err != nil {
		return err
	}
	tableFiles := files(tableFiles_)
	tableFiles.sort()

	var mSeq uint64
	var good, corrupted int
	rec := new(sessionRecord)
	bpool := util.NewBufferPool(o.GetBlockSize() + 5)
	buildTable := func(iter iterator.Iterator) (tmp storage.File, size int64, err error) {
		tmp = s.newTemp()
		writer, err := tmp.Create()
		if err != nil {
			return
		}
		defer func() {
			writer.Close()
			if err != nil {
				tmp.Remove()
				tmp = nil
			}
		}()

		// Copy entries.
		tw := table.NewWriter(writer, o)
		for iter.Next() {
			key := iter.Key()
			if validIkey(key) {
				err = tw.Append(key, iter.Value())
				if err != nil {
					return
				}
			}
		}
		err = iter.Error()
		if err != nil {
			return
		}
		err = tw.Close()
		if err != nil {
			return
		}
		err = writer.Sync()
		if err != nil {
			return
		}
		size = int64(tw.BytesLen())
		return
	}
	recoverTable := func(file storage.File) error {
		s.logf("[email protected] recovering @%d", file.Num())
		reader, err := file.Open()
		if err != nil {
			return err
		}
		defer reader.Close()

		// Get file size.
		size, err := reader.Seek(0, 2)
		if err != nil {
			return err
		}

		var tSeq uint64
		var tgood, tcorrupted, blockerr int
		var imin, imax []byte
		tr := table.NewReader(reader, size, nil, bpool, o)
		iter := tr.NewIterator(nil, nil)
		iter.(iterator.ErrorCallbackSetter).SetErrorCallback(func(err error) {
			s.logf("[email protected] found error @%d %q", file.Num(), err)
			blockerr++
		})

		// Scan the table.
		for iter.Next() {
			key := iter.Key()
			_, seq, _, ok := parseIkey(key)
			if !ok {
				tcorrupted++
				continue
			}
			tgood++
			if seq > tSeq {
				tSeq = seq
			}
			if imin == nil {
				imin = append([]byte{}, key...)
			}
			imax = append(imax[:0], key...)
		}
		if err := iter.Error(); err != nil {
			iter.Release()
			return err
		}
		iter.Release()

//.........这里部分代码省略.........

func recoverTable(s *session, o *opt.Options) error {
	o = dupOptions(o)
	// Mask StrictReader, lets StrictRecovery doing its job.
	o.Strict &= ^opt.StrictReader

	// Get all tables and sort it by file number.
	tableFiles_, err := s.getFiles(storage.TypeTable)
	if err != nil {
		return err
	}
	tableFiles := files(tableFiles_)
	tableFiles.sort()

	var (
		maxSeq                                                            uint64
		recoveredKey, goodKey, corruptedKey, corruptedBlock, droppedTable int

		// We will drop corrupted table.
		strict = o.GetStrict(opt.StrictRecovery)

		rec   = &sessionRecord{numLevel: o.GetNumLevel()}
		bpool = util.NewBufferPool(o.GetBlockSize() + 5)
	)
	buildTable := func(iter iterator.Iterator) (tmp storage.File, size int64, err error) {
		tmp = s.newTemp()
		writer, err := tmp.Create()
		if err != nil {
			return
		}
		defer func() {
			writer.Close()
			if err != nil {
				tmp.Remove()
				tmp = nil
			}
		}()

		// Copy entries.
		tw := table.NewWriter(writer, o)
		for iter.Next() {
			key := iter.Key()
			if validIkey(key) {
				err = tw.Append(key, iter.Value())
				if err != nil {
					return
				}
			}
		}
		err = iter.Error()
		if err != nil {
			return
		}
		err = tw.Close()
		if err != nil {
			return
		}
		err = writer.Sync()
		if err != nil {
			return
		}
		size = int64(tw.BytesLen())
		return
	}
	recoverTable := func(file storage.File) error {
		s.logf("[email protected] recovering @%d", file.Num())
		reader, err := file.Open()
		if err != nil {
			return err
		}
		var closed bool
		defer func() {
			if !closed {
				reader.Close()
			}
		}()

		// Get file size.
		size, err := reader.Seek(0, 2)
		if err != nil {
			return err
		}

		var (
			tSeq                                     uint64
			tgoodKey, tcorruptedKey, tcorruptedBlock int
			imin, imax                               []byte
		)
		tr, err := table.NewReader(reader, size, storage.NewFileInfo(file), nil, bpool, o)
		if err != nil {
			return err
		}
		iter := tr.NewIterator(nil, nil)
		iter.(iterator.ErrorCallbackSetter).SetErrorCallback(func(err error) {
			if errors.IsCorrupted(err) {
				s.logf("[email protected] block corruption @%d %q", file.Num(), err)
				tcorruptedBlock++
			}
		})

		// Scan the table.
//.........这里部分代码省略.........

// NewReader creates a new initialized table reader for the file.
// The fi, cache and bpool is optional and can be nil.
//
// The returned table reader instance is goroutine-safe.
func NewReader(f io.ReaderAt, size int64, fd storage.FileDesc, cache *cache.CacheGetter, bpool *util.BufferPool, o *opt.Options) (*Reader, error) {
	if f == nil {
		return nil, errors.New("leveldb/table: nil file")
	}

	r := &Reader{
		fd:             fd,
		reader:         f,
		cache:          cache,
		bpool:          bpool,
		o:              o,
		cmp:            o.GetComparer(),
		verifyChecksum: o.GetStrict(opt.StrictBlockChecksum),
	}

	if size < footerLen {
		r.err = r.newErrCorrupted(0, size, "table", "too small")
		return r, nil
	}

	footerPos := size - footerLen
	var footer [footerLen]byte
	if _, err := r.reader.ReadAt(footer[:], footerPos); err != nil && err != io.EOF {
		return nil, err
	}
	if string(footer[footerLen-len(magic):footerLen]) != magic {
		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad magic number")
		return r, nil
	}

	var n int
	// Decode the metaindex block handle.
	r.metaBH, n = decodeBlockHandle(footer[:])
	if n == 0 {
		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad metaindex block handle")
		return r, nil
	}

	// Decode the index block handle.
	r.indexBH, n = decodeBlockHandle(footer[n:])
	if n == 0 {
		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad index block handle")
		return r, nil
	}

	// Read metaindex block.
	metaBlock, err := r.readBlock(r.metaBH, true)
	if err != nil {
		if errors.IsCorrupted(err) {
			r.err = err
			return r, nil
		} else {
			return nil, err
		}
	}

	// Set data end.
	r.dataEnd = int64(r.metaBH.offset)

	// Read metaindex.
	metaIter := r.newBlockIter(metaBlock, nil, nil, true)
	for metaIter.Next() {
		key := string(metaIter.Key())
		if !strings.HasPrefix(key, "filter.") {
			continue
		}
		fn := key[7:]
		if f0 := o.GetFilter(); f0 != nil && f0.Name() == fn {
			r.filter = f0
		} else {
			for _, f0 := range o.GetAltFilters() {
				if f0.Name() == fn {
					r.filter = f0
					break
				}
			}
		}
		if r.filter != nil {
			filterBH, n := decodeBlockHandle(metaIter.Value())
			if n == 0 {
				continue
			}
			r.filterBH = filterBH
			// Update data end.
			r.dataEnd = int64(filterBH.offset)
			break
		}
	}
	metaIter.Release()
	metaBlock.Release()

	// Cache index and filter block locally, since we don't have global cache.
	if cache == nil {
		r.indexBlock, err = r.readBlock(r.indexBH, true)
		if err != nil {
			if errors.IsCorrupted(err) {
//.........这里部分代码省略.........