示例#1
0
func (w *Writer) writeBlock(buf *util.Buffer, compression opt.Compression) (bh blockHandle, err error) {
	// Compress the buffer if necessary.
	var b []byte
	if compression == opt.SnappyCompression {
		// Allocate scratch enough for compression and block trailer.
		if n := snappy.MaxEncodedLen(buf.Len()) + blockTrailerLen; len(w.compressionScratch) < n {
			w.compressionScratch = make([]byte, n)
		}
		var compressed []byte
		compressed, err = snappy.Encode(w.compressionScratch, buf.Bytes())
		if err != nil {
			return
		}
		n := len(compressed)
		b = compressed[:n+blockTrailerLen]
		b[n] = blockTypeSnappyCompression
	} else {
		tmp := buf.Alloc(blockTrailerLen)
		tmp[0] = blockTypeNoCompression
		b = buf.Bytes()
	}

	// Calculate the checksum.
	n := len(b) - 4
	checksum := util.NewCRC(b[:n]).Value()
	binary.LittleEndian.PutUint32(b[n:], checksum)

	// Write the buffer to the file.
	_, err = w.writer.Write(b)
	if err != nil {
		return
	}
	bh = blockHandle{w.offset, uint64(len(b) - blockTrailerLen)}
	w.offset += uint64(len(b))
	return
}
示例#2
0
文件: db.go 项目: zangfong/goleveldb
func (d *DB) recoverJournal() error {
	s := d.s
	icmp := s.cmp

	ff0, err := s.getFiles(storage.TypeJournal)
	if err != nil {
		return err
	}
	ff1 := files(ff0)
	ff1.sort()
	ff2 := make([]storage.File, 0, len(ff1))
	for _, file := range ff1 {
		if file.Num() >= s.stJournalNum || file.Num() == s.stPrevJournalNum {
			s.markFileNum(file.Num())
			ff2 = append(ff2, file)
		}
	}

	var jr *journal.Reader
	var of storage.File
	var mem *memdb.DB
	batch := new(Batch)
	cm := newCMem(s)
	buf := new(util.Buffer)
	// Options.
	strict := s.o.GetStrict(opt.StrictJournal)
	checksum := s.o.GetStrict(opt.StrictJournalChecksum)
	writeBuffer := s.o.GetWriteBuffer()
	recoverJournal := func(file storage.File) error {
		s.logf("journal@recovery recovering @%d", file.Num())
		reader, err := file.Open()
		if err != nil {
			return err
		}
		defer reader.Close()
		if jr == nil {
			jr = journal.NewReader(reader, dropper{s, file}, strict, checksum)
		} else {
			jr.Reset(reader, dropper{s, file}, strict, checksum)
		}
		if of != nil {
			if mem.Len() > 0 {
				if err := cm.flush(mem, 0); err != nil {
					return err
				}
			}
			if err := cm.commit(file.Num(), d.seq); err != nil {
				return err
			}
			cm.reset()
			of.Remove()
			of = nil
		}
		// Reset memdb.
		mem.Reset()
		for {
			r, err := jr.Next()
			if err != nil {
				if err == io.EOF {
					break
				}
				return err
			}
			buf.Reset()
			if _, err := buf.ReadFrom(r); err != nil {
				if strict {
					return err
				}
				continue
			}
			if err := batch.decode(buf.Bytes()); err != nil {
				return err
			}
			if err := batch.memReplay(mem); err != nil {
				return err
			}
			d.seq = batch.seq + uint64(batch.len())
			if mem.Size() >= writeBuffer {
				// Large enough, flush it.
				if err := cm.flush(mem, 0); err != nil {
					return err
				}
				// Reset memdb.
				mem.Reset()
			}
		}
		of = file
		return nil
	}
	// Recover all journals.
	if len(ff2) > 0 {
		s.logf("journal@recovery F·%d", len(ff2))
		mem = memdb.New(icmp, toPercent(writeBuffer, kWriteBufferPercent))
		for _, file := range ff2 {
			if err := recoverJournal(file); err != nil {
				return err
			}
		}
		// Flush the last journal.
		if mem.Len() > 0 {
			if err := cm.flush(mem, 0); err != nil {
				return err
			}
		}
	}
	// Create a new journal.
	if _, err := d.newMem(); err != nil {
		return err
	}
	// Commit.
	if err := cm.commit(d.journalFile.Num(), d.seq); err != nil {
		return err
	}
	// Remove the last journal.
	if of != nil {
		of.Remove()
	}
	return nil
}