Golang journal.NewWriter函数代码示例

// Create new memdb and froze the old one; need external synchronization.
// newMem only called synchronously by the writer.
func (d *DB) newMem() (mem *memdb.DB, err error) {
	s := d.s

	num := s.allocFileNum()
	file := s.getJournalFile(num)
	w, err := file.Create()
	if err != nil {
		s.reuseFileNum(num)
		return
	}
	d.memMu.Lock()
	if d.journal == nil {
		d.journal = journal.NewWriter(w)
	} else {
		d.journal.Reset(w)
		d.journalWriter.Close()
		d.frozenJournalFile = d.journalFile
	}
	d.journalWriter = w
	d.journalFile = file
	d.frozenMem = d.mem
	d.mem = memdb.New(s.cmp, toPercent(d.s.o.GetWriteBuffer(), kWriteBufferPercent))
	mem = d.mem
	// The seq only incremented by the writer.
	d.frozenSeq = d.seq
	d.memMu.Unlock()
	return
}

// Create new memdb and froze the old one; need external synchronization.
// newMem only called synchronously by the writer.
func (db *DB) newMem(n int) (mem *memDB, err error) {
	fd := storage.FileDesc{Type: storage.TypeJournal, Num: db.s.allocFileNum()}
	w, err := db.s.stor.Create(fd)
	if err != nil {
		db.s.reuseFileNum(fd.Num)
		return
	}

	db.memMu.Lock()
	defer db.memMu.Unlock()

	if db.frozenMem != nil {
		panic("still has frozen mem")
	}

	if db.journal == nil {
		db.journal = journal.NewWriter(w)
	} else {
		db.journal.Reset(w)
		db.journalWriter.Close()
		db.frozenJournalFd = db.journalFd
	}
	db.journalWriter = w
	db.journalFd = fd
	db.frozenMem = db.mem
	mem = db.mpoolGet(n)
	mem.incref() // for self
	mem.incref() // for caller
	db.mem = mem
	// The seq only incremented by the writer. And whoever called newMem
	// should hold write lock, so no need additional synchronization here.
	db.frozenSeq = db.seq
	return
}

// Create new memdb and froze the old one; need external synchronization.
// newMem only called synchronously by the writer.
func (db *DB) newMem(n int) (mem *memdb.DB, err error) {
	num := db.s.allocFileNum()
	file := db.s.getJournalFile(num)
	w, err := file.Create()
	if err != nil {
		db.s.reuseFileNum(num)
		return
	}

	db.memMu.Lock()
	defer db.memMu.Unlock()

	if db.journal == nil {
		db.journal = journal.NewWriter(w)
	} else {
		db.journal.Reset(w)
		db.journalWriter.Close()
		db.frozenJournalFile = db.journalFile
	}
	db.journalWriter = w
	db.journalFile = file
	db.frozenMem = db.mem
	db.mem = memdb.New(db.s.icmp, maxInt(db.s.o.GetWriteBuffer(), n))
	mem = db.mem
	// The seq only incremented by the writer. And whoever called newMem
	// should hold write lock, so no need additional synchronization here.
	db.frozenSeq = db.seq
	return
}

// Create a new manifest file; need external synchronization.
func (s *session) newManifest(rec *sessionRecord, v *version) (err error) {
	num := s.allocFileNum()
	file := s.stor.GetFile(num, storage.TypeManifest)
	writer, err := file.Create()
	if err != nil {
		return
	}
	jw := journal.NewWriter(writer)

	if v == nil {
		v = s.version()
		defer v.release()
	}
	if rec == nil {
		rec = &sessionRecord{}
	}
	s.fillRecord(rec, true)
	v.fillRecord(rec)

	defer func() {
		if err == nil {
			s.recordCommited(rec)
			if s.manifest != nil {
				s.manifest.Close()
			}
			if s.manifestWriter != nil {
				s.manifestWriter.Close()
			}
			if s.manifestFile != nil {
				s.manifestFile.Remove()
			}
			s.manifestFile = file
			s.manifestWriter = writer
			s.manifest = jw
		} else {
			writer.Close()
			file.Remove()
			s.reuseFileNum(num)
		}
	}()

	w, err := jw.Next()
	if err != nil {
		return
	}
	err = rec.encode(w)
	if err != nil {
		return
	}
	err = jw.Flush()
	if err != nil {
		return
	}
	err = s.stor.SetManifest(file)
	return
}

func newJournalWriter(file storage.File) (p *journalWriter, err error) {
	w := new(journalWriter)
	w.file = file
	w.writer, err = file.Create()
	if err != nil {
		return
	}
	w.journal = journal.NewWriter(w.writer)
	return w, nil
}

// Create a new manifest file; need external synchronization.
func (s *session) newManifest(rec *sessionRecord, v *version) (err error) {
	fd := storage.FileDesc{storage.TypeManifest, s.allocFileNum()}
	writer, err := s.stor.Create(fd)
	if err != nil {
		return
	}
	jw := journal.NewWriter(writer)

	if v == nil {
		v = s.version()
		defer v.release()
	}
	if rec == nil {
		rec = &sessionRecord{}
	}
	s.fillRecord(rec, true)
	v.fillRecord(rec)

	defer func() {
		if err == nil {
			s.recordCommited(rec)
			if s.manifest != nil {
				s.manifest.Close()
			}
			if s.manifestWriter != nil {
				s.manifestWriter.Close()
			}
			if !s.manifestFd.Nil() {
				s.stor.Remove(s.manifestFd)
			}
			s.manifestFd = fd
			s.manifestWriter = writer
			s.manifest = jw
		} else {
			writer.Close()
			s.stor.Remove(fd)
			s.reuseFileNum(fd.Num)
		}
	}()

	w, err := jw.Next()
	if err != nil {
		return
	}
	err = rec.encode(w)
	if err != nil {
		return
	}
	err = jw.Flush()
	if err != nil {
		return
	}
	err = s.stor.SetMeta(fd)
	return
}

// Create new memdb and froze the old one; need external synchronization.
// newMem only called synchronously by the writer.
func (db *DB) newMem(n int) (mem *memDB, err error) {
	num := db.s.allocFileNum()
	file := db.s.getJournalFile(num)
	w, err := file.Create()
	if err != nil {
		db.s.reuseFileNum(num)
		return
	}

	db.memMu.Lock()
	defer db.memMu.Unlock()

	if db.frozenMem != nil {
		panic("still has frozen mem")
	}

	if db.journal == nil {
		db.journal = journal.NewWriter(w)
	} else {
		db.journal.Reset(w)
		db.journalWriter.Close()
		db.frozenJournalFile = db.journalFile
	}
	db.journalWriter = w
	db.journalFile = file
	db.frozenMem = db.mem
	mem, ok := db.memPool.Get().(*memDB)
	if ok && mem.db.Capacity() >= n {
		mem.db.Reset()
		mem.incref()
	} else {
		mem = &memDB{
			pool: db.memPool,
			db:   memdb.New(db.s.icmp, maxInt(db.s.o.GetWriteBuffer(), n)),
			ref:  1,
		}
	}
	mem.incref()
	db.mem = mem
	// The seq only incremented by the writer. And whoever called newMem
	// should hold write lock, so no need additional synchronization here.
	db.frozenSeq = db.seq
	return
}

// Create new memdb and froze the old one; need external synchronization.
// newMem only called synchronously by the writer.
func (db *DB) newMem(n int) (mem *memDB, err error) {
	fd := storage.FileDesc{Type: storage.TypeJournal, Num: db.s.allocFileNum()}
	w, err := db.s.stor.Create(fd)
	if err != nil {
		db.s.reuseFileNum(fd.Num)
		return
	}

	db.memMu.Lock()
	defer db.memMu.Unlock()

	if db.frozenMem != nil {
		panic("still has frozen mem")
	}

	if db.journal == nil {
		db.journal = journal.NewWriter(w)
	} else {
		db.journal.Reset(w)
		db.journalWriter.Close()
		db.frozenJournalFd = db.journalFd
	}
	db.journalWriter = w
	db.journalFd = fd
	db.frozenMem = db.mem
	mdb := db.mpoolGet()
	if mdb == nil || mdb.Capacity() < n {
		mdb = memdb.New(db.s.icmp, maxInt(db.s.o.GetWriteBuffer(), n))
	}
	mem = &memDB{
		db:  db,
		DB:  mdb,
		ref: 2,
	}
	db.mem = mem
	// The seq only incremented by the writer. And whoever called newMem
	// should hold write lock, so no need additional synchronization here.
	db.frozenSeq = db.seq
	return
}