add other session providers (#5963)

vendor/github.com/syndtr/goleveldb/leveldb/session.go

@@ -0,0 +1,210 @@
+// 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 leveldb
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"sync"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/journal"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+// ErrManifestCorrupted records manifest corruption. This error will be
+// wrapped with errors.ErrCorrupted.
+type ErrManifestCorrupted struct {
+	Field  string
+	Reason string
+}
+
+func (e *ErrManifestCorrupted) Error() string {
+	return fmt.Sprintf("leveldb: manifest corrupted (field '%s'): %s", e.Field, e.Reason)
+}
+
+func newErrManifestCorrupted(fd storage.FileDesc, field, reason string) error {
+	return errors.NewErrCorrupted(fd, &ErrManifestCorrupted{field, reason})
+}
+
+// session represent a persistent database session.
+type session struct {
+	// Need 64-bit alignment.
+	stNextFileNum    int64 // current unused file number
+	stJournalNum     int64 // current journal file number; need external synchronization
+	stPrevJournalNum int64 // prev journal file number; no longer used; for compatibility with older version of leveldb
+	stTempFileNum    int64
+	stSeqNum         uint64 // last mem compacted seq; need external synchronization
+
+	stor     *iStorage
+	storLock storage.Locker
+	o        *cachedOptions
+	icmp     *iComparer
+	tops     *tOps
+	fileRef  map[int64]int
+
+	manifest       *journal.Writer
+	manifestWriter storage.Writer
+	manifestFd     storage.FileDesc
+
+	stCompPtrs []internalKey // compaction pointers; need external synchronization
+	stVersion  *version      // current version
+	vmu        sync.Mutex
+}
+
+// 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:     newIStorage(stor),
+		storLock: storLock,
+		fileRef:  make(map[int64]int),
+	}
+	s.setOptions(o)
+	s.tops = newTableOps(s)
+	s.setVersion(newVersion(s))
+	s.log("log@legend F·NumFile S·FileSize N·Entry C·BadEntry B·BadBlock Ke·KeyError D·DroppedEntry L·Level Q·SeqNum T·TimeElapsed")
+	return
+}
+
+// Close session.
+func (s *session) close() {
+	s.tops.close()
+	if s.manifest != nil {
+		s.manifest.Close()
+	}
+	if s.manifestWriter != nil {
+		s.manifestWriter.Close()
+	}
+	s.manifest = nil
+	s.manifestWriter = nil
+	s.setVersion(&version{s: s, closing: true})
+}
+
+// Release session lock.
+func (s *session) release() {
+	s.storLock.Unlock()
+}
+
+// Create a new database session; need external synchronization.
+func (s *session) create() error {
+	// create manifest
+	return s.newManifest(nil, nil)
+}
+
+// Recover a database session; need external synchronization.
+func (s *session) recover() (err error) {
+	defer func() {
+		if os.IsNotExist(err) {
+			// Don't return os.ErrNotExist if the underlying storage contains
+			// other files that belong to LevelDB. So the DB won't get trashed.
+			if fds, _ := s.stor.List(storage.TypeAll); len(fds) > 0 {
+				err = &errors.ErrCorrupted{Fd: storage.FileDesc{Type: storage.TypeManifest}, Err: &errors.ErrMissingFiles{}}
+			}
+		}
+	}()
+
+	fd, err := s.stor.GetMeta()
+	if err != nil {
+		return
+	}
+
+	reader, err := s.stor.Open(fd)
+	if err != nil {
+		return
+	}
+	defer reader.Close()
+
+	var (
+		// Options.
+		strict = s.o.GetStrict(opt.StrictManifest)
+
+		jr      = journal.NewReader(reader, dropper{s, fd}, strict, true)
+		rec     = &sessionRecord{}
+		staging = s.stVersion.newStaging()
+	)
+	for {
+		var r io.Reader
+		r, err = jr.Next()
+		if err != nil {
+			if err == io.EOF {
+				err = nil
+				break
+			}
+			return errors.SetFd(err, fd)
+		}
+
+		err = rec.decode(r)
+		if err == nil {
+			// save compact pointers
+			for _, r := range rec.compPtrs {
+				s.setCompPtr(r.level, internalKey(r.ikey))
+			}
+			// commit record to version staging
+			staging.commit(rec)
+		} else {
+			err = errors.SetFd(err, fd)
+			if strict || !errors.IsCorrupted(err) {
+				return
+			}
+			s.logf("manifest error: %v (skipped)", errors.SetFd(err, fd))
+		}
+		rec.resetCompPtrs()
+		rec.resetAddedTables()
+		rec.resetDeletedTables()
+	}
+
+	switch {
+	case !rec.has(recComparer):
+		return newErrManifestCorrupted(fd, "comparer", "missing")
+	case rec.comparer != s.icmp.uName():
+		return newErrManifestCorrupted(fd, "comparer", fmt.Sprintf("mismatch: want '%s', got '%s'", s.icmp.uName(), rec.comparer))
+	case !rec.has(recNextFileNum):
+		return newErrManifestCorrupted(fd, "next-file-num", "missing")
+	case !rec.has(recJournalNum):
+		return newErrManifestCorrupted(fd, "journal-file-num", "missing")
+	case !rec.has(recSeqNum):
+		return newErrManifestCorrupted(fd, "seq-num", "missing")
+	}
+
+	s.manifestFd = fd
+	s.setVersion(staging.finish())
+	s.setNextFileNum(rec.nextFileNum)
+	s.recordCommited(rec)
+	return nil
+}
+
+// Commit session; need external synchronization.
+func (s *session) commit(r *sessionRecord) (err error) {
+	v := s.version()
+	defer v.release()
+
+	// spawn new version based on current version
+	nv := v.spawn(r)
+
+	if s.manifest == nil {
+		// manifest journal writer not yet created, create one
+		err = s.newManifest(r, nv)
+	} else {
+		err = s.flushManifest(r)
+	}
+
+	// finally, apply new version if no error rise
+	if err == nil {
+		s.setVersion(nv)
+	}
+
+	return
+}