path: root/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/session_util.go

// 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"
    "sync/atomic"

    "github.com/syndtr/goleveldb/leveldb/journal"
    "github.com/syndtr/goleveldb/leveldb/storage"
)

// Logging.

type dropper struct {
    s    *session
    file storage.File
}

func (d dropper) Drop(err error) {
    if e, ok := err.(*journal.ErrCorrupted); ok {
        d.s.logf("journal@drop %s-%d S·%s %q", d.file.Type(), d.file.Num(), shortenb(e.Size), e.Reason)
    } else {
        d.s.logf("journal@drop %s-%d %q", d.file.Type(), d.file.Num(), err)
    }
}

func (s *session) log(v ...interface{})                 { s.stor.Log(fmt.Sprint(v...)) }
func (s *session) logf(format string, v ...interface{}) { s.stor.Log(fmt.Sprintf(format, v...)) }

// File utils.

func (s *session) getJournalFile(num uint64) storage.File {
    return s.stor.GetFile(num, storage.TypeJournal)
}

func (s *session) getTableFile(num uint64) storage.File {
    return s.stor.GetFile(num, storage.TypeTable)
}

func (s *session) getFiles(t storage.FileType) ([]storage.File, error) {
    return s.stor.GetFiles(t)
}

func (s *session) newTemp() storage.File {
    num := atomic.AddUint64(&s.stTempFileNum, 1) - 1
    return s.stor.GetFile(num, storage.TypeTemp)
}

func (s *session) tableFileFromRecord(r atRecord) *tFile {
    return newTableFile(s.getTableFile(r.num), r.size, r.imin, r.imax)
}

// Session state.

// Get current version. This will incr version ref, must call
// version.release (exactly once) after use.
func (s *session) version() *version {
    s.vmu.Lock()
    defer s.vmu.Unlock()
    s.stVersion.ref++
    return s.stVersion
}

// Set current version to v.
func (s *session) setVersion(v *version) {
    s.vmu.Lock()
    v.ref = 1 // Holds by session.
    if old := s.stVersion; old != nil {
        v.ref++ // Holds by old version.
        old.next = v
        old.releaseNB()
    }
    s.stVersion = v
    s.vmu.Unlock()
}

// Get current unused file number.
func (s *session) nextFileNum() uint64 {
    return atomic.LoadUint64(&s.stNextFileNum)
}

// Set current unused file number to num.
func (s *session) setNextFileNum(num uint64) {
    atomic.StoreUint64(&s.stNextFileNum, num)
}

// Mark file number as used.
func (s *session) markFileNum(num uint64) {
    nextFileNum := num + 1
    for {
        old, x := s.stNextFileNum, nextFileNum
        if old > x {
            x = old
        }
        if atomic.CompareAndSwapUint64(&s.stNextFileNum, old, x) {
            break
        }
    }
}

// Allocate a file number.
func (s *session) allocFileNum() uint64 {
    return atomic.AddUint64(&s.stNextFileNum, 1) - 1
}

// Reuse given file number.
func (s *session) reuseFileNum(num uint64) {
    for {
        old, x := s.stNextFileNum, num
        if old != x+1 {
            x = old
        }
        if atomic.CompareAndSwapUint64(&s.stNextFileNum, old, x) {
            break
        }
    }
}

// Manifest related utils.

// Fill given session record obj with current states; need external
// synchronization.
func (s *session) fillRecord(r *sessionRecord, snapshot bool) {
    r.setNextFileNum(s.nextFileNum())

    if snapshot {
        if !r.has(recJournalNum) {
            r.setJournalNum(s.stJournalNum)
        }

        if !r.has(recSeqNum) {
            r.setSeqNum(s.stSeqNum)
        }

        for level, ik := range s.stCompPtrs {
            if ik != nil {
                r.addCompPtr(level, ik)
            }
        }

        r.setComparer(s.icmp.uName())
    }
}

// Mark if record has been committed, this will update session state;
// need external synchronization.
func (s *session) recordCommited(r *sessionRecord) {
    if r.has(recJournalNum) {
        s.stJournalNum = r.journalNum
    }

    if r.has(recPrevJournalNum) {
        s.stPrevJournalNum = r.prevJournalNum
    }

    if r.has(recSeqNum) {
        s.stSeqNum = r.seqNum
    }

    for _, p := range r.compPtrs {
        s.stCompPtrs[p.level] = iKey(p.ikey)
    }
}

// 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{numLevel: s.o.GetNumLevel()}
    }
    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
}

// Flush record to disk.
func (s *session) flushManifest(rec *sessionRecord) (err error) {
    s.fillRecord(rec, false)
    w, err := s.manifest.Next()
    if err != nil {
        return
    }
    err = rec.encode(w)
    if err != nil {
        return
    }
    err = s.manifest.Flush()
    if err != nil {
        return
    }
    err = s.manifestWriter.Sync()
    if err != nil {
        return
    }
    s.recordCommited(rec)
    return
}