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// Copyright (c) 2013, 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 (
"errors"
"sync/atomic"
"time"
"github.com/syndtr/goleveldb/leveldb/journal"
"github.com/syndtr/goleveldb/leveldb/memdb"
"github.com/syndtr/goleveldb/leveldb/storage"
)
var (
errHasFrozenMem = errors.New("has frozen mem")
)
type memDB struct {
db *DB
*memdb.DB
ref int32
}
func (m *memDB) getref() int32 {
return atomic.LoadInt32(&m.ref)
}
func (m *memDB) incref() {
atomic.AddInt32(&m.ref, 1)
}
func (m *memDB) decref() {
if ref := atomic.AddInt32(&m.ref, -1); ref == 0 {
// Only put back memdb with std capacity.
if m.Capacity() == m.db.s.o.GetWriteBuffer() {
m.Reset()
m.db.mpoolPut(m.DB)
}
m.db = nil
m.DB = nil
} else if ref < 0 {
panic("negative memdb ref")
}
}
// Get latest sequence number.
func (db *DB) getSeq() uint64 {
return atomic.LoadUint64(&db.seq)
}
// Atomically adds delta to seq.
func (db *DB) addSeq(delta uint64) {
atomic.AddUint64(&db.seq, delta)
}
func (db *DB) setSeq(seq uint64) {
atomic.StoreUint64(&db.seq, seq)
}
func (db *DB) sampleSeek(ikey internalKey) {
v := db.s.version()
if v.sampleSeek(ikey) {
// Trigger table compaction.
db.compTrigger(db.tcompCmdC)
}
v.release()
}
func (db *DB) mpoolPut(mem *memdb.DB) {
if !db.isClosed() {
select {
case db.memPool <- mem:
default:
}
}
}
func (db *DB) mpoolGet(n int) *memDB {
var mdb *memdb.DB
select {
case mdb = <-db.memPool:
default:
}
if mdb == nil || mdb.Capacity() < n {
mdb = memdb.New(db.s.icmp, maxInt(db.s.o.GetWriteBuffer(), n))
}
return &memDB{
db: db,
DB: mdb,
}
}
func (db *DB) mpoolDrain() {
ticker := time.NewTicker(30 * time.Second)
for {
select {
case <-ticker.C:
select {
case <-db.memPool:
default:
}
case <-db.closeC:
ticker.Stop()
// Make sure the pool is drained.
select {
case <-db.memPool:
case <-time.After(time.Second):
}
close(db.memPool)
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 {
return nil, errHasFrozenMem
}
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
}
// Get all memdbs.
func (db *DB) getMems() (e, f *memDB) {
db.memMu.RLock()
defer db.memMu.RUnlock()
if db.mem != nil {
db.mem.incref()
} else if !db.isClosed() {
panic("nil effective mem")
}
if db.frozenMem != nil {
db.frozenMem.incref()
}
return db.mem, db.frozenMem
}
// Get effective memdb.
func (db *DB) getEffectiveMem() *memDB {
db.memMu.RLock()
defer db.memMu.RUnlock()
if db.mem != nil {
db.mem.incref()
} else if !db.isClosed() {
panic("nil effective mem")
}
return db.mem
}
// Check whether we has frozen memdb.
func (db *DB) hasFrozenMem() bool {
db.memMu.RLock()
defer db.memMu.RUnlock()
return db.frozenMem != nil
}
// Get frozen memdb.
func (db *DB) getFrozenMem() *memDB {
db.memMu.RLock()
defer db.memMu.RUnlock()
if db.frozenMem != nil {
db.frozenMem.incref()
}
return db.frozenMem
}
// Drop frozen memdb; assume that frozen memdb isn't nil.
func (db *DB) dropFrozenMem() {
db.memMu.Lock()
if err := db.s.stor.Remove(db.frozenJournalFd); err != nil {
db.logf("journal@remove removing @%d %q", db.frozenJournalFd.Num, err)
} else {
db.logf("journal@remove removed @%d", db.frozenJournalFd.Num)
}
db.frozenJournalFd = storage.FileDesc{}
db.frozenMem.decref()
db.frozenMem = nil
db.memMu.Unlock()
}
// Clear mems ptr; used by DB.Close().
func (db *DB) clearMems() {
db.memMu.Lock()
db.mem = nil
db.frozenMem = nil
db.memMu.Unlock()
}
// Set closed flag; return true if not already closed.
func (db *DB) setClosed() bool {
return atomic.CompareAndSwapUint32(&db.closed, 0, 1)
}
// Check whether DB was closed.
func (db *DB) isClosed() bool {
return atomic.LoadUint32(&db.closed) != 0
}
// Check read ok status.
func (db *DB) ok() error {
if db.isClosed() {
return ErrClosed
}
return nil
}
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