--- /dev/null
+// 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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