github.com/zuoyebang/bitalosdb@v1.1.1-0.20240516111551-79a8c4d8ce20/read_state.go (about) 1 // Copyright 2021 The Bitalosdb author(hustxrb@163.com) and other contributors. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package bitalosdb 16 17 import "sync/atomic" 18 19 type readState struct { 20 refcnt atomic.Int32 21 memtables flushableList 22 } 23 24 func (s *readState) ref() { 25 s.refcnt.Add(1) 26 } 27 28 func (s *readState) unref() { 29 if s.refcnt.Add(-1) != 0 { 30 return 31 } 32 for _, mem := range s.memtables { 33 mem.readerUnref() 34 } 35 } 36 37 func (s *Bitower) loadReadState() *readState { 38 s.readState.RLock() 39 state := s.readState.val 40 state.ref() 41 s.readState.RUnlock() 42 return state 43 } 44 45 func (s *Bitower) updateReadState() { 46 rs := &readState{ 47 memtables: s.mu.mem.queue, 48 } 49 rs.refcnt.Store(1) 50 51 for _, mem := range rs.memtables { 52 mem.readerRef() 53 } 54 55 s.readState.Lock() 56 old := s.readState.val 57 s.readState.val = rs 58 s.readState.Unlock() 59 60 if old != nil { 61 old.unref() 62 } 63 }