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  }