github.com/matrixorigin/matrixone@v1.2.0/pkg/fileservice/memorycache/refcnt.go (about)

     1  // Copyright 2022 Matrix Origin
     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 memorycache
    16  
    17  import (
    18  	"fmt"
    19  	"sync/atomic"
    20  )
    21  
    22  // refcnt is an atomic reference counter
    23  type refcnt struct {
    24  	val atomic.Int32
    25  }
    26  
    27  func (r *refcnt) init(val int32) {
    28  	r.val.Store(val)
    29  }
    30  
    31  func (r *refcnt) refs() int32 {
    32  	return r.val.Load()
    33  }
    34  
    35  func (r *refcnt) acquire() {
    36  	switch v := r.val.Add(1); {
    37  	case v <= 1:
    38  		panic(fmt.Sprintf("inconsistent refcnt count: %d", v))
    39  	}
    40  }
    41  
    42  func (r *refcnt) release() bool {
    43  	switch v := r.val.Add(-1); {
    44  	case v < 0:
    45  		panic(fmt.Sprintf("inconsistent refcnt count: %d", v))
    46  	case v == 0:
    47  		return true
    48  	default:
    49  		return false
    50  	}
    51  }