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refs.go
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refs.go
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// Copyright 2021 Matrix Origin
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package common
import (
"sync/atomic"
)
type PinnedItem[T IRef] struct {
Val T
}
func (item *PinnedItem[T]) Close() {
item.Val.Unref()
}
func (item *PinnedItem[T]) Item() T { return item.Val }
// IRef is the general representation of the resources
// that should be managed with a reference count.
// Once the reference count reached 0, the OnZeroCB
// would be called.
type IRef interface {
RefCount() int64
// RefIfHasRef increment refcnt if existing cnt > 0 and return true,
// return false if cnt is zero. Note: the udpate is atomic
RefIfHasRef() bool
Ref()
Unref()
}
type OnZeroCB func()
type RefHelper struct {
Refs atomic.Int64
OnZeroCB OnZeroCB
}
func (helper *RefHelper) RefCount() int64 {
return helper.Refs.Load()
}
func (helper *RefHelper) Ref() {
helper.Refs.Add(1)
}
func (helper *RefHelper) RefIfHasRef() bool {
for val := helper.Refs.Load(); val > 0; val = helper.Refs.Load() {
if helper.Refs.CompareAndSwap(val, val+1) {
return true
}
}
return false
}
func (helper *RefHelper) Unref() {
v := helper.Refs.Add(-1)
if v == 0 {
if helper.OnZeroCB != nil {
helper.OnZeroCB()
}
} else if v < 0 {
panic("logic error")
}
}