39 lines
882 B
Go
39 lines
882 B
Go
|
/*
|
|||
|
|
* Copyright (C) THL A29 Limited, a Tencent company. All rights reserved.
|
|||
|
|
*
|
|||
|
|
* SPDX-License-Identifier: Apache-2.0
|
|||
|
|
*
|
|||
|
|
*/
|
|||
|
|
|
|||
|
|
package lockfree
|
|||
|
|
|
|||
|
|
import (
|
|||
|
|
"sync/atomic"
|
|||
|
|
)
|
|||
|
|
|
|||
|
|
// sequencer 序号产生器，维护读和写两个状态，写状态具体由内部游标（cursor）维护。
|
|||
|
|
// 读取状态由自身维护，变量read即可
|
|||
|
|
type sequencer struct {
|
|||
|
|
rc uint64 // 读取游标，因为该值仅会被一个g修改，所以不需要使用cursor
|
|||
|
|
capacity uint64
|
|||
|
|
wc *cursor
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func newSequencer(capacity int) *sequencer {
|
|||
|
|
return &sequencer{
|
|||
|
|
wc: newCursor(),
|
|||
|
|
rc: 1,
|
|||
|
|
capacity: uint64(capacity),
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// nextRead 获取下个要读取的位置
|
|||
|
|
// 使用原子操作解决data race问题
|
|||
|
|
func (s *sequencer) nextRead() uint64 {
|
|||
|
|
return atomic.LoadUint64(&s.rc)
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func (s *sequencer) readIncrement() uint64 {
|
|||
|
|
return atomic.AddUint64(&s.rc, 1)
|
|||
|
|
}
|