github.com/coocood/badger@v1.5.1-0.20200528065104-c02ac3616d04/epoch/epoch.go (about)

     1  package epoch
     2  
     3  import "sync/atomic"
     4  
     5  // The least significant bit of epoch is active flag.
     6  type epoch uint64
     7  
     8  func (e epoch) isActive() bool {
     9  	return uint64(e)&1 == 1
    10  }
    11  
    12  func (e epoch) activate() epoch {
    13  	return epoch(uint64(e) | 1)
    14  }
    15  
    16  func (e epoch) deactivate() epoch {
    17  	return epoch(uint64(e) & ^uint64(1))
    18  }
    19  
    20  func (e epoch) sub(a epoch) int {
    21  	return int((uint64(e) >> 1) - (uint64(a) >> 1))
    22  }
    23  
    24  func (e epoch) successor() epoch {
    25  	return epoch(uint64(e) + 2)
    26  }
    27  
    28  type atomicEpoch struct {
    29  	epoch uint64
    30  }
    31  
    32  func (e *atomicEpoch) load() epoch {
    33  	return (epoch)(atomic.LoadUint64(&e.epoch))
    34  }
    35  
    36  func (e *atomicEpoch) store(new epoch) {
    37  	atomic.StoreUint64(&e.epoch, uint64(new))
    38  }