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sequences.go
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sequences.go
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package registry
import (
"errors"
"sync"
"time"
"github.com/libp2p/go-libp2p/core/peer"
)
const defaultMaxAge = 48 * time.Hour
const seqRetireInterval = time.Hour
type sequences struct {
lastRetire time.Time
maxAge time.Duration
mutex sync.Mutex
seqs map[peer.ID]uint64
}
func newSequences(maxAge time.Duration) *sequences {
if maxAge == 0 {
maxAge = defaultMaxAge
}
return &sequences{
maxAge: maxAge,
seqs: make(map[peer.ID]uint64),
}
}
func (s *sequences) check(id peer.ID, sequence uint64) error {
oldestAllowed := uint64(time.Now().Add(-s.maxAge).UnixNano())
if sequence < oldestAllowed {
return errors.New("sequence too small")
}
s.mutex.Lock()
defer s.mutex.Unlock()
prevSeq, ok := s.seqs[id]
if ok && sequence <= prevSeq {
return errors.New("sequence less than or equal to last seen")
}
s.seqs[id] = sequence
if time.Since(s.lastRetire) > seqRetireInterval {
go s.retire()
}
return nil
}
func (s *sequences) retire() {
oldestAllowed := uint64(time.Now().Add(-s.maxAge).UnixNano())
active := make(map[peer.ID]uint64)
s.mutex.Lock()
defer s.mutex.Unlock()
for id, seq := range s.seqs {
if seq > oldestAllowed {
active[id] = seq
}
}
s.seqs = active
s.lastRetire = time.Now()
}