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92 lines
1.7 KiB
92 lines
1.7 KiB
package pow
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import (
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"errors"
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"sync"
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"time"
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"github.com/tilinna/clock"
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)
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// ErrSeedSolved is used to indicate a seed has already been solved.
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var ErrSeedSolved = errors.New("seed already solved")
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// Store is used to track information related to proof-of-work challenges and
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// solutions.
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type Store interface {
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// MarkSolved will return ErrSeedSolved if the seed was already marked. The
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// seed will be cleared from the Store once expiresAt is reached.
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MarkSolved(seed []byte, expiresAt time.Time) error
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Close() error
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}
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type inMemStore struct {
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clock clock.Clock
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m map[string]time.Time
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l sync.Mutex
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closeCh chan struct{}
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spinLoopCh chan struct{} // only used by tests
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}
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const inMemStoreGCPeriod = 5 * time.Second
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// NewMemoryStore initializes and returns an in-memory Store implementation.
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func NewMemoryStore(clock clock.Clock) Store {
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s := &inMemStore{
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clock: clock,
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m: map[string]time.Time{},
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closeCh: make(chan struct{}),
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spinLoopCh: make(chan struct{}, 1),
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}
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go s.spin(s.clock.NewTicker(inMemStoreGCPeriod))
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return s
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}
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func (s *inMemStore) spin(ticker *clock.Ticker) {
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defer ticker.Stop()
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for {
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select {
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case <-ticker.C:
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now := s.clock.Now()
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s.l.Lock()
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for seed, expiresAt := range s.m {
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if !now.Before(expiresAt) {
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delete(s.m, seed)
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}
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}
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s.l.Unlock()
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case <-s.closeCh:
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return
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}
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select {
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case s.spinLoopCh <- struct{}{}:
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default:
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}
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}
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}
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func (s *inMemStore) MarkSolved(seed []byte, expiresAt time.Time) error {
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seedStr := string(seed)
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s.l.Lock()
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defer s.l.Unlock()
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if _, ok := s.m[seedStr]; ok {
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return ErrSeedSolved
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}
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s.m[seedStr] = expiresAt
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return nil
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}
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func (s *inMemStore) Close() error {
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close(s.closeCh)
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return nil
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}
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