package backend import "github.com/restic/restic/internal/errors" // Semaphore limits access to a restricted resource. type Semaphore struct { ch chan struct{} } // NewSemaphore returns a new semaphore with capacity n. func NewSemaphore(n uint) (*Semaphore, error) { if n <= 0 { return nil, errors.New("must be a positive number") } return &Semaphore{ ch: make(chan struct{}, n), }, nil } // GetToken blocks until a Token is available. func (s *Semaphore) GetToken() { s.ch <- struct{}{} } // ReleaseToken returns a token. func (s *Semaphore) ReleaseToken() { <-s.ch }