restic/internal/backend/sema/semaphore.go

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// Package sema implements semaphores.
package sema
import (
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
)
// A 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 semaphore{}, errors.New("capacity 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{}{}
debug.Log("acquired token")
}
// ReleaseToken returns a token.
func (s semaphore) ReleaseToken() { <-s.ch }